NIMP| Marcela SOCOL, Author at NIMP

Expertize

organic photovoltaic (OPV) and organic light emitting diode (OLED) structures obtained by different methods (vacuum evaporation, spin-coating, matrix assisted pulsed laser evaporation-MAPLE);
transparent conductive oxides (ITO, AZO, IZO, ZnO/Ag/ZnO) deposited on glass and flexible substrates: deposition and characterization;
atomic force microscopy (AFM); near scanning optical microscopy (NSOM); x-ray diffraction (XRD), UV-VIS, FTIR;
organic crystals growth

Books

Chapter 3: Laser prepared thin films for optoelectronic applications, M. Socol, G. Socol, N. Preda, A. Stanculescu, F. Stanculescu, Nanoscaled films and layers, pag. 51-80, 2017, editor: L. Nanai, InTech – Rijeka, ISBN 978-953-51-3143-4;
Chapter 5: Heterostructures based on porphyrin / phthalocyanine thin films for organic device applications,M. Socol, N. Preda, A. Stanculescu, F. Stanculescu, G. Socol , Phthalocyanines and some current applications, pag. 85-118, 2017, editor: Y. Yilmaz, InTech –Rijeka, ISBN 978-953-51-3255-4;
Chapter 5: Zinc Oxide and Polysaccharides: Promising Candidates for Functional Nanomaterials, N. Preda, M. Enculescu, I. Zgura, M. Socol, C. Florica, A. Evanghelidis, E. Matei, I. Enculescu, Size Effects in Nanostructures – Basics and Applications; Springer Series in Materials Science,vol. 205, pag. 109-136, 2014, editori: V. Kuncser, L. Miu, Springer-Verlag Berlin Heidelberg, ISBN 978-3-662-44478-8

Patents

Patent request:

Process for obtaining nanostructured array-like films formed of monodisperse structures of zinc oxide, by chemical deposition, patent number(s): ro130846-a2, Preda N, Florica C, Enculescu M, Zgura I, Socol M, Evanchelidis A I, Costas L, Oancea M, Busuioc C, Matei E, Enculescu I, Derwent primary accession number: 2016-07575b [18].

Projects

1. Photovoltaic cells with multilayer transparent conductive electrode developed on rigid and flexible substrates

Project Type: TE, Start Date: 2025-01-08 End Date: 2026-12-31

2. Flexible hybrid photovoltaic cell structures

Project Type: PED, Start Date: 2025-01-03 End Date: 2026-12-31

3. Metallic Electrode with 2D Photonic Crystal type Architecture for Bio(organic) Multilayer Structures

Project Type: HUMBERT CURIEN-BRANCUSI PROGRAM, Start Date: 2015-02-01 End Date: 2016-02-01

Publications

1. Composite Films Based on Poly(3-hexylthiophene):Perylene Diimide Derivative:Copper Sulfide Nanoparticles Deposited by Matrix Assisted Pulsed Laser Evaporation on Flexible Substrates for Photovoltaic Applications

Authors: Socol, M; Preda, N; Costas, A; Petre, G; Stochioiu, A; Popescu-Pelin, G; Iftimie, S; Catargiu, AM; Socol, G; Stanculescu, A

Published: APR 1 2025, JOURNAL OF COMPOSITES SCIENCE, 9, 172, DOI: 10.3390/jcs9040172

Today, flexible and lightweight electronics are regarded as a viable alternative to conventional rigid and heavy devices in various application fields. In the optoelectronic area, organic semiconductors offer advantages such as high absorption coefficients, low processing temperatures, mechanical flexibility and compatibility with plastic substrates, while inorganic nanostructures provide good electronic properties and high thermal stability. Thus, composite films with enhanced properties can be achieved by inserting inorganic nanostructures within organic layers. In this research work, CuS nanoparticles were prepared by wet chemical precipitation and then added to an organic mixture containing poly(3-hexylthiophene) (P3HT) and N,N-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14), a chemically synthesized semiconductor, for fabricating hybrid composite films by matrix assisted pulsed laser evaporation (MAPLE) on indium tin oxide/poly(ethylene terephthalate) (ITO/PET) flexible substrates. A comparative assessment of the morphological, compositional, optical and electrical properties of the composite (P3HT:AMC14:CuS) and organic (P3HT:AMC14) layers was performed to evaluate their applicability in the photovoltaic cells. The transmission and emission spectra of the composite films are dominated by the optical features of AMC14, a perylene diimide derivative compound used as acceptor. In the case of devices based on MAPLE deposited composite layer fabricated on ITO/PET substrates, the electrical measurements carried under illumination revealed an improvement in the open circuit voltage parameter emphasizing their potential applications in the flexible device area.

Open Access

2. Influence of flexible substrate nature covered with ITO on the characteristics of organic heterostructures fabricated by laser deposition techniques

Authors: Socol, M; Preda, N; Costas, A; Petre, G; Stanculescu, A; Stavarache, I; Popescu-Pelin, G; Iftimie, S; Stochioiu, A; Catargiu, AM; Socol, G

Published: JAN 2025, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 131, 17, DOI: 10.1007/s00339-024-08149-4

Laser thin layer deposition technologies were applied to develop organic heterostructures on flexible transparent conductive electrode (TCE). Flexible substrates such as flexible glass (FG), polyethersulfone (PES), amorphous polyethylene terephthalate (PET-A) and biaxially-oriented polyethylene terephthalate (PET-B) were employed to assess the influence of the substrate type on the optical and electrical characteristics of the organic devices. For comparison reason, the organic heterostructures were fabricated on rigid glass substrate and commercially available indium tin oxide (ITO)-coated PET. Hence, flexible and rigid glass substrates were coated with ITO film by pulsed laser deposition (PLD) at low fluence, subsequently a blend layer based on zinc phthalocyanine (ZnPc) and N, N '-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14) being deposited by matrix assisted pulsed laser evaporation (MAPLE) on the TCE film. The investigations evidenced that the roughness and the substrate type can strongly influence the properties of the ITO layer deposited by PLD as well as the optical and electrical characteristics of the organic heterostructures based on the blend layer deposited by MAPLE. Thus, the lowest roughness (0.8 nm) and the best Hall mobility (41.9 cm2/V center dot s) were achieved for ITO coatings deposited on flexible glass substrate. Also, the highest current density value (9.3 x 10- 4 A/cm2 at 0.5 V) was reached for the organic heterostructures fabricated on this type of flexible substrate.

Open Access

3. Aluminum doped zinc oxide nanoplatelets based sensor with enhanced hydrogen sulfide detection

Authors: Ydir, B; Ajdour, A; Antohe, I; Socol, G; Socol, M; Toderascu, LI; Saadaoui, D; Choulli, I; Leghrib, R; Lahlou, H

Published: MAR 13 2025, SCIENTIFIC REPORTS, 15, 8633, DOI: 10.1038/s41598-025-93252-6

This study explores the development of highly sensitive hydrogen sulfide (H2S) gas sensors employing hierarchical aluminum-doped zinc oxide (AZO) nanostructures. Vertically oriented AZO nanoplatelets with Al/ZnO molar ratios of 4% and 6% were successfully synthesized using an automated successive ionic layer adsorption and reaction (SILAR) technique. The morphological features of the AZO films significantly changed with the Al content. The AZO thin films exhibited a polycrystalline wurtzite structure and an increase in crystallite size with increasing Al concentrations. This work demonstrates that our AZO sensor structures achieved a maximum response at 150 ppm H2S and 573 K of 23.3%, being characterized by fast response and recovery times of 28 and 464 s, respectively. Notably, the 6% AZO samples exhibited an augmented selective sensitivity to H2S, demonstrating stable detection performance. Additionally, the significant improvement in detection capabilities can be attributed to the synergistic effects of electronic and chemical sensitization. These effects enhance the formation of active sites and create doping-induced defects while providing shorter and more efficient diffusion paths for the electrons, significantly improving the sensor's sensitivity and response speed.

4. Induced Effects of Nano-Patterned Substrates on the Electrical and Photo-Electrical Properties of PTB7-Th:ICBA (1:1, wt.%) Bulk-Heterojunction Solar Cells

Authors: Suteu, T; Antohe, VA; Antohe, S; Stavarache, I; Balasin, MC; Socol, G; Socol, M; Rasoga, O; Iftimie, S

Published: MAY 1 2025, SURFACES, 8, 30, DOI: 10.3390/surfaces8020030

In this study, we detailed the fabrication and characterization of photovoltaic structures based on PTB7:ICBA (1:1, wt.%) bulk-heterojunction on optical glass substrates by spin-coating. Some samples were deposited on a flat substrate, and others were placed on a patterned substrate obtained by nano-imprinting lithography; the induced effects were analyzed. We demonstrated that using a patterned substrate enhanced the maximum output power, primarily because the short-circuit current density increased. This can be considered a direct consequence of reduced optical reflection and improved optical absorption. The topological parameters evaluated by atomic force microscopy, namely, the root mean square, Skewness, and Kurtosis, had small values of around 2 nm and 1 nm, respectively. This proves that the mixture of a conductive polymer and a fullerene derivative creates a thin film network with a high flatness degree. The samples discussed in this paper were fabricated and characterized in air; we can admit that the results are encouraging, but further optimization is needed.

Open Access

5. Reduced graphene oxide- based multilayer transparent conductive electrodes

Authors: Socol, M; Preda, N; Costas, A; Stanculescu, A; Rasoga, O; Stavarache, I; Petre, G; Popescu-Pelin, G; Toderascu, I; Breazu, C; Socol, G

Published: MAR 2025, VACUUM, 233, 113943, DOI: 10.1016/j.vacuum.2024.113943

In this work, we investigated the influence of reduced graphene oxide (RGO) on the electrical performances of ZnO/Ag multilayer transparent conductive electrodes. RGO flakes were successfully laser transferred by matrix assisted pulsed laser evaporation (MAPLE) using frozen targets obtained from suspensions of commercially chemically RGO powder dispersed in dimethyl sulfoxide (DMSO). The main deposition parameters such as RGO concentration, laser fluence, number of the laser pulses and deposition pressure were varied to identify the optimal morphological and optical characteristics. The laser transfer conditions for the RGO structures with the best transmittance were further employed in preparation of RGO/Ag/ZnO multilayer transparent conductive electrodes (MTCE). Thus, the MAPLE deposited RGO structures were covered with metal (Ag) by vacuum thermal evaporation (VTE) and subsequently with metal oxide (ZnO) by radio frequency magnetron sputtering (RF-MS). In comparison to the optical and electrical properties of a ZnO/Ag/ZnO reference structure, the results emphasize that the RGO/Ag/ZnO are featured by a similar transmittance (similar to 82-85 %) and improved sheet resistance (similar to 10.6 Omega/square, meaning up to 2-fold smaller).

6. ASSESSING THE COMBINED EFFECTS OF CHEMICAL AND MECHANICAL PARAMETERS ON SILAR-GROWN NANOSTRUCTURED ZnO THIN FILMS

Authors: Ydir, B; Ajdour, A; Soumane, M; Achouch, S; Ben Hmamou, D; Antohe, I; Socol, G; Toderascu, LI; Socol, M; Luculescu, C; Leghrib, R; Lahlou, H

Published: 2024, ROMANIAN REPORTS IN PHYSICS, 76, 508, DOI: 10.59277/RomRepPhys.2024.76.508

In the literature, a comprehensive assessment of the combined impacts of chemical and mechanical parameters on the properties of thin films grown by SILAR is missing. In this work, ZnO film formation is investigated under variable precursor concentration, pH, withdrawal speed and number of cycles. Interestingly, the produced ZnO films displayed remarkable aspect ratio and morphological variability, ranging from the commonly obtained nanograins shape towards hexagonal nanorods, flowerlike rods and nanoneedles, which to our knowledge have not yet been achieved by using single step SILAR process. More particularly, low concentration and intermediate pH and withdrawal rates were favorable for nanorods formation. In addition, increasing the withdrawal speed from 26 to 30 cm<middle dot>min(-1 )resulted in a thinner film with improved rod uniformity and reduced crystallite size. This is the first study on the impact of substrate withdrawal speed on SILAR films. Among all studied parameters, the number of cycles was particularly useful for tuning film thickness, while preserving its target shape. In addition, the films grown under a higher number of cycles showed improved film crystallinity and rod orientation with reduced dislocation density, microstrain and bandgap energy. In our conditions, the most suitable combination of parameters required for exhibiting optimized nanorod-shaped coating are: a concentration of 0.07 M, pH of 10.5, speed of 30 cm<middle dot>min(-1 ) and 40 cycles. In this case, XRD, XPS, Raman and FTIR spectra displayed typical features of hexagonal Wurtzite structure of ZnO with no impurities within the film surface, whereas AFM measured a thickness of 1.4 mu m with 243 nm surface roughness.

Open Access

7. Organic Heterostructures with Dendrimer Based Mixed Layer for Electronic Applications

Authors: Rasoga, O; Yonkeu, ALD; Breazu, C; Socol, M; Preda, N; Stanculescu, F; Stanculescu, A; Iwuoha, E

Published: SEP 2024, MOLECULES, 29, 4155, DOI: 10.3390/molecules29174155

Recently, much research has focused on the search for new mixed donor-acceptor layers for applications in organic electronics. Organic heterostructures with layers based on the generation 1 poly(propylene thiophenoimine) (G1PPT) dendrimer, N,N '-diisopropylnaphthalene diimide (MNDI), and a combination of the two were prepared and their electrical properties were investigated. Single layers of G1PPT and MNDI and a mixed layer (G1PPT:MNDI) were obtained via spin coating on quartz glass, silicon, and glass/ITO substrates, using chloroform as a solvent. The absorption mechanism was investigated, the degree of disorder was estimated, and the emission properties of the layers were highlighted using spectroscopic methods (UV-Vis transmission and photoluminescence). The effects of the concentration and surface topographical particularities on the properties of the layers were analyzed via atomic force microscopy. All of the heterostructures realized with ITO and Au electrodes showed good conduction, with currents of the order of mA. Additionally, the heterostructure with a mixed layer exhibited asymmetry in the current-voltage curve between forward and reverse polarization in the lower range of the applied voltages, which was more significant at increased concentrations and could be correlated with rectifier diode behavior. Consequently, the mixed-layer generation 1 poly(propylene thiophenoimine) dendrimer with N,N '-diisopropylnaphthalene diimide can be considered promising for electronic applications.

Open Access

8. Editorial for Special Issue: "Thin Films Based on Nanocomposites (2nd Edition)"

Authors: Socol, M; Preda, N

Published: DEC 2024, NANOMATERIALS, 14, 2049, DOI: 10.3390/nano14242049

Open Access

9. MAPLE deposition of hybrid PLGA-Fe3O4-Cypress-PEDOT: PSS coatings

Authors: Stefan, N; Visan, AI; Grumezescu, V; Kuncser, V; Kuncser, A; Iacob, N; Schinteie, G; Socol, M; Florica, C; Zgura, I; Popescu, RC; Holban, AM; Socol, G

Published: JUN 2024, GIANT, 18, 100250, DOI: 10.1016/j.giant.2024.100250

We report on the Matrix Assisted Pulsed Laser Evaporation, laser technology for depositing biocompatible, antimicrobial, hydrophilic, and biodegradable complex hybrid polymeric system loaded with essential cypress-oil and magnetite nanoparticles as resorbable implants, capable of targeting possible hyperthermia applications, an anticancer moderate field heating therapy. Magnetite nanoparticles based on iron oxide (Fe3O4) coated with Cypress essential oil (denoted: Fe3O4- Cypress) and embedded in PLGA (poly(lactic-co-glycolic acid) (denoted: PLGA-Fe3O4- Cypress-) and PLGA - poly(3,4ethylene dioxythiophene) doped with poly(styrene sulfonate) anions) (PEDOT: PSS) mixture (denoted: PLGA-Fe3O4- Cypress- PEDOT: PSS) were used as MAPLE targets. The controlled drug delivery of the active Cypress oil, an antimicrobial therapeutic agent from Fe3O4- Cypress nanoparticles could be possible by applying an external radio frequency (RF) magnetic field. The Fe3O4-Cypress-based powders as well as the final hybrid coatings have been characterized in terms of stoichiometry, morphology, magnetic, antimicrobial properties, biocompatibility, and response to external physical stimuli. FTIR analyses confirmed the quasi-stoichiometric laser transfer of organic compounds while the XRD evidenced the semicrystalline structure of deposited thin films. SEM and AFM images evidence that conductive polymer addition led to the films' relief flattening and a decrease in the coatings' thickness and roughness by changing the polymeric packaging. The samples containing conductive polymer exhibited 3 times higher current and corrosion rate values. All coatings are hydrophilic and revealed enhanced cellular viability when cultured with osteoblast-like MG-63 cells. The composite structures exhibited significant antimicrobial activity against Gram-positive (Staphylococcus aureus), and Gram -negative (Escherichia coli ) bacteria, as well as to the opportunistic yeast Candida albicans.

Open Access

10. MAPLE-Deposited Perylene Diimide Derivative Based Layers for Optoelectronic Applications

Authors: Breazu, C; Girtan, M; Stanculescu, A; Preda, N; Rasoga, O; Costas, A; Catargiu, AM; Socol, G; Stochioiu, A; Popescu-Pelin, G; Iftimie, S; Petre, G; Socol, M

Published: NOV 2024, NANOMATERIALS, 14, 1733, DOI: 10.3390/nano14211733

Nowadays, the development of devices based on organic materials is an interesting research challenge. The performance of such devices is strongly influenced by material selection, material properties, design, and the manufacturing process. Usually, buckminsterfullerene (C60) is employed as electron transport material in organic photovoltaic (OPV) devices due to its high mobility. However, considering its low solubility, there have been many attempts to replace it with more soluble non-fullerene compounds. In this study, bulk heterojunction thin films with various compositions of zinc phthalocyanine (ZnPc), a perylene diimide derivative, or C60 were prepared by matrix-assisted pulsed laser evaporation (MAPLE) technique to assess the influence of C60 replacement on fabricated heterostructure properties. The investigations revealed that the optical features and the electrical parameters of the organic heterostructures based on this perylene diimide derivative used as an organic acceptor were improved. An increase in the JSC value (4.3 x 10-4 A/cm2) was obtained for the structures where the perylene diimide derivative acceptor entirely replaced C60 compared to the JSC value (7.5 x 10-8 A/cm2) for the heterostructure fabricated only with fullerene. These results are encouraging, demonstrating the potential of non-fullerene compounds as electron transport material in OPV devices.

11. Organic heterostructures based on thermal evaporated phthalocyanine and porphyrin as mixed (ZnPc:TPyP) or stacked (ZnPc/TPyP) films

Authors: Petre, G; Socol, M; Preda, N; Breazu, C; Rasoga, O; Stanculescu, F; Costas, A; Antohe, S; Iftimie, S; Socol, G; Stanculescu, A

Published: DEC 31 2023, THIN SOLID FILMS, 787, 140140, DOI: 10.1016/j.tsf.2023.140140

A metallic phthalocyanine (zinc phthalocyanine - ZnPc) and a non-metallic porphyrin (10,15,20-tetra(4-pyridyl) 21H,23H-porphyne -TPyP) were used to deposit mixed and stacked organic thin films by vacuum thermal evaporation method. The obtained layers were analyzed in a comparative manner from optical, structural, morphological and electrical point of view. The ultraviolet-visible spectra of the deposited layers showed that both organic components have absorption bands in the visible part of the solar spectrum, which means that the acceptor TPyP also contributes to absorption together with the donor. The photoluminescence spectra revealed only the emission bands associated to the porphyrin, especially in the single and stacked layers, while a quenching effect of the photoluminescence was noted in the mixed ones. The X-ray diffraction showed that the prepared layers are in general amorphous. The constituent materials in the single layers and the ratio between the two organic components in the mixed layers affect the morphology of the deposited films as was emphasized by scanning electron microscopy and atomic force microscopy analysis. The current density-voltage characteristics plotted under illumination revealed that the highest short-circuit current value was achieved in the case of the structure based on the layer showing the lowest roughness and thickness emphasizing the significant role played by these parameters of the layers considered for possible applications in the optoelectronic device area.

Open Access

12. Macrocyclic Compounds: Metal Oxide Particles Nanocomposite Thin Films Deposited by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Costas, A; Rasoga, O; Petre, G; Popescu-Pelin, G; Iftimie, S; Stochioiu, A; Socol, G; Stanculescu, A

Published: MAR 2023, MATERIALS, 16, 2480, DOI: 10.3390/ma16062480

Nanocomposite films based on macrocyclic compounds (zinc phthalocyanine (ZnPc) and 5,10,15,20-tetra(4-pyridyl) 21H,23H-porphyrin (TPyP)) and metal oxide nanoparticles (ZnO or CuO) were deposited by matrix-assisted pulsed laser evaporation (MAPLE). 1,4-dioxane was used as a solvent in the preparation of MAPLE targets that favor the deposition of films with a low roughness, which is a key feature for their integration in structures for optoelectronic applications. The influence of the addition of ZnO nanoparticles (similar to 20 nm in size) or CuO nanoparticles (similar to 5 nm in size) in the ZnPc:TPyP mixture and the impact of the added metal oxide amount on the properties of the obtained composite films were evaluated in comparison to a reference layer based only on an organic blend. Thus, in the case of nanocomposite films, the vibrational fingerprints of both organic compounds were identified in the infrared spectra, their specific strong absorption bands were observed in the UV-Vis spectra, and a quenching of the TPyP emission band was visible in the photoluminescence spectra. The morphological analysis evidenced agglomerated particles on the composite film surface, but their presence has no significant impact on the roughness of the MAPLE deposited layers. The current density-voltage (J-V) characteristics of the structures based on the nanocomposite films deposited by MAPLE revealed the critical role played by the layer composition and component ratio, an improvement in the electrical parameters values being achieved only for the films with a certain type and optimum amount of metal oxide nanoparticles.

Open Access

13. Effects of Solvent Additive and Micro-Patterned Substrate on the Properties of Thin Films Based on P3HT:PC70BM Blends Deposited by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Petre, G; Stanculescu, A; Stavarache, I; Popescu-Pelin, G; Stochioiu, A; Socol, G; Iftimie, S; Thanner, C; Rasoga, O

Published: JAN 2023, MATERIALS, 16, 144, DOI: 10.3390/ma16010144

Lately, there is a growing interest in organic photovoltaic (OPV) cells due to the organic materials' properties and compatibility with various types of substrates. However, their efficiencies are low relative to the silicon ones; therefore, other ways (i.e., electrode micron/nanostructuring, synthesis of new organic materials, use of additives) to improve their performances are still being sought. In this context, we studied the behavior of the common organic bulk heterojunction (P3HT:PC70BM) deposited by matrix-assisted pulsed laser evaporation (MAPLE) with/without 0.3% of 1,8-diiodooctane (DIO) additive on flat and micro-patterned ITO substrates. The obtained results showed that in the MAPLE process, a small quantity of additive can modify the morphology of the organic films and decrease their roughness. Besides the use of the additive, the micro-patterning of the electrode leads to a greater increase in the absorption of the studied photovoltaic structures. The inferred values of the filling factors for the measured cells in ambient conditions range from 19% for the photovoltaic structures with no additive and without substrate patterning to 27% for the counterpart structures with patterning and a small quantity of additive.

14. Effect of dopants on the optical properties of benzil crystals

Authors: Stanculescu, F; Socol, M; Rasoga, O; Preda, N; Ionita, I; Petre, G; Breazu, C; Stanculescu, A

Published: APR 15 2022, JOURNAL OF CRYSTAL GROWTH, 584, 126577, DOI: 10.1016/j.jcrysgro.2022.126577

Single-doped [Ag, Na, iodine, naphthalene (Naph), meta-dintrobenzene (m-DNB)] and double-doped, organic-inorganic (Naph + iodine; m-DNB + iodine) benzil (Bz) crystals have been grown from melt in a Bridgman-Stockbarger configuration. All crystals have been grown in the same experimental conditions, temperature variation at the growth interface = 30 K and moving speed of the growth ampoule = 1 mm/h. These conditions have been estimated from the theoretical analysis involving the solution of the classical (conventional) Stefan problem for flat solid-liquid interface in the boundary conditions imposed by our growth system. The effect of doping on the disorder degree, photoluminescence and dielectric constant of the Bz matrix has been investigated. The disorder in the crystals increased with the increase of dopant concentration. The highest disorder was induced by the organic dopant m-DNB, whose molecules does not show an adequate geometrical similarity with Bz molecules. The position of the photoluminescence peak, both at excitation with 335 nm and 435 nm, has not been affected by the presence of dopant(s). All doped samples show Second Harmonic Generation, even those with a significant degree of disorder. The effect of the single and double-doping on the second-order ONL co-efficient was analyzed by comparison with the second-order ONL coefficient of pure Bz crystals. In the case of the double-doping, the highest second-order optical nonlinear coefficient has been evidenced in the Bz crystals simultaneously doped with m-DNB and iodine in the same concentration (1%).

Open Access

15. Editorial for Special Issue: "Thin Films Based on Nanocomposites"

Authors: Socol, M; Preda, N

Published: OCT 2022, NANOMATERIALS, 12, 3301, DOI: 10.3390/nano12193301

16. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

Authors: Petre, G; Stanculescu, A; Girtan, M; Socol, M; Breazu, C; Vacareanu, L; Preda, N; Rasoga, O; Stanculescu, F; Doroshkevich, AS

Published: AUG 2022, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 219, 2100521, DOI: 10.1002/pssa.202100521

Herein, the properties of the organic heterostructures with triple-layer ZnO/Ag/ZnO as a replacement for ITO and mixed layer containing arylenevinylene oligomer (based on triphenylamine or carbazole) donor and nonfullerene (perylene diimide) acceptor mixed in the ratio 1:2 and the effect of a buffer layer of PEDOT-PSS intercalated between triple layer and mixed organic layer are discussed. The UV-vis transmission and photoluminescence (PL) properties are investigated in correlation with the surface topography and reveal a good match between the absorption and emission domain, which can favor the generation of the charge carriers. The heterostructure with the mixed layer based on triphenylamine oligomer shows the widest absorption domain, and the PL spectra of the heterostructures realized with either triphenylamine or carbazole oligomer show peaks corresponding to the radiative decay of the donor and acceptor. The I-V characteristics in the dark indicate a slightly nonlinear behavior and the current is affected by the charge carriers recombination on the defects present in the thick mixed layer deposited by matrix-assisted pulsed laser evaporation. The effect of the PEDOT-PSS buffer layer on the electrical properties of the organic heterostructure with ZnO/Ag/ZnO electrode is also investigated.

Open Access

17. Effect of Aluminum Nanostructured Electrode on the Properties of Bulk Heterojunction Based Heterostructures for Electronics

Authors: Rasoga, O; Breazu, C; Socol, M; Solonaru, AM; Vacareanu, L; Petre, G; Preda, N; Stanculescu, F; Socol, G; Girtan, M; Stanculescu, A

Published: DEC 2022, NANOMATERIALS, 12, 4230, DOI: 10.3390/nano12234230

The properties of organic heterostructures with mixed layers made of arylenevinylene-based polymer donor and non-fullerene perylene diimide acceptor, deposited using Matrix Assisted Pulsed Laser Evaporation on flat Al and nano-patterned Al electrodes, were investigated. The Al layer electrode deposited on the 2D array of cylindrical nanostructures with a periodicity of 1.1 mu m, developed in a polymeric layer using UV-Nanoimprint Lithography, is characterized by an inflorescence-like morphology. The effect of the nanostructuring on the optical and electrical properties was studied by comparison with those of the heterostructures based on a mixed layer with fullerene derivative acceptor. The low roughness of the mixed layer deposited on flat Al was associated with high reflectance. The nano-patterning, which was preserved in the mixed layer, determining the light trapping by multiple scattering, correlated with the high roughness and led to lower reflectance. A decrease was also revealed in photoluminescence emission both at UV and Vis excitation of the mixed layer, with the non-fullerene acceptor deposited on nano-patterned Al. An injector contact behavior was highlighted for all Al/mixed layer/ITO heterostructures by I-V characteristics in dark. The current increased, independently of acceptor (fullerene or non-fullerene), in the heterostructures with nano-patterned Al electrodes for shorter conjugation length polymer donors.

Open Access

18. Thin Film Fabrication by Pulsed Laser Deposition from TiO2 Targets in O2, N2, He, or Ar for Dye-Sensitized Solar Cells

Authors: Albu, DF; Lungu, J; Popescu-Pelin, G; Mihailescu, CN; Socol, G; Georgescu, A; Socol, M; Banica, A; Ciupina, V; Mihailescu, IN

Published: MAR 2022, COATINGS, 12, 293, DOI: 10.3390/coatings12030293

Active semiconductor layers of TiO2 were synthesized via pulsed laser deposition in He, N-2, O-2, or Ar to manufacture DSSC structures. As-prepared nanostructured TiO2 coatings grown on FTO were photosensitized by the natural absorption of the N719 (Ruthenium 535-bis TBA) dye to fabricate photovoltaic structures. TiO2 photoanode nanostructures with increased adsorption areas of the photosensitizer (a combination with voluminous media) were grown under different deposition conditions. Systematic SEM, AFM, and XRD investigations were carried out to study the morphological and structural characteristics of the TiO2 nanostructures. It was shown that the gas nature acts as a key parameter of the architecture and the overall performance of the deposited films. The best electro-optical performance was reached for photovoltaic structures based on TiO2 coatings grown in He, as was demonstrated by the short-circuit current (Isc) of 5.40 mA, which corresponds to the higher recorded roughness (of 44 +/- 2.9 nm RMS). The higher roughness is thus reflected in a more efficient and deeper penetration of the dye inside the nanostructured TiO2 coatings. The photovoltaic conversion efficiency (eta) was 1.18 and 2.32% for the DSSCs when the TiO2 coatings were deposited in O-2 and He, respectively. The results point to a direct correlation between the electro-optical performance of the prepared PV cells, the morphology of the TiO2 deposited layers, and the crystallinity features, respectively.

19. The effect of fullerene layer on the aggregates formation in amyloid beta Langmuir-Blodgett films

Authors: Breazu, C; Rasoga, O; Socol, M; Ganea, P; Tite, T; Matei, E; Stanculescu, F; Stanculescu, A

Published: JAN 30 2021, APPLIED SURFACE SCIENCE, 537, 147800, DOI: 10.1016/j.apsusc.2020.147800

The investigation of the effect of carbon nanomaterials and lipids on the aggregation particularities of the amyloid beta/A beta(1-42) layers is important for understanding the generation mechanism of neuronal disorder and how it can be inhibited. Additionally, amyloids are nanomaterials with a wide area of potential applications from nanotechnology to biotechnology. This paper presents a study about the preparation of A beta(1-42) layer by two different methods, Langmuir-Blodgett (L-B) and drop cast (DC), on Si and Si covered by a layer of Buckminster fullerene, C-60, and on the effect of fullerene layer or/and cholesterol (Ch) on the generation of A beta(1-42) secondary structure forms, relevant for specific applications. AFM, SEM FTIR and Raman analysis offered details about the layer surface topography, morphology and particularities of the secondary structure generated in the process of A beta(1-42) molecules aggregation. This study showed that the presence of Ch inhibited the formation of fibrils in A beta(1-42) film deposited by L-B on Si covered by C-60 The structures developed during aggregation were correlated with the topography and roughness of the films. The presence of Ch determined a decrease in roughness for L-B film and increase in roughness for DC film deposited on Si covered by C-60 layer.

20. Electro-active properties of nanostructured films of cytosine and guanine nucleobases

Authors: Socol, M; Trupina, L; Galca, AC; Chirila, C; Stan, GE; Vlaicu, AM; Stanciu, AE; Boni, AG; Botea, M; Stanculescu, A; Pintilie, L; Borca, B

Published: OCT 8 2021, NANOTECHNOLOGY, 32, 415702, DOI: 10.1088/1361-6528/ac10e4

The discovery of multifunctional properties related to electro-activity of organic systems of biomolecules is important for a variety of applications, especially for devices in the realm of biocompatible sensors and/or bioactuators. A further step towards such applications is to prepare thin films with the required properties. Here, the investigation is focused on the characterization of films of guanine and cytosine nucleobases, prepared by thermal evaporation-an industrial accessible deposition technique. The cytosine films have an orthorhombic non-centrosymmetric structure and grow in two interconnected nanostructured fractal patterns, of nearly equal proportion. Piezoresponse force microscopy images acquired at room temperature on the cytosine films display large zones with antiparallel alignment of the vertical components of the polarization vector. Guanine films have a dense nano-grained morphology. Our studies reveal electrical polarization switching effects which can be related to ferroelectricity in the films of guanine molecules. Characteristic ferroelectric polarization-electric-field hysteresis loops showing large electrical polarization are observed at low temperatures up to 200 K. Above this temperature, the guanine films have a preponderant paraelectric phase containing residual or locally induced nano-scopic ferroelectric domains, as observed by piezoresponse force microscopy at room temperature.

Open Access

21. Nucleobases thin films deposited on nanostructured transparent conductive electrodes for optoelectronic applications

Authors: Breazu, C; Socol, M; Preda, N; Rasoga, O; Costas, A; Socol, G; Petre, G; Stanculescu, A

Published: APR 6 2021, SCIENTIFIC REPORTS, 11, 7551, DOI: 10.1038/s41598-021-87181-3

Environmentally-friendly bio-organic materials have become the centre of recent developments in organic electronics, while a suitable interfacial modification is a prerequisite for future applications. In the context of researches on low cost and biodegradable resource for optoelectronics applications, the influence of a 2D nanostructured transparent conductive electrode on the morphological, structural, optical and electrical properties of nucleobases (adenine, guanine, cytosine, thymine and uracil) thin films obtained by thermal evaporation was analysed. The 2D array of nanostructures has been developed in a polymeric layer on glass substrate using a high throughput and low cost technique, UV-Nanoimprint Lithography. The indium tin oxide electrode was grown on both nanostructured and flat substrate and the properties of the heterostructures built on these two types of electrodes were analysed by comparison. We report that the organic-electrode interface modification by nano-patterning affects both the optical (transmission and emission) properties by multiple reflections on the walls of nanostructures and the electrical properties by the effect on the organic/electrode contact area and charge carrier pathway through electrodes. These results encourage the potential application of the nucleobases thin films deposited on nanostructured conductive electrode in green optoelectronic devices.

Open Access

22. Hybrid Nanocomposite Thin Films for Photovoltaic Applications: A Review

Authors: Socol, M; Preda, N

Published: MAY 2021, NANOMATERIALS, 11, 1117, DOI: 10.3390/nano11051117

Continuing growth in global energy consumption and the growing concerns regarding climate change and environmental pollution are the strongest drivers of renewable energy deployment. Solar energy is the most abundant and cleanest renewable energy source available. Nowadays, photovoltaic technologies can be regarded as viable pathways to provide sustainable energy generation, the achievement attained in designing nanomaterials with tunable properties and the progress made in the production processes having a major impact in their development. Solar cells involving hybrid nanocomposite layers have, lately, received extensive research attention due to the possibility to combine the advantages derived from the properties of both components: flexibility and processability from the organic part and stability and optoelectronics features from the inorganic part. Thus, this review provides a synopsis on hybrid solar cells developed in the last decade which involve composite layers deposited by spin-coating, the most used deposition method, and matrix-assisted pulsed laser evaporation, a relatively new deposition technique. The overview is focused on the hybrid nanocomposite films that can use conducting polymers and metal phthalocyanines as p-type materials, fullerene derivatives and non-fullerene compounds as n-type materials, and semiconductor nanostructures based on metal oxide, chalcogenides, and silicon. A survey regarding the influence of various factors on the hybrid solar cell efficiency is given in order to identify new strategies for enhancing the device performance in the upcoming years.

Open Access

23. Organic Thin Films Deposited by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) for Photovoltaic Cell Applications: A Review

Authors: Socol, M; Preda, N; Socol, G

Published: NOV 2021, COATINGS, 11, 1368, DOI: 10.3390/coatings11111368

Human society's demand for energy has increased faster in the last few decades due to the world's population growth and economy development. Solar power can be a part of a sustainable solution to this world's energy need, taking into account that the cost of the renewable energy recently dropped owed to the remarkable progress achieved in the solar panels field. Thus, this inexhaustible source of energy can produce cheap and clean energy with a beneficial impact on the climate change. The considerable potential of the organic photovoltaic (OPV) cells was recently emphasized, with efficiencies exceeding 18% being achieved for OPV devices with various architectures. The challenges regarding the improvement in the OPV performance consist of the selection of the adequate raw organic compounds and manufacturing techniques, both strongly influencing the electrical parameters of the fabricated OPV devices. At the laboratory level, the solution-based techniques are used in the preparation of the active films based on polymers, while the vacuum evaporation is usually involved in the deposition of small molecule organic compounds. The major breakthrough in the OPV field was the implementation of the bulk heterojunction concept but the deposition of mixed films from the same solvent is not always possible. Therefore, this review provides a survey on the development attained in the deposition of organic layers based on small molecules compounds, oligomers and polymers using matrix-assisted pulsed laser evaporation (MAPLE)-based deposition techniques (MAPLE, RIR-MAPLE and emulsion-based RIR-MAPLE). An overview of the influence of various experimental parameters involved in these laser deposition methods on the properties of the fabricated layers is given in order to identify, in the forthcoming years, new strategies for enhancing the OPV cells performance.

Open Access

24. Silicon Metalens Fabrication from Electron Beam to UV-Nanoimprint Lithography

Authors: Baracu, AM; Avram, MA; Breazu, C; Bunea, MC; Socol, M; Stanculescu, A; Matei, E; Thrane, PCV; Dirdal, CA; Dinescu, A; Rasoga, O

Published: SEP 2021, NANOMATERIALS, 11, 2329, DOI: 10.3390/nano11092329

This study presents the design and manufacture of metasurface lenses optimized for focusing light with 1.55 mu m wavelength. The lenses are fabricated on silicon substrates using electron beam lithography, ultraviolet-nanoimprint lithography and cryogenic deep reactive-ion etching techniques. The designed metasurface makes use of the geometrical phase principle and consists of rectangular pillars with target dimensions of height h = 1200 nm, width w = 230 nm, length l = 354 nm and periodicity p = 835 nm. The simulated efficiency of the lens is 60%, while the master lenses obtained by using electron beam lithography are found to have an efficiency of 45%. The lenses subsequently fabricated via nanoimprint are characterized by an efficiency of 6%; the low efficiency is mainly attributed to the rounding of the rectangular nanostructures during the pattern transfer processes from the resist to silicon due to the presence of a thicker residual layer.

Open Access

25. Arylenevinylene Oligomer-Based Heterostructures on Flexible AZO Electrodes

Authors: Stanculescu, A; Socol, M; Rasoga, O; Breazu, C; Preda, N; Stanculescu, F; Socol, G; Vacareanu, L; Girtan, M; Doroshkevich, AS

Published: DEC 2021, MATERIALS, 14, 7688, DOI: 10.3390/ma14247688

We investigated the optical and electrical properties of flexible single and bi-layer organic heterostructures prepared by vacuum evaporation with a p-type layer of arylenevinylene oligomers, based on carbazole, 3,3 ' bis(N hexylcarbazole)vinylbenzene = L13, or triphenylamine, 1,4 bis [4 (N,N' diphenylamino)phenylvinyl] benzene = L78, and an n-type layer of 5,10,15,20-tetra(4-pyrydil)21H,23H-porphyne = TPyP. Transparent conductor films of Al-doped ZnO (AZO) with high transparency, >90% for wavelengths > 400 nm, and low resistivity, between 6.9 x 10(-4) ohm center dot cm and 23 x 10(-4) ohm center dot cm, were deposited by pulsed laser deposition on flexible substrates of polyethylene terephthalate (PET). The properties of the heterostructures based on oligomers and zinc phthalocyanine (ZnPc) were compared, emphasizing the effect of the surface morphology. The measurements revealed a good absorption in the visible range of the PET/AZO/arylenevinylene oligomer/TPyP heterostructures and a typical injection contact behavior with linear (ZnPc, L78) or non-linear (L13) J-V characteristics in the dark, at voltages < 0.4 V. The heterostructure PET/AZO/L78/TPyP/Al showed a current density of similar to 1 mA/cm(2) at a voltage of 0.3 V. The correlation between the roughness exponent, evaluated from the height-height correlation function, grain shape, and electrical behavior was analyzed. Consequently, the oligomer based on triphenylamine could be a promising replacement of donor ZnPc in flexible electronic applications.

26. Hybrid organic-inorganic thin films based on zinc phthalocyanine and zinc oxide deposited by MAPLE

Authors: Socol, M; Preda, N; Costas, A; Breazu, C; Stanculescu, A; Rasoga, O; Popescu-Pelin, G; Mihailescu, A; Socol, G

Published: FEB 15 2020, APPLIED SURFACE SCIENCE, 503, 144317, DOI: 10.1016/j.apsusc.2019.144317

Hybrid organic-inorganic thin films based on zinc phthalocyanine (ZnPc) and ZnO nanoparticles were deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE). Synthesized by a simple wet chemical precipitation method, the ZnO nanoparticles were featured by a hexagonal wurtzite structure, a band-gap value of similar to 3.3 eV and emission bands typical for this semiconductor. The hybrid films containing ZnPc and various amounts of ZnO nanoparticles were evaluated from morphological, compositional, structural, optical and electrical point of view. No chemical decomposition of the organic compound was observed in the FTIR spectra of the deposited layers. The transmittance and photoluminescence spectra recorded on hybrid films disclose the optical signature of both organic (ZnPc) and inorganic (ZnO) components. The electrical measurements carried out under illumination emphasized the importance of the quantity of the inorganic component on the performance parameters of the structures prepared with the hybrid films. Our study provides new insight in the MAPLE deposition of the organic-inorganic hybrid films with potential applications in the photovoltaic cells area.

Open Access

27. Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation

Authors: Socol, M; Preda, N; Costas, A; Borca, B; Popescu-Pelin, G; Mihailescu, A; Socol, G; Stanculescu, A

Published: MAR 2020, NANOMATERIALS, 10, 468, DOI: 10.3390/nano10030468

Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet-visible (UV-Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.

Open Access

28. Organic Thin Films Based on DPP-DTT:C60 Blends Deposited by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Costas, A; Petre, G; Stanculescu, A; Popescu-Pelin, G; Mihailescu, A; Socol, G

Published: DEC 2020, NANOMATERIALS, 10, 2366, DOI: 10.3390/nano10122366

The matrix-assisted pulsed laser evaporation (MAPLE) technique was used for depositing thin films based on a recently developed conjugated polymer, poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPP-DTT) and fullerene C60 blends. The targets used in the MAPLE process were obtained by freezing chloroform solutions with different DPP-DTT:C60 weight ratios, with the MAPLE deposition being carried at a low laser fluence, varying the number of laser pulses. The structural, morphological, optical, and electrical properties of the DPP-DTT:C60 blend layers deposited by MAPLE were investigated in order to emphasize the influence of the DPP-DTT:C60 weight ratio and the number of laser pulses on these features. The preservation of the chemical structure of both DPP-DTT and C60 during the MAPLE deposition process is confirmed by the presence of their vibrational fingerprints in the FTIR spectra of the organic thin films. The UV-VIS and photoluminescence spectra of the obtained organic layers reveal the absorption bands attributed to DPP-DTT and the emission bands associated with C60, respectively. The morphology of the DPP-DTT:C60 blend films consists of aggregates and fibril-like structures. Regardless the DPP-DTT:C60 weight ratio and the number of laser pulses used during the MAPLE process, the current-voltage characteristics recorded, under illumination, of all structures developed on the MAPLE deposited layers evidenced a photovoltaic cell behavior. The results proved that the MAPLE emerges as a viable technique for depositing thin films based on conjugated polymers featured by a complex structure that can be further used to develop devices for applications in the solar cell area.

Open Access

29. MAPLE Deposition of Binary and Ternary Organic Bulk Heterojunctions Based on Zinc Phthalocyanine

Authors: Socol, M; Preda, N; Petre, G; Costas, A; Rasoga, O; Popescu-Pelin, G; Mihailescu, A; Stanculescu, A; Socol, G

Published: OCT 2020, COATINGS, 10, 956, DOI: 10.3390/coatings10100956

Organic bulk heterojunctions (BHJ) based on zinc phthalocyanine (ZnPc), fullerene compounds (C60 fullerene and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM)), and 5,6,11,12-tetraphenylnaphthacene (rubrene) were fabricated through the matrix-assisted pulsed-laser evaporation (MAPLE) technique. Thus, ZnPc:C60 and ZnPc:PC70BM binary BHJ and ZnPc:rubrene:PC70BM ternary BHJ were deposited as thin films on various substrates. The preservation of the chemical structure of the organic compounds during the MAPLE deposition was confirmed by infrared spectroscopy. The structural, optical, and morphological properties of the deposited layers were investigated by X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence (PL), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM), respectively. Further, the electrical properties of the developed structures based on ZnPc:C60, ZnPc:PC70BM, and ZnPc:rubrene:PC70BM were evaluated. The J-V characteristics of the organic structures, recorded under illumination, show that an increase in the open-circuit voltage (V-OC) is achieved in the case of the ternary blend in comparison with that obtained for the binary blends. The results evidenced that MAPLE-deposited thin films containing binary and ternary organic bulk heterojunctions can find applications in the field of photovoltaic devices.

Open Access

30. Long-Term Evaluation of Dip-Coated PCL-Blend-PEG Coatings in Simulated Conditions

Authors: Visan, AI; Popescu-Pelin, G; Gherasim, O; Mihailescu, A; Socol, M; Zgura, I; Chiritoiu, M; Sima, LE; Antohe, F; Ivan, L; Vranceanu, DM; Cotrut, CM; Cristescu, R; Socol, G

Published: MAR 2020, POLYMERS, 12, 717, DOI: 10.3390/polym12030717

Our study focused on the long-term degradation under simulated conditions of coatings based on different compositions of polycaprolactone-polyethylene glycol blends (PCL-blend-PEG), fabricated for titanium implants by a dip-coating technique. The degradation behavior of polymeric coatings was evaluated by polymer mass loss measurements of the PCL-blend-PEG during immersion in SBF up to 16 weeks and correlated with those yielded from electrochemical experiments. The results are thoroughly supported by extensive compositional and surface analyses (FTIR, GIXRD, SEM, and wettability investigations). We found that the degradation behavior of PCL-blend-PEG coatings is governed by the properties of the main polymer constituents: the PEG solubilizes fast, immediately after the immersion, while the PCL degrades slowly over the whole period of time. Furthermore, the results evidence that the alteration of blend coatings is strongly enhanced by the increase in PEG content. The biological assessment unveiled the beneficial influence of PCL-blend-PEG coatings for the adhesion and spreading of both human-derived mesenchymal stem cells and endothelial cells.

31. EFFECTS OF ANNEALING ON THE PHYSICAL PROPERTIES OF ITO THIN FILMS GROWN BY RADIO FREQUENCY MAGNETRON SPUTTERING

Authors: Radu, A; Locovei, C; Antohe, VA; Socol, M; Coman, D; Manica, M; Dumitru, A; Dan, L; Radu, C; Raduta, AM; Ion, L; Iftimie, S; Antohe, S

Published: JUL-SEP 2020, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 15, DOI:

Indium-doped tin oxide (ITO) thin films were fabricated by radio frequency magnetron sputtering and were subjected to in-situ and ex-situ annealing, at 200 degrees C, 300 degrees C and 400 degrees C, respectively. The in-situ thermal treatment consisted to intentionally heating the samples' substrates, while the ex-situ annealing was performed using an oven, under ambient atmosphere. For the ITO samples subjected to ex-situ annealing, the density of oxygen vacancies increased leading to the decrease of the electrical resistivity. No significant changes were noticed in terms of transmission spectroscopy after the thermal treatment; while by evaluating the Skewness parameter was determined that the annealing improves the planarity of samples' surface.

32. Effect of ITO electrode patterning on the properties of organic heterostructures based on non-fullerene acceptor prepared by MAPLE

Authors: Stanculescu, A; Breazu, C; Socol, M; Rasoga, O; Preda, N; Petre, G; Solonaru, AM; Grigoras, M; Stanculescu, F; Socol, G; Popescu-Pelin, G; Girtan, M

Published: APR 15 2020, APPLIED SURFACE SCIENCE, 509, 145351, DOI: 10.1016/j.apsusc.2020.145351

This paper presents some studies on the organic heterostructures realized by Matrix Assisted Pulsed Laser Evaporation in both bi-layer and mixed layer configurations on glass substrates covered by flat or nano-patterned ITO. The donor, a star-shaped arylenevinylene compound, 4,4',4 ''-tris[(4'-diphenylamino) styryl] triphenylamine, and acceptor, a non-fullerene compound, N,N'-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide, were blended in three weight ratios: 1:2, 1:3 and 1:4. A grating of cylindrical pillars with a periodicity of 1.1 mu m has been developed by UV-Nanoimprint Lithography in a polymer layer. The shape of the nanostructures changed to cone trunk by the Pulsed Laser Deposition of ITO on this nanostructured surface. The effect of the nanostructures and composition on the optical and electrical properties of the heterostructures was analyzed. The nano-patterning affected both the UV-Vis transmission and photoluminescence through the multiple reflections inside the cavities and at interfaces and the particularities of the molecular arrangement. The patterning was preserved independently of composition, but the roughness increased with increasing acceptor amount. The I-V characteristics drawn at room temperature in dark revealed an ohmic contact behavior for all heterostructures. The nano-patterning had a similar effect on the current in the heterostructures with mixed layer (1:2) and stacked bi-layer.

Open Access

33. On the Physical Properties PEDOT:PSS Thin Films

Authors: Girtan, M; Mallet, R; Socol, M; Stanculescu, A

Published: MAR 2020, MATERIALS TODAY COMMUNICATIONS, 22, 100735, DOI: 10.1016/j.mtcomm.2019.100735

A complete characterization from optical, morphological, electrical, photo-electrical and thermo-electrical point of view was done for PEDOT:PSS thin films and DMSO and EG sensitized PEDOT:PSS films. The studies on the electrical conductivity and electrical photoconductivity allowed the calculation of different relaxation times. The relaxation time of the electrical conductivity is of order of femtosecond and is multiplied by a factor 10 when PEDOT: PSS thin films were deposited on surfaces sensitized with DMSO and EG. Besides, the photoconduction excitation and relaxation times are of order of seconds. An increase in the relaxation photoconduction time by 2 was observed for films deposited on surfaces sensitized with DMSO and by 1.2 for films deposited on surfaces sensitized with EG. The time response of electrical conductivity after exposure to light adds supplementary knowledge for the understanding of the inertial processes, or hysteresis behavior of organic or perovskite solar cells involving PEDOT:PSS films. The electrical conductivity increases with the temperature and the use of DMSO and EG as surfactants lead to higher values of electrical conductivity and Seebeck coefficient. A better stability of the electrical conductivity with the temperature increase, was noticed for films deposited on surfaces sensitized with DMSO.

Open Access

34. Influence of Reduced Graphene Oxide on the Electropolymerization of 5-Amino-1-naphthol and the Interaction of 1,4-Phenylene Diisothiocyanate with the Poly(5-Amino-1-naphtol)/Reduced Graphene Oxide Composite

Authors: Baibarac, M; Daescu, M; Socol, M; Bartha, C; Negrila, C; Fejer, SN

Published: JUN 2020, POLYMERS, 12, 1299, DOI: 10.3390/polym12061299

A new composite base on reduced graphene oxide (RGO) and poly(5-amino-1-naphthol) (P5A1N) was synthesized by the electrochemical polymerization of 5-amino-1-naphthol (5A1N) in the presence of HClO(4)and H(4)SiW(12)O(40)onto the surface of Au electrode covered with the RGO sheets. The linear dependence of the current densities of the anodic and cathodic peaks with the scan rate of the potential range (0; 0.8) V vs. SCE, reported during electropolymerization of 5A1N, indicates an electron transfer that is controlled by diffusion. A covalent functionalization of the RGO sheets with P5A1N is argued by: (i) the simultaneous disappearance of the IR band at 1584 cm(-1)and the appearance of the new IR bands at 812, 976 and 3744 cm(-1), and (ii) the appearance of two Raman lines at 738 and 1428 cm(-1). An application of the RGO sheets covalently functionalized with P5A1N is demonstrated to support 1,4-phenylene diisothiocyanate (PDITC), a compound used as a cross-linking agent for various biological applications. The chemical adsorption of PDITC onto the RGO sheets covalently functionalized with P5A1N, which involves the appearance of new functional groups of the type thiourea, was proven by Raman scattering and IR spectroscopy.

Open Access

35. Reduced Graphene Oxide Sheets as Inhibitors of the Photochemical Reactions of α-Lipoic Acid in the Presence of Ag and Au Nanoparticles

Authors: Toulbe, N; Stroe, MS; Daescu, M; Cercel, R; Mogos, A; Dragoman, D; Socol, M; Mercioniu, I; Baibarac, M

Published: NOV 2020, NANOMATERIALS, 10, 2238, DOI: 10.3390/nano10112238

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of alpha-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in the presence of trisodium citrate. The presence of excipients did not induce further changes when ALA interacts with Ag and Au nanoparticles with sizes of 5 and 10 nm by exposure to UV light. Compared to the Raman spectrum of ALA powder, changes in Raman lines' position and relative intensities when ALA has interacted with films obtained from Au nanoparticles with sizes between 5 and 50 nm were significant. These changes were explained by considering the chemical mechanism of surface-enhanced Raman scattering (SERS) spectroscopy. The photodegradation of ALA that had interacted with metallic nanoparticles was inhibited in the presence of RGO sheets.

36. Laser Processed Antimicrobial Nanocomposite Based on Polyaniline Grafted Lignin Loaded with Gentamicin-Functionalized Magnetite

Authors: Visan, AI; Popescu-Pelin, G; Gherasim, O; Grumezescu, V; Socol, M; Zgura, I; Florica, C; Popescu, RC; Savu, D; Holban, AM; Cristescu, R; Matei, CE; Socol, G

Published: FEB 2019, POLYMERS, 11, DOI: 10.3390/polym11020283

Composite thin coatings of conductive polymer (polyaniline grafted lignin, PANI-LIG) embedded with aminoglycoside Gentamicin sulfate (GS) or magnetite nanoparticles loaded with GS (Fe3O4@GS) were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. The aim was to obtain such nanostructured coatings for titanium-based biomedical surfaces, which would induce multi-functional properties to implantable devices, such as the controlled release of the therapeutically active substance under the action of a magnetic and/or electric field. Thus, the unaltered laser transfer of the initial biomaterials was reported, and the deposited thin coatings exhibited an appropriate nanostructured surface, suitable for bone-related applications. The laser processing of PANI-LIG materials had a meaningful impact on the composites' wettability, since the contact angle values corresponding to the composite laser processed materials decreased in comparison with pristine conductive polymer coatings, indicating more hydrophilic surfaces. The corrosion resistant structures exhibited significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans strains. In vitro cytotoxicity studies demonstrated that the PANI-LIG-modified titanium substrates can allow growth of bone-like cells. These results encourage further assessment of this type of biomaterial for their application in controlled drug release at implantation sites by external activation.

37. Deposition temperature influence on the wear behaviour of carbon-based coatings deposited on hardened steel

Authors: Feldiorean, D; Cristea, D; Tierean, M; Croitoru, C; Gabor, C; Jakab-Farkas, L; Cunha, L; Barradas, NP; Alves, E; Craciun, V; Marin, A; Moura, C; Leme, J; Socol, M; Craciun, D; Cosnita, M; Munteanu, D

Published: MAY 1 2019, APPLIED SURFACE SCIENCE, 475, 773, DOI: 10.1016/j.apsusc.2019.01.028

This paper presents an evaluation regarding the influence of substrate material characteristics and deposition parameters on the tribological behaviour of carbon-based coatings. Chromium nitride ceramic interlayers and carbon-based thin films were deposited by magnetron sputtering on hardened AISI 5115 (16MnCr5) case hardening steel. The physical vapour deposition (PVD) deposition was performed at three different temperatures: 180 degrees C, 200 degrees C and 250 degrees C. The chemical composition of the samples was assessed by Rutherford Backscattering Spectroscopy (RBS), the structure by X-ray Diffraction (XRD), and the surface morphology by Atomic Force Microscopy (AFM). The surface chemistry was analysed by X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The coatings are homogeneous, amorphous, with a smooth surface. The mechanical behaviour has been assessed on a pin-on disk rotational tribometer (wear characteristics), on a micro scratch tester (adhesion to the substrate), by ball-cratering (film thickness) and by nanoindentation (hardness and the modulus of elasticity). A strong correlation has been observed between the substrate characteristics and, more importantly, the deposition temperature, and the mechanical properties of the assembly. The fracture toughness is positively influenced by the presence of the ceramic chromium nitride interlayer. The modulus of elasticity and friction coefficient (both in dry and lubricated conditions) are decreased for higher deposition temperatures, however the higher deposition temperature negatively affects the mechanical characteristics of the steel substrate.

38. Pulsed Laser Deposition of Indium Tin Oxide Thin Films on Nanopatterned Glass Substrates

Authors: Socol, M; Preda, N; Rasoga, O; Costas, A; Stanculescu, A; Breazu, C; Gherendi, F; Socol, G

Published: JAN 2019, COATINGS, 9, DOI: 10.3390/coatings9010019

Indium tin oxide (ITO) thin films were grown on nanopatterned glass substrates by the pulsed laser deposition (PLD) technique. The deposition was carried out at 1.2 J/cm(2) laser fluence, low oxygen pressure (1.5 Pa) and on unheated substrate. Arrays of periodic pillars with widths of similar to 350 nm, heights of similar to 250 nm, and separation pitches of similar to 1100 nm were fabricated on glass substrates using UV nanoimprint lithography (UV-NIL), a simple, cost-effective, and high throughput technique used to fabricate nanopatterns on large areas. In order to emphasize the influence of the periodic patterns on the properties of the nanostructured ITO films, this transparent conductive oxide (TCO) was also grown on flat glass substrates. Therefore, the structural, compositional, morphological, optical, and electrical properties of both non-patterned and patterned ITO films were investigated in a comparative manner. The energy dispersive X-ray analysis (EDX) confirms that the ITO films preserve the In2O3:SnO2 weight ratio from the solid ITO target. The SEM and atomic force microscopy (AFM) images prove that the deposited ITO films retain the pattern of the glass substrates. The optical investigations reveal that patterned ITO films present a good optical transmittance. The electrical measurements show that both the non-patterned and patterned ITO films are characterized by a low electrical resistivity (<2.8 x 10(-4)). However, an improvement in the Hall mobility was achieved in the case of the nanopatterned ITO films, evidencing the potential applications of such nanopatterned TCO films obtained by PLD in photovoltaic and light emitting devices.

39. ORGANIC HETEROSTRUCTURES DEPOSITED BY MAPLE ON PATTERNED AZO ELECTRODES

Authors: Socol, M; Preda, N; Breazu, C; Rasoga, O; Stanculescu, A; Popescu-Pelin, G; Gherendi, F; Socol, G; Vacareanu, L

Published: OCT-DEC 2018, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 13, 1053, DOI:

The paper is focused on the investigation of the properties of some organic heterostructures deposited on patterned AZO electrodes. In the first step, 2D patterned arrays based on commercially photoresist were fabricated on glass substrates using nanoimprint litography. Next, on these periodic nanostructures, the transparent AZO layers were deposited by pulsed laser deposition. Further, heterostructures consisting in organic thin films such as 4,7 diphenyl-1,10-phenanthroline (BPhen) (electron transport layer), N,N'-di(1-naftalenil)-N,N'-diafenil-(1,1'-bifenil)-4,4'-diamina (alpha-NPD) (hole transport layer) and arylenevinylene oligomers (3,3-bis (N-hexylcarbazole)vinylbenzene (P13) and 1,4-bis [4-(N,N-diphenylamino)phenylvinyl] benzene (P78)) were obtained by matrix assisted pulsed laser evaporation. The fabricated multilayer organic structures have been investigated from optical (UV-VIS spectroscopy), morphological (scanning electron microscopy and atomic force microscopy) and electrical (I-V characteristics) point of view. An improvement in the current value recorded on the samples prepared on nanostructured electrode was recorded. The results evidence the possibility to integrate these heterostructures in organic electronic devices.

40. Flexible organic heterostructures obtained by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Stanculescu, A; Costas, A; Stanculescu, F; Girtan, M; Gherendi, F; Popescu-Pelin, G; Socol, G

Published: SEP 2018, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 124, DOI: 10.1007/s00339-018-1960-3

Organic heterostructures based on zinc phthalocyanine (ZnPc) and perylene tetracarboxylic dianhydride (PTCDA) were deposited by matrix-assisted pulsed laser evaporation (MAPLE) technique on conductive flexible substrate (ITO/PET) in three configurations: ZnPc/PTCDA (stacked layers), ZnPc:PTCDA (blend) and ZnPc/ZnPc:PTCDA/PTCDA. The effect of the configuration on the optical and electrical properties of the obtained heterostructures was investigated. For all heterostructures was observed an improved optical absorption in visible domain. The I-V characteristics recorded under illumination, revealed higher short circuit current (I (SC)) values for the ZnPc:PTCDA and ZnPc/ZnPc:PTCDA/PTCDA structures in comparison with that of the ZnPc/PTCDA structure. The results proved that by MAPLE can be obtained flexible organic heterostructures (in different configurations) with properties adequate for applications in flexible electronics and solar cell fields.

41. On the properties of organic heterostructures prepared with nano-patterned metallic electrode

Authors: Breazu, C; Socol, M; Preda, N; Matei, E; Rasoga, O; Girtan, M; Mallet, R; Stanculescu, F; Stanculescu, A

Published: JUN 15 2018, APPLIED SURFACE SCIENCE, 443, 602, DOI: 10.1016/j.apsusc.2018.02.103

This paper presents a comparative study between the properties of the heterostructures realized with single/multi layer organic (zinc phthalocyanine or/and fullerene) prepared on Si substrate between flat or patterned aluminum (Al) layer metallic electrode and multi layer ZnO/Au/ZnO transparent conductor electrode (TCE). The UV-Nanoimprint Lithography was used for the realization of a 2D array of nanostructures (holes/pillars) characterized by a periodicity of 1.1 mu m and cylindrical shape: diameter = 400 nm and depth/height = 300 nm. The effect of the electrode patterning on the properties of the organic heterostructures was analyzed. For the samples with patterned Al electrode was remarked a slight red shift of the peaks in the reflection spectra determined by an increased interaction between the organic molecules in the delimited region of the patterned holes. The shape of the emission spectra at excitation with UV light showed a narrow intense peak around 500 nm associated with the intense resonance phenomena between the energy of the incident light and the surface plasmons in the patterned Al layer. The TCE followed the morphology of the organic film on which it was deposited. The significant differences between the morphology of the top layer in the heterostructures realized on flat and patterned Al are correlated with the total thickness of the successively deposited layers and with the particularities of the molecular arrangement, leading to the preservation or deleting of patterning. An injection contact behavior was evidence for most heterostructures built on flat and patterned Al. The slight increase in current at an applied bias <1 V in the heterostructure Si/Al/ZnPc/TCE is attributed to the larger interfacial area between the patterned Al electrode and ZnPc layer compared to the interface area between flat Al and ZnPc. A buffer layer of 1,4,5,8-naphthalen-tetracarboxylic dianhydride (NTCDA), sandwiched between the flat metallic electrode and organic film in the heterostructure Si/Al/C60/ZnPc/TCE has determined an increase in the current at low applied voltages. (C) 2018 Elsevier B.V. All rights reserved.

42. Organic heterostructures obtained on ZnO/Ag/ZnO electrode

Authors: Socol, M; Preda, N; Breazu, C; Florica, C; Costas, A; Istrate, CM; Stanculescu, A; Girtan, M; Gherendi, F

Published: AUG 2018, VACUUM, 154, 370, DOI: 10.1016/j.vacuum.2018.05.039

This work is focused on the use of multilayer transparent conductive electrode (TCE) based on ZnO/Ag/ZnO in the fabrication of the organic heterostructures. The ZnO/Ag/ZnO obtained combining sputtering/thermal evaporation/sputtering techniques is featured by a good optical transmittance, a low electrical resistivity and a reduced roughness. All these characteristics recommend it as a viable alternative to indium tin oxide (ITO) for different applications. The organic materials, N,N' - diphenyl N,N' - bis (1 - aphthyl) 1,1' - biphenyl 4,4' - diamine (alpha-NPD), 5,12-Dihydro-5-12-dimethylquino [2,3-b]acridine-7,14dione (DMQA) and 4,7 diphenyl-1,10-phenanthroline (BPhen) were deposited by vacuum thermal evaporation (VTE) method, the properties of the obtained layers being investigated by FTIR, UV-VIS and PL) spectroscopy. The I-V characteristic (recorded in dark) of the organic heterostructure fabricated on the ZnO/Ag/ZriO electrode shows diode behavior, revealing its potential applications in the organic light emitting devices (OLED).

43. Lincomycin-embedded PANI-based coatings for biomedical applications

Authors: Popescu-Pelin, G; Fufa, O; Popescu, RC; Savu, D; Socol, M; Zgura, I; Holban, AM; Vasile, BS; Grumezescu, V; Socol, G

Published: OCT 15 2018, APPLIED SURFACE SCIENCE, 455, 666, DOI: 10.1016/j.apsusc.2018.06.016

We report on the successful laser transfer of biocompatible composite coatings based on polyaniline (PANI) embedded with magnetite (PANI-Fe3O4) and Lincomycin hydrochloride (PANI-Lincomycin) or Lincomycin-functionalized magnetite (PANI-Fe3O4@Lincomycin) by matrix assisted pulsed laser evaporation (MAPLE) technique. The physico-chemical investigations revealed relevant data regarding the stoichiometric deposition, morphology and topography of the as-deposited coatings. Regarding the MAPLE coatings, the FTIR studies evidenced the vibrational bands characteristic to pristine PANI material, while the SEM investigations unveiled a preferential particulate morphology (with aggregates shape and size depending on the deposited material). Additionally, the AFM measurements indicated variations of RMS value, following the Lincomycin and magnetite incorporation. The wettability measurements displayed a hydrophilic behavior of the synthesized coatings, while the electrochemical studies emphasized an enhanced resistance against corrosion in simulated body fluid when compared with bare Ti. Cellular viability, immunofluorescence and SEM results proved that the MAPLE coatings were suitable materials for beneficial adhesion, spreading and proliferation of osteoblast-like cells (MG-63). Moreover, an increased efficiency was evidenced against Staphylococcus aureus biofilm development. The multifunctional properties of the laser processed composite coatings - confirmed by cumulative biocompatible, antimicrobial and anticorrosive behaviors - recommend them as promising solutions for biomedical applications.

44. Titanium implants' surface functionalization by pulsed laser deposition of TiN, ZrC and ZrN hard films

Authors: Floroian, L; Craciun, D; Socol, G; Dorcioman, G; Socol, M; Badea, M; Craciun, V

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 182, DOI: 10.1016/j.apsusc.2017.03.068

Thin films of TiN, ZrC, and ZrN were deposited at room temperature on highly polished Ti and Si samples using the pulsed laser deposition technique. Grazing incidence X-ray diffraction investigations showed that films were nanocrystalline, with grain sizes from 5 to 12 nm and under compression. Simulations of X-ray reflectivity curves acquired from the samples indicated that the deposited layers were dense and smooth. Electrochemical tests performed in simulated body fluid showed that the deposited coatings significantly improved the corrosion resistance of Ti samples. The comparative study found out that the best sample was ZrN/Ti, its corrosion current after 32 days immersion in simulated body fluids being half of that measured for the bare Ti sample and in the same time almost unchanged from the initial value. (C) 2017 Elsevier B.V. All rights reserved.

45. Biocomposite coatings based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/calcium phosphates obtained by MAPLE for bone tissue engineering

Authors: Rasoga, O; Sima, L; Chiritoiu, M; Popescu-Pelin, G; Fufa, O; Grumezescu, V; Socol, M; Stanculescu, A; Zgura, I; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 212, DOI: 10.1016/j.apsusc.2017.01.205

The aim of our research was to synthesize and investigate the physico-chemical and biological features of composite coatings based on poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and commercial calcium phosphates (CaPs), hydroxyapatite and beta-tricalcium phosphate, obtained by means of matrix assisted pulsed laser evaporation (MAPLE) technique. In this respect, laser fluence and dropcast studies were performed for pristine polymer and PHBV-CaPs composites. The microstructure of the synthesized coatings was investigated by scanning electron microscopy, while for the chemical structure and functional integrity we performed Fourier transform infrared spectroscopy comparative analysis. By using the X-ray diffraction measurements we experimentally evaluated the crystalline nature of the obtained composite materials, while relevant data regarding the hydrophilic/hydrophobic behavior of the synthesized coatings were obtained by performing static CA measurements. The biocompatibility of PHBV/CaPs coatings was evaluated by performing cellular adhesion and differentiation in vitro assays on mesenchymal stem cells. (C) 2017 Elsevier B.V. All rights reserved.

46. IZO deposited by PLD on flexible substrate for organic heterostructures

Authors: Socol, M; Preda, N; Stanculescu, A; Breazu, C; Florica, C; Rasoga, O; Stanculescu, F; Socol, G

Published: MAY 2017, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 123, DOI: 10.1007/s00339-017-0992-4

In: ZnO (IZO) thin films were deposited on flexible plastic substrates by pulsed laser deposition (PLD) method. The obtained layers present adequate optical and electrical properties competitive with those based on indium tin oxide (ITO). The figure of merit (9 X 10(-3) Omega(-1)) calculated for IZO layers demonstrates that high quality coatings can be prepared by this deposition technique. A thermal annealing (150 degrees C for 1 h) or an oxygen plasma etching (6 mbar for 10 min.) were applied to the IZO layers to evaluate the influence of these treatments on the properties of the transparent coatings. Using vacuum evaporation, organic heterostructures based on cooper phthalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were deposited on the untreated and treated IZO layers. The optical and electrical properties of the heterostructures were investigated by UVVis, FTIR and current-voltage (I-V) measurements. For the heterostructure fabricated on IZO treated in oxygen plasma, an improvement in the current value with at least one order of magnitude was evidenced in the I-V characteristics recorded in dark conditions. Also, an increase in the current value for the heterostructure deposited on untreated IZO layer can be achieved by adding an organic layer such as tris-8-hydroxyquinoline aluminium (Alq(3)).

47. Effect of heavy ions irradiation on the properties of benzil crystals

Authors: Stanculescu, F; Socol, M; Matei, E; Stanculescu, A

Published: AUG 2017, CRYSTAL RESEARCH AND TECHNOLOGY, 52, DOI: 10.1002/crat.201700047

Thick slices mechanically polished cut from a pure benzil ingot grown from melt in a modified Bridgman-Stockbarger configuration were irradiated with Ni ions having a specific energy of 11.4 MeV/u at different fluences. The effect of radiation on the properties of bulk benzil has been investigated. The chemical structure was not substantially affected as shown by infrared spectrum. The changes induced on the disorder degree have been evaluated from the Urbach law and X Ray Diffraction measurements. The morphology and surface topography have been analyzed emphasising a decrease in the size of granules and an increase in the surface roughness by irradiation. No effect of irradiation on the photoluminescence emission and optical nonlinear properties has been evidenced. These results recommend benzil as candidate for applications in space technology.

48. Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study

Authors: Popescu-Pelin, G; Sima, F; Sima, LE; Mihailescu, CN; Luculescu, C; Iordache, I; Socol, M; Socol, G; Mihailescu, IN

Published: OCT 1 2017, APPLIED SURFACE SCIENCE, 418, 588, DOI: 10.1016/j.apsusc.2016.10.043

Pulsed Laser Deposition (PLD) and Matrix Assisted Pulsed Laser Evaporation (MAPLE) techniques were applied for growing hydroxyapatite (HA) thin films on titanium substrates. All experiments were conducted in a reaction chamber using a KrP* excimer laser source (lambda = 248 nm, TEWHM approximate to 25 ns). Half of the samples were post-deposition thermally treated at 500 degrees C in a flux of water vapours in order to restore crystallinity and improve adherence. Coating surface morphologies and topographies specific to the deposition method were evidenced by scanning electron, atomic force microscopy investigations and profilometry. They were shown to depend on deposition technique and also on the post-deposition treatment. Crystalline structure of the coatings evaluated by X-ray diffraction was improved after thermal treatment. Biocompatibility of coatings, cellular adhesion, proliferation and differentiation tests were conducted using human mesenchymal stem cells (MSCs). Results showed that annealed MAPLE deposited HA coatings were supporting MSCs proliferation, while annealed PLD obtained films were stimulating osteogenic differentiation. (C) 2016 Elsevier B.V. All rights reserved.

49. Antimicrobial polycaprolactone/polyethylene glycol embedded lysozyme coatings of Ti implants for osteoblast functional properties in tissue engineering

Authors: Visan, A; Cristescu, R; Stefan, N; Miroiu, M; Nita, C; Socol, M; Florica, C; Rasoga, O; Zgura, I; Sima, LE; Chiritoiu, M; Chifiriuc, MC; Holban, AM; Mihailescu, IN; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 243, DOI: 10.1016/j.apsusc.2016.11.129

In this study, coatings based on lysozyme embedded into a matrix of polyethylene glycol (PEG) and polycaprolactone (PCL) were fabricated by two different methods (Matrix Assisted Pulsed Laser Evaporation -MAPLE and Dip Coating) for obtaining antimicrobial coatings envisaged for long term medical applications. Coatings with different PEG: PCL compositions (3: 1; 1: 1; 1: 3) were synthesized in order to evaluate the antimicrobial activity of lysozyme embedded into the polymeric matrix. The main surface features, such as roughness and wettability, with impact on the microbial adhesion as well as on the eukaryote cell function were measured. The obtained composite coatings exhibited a significant antibacterial activity against Escherichia coli, Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus strains. As well, specific blended coatings showed appropriate viability, good spreading and normal cell morphology of SaOs2 human osteoblasts and mesenchymal stem cells (MSCs). These investigations highlight the suitability of biodegradable composites as implant coatings for decreasing the risk of bacterial contamination associated with prosthetic procedures. (C) 2016 Elsevier B.V. All rights reserved.

50. MAPLE prepared heterostructures with oligoazomethine: Fullerene derivative mixed layer for photovoltaic applications

Authors: Stanculescu, A; Rasoga, O; Socol, M; Vacareanu, L; Grigoras, M; Socol, G; Stanculescu, F; Breazu, C; Matei, E; Preda, N; Girtan, M

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 195, DOI: 10.1016/j.apsusc.2017.03.053

Mixed layers of azomethine oligomers containing 2,5-diamino-3,4-dicyanothiophene as central unit and triphenylamine (LV5) or carbazol (LV4) at both ends as donor and fullerene derivative, [6,6]-phenylC61 butyric acid butyl ester ([C60] PCB-C4) as acceptor, have been prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) on glass/ITO and Si substrates. The effect of weight ratio between donor and acceptor (1: 1; 1: 2) and solvent type (chloroform, dimethylsulphoxide) on the optical (UV-vis transmission/absorption, photoluminescence) and morphological properties of LV4 (LV5): [C60] PCB-C4 mixed layers has been evidenced. Dark and under illumination I-V characteristics of the heterostructures realized with these mixed layers sandwiched between ITO and Al electrodes have revealed a solar cell behavior for the heterostructures prepared with both LV4 and LV5 using chloroform as matrix solvent. The solar cell structure realized with oligomer LV5, glass/ITO/LV5: [C60] PCB-C4 (1: 1) has shown the best parameters. (C) 2017 Elsevier B.V. All rights reserved.

51. MEASUREMENT OF CHARGE CARRIER MOBILITY IN PEROVSKITE NANOWIRE FILMS BY PHOTO-CELIV METHOD

Authors: Aukstuolis, A; Girtan, M; Mousdis, GA; Mallet, R; Socol, M; Rasheed, M; Stanculescu, A

Published: JAN-MAR 2017, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 18, 41, DOI:

In this paper the holes' mobility for the configuration FTO/TiO2/CH3NH3PbI3/SpiroMeOTAD/Au was measured for the first time by the Photo-CELIV method. The TiO2 dense film was deposited by reactive sputtering at room temperature on FTO glass substrates. High crystalized perovskite films were deposited from solutions in one step by spin coating. Spiro-MeOTAD molecular glass was used as holes transporting layer. The highest holes' mobility from TiO2 thin film through the perovskite and Spiro MeOTAD film to the top gold electrode was of Order 8.5x10(-7) cm(2)/Vs.

52. MAPLE DEPOSITION OF PLGA MICROSPHERES FOR MEDICAL APPLICATIONS

Authors: Fufa, O; Socol, M; Preda, N; Grigorescu, S; Croitoru, S; Socol, G

Published: JAN-MAR 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 80, DOI:

The aim of our study was to synthesize and evaluate the physicochemical and biological properties of composite films based on poly(lactic-co-glycolic acid) copolymer and quercetin (PLGA/Q) microspheres. During our experiments, we firstly synthesized the PLGA/Q microspheres by using an oil-in-water emulsion-diffusion-evaporation method. Subsequently, the as-prepared composite material was subjected to the matrix assisted pulsed laser evaporation (MAPLE) technique, in order to obtain the PLGA/Q coatings. Relevant compositional and microstructural features of the synthesized samples were obtained by means of Fourier transform infrared spectroscopy (FTIR) and AFM (atomic force microscopy). The long-term biocompatibility of the synthesized films was in vitro evaluated by cellular viability and immunofluorescence assays.

53. Organic heterostructures deposited by MAPLE on AZO substrate

Authors: Socol, M; Preda, N; Stanculescu, A; Breazu, C; Florica, C; Stanculescu, F; Iftimie, S; Girtan, M; Popescu-Pelin, G; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 203, DOI: 10.1016/j.apsusc.2017.02.260

Organic heterostructures based on poly(3-hexylthiophene) (P3HT) and fullerene (C60) as blends or multilayer were deposited on Al:ZnO (AZO) by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The AZO layers were obtained by Pulsed Laser Deposition (PLD) on glass substrate, the high quality of the films being reflected by the calculated figure of merit. The organic heterostructures were investigated from morphological, optical and electrical point of view by atomic force microscopy (AFM), UV-vis spectroscopy, photoluminescence (PL) and current-voltage (I-V) measurements, respectively. The increase of the C60 content in the blend heterostructure has as result a high roughness. Compared with the multilayer heterostructure, those based on blends present an improvement in the electrical properties. Under illumination, the highest current value was recorded for the heterostructure based on the blend with the higher C60 amount. The obtained results showed that MAPLE is a useful technique for the deposition of the organic heterostructures on AZO as transparent conductor electrode. (C) 2017 Elsevier B.V. All rights reserved.

54. Oxide/metal/oxide electrodes for solar cell applications

Authors: Hrostea, L; Boclinca, M; Socol, M; Leontie, L; Stanculescu, A; Girtan, M

Published: APR 2017, SOLAR ENERGY, 146, 469, DOI: 10.1016/j.solener.2017.03.017

In this paper the influence of the heat treatment on the structural and optical properties of oxide single layer and multilayer transparent thin film structures of ITO/Au/ITO, AZO/Au/AZO, TiO2/Au/TiO2 and Bi2O3/Au/Bi2O3 type is studied. The single-layer oxides and respective multilayer structures have been deposited on glass substrates by successive DC magnetron sputtering using metallic targets ln:Sn, Zn:Al, Ti and Bi, in reactive (for the oxide films) or inert (for the metallic Au interlayer films) atmosphere. Good quality transparent conducting thin film structures have been obtained, with resistivity similar to 10(-4) Omega cm and transmittance similar to 75%. The wetting surface properties in function of time exposure at UV radiation (254 nm) have been also studied before and after heat treatment performed at 450 degrees C. (C) 2017 Elsevier Ltd. All rights reserved.

55. Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition

Authors: Duta, L; Stan, GE; Popa, AC; Husanu, MA; Moga, S; Socol, M; Zgura, I; Miculescu, F; Urzica, I; Popescu, AC; Mihailescu, IN

Published: JAN 2016, MATERIALS, 9, DOI: 10.3390/ma9010038

We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility.

56. INVESTIGATIONS ON THE PROPERTIES OF A TWO-DIMENSIONAL NANOPATTERNED METALLIC FILM

Authors: Breazu, C; Preda, N; Socol, M; Stanculescu, F; Matei, E; Stavarache, I; Iordache, G; Girtan, M; Rasoga, O; Stanculescu, A

Published: OCT-DEC 2016, Digest Journal of Nanomaterials and Biostructures, 11, 1229, DOI:

This paper presents some investigations of the effect of nanopatterning on the properties of aluminum layer deposited by sputtering. UV-Nanoimprint Lithography technique has been used for the realization of a 2D array of nanostructures (pillars) in aluminum film characterized by cylindrical shape and the following structural parameters: diameter between 400 nm and 490 nm, depth between 320 nm and 420 nm and periodicity of 1.1 mu m, which have been revealed by SEM and AFM measurements. The UV-Vis transmission, reflection and photoluminescence measurements have evidenced the effect of the nanopatterning on the optical properties of the A1 layer.

57. Investigations of Ar ion irradiation effects on nanocrystalline SiC thin films

Authors: Craciun, V; Craciun, D; Socol, G; Behdad, S; Boesl, B; Himcinschi, C; Makino, H; Socol, M; Simeone, D

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 345, DOI: 10.1016/j.apsusc.2015.12.130

The effects of 800 keV Ar ion irradiation on thin nanocrystalline SiC films grown on (100) Si substrates using the pulsed laser deposition (PLD) technique were investigated. On such PLD grown films, which were very dense, flat and smooth, X-ray reflectivity, glancing incidence X-ray diffraction and nanoindentation investigations were easily performed to evaluate changes induced by irradiation on the density, surface roughness, crystalline structure, and mechanical properties. Results indicated that the SiC films retained their crystalline nature, the cubic phase partially transforming into the hexagonal phase, which had a slightly higher lattice parameter then the as-deposited films. Simulations of X-ray reflectivity curves indicated a 3% decrease of the films density after irradiation. Nanoindentation results showed a significant decrease of the hardness and Young's modulus values with respect to those measured on as-deposited films. Raman and X-ray photoelectron spectroscopy investigations found an increase of the C-C bonds and a corresponding decrease of the Si-C bonds in the irradiated area, which could explain the degradation of mechanical properties. (C) 2015 Elsevier B.V. All rights reserved.

58. MAPLE preparation and characterization of mixed arylenevinylene based oligomers:C-60 layers

Authors: Stanculescu, A; Socol, G; Vacareanu, L; Socol, M; Rasoga, O; Breazu, C; Girtan, M; Stanculescu, F

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 289, DOI: 10.1016/j.apsusc.2015.11.250

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) of mixed layers based on two arylenevinylene oligomers, 1,4-bis [4-(N,N'-diphenylamino)phenylvinyl] benzene (L78) and 3,3'-bis(N-hexylcarbazole)vinylbenzene (L13) as donor and buckminsterfullerene (C-60) as acceptor, blended in three different weight ratios: 1:1, 1:2 and 1:3. The optical, morphological, structural and electrical properties of these mixed layers have been investigated emphasizing the effect of the layer composition and of the significant degree of disorder. I-V characteristics have revealed typically solar cell behaviour for the heterostructures prepared with mixed layers containing L78 (L13) and fullerene blended in a weight ratio of 1:2. The solar cell structure glass/ITO/L13:C-60/Al has shown the best parameters. (C) 2015 Elsevier B.V. All rights reserved.

59. Flexible heterostructures based on metal phthalocyanines thin films obtained by MAPLE

Authors: Socol, M; Preda, N; Rasoga, O; Breazu, C; Stavarache, I; Stanculescu, F; Socol, G; Gherendi, F; Grumezescu, V; Popescu-Pelin, G; Girtan, M; Stefan, N

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 410, DOI: 10.1016/j.apsusc.2015.10.166

Heterostructures based on zinc phthalocyanine (ZnPc), magnesium phthalocyanine (MgPc) and 5,10,15,20-tetra(4-pyrydil)21H,23H-porphine (TPyP) were deposited on ITO flexible substrates by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Organic heterostructures containing (TPyP/ZnPc(MgPc)) stacked or (ZnPc(MgPc):TPyP) mixed layers were characterized by X-ray diffraction-XRD, photoluminescence-PL, UV-vis and FTIR spectroscopy. No chemical decomposition of the initial materials was observed. The investigated structures present a large spectral absorption in the visible range making them suitable for organic photovoltaics applications (OPV). Scanning electron microscopy-SEM and atomic force microscopy-AFM revealed morphologies typical for the films prepared by MAPLE. The current-voltage characteristics of the investigated structures, measured in dark and under light, present an improvement in the current value (similar to 3 order of magnitude larger) for the structure based on the mixed layer (Al/MgPc:TPyP/ITO) in comparison with the stacked layer (Al/MgPc//TPyP/ITO). A photogeneration process was evidenced in the case of structures Al/ZnPc:TPyP/ITO with mixed layers. (C) 2015 Elsevier B.V. All rights reserved.

60. Surface-enhanced Raman scattering activity of niobium surface after irradiation with femtosecond laser pulses

Authors: Ivanov, VG; Vlakhov, ES; Stan, GE; Zamfirescu, M; Albu, C; Mihailescu, N; Negut, I; Luculescu, C; Socol, M; Ristoscu, C; Mihailescu, IN

Published: NOV 28 2015, JOURNAL OF APPLIED PHYSICS, 118, DOI: 10.1063/1.4936363

The chemical modification of the niobium (Nb) surface after irradiation with femtosecond laser pulses was investigated by scanning electron microscopy coupled with energy dispersive spectroscopy, atomic force microscopy, grazing incidence X-ray diffraction, and micro-Raman spectroscopy. The physical-chemical analyses indicated that the laser treatment results in oxidation of the Nb surface, as well as in the formation of Nb hydrides. Remarkably, after the samples' washing in ethanol, a strong Surface-Enhanced Raman Scattering (SERS) signal originating from the toluene residual traces was evidenced. Further, it was observed that the laser irradiated Nb surface is able to provide a SERS enhancement of similar to 1.3 x 10(3) times for rhodamine 6G solutions. Thus, for the first time it was shown that Nb/Nb oxide surfaces could exhibit SERS functionality, and so one can expect applications in biological/biochemical screening or for sensing of dangerous environmental substances. (C) 2015 AIP Publishing LLC.

61. INVESTIGATIONS OF PULSED LASER DEPOSITED TiN THIN FILMS FOR TITANIUM IMPLANTS

Authors: Popescu-Pelin, G; Craciun, D; Socol, G; Cristea, D; Floroian, L; Badea, M; Socol, M; Craciun, V

Published: 2015, ROMANIAN REPORTS IN PHYSICS, 67, 1502, DOI:

TiN thin films were deposited at room temperature on polished Ti samples by PLD. GIXRD investigations showed that films were crystalline, with grain sizes around 25 run. Simulations of XRR curves indicated that the layers were dense and only slightly rougher than Ti substrates. Nanoindentation results showed that TiN films possessed a hardness of 26.8 GPa, much harder than Ti substrate, while scratch and wear tests found that films were adherent and exhibited a low friction coefficient of 0.16. Electrochemical tests performed in SBF indicated that the coated Ti samples exhibited significantly better behavior against corrosion than bare Ti samples.

62. HETEROSTRUCTURES BASED ON SMALL MOLECULES ORGANIC COMPOUNDS

Authors: Socol, M; Rasoga, O; Breazu, C; Socol, G; Preda, N; Pasuk, I; Visan, D; Stavarache, I; Gherendi, F; Girtan, M; Sidwaba, U

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1392, DOI:

Heterostructures with layers from small molecules organic compounds were deposited on ITO/glass substrate by thermal vacuum evaporation (TVE) technique. Structural, optical and morphological investigations were carried out on the realised layers (zinc phthalocyanine-ZnPc, fullerene-C60 and 1,4,5,8-naphthalene-tetracarboxylic dianhydride-NTCDA). The films are polycrystalline keeping the morphological features characteristic to these materials. The prepared heterostructures reveal a large absorption domain in the visible domain. The current-voltage (I-V) characteristics of the investigated structures, recorded in dark, present an improvement in the current value (similar to one order of magnitude) for the standard structure (ITO/PEDOT: PSS/ZnPc/C60/NTCDA/Al) with a supplimentary layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). For the inverted structure (Al/NTCDA/C60/ZnPc/ITO) was also noticed an increased curent value in comparasion with that observed for the standard structure.

63. MAPLE prepared heterostructures with arylene based polymer active layer for photovoltaic applications

Authors: Stanculescu, F; Rasoga, O; Catargiu, AM; Vacareanu, L; Socol, M; Breazu, C; Preda, N; Socol, G; Stanculescu, A

Published: MAY 1 2015, APPLIED SURFACE SCIENCE, 336, 248, DOI: 10.1016/j.apsusc.2014.11.146

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of heterostructures with single layer of arylene based polymer, poly[N-(2-ethylhexy1)2.7-carbazoly1 vinylene]/AMC16 and poly[N-(2-ethylhexy1)2.7-carbazolyl 1.4-phenylene ethynylene]/AMC22, and with layers of these polymers mixed with Buckminsterfullerene/C-60 in the weight ratio of 1:2 (AMC16: C60) and 1:3 (AMC22: C60). The deposited layers have been characterized by spectroscopic (UV-Vis-NIR, PL, FTIR) and microscopic (SEM, AFM) methods. The effect of the polymer particularities on the optical and electrical properties of the structures based on polymer and polymer: C-60 mixed layer has been analyzed. The study of the electrical properties has revealed typical solar cell behavior for the heterostructure prepared by MAPLE on glass/ITO/PEDOT-PSS with AMC16, AMC22 and AMC22: C-60 layer, confirming that this method is adequate for the preparation of polymeric and mixed active layers for solar cells applications. The highest photovoltaic effect was shown by the solar cell structure realized with single layer of AMC16 polymer: g1a55/ITO/PEDOT-PSSIA1VIC16/A1. (C) 2014 Elsevier B.V. All rights reserved.

64. Composite biodegradable biopolymer coatings of silk fibroin - Poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) for biomedical applications

Authors: Miroiu, FM; Stefan, N; Visan, AI; Nita, C; Luculescu, CR; Rasoga, O; Socol, M; Zgura, I; Cristescu, R; Craciun, D; Socol, G

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1131, DOI: 10.1016/j.apsusc.2015.07.120

Composite silk fibroin-poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) (SF-PHBV) biodegradable coatings were grown by Matrix Assisted Pulsed Laser Evaporation on titanium substrates. Their physicochemical properties and particularly the degradation behavior in simulated body fluid at 37 degrees C were studied as first step of applicability in local controlled release for tissue regeneration applications. SF and PHBV, natural biopolymers with excellent biocompatibility, but different biodegradability and tensile strength properties, were combined in a composite to improve their properties as coatings for biomedical uses. FTIR analyses showed the stoichiometric transfer from targets to coatings by the presence in the spectra of the main absorption maxima characteristic of both polymers. XRD investigations confirmed the FTIR results showing differences in crystallization behavior with respect to the SF and PHBV content. Contact angle values obtained through wettability measurements indicated the MAPLE deposited coatings were highly hydrophilic; surfaces turning hydrophobic with the increase of the PHBV component. Degradation assays proved that higher PHBV contents resulted in enhanced resistance and a slower degradation rate of composite coatings in SBF. Distinct drug-release schemes could be obtained by adjusting the SF:PHBV ratio to controllably tuning the coatings degradation rate, from rapid-release formulas, where SF predominates, to prolonged sustained ones, for larger PHBV content. (C) 2015 Elsevier B.V. All rights reserved.

65. EFFECT OF CHOLESTEROL ON THE DEPOSITION OF BETA-AMYLOID 1-40 AND 1-42 FILMS

Authors: Breazu, C; Stanculescu, A; Socol, M; Rasoga, O

Published: JAN-MAR 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 313, DOI:

We report the pressure vs area isotherms of Langmuir films of pure and doped with cholesterol (Ch) amyloid beta, A beta (1-40) and (1-42) at the air-water interface and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies of A beta (1-40) and (1-42) layers deposited from solution by drop cast and/or dipping and/or Langmuir-Blodgett on substrates of quartz and Si. The particularity of the substrate surface morphology determines the adhesion forces and plays an important role in the formation and stability of the multilayer films which are deposited on these substrates. The effect of cholesterol on the morphology of amyloids films and appearance of fibril structures is also analysed. AFM investigations have revealed the particularities of the aggregation process of the strongly hydrophobic A beta (1-42) on cholesterol films deposited by Langmuir-Blodgett on solid support of quartz and Si.

66. Organic heterostructures based on arylenevinylene oligomers deposited by MAPLE

Authors: Socol, M; Preda, N; Vacareanu, L; Grigoras, M; Socol, G; Mihailescu, N; Stanculescu, F; Jelinek, M; Stanculescu, A; Stoicanescu, M

Published: MAY 30 2014, APPLIED SURFACE SCIENCE, 302, 222, DOI: 10.1016/j.apsusc.2013.12.091

Organic heterostructures were fabricated by matrix assisted pulsed laser evaporation (MAPLE) method using arylenevinylene oligomers based on triphenylamine (P78)/carbazole (P13) group and tris(8-hydroxyquinolinato)aluminum salt (Alq3). Optical properties of the organic multilayer structures were characterized by spectroscopic techniques: FTIR, UV-vis and photoluminescence (PL). A good transparency (over 60%) was remarked for the structures with two organic layers in the 550-800 nm range. Photoluminescence (PL) spectra proved that the emission characteristics of the materials have been preserved. I-V characteristics of (ITO/oligomer/Alq3/Al and ITO/Alq3/Al) heterostructures were symmetrically while rectifying properties of these heterostructures have not been observed. A comparison between the heterostructures made of layers with different thickness reveals that the higher current (8 x 10(-6) A at 1 V) was obtained for the ITO/P78/Alq3/Al heterostructure, which is characterized by a larger thickness of the double organic layer. AFM measurements revealed a similar topography while RMS values of the reported structures depend on the organic material. (C) 2013 Elsevier B.V. All rights reserved.

67. The Influence of the Microstructure and Morphology of CeO2 Buffer Layer on the Properties of YBCO Films PLD Grown on Ni Tape

Authors: Mihalache, V; Stefan, N; Enculescu, I; Mihailescu, IN; Socol, M; Miroi, M

Published: NOV 2014, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 27, 2485, DOI: 10.1007/s10948-014-2679-9

YBa2Cu3O7-delta films were deposited on CeO2-buffered nickel substrates, with different buffer thickness. Full width at half maximum of rocking curve, Delta(omega), of CeO2 and yttrium barium copper oxide (YBCO), as well as the critical temperature, T-c, of YBCO were shown to be strongly dependent on buffer thickness. They behave similarly but not proportional to the buffer thickness increase. This and the fact that Delta(omega) vs. buffer thickness and T-c vs. buffer thickness for YBCO behave similar with RMS roughness vs. thickness of CeO2 indicates that the surface peculiarity of buffers is responsible for YBCO properties. More precisely, the surface of CeO2 films prepared by the chemical solution route based on propionic acid is prone to agglomerate (de-wet) and the degree of agglomeration depends in an intricate way on buffer thickness. We showed that nor RMS roughness neither (00l) texture degree can define alone the surface suitable for c-axis YBCO nucleation. The {111} faceted grains (even in the case of high (00l) texture) and other defects generated by agglomeration supply a low fraction of (00l) flat terminations of buffer that affect the nucleation of c-axis-oriented YBCO phase. Moreover, the thermal instability of the surface morphology of CeO2 buffers (further development of de-wetting process, {111} faceted grains, etc. during superconducting layer deposition) influence the quality of YBCO films.

68. Superhydrophobic ZnO networks with high water adhesion

Authors: Florica, C; Preda, N; Enculescu, M; Zgura, I; Socol, M; Enculescu, I

Published: AUG 8 2014, NANOSCALE RESEARCH LETTERS, 9, DOI: 10.1186/1556-276X-9-385

ZnO structures were deposited using a simple chemical bath deposition technique onto interdigitated electrodes fabricated by a conventional photolithography method on SiO2/Si substrates. The X-ray diffraction studies show that the ZnO samples have a hexagonal wurtzite crystalline structure. The scanning electron microscopy observations prove that the substrates are uniformly covered by ZnO networks formed by monodisperse rods. The ZnO rod average diameter and length were tuned by controlling reactants' concentration and reaction time. Optical spectroscopy measurements demonstrate that all the samples display bandgap values and emission bands typical for ZnO. The electrical measurements reveal percolating networks which are highly sensitive when the samples are exposed to ammonia vapors, a variation in their resistance with the exposure time being evidenced. Other important characteristics are that the ZnO rod networks exhibit superhydrophobicity, with water contact angles exceeding 150 degrees and a high water droplet adhesion. Reproducible, easily scalable, and low-cost chemical bath deposition and photolithography techniques could provide a facile approach to fabricate such ZnO networks and devices based on them for a wide range of applications where multifunctionality, i.e., sensing and superhydrophobicity, properties are required.

69. Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates

Authors: Erakovic, S; Jankovic, A; Ristoscu, C; Duta, L; Serban, N; Visan, A; Mihailescu, IN; Stan, GE; Socol, M; Iordache, O; Dumitrescu, I; Luculescu, CR; Janackovic, D; Miskovic-Stankovic, V

Published: FEB 28 2014, APPLIED SURFACE SCIENCE, 293, 45, DOI: 10.1016/j.apsusc.2013.12.029

Hydroxyapatite (HA) is a widely used biomaterial for implant thin films, largely recognized for its excellent capability to chemically bond to hard tissue inducing the osteogenesis without immune response from human tissues. Nowadays, intense research efforts are focused on development of antimicrobial HA doped thin films. In particular, HA doped with Ag (Ag:HA) is expected to inhibit the attachment of microbes and contamination of metallic implant surface. We herewith report on nano-sized HA and Ag:HA thin films synthesized by pulsed laser deposition on pure Ti and Ti modified with 100 nm diameter TiO2 nanotubes (fabricated by anodization of Ti plates) substrates. The HA-based thin films were characterized by SEM, AFM, EDS, FUR, and XRD. The cytotoxic activity was tested with HEp2 cells against controls. The antifungal efficiency of the deposited layers was tested against the Candida albicans and Aspergillus niger strains. The Ti substrates modified with TiO2 nanotubes covered with Ag:HA thin films showed the highest antifungal activity. (C) 2013 Elsevier B.V. All rights reserved.

70. Laser synthesis of nanometric iron oxide films for thermo-sensing applications

Authors: Serban, N; Ristoscu, C; Socol, G; Stefan, N; Mihailescu, CN; Socol, M; Mulenko, SA; Petrov, YN; Gorbachuk, NT; Mihailescu, IN

Published: FEB 2014, MATERIALS RESEARCH BULLETIN, 50, 154, DOI: 10.1016/j.materresbull.2013.10.042

KrF* excimer laser pulses of 248 nm were used for the synthesis of nanometric iron oxide films with variable thickness, stoichiometry and electrical properties. Film deposition was carried out on <1 0 0> Si and SiO2 substrates. The number of laser pulses was increased from 4000 to 6000, while ambient reactive oxygen pressure varied from 0.1 to 1.0 Pa. The film thickness depends on oxygen pressure, number of laser pulses and substrate nature. All films demonstrated semiconducting temperature behaviour with variable band gap (E-g) depending on oxygen pressure, substrate nature and temperature. Eg value was less than 1.0 eV for all deposited films. XRD analysis evidenced that films deposited on Si substrate have polycrystalline structure, while films deposited on SiO2 were amorphous. The higher oxygen pressure, the lower crystallinity of the deposited film was observed, resulting in change of thermo electromotive force coefficient (S) value. For larger substrate temperature, a better crystallization was observed in the deposited films, resulting in increased S coefficient value. The largest value of the S coefficient was about 8.7 mV/K in the range 290-295 K and it decreased to 1.0-1.6 mV/K when heating temperature changed from 240 to 330 K. The figure of merit of deposited structures was ZT = 3-6 in the range 240-330 K with a maximum of 12 at 300-304 K. We have shown that thermo-sensing characteristics of the films strongly depend on their electrical and structural properties. (C) 2013 Elsevier Ltd. All rights reserved.

71. Zinc Oxide and Polysaccharides: Promising Candidates for Functional Nanomaterials

Authors: Preda, N; Enculescu, M; Zgura, I; Socol, M; Florica, C; Evanghelidis, A; Matei, E; Enculescu, I

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 136, DOI: 10.1007/978-3-662-44479-5_5

Recently, ZnO and natural polysaccharides have received more and more attention as interesting components for designing complex functional nanomaterials, key elements being their high occurrence and low-cost. In this chapter are presented possibilities for tailoring the ZnO properties by using polysaccharides in the synthesis process as well as reports on the functionalization of cellulose-based natural fabrics with ZnO. In both cases, in the preparation step were used only simple and scalable wet chemical methods. The resulting materials with suitable characteristics, e.g. dependence of the ZnO nanostructures optical properties on their morphology or high-UV blocking and superhydrophobicity for ZnO-functionalized fabrics, can find applications in domains where such qualities are required.

72. Laser prepared organic heterostructures based on star-shaped arylenevinylene compounds

Authors: Stanculescu, A; Socol, G; Grigoras, M; Ivan, T; Vacareanu, L; Socol, M; Rasoga, O; Breazu, C; Mihailescu, IN; Iordache, I; Preda, N; Stanculescu, F

Published: OCT 2014, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 117, 268, DOI: 10.1007/s00339-014-8521-1

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of organic bulk heterojunctions made from the mixture of a star-shaped arylenevinylene compound, 4,4',4aEuro(3)-tris[(4'-diphenylamino)styryl] triphenylamine as donor and fullerene derivative, [6, 6]-phenyl C61 butyric acid butyl ester, as acceptor, in the weight ratio 1:2. The mixed layer has been characterized by spectroscopic (UV-Vis, Fourier transform infrared) and microscopic (AFM) methods, and the effects of the deposition conditions (number of pulses) and of a buffer layer of poly(aniline-co-aniline propane sulfonic acid) or poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) have been analyzed. The study of the electrical properties has revealed a typical solar cell behavior for the heterostructure glass/ITO/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/4,4',4aEuro(3)-tris[(4'-diphenylamino)styryl] triphenylamine: [6, 6]-phenyl C61 butyric acid butyl ester/Al, confirming that MAPLE could be an adequate method for the preparation of active layer based on bulk heterojunction for solar cells.

73. Laser prepared organic heterostuctures on glass/AZO substrates

Authors: Stanculescu, A; Socol, M; Rasoga, O; Mihailescu, IN; Socol, G; Preda, N; Breazu, C; Stanculescu, F

Published: MAY 30 2014, APPLIED SURFACE SCIENCE, 302, 176, DOI: 10.1016/j.apsusc.2014.01.181

This paper presents some studies about the bi-layer organic heterostructures realized with zinc phthalocyanine (ZnPc) as donor layer and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) as acceptor layer, on substrate of glass covered by Al doped ZnO (AZO) layer. These heterostructures have been prepared using laser techniques: pulsed laser deposition (PLD) in an atmosphere of oxygen for AZO films deposition and matrix assisted pulsed laser evaporation (MAPLE) for organic films deposition. The influence of the deposition conditions on the transmission of the organic films has been analysed. The effect of the oxygen plasma treatment, with duration of 5 min and 10 min, on the surface topography, structural and optical properties of AZO layers deposited by PLD and, as consequence, on the optical and electrical properties of the single layer (ZnPc) and bi-layer (ZnPc/NTCDA) organic heterostructure, deposited by MAPLE, was investigated. (C) 2014 Elsevier B.V. All rights reserved.

74. MAPLE DEPOSITION OF PLGA MICRO- AND NANOPARTICLES EMBEDDED INTO POLYMERIC COATINGS

Authors: Socol, G; Preda, N; Socol, M; Sima, L; Luculescu, CR; Sima, F; Miroiu, M; Axente, E; Visan, A; Stefan, N; Cristescu, R; Dorcioman, G; Stanculescu, A; Radulescu, L; Mihailescu, IN

Published: APR-JUN 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 630, DOI:

We report the film deposition of Poly(D, L-lactide-co-glycolide) (PLGA) particle systems by matrix assisted pulsed laser evaporation (MAPLE) technique. PLGA+polyvinyl alcohol (PVA), PLGA+PVA+ bovine serum albumin (BSA) and PLGA+PVA+chitosan (CH) nanoparticles were prepared by an oil-in-water emulsion-diffusion-evaporation method. The average diameter of PLGA particles was between 180-250 nm. The coatings were obtained by laser evaporation of frozen targets prepared by mixing appropriate PLGA aqueous suspensions and dimethyl sulfoxide (DMSO) in three ratios. Depending on the DMSO content, we deposited PLGA particles embedded into polymeric layer mainly obtained due to the entirely or partially dissolving of nanoparticles into the initial solution. In vitro results showed that the distribution and morphology of osteoblast-like SaOs-2 cells on some PLGA particle coatings were similar with that of the positive control. The purpose of this study was to develop layers of PLGA particles for local controlled drug delivery.

75. Superhydrophobic properties of cotton fabrics functionalized with ZnO by electroless deposition

Authors: Preda, N; Enculescu, M; Zgura, I; Socol, M; Matei, E; Vasilache, V; Enculescu, I

Published: FEB 15 2013, MATERIALS CHEMISTRY AND PHYSICS, 138, 261, DOI: 10.1016/j.matchemphys.2012.11.054

Cotton fabrics were coated with arrays of ZnO hexagonal prisms using an electroless (catalytic/auto-catalytic) deposition process. A typical three step method, similar to those used for electroless deposition of metals on insulating substrates, consisting of pre-activation, activation and deposition steps was employed. The low-dimensional ZnO particles were grown from an aqueous solution containing zinc nitrate as source of zinc ions and dimethylamineborane as reducing agent. The as-obtained ZnO-coated cotton fabrics were characterized from the point of view of structure by X-ray diffraction (XRD) and morphology by scanning electron microscopy (SEM). The XRD studies demonstrate that the ZnO particles have a hexagonal wurtzite crystalline structure. The SEM observations prove that the cotton fibers are homogeneously covered by hexagonal prisms which have uniform base size of approximately 500 nm and height of 1 mu m. Optical spectroscopy measurements show that the functionalization with ZnO strongly decreases the transmittance in the UV vis region of the cotton fabrics. An important characteristic is that the ZnO-functionalized cotton fabrics exhibit superhydrophobicity, with water contact angles exceeding 150 degrees. The technique described is highly reproducible, easy scalable and cheap, allowing a wide range of applications. (C) 2012 Elsevier B.V. All rights reserved.

76. Growth and structural characterization of orthorhombic and tetragonal SrCuO2 thin films

Authors: Mihailescu, CN; Pasuk, I; Athanasopoulos, GI; Luculescu, C; Socol, M; Saint-Martin, R; Revcolevschi, A; Giapintzakis, J

Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 135, DOI: 10.1016/j.apsusc.2012.12.029

Epitaxial SrCuO2 thin films were grown on (0 0 1) SrTiO3 substrates by pulsed laser deposition using a stoichiometric target. X-ray diffraction indicated that the SrCuO2 films undergo a structural phase transition as a function of the substrate temperature. Films deposited at temperatures below 600 degrees C exhibit a tetragonal phase with the c-axis oriented along the growth direction while films deposited at temperatures above 700 degrees C exhibit an orthorhombic phase with the b-axis oriented along the growth direction. Atomic force microscopy indicated that the as-grown film surfaces are rather smooth and the roughness increases with increasing substrate temperature. Energy dispersive X-ray spectroscopy in agreement with X-ray diffraction intensity ratio data revealed that all films are non-stoichiometric and contain Sr vacancies (Sr/Cu similar to 0.8). The influence of film-substrate lattice matching and substrate temperature on the structural phase transition is discussed. (C) 2012 Elsevier B.V. All rights reserved.

77. COMBINATORIAL PULSED LASER DEPOSITION OF AG-CONTAINING CALCIUM PHOSPHATE COATINGS

Authors: Socol, G; Socol, M; Sima, L; Petrescu, S; Enculescu, M; Sima, F; Miroiu, M; Popescu-Pelin, G; Stefan, N; Cristescu, R; Mihailescu, CN; Stanculescu, A; Sutan, C; Mihailescu, IN

Published: APR-JUN 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 576, DOI:

Embedding silver (Ag) into CaPs one could expect the enhancement of the antimicrobial performances of coatings for load bearing implants. The aim of this research was to evaluate whether the cellular morphology is influenced by the variation of Ag content, as well as by the solubility and morphological features of Ag-containing CaP coatings obtained by combinatorial pulsed laser deposition technique. In this view, we developed compositional libraries of either Ag and hydroxyapatite (HA) or Ag and beta-tricalcium phosphate (beta-TCP). The Ag content along the length of the combinatorial CaP coatings increased up to a maximum of similar to 1 at.%. SEM and AFM images evidenced the abundant presence of particulates typical for CaP coatings deposited by PLD. AFM histograms showed that the samples were rough with RMS values within 61-209 nm range. Ag content values up to 0.6 at. % into HA coatings were found nontoxic for mesenchymal stem cell (MSC) growth.

78. Pulsed laser deposition of transparent conductive oxide thin films on flexible substrates

Authors: Socol, G; Socol, M; Stefan, N; Axente, E; Popescu-Pelin, G; Craciun, D; Duta, L; Mihailescu, CN; Mihailescu, IN; Stanculescu, A; Visan, D; Sava, V; Galca, AC; Luculescu, CR; Craciun, V

Published: NOV 1 2012, APPLIED SURFACE SCIENCE, 260, 46, DOI: 10.1016/j.apsusc.2012.02.148

The influence of target-substrate distance during pulsed laser deposition of indium zinc oxide (IZO), indium tin oxide (ITO) and aluminium-doped zinc oxide (AZO) thin films grown on polyethylene terephthalate (PET) substrates was investigated. It was found that the properties of such flexible transparent conductive oxide (TCO)/PET electrodes critically depend on this parameter. The TCO films that were deposited at distances of 6 and 8 cm exhibited an optical transmittance higher than 90% in the visible range and electrical resistivities around 5 x 10(-4) Omega cm. In addition to these excellent electrical and optical characteristics the films grown at 8 cm distance were homogenous, smooth, adherent, and without cracks or any other extended defects, being suitable for opto-electronic device applications. (C) 2012 Elsevier B. V. All rights reserved.

79. Matrix assisted pulsed laser evaporation of Mn-12(Propionate) thin films

Authors: Pervolaraki, M; Sima, F; Socol, G; Teodorescu, CM; Gheorghe, NG; Socol, M; Mihailescu, IN; Moushi, EE; Tasiopoulos, AJ; Athanasopoulos, GI; Viskadourakis, Z; Giapintzakis, J

Published: SEP 15 2012, APPLIED SURFACE SCIENCE, 258, 9474, DOI: 10.1016/j.apsusc.2011.10.136

Single molecule magnets are of great interest due to a multitude of potential applications for some of which thin films are required. Traditional physical vapor deposition techniques are not suitable for the deposition of these fragile materials with low decomposition temperatures. Matrix Assisted Pulsed Laser Evaporation technique has been employed for the growth of thin films of the single molecule magnet Mn-12(Propionate) on Si and glass substrates. In this paper we report on the appropriate growth conditions and also the morphology, chemical composition and magnetic behavior of the films. Continuous Mn-12(Propionate) films with properties similar to bulk materials have been obtained. (c) 2011 Elsevier B.V. All rights reserved.

80. Effect of the morphology on the optical and electrical properties of polycarbonate film doped with aniline derivatives monomers

Authors: Stanculescu, F; Stanculescu, A; Girtan, M; Socol, M; Rasoga, O

Published: JAN 2012, SYNTHETIC METALS, 161, 2597, DOI: 10.1016/j.synthmet.2011.09.012

In this paper we present some comparative studies between the optical and electrical properties of the films prepared by vacuum evaporation from amidic monomeric compounds obtained from maleic anhydride and aniline derivative with different functional groups [CN; NO2], and the composite films prepared by spin-coating from a polycarbonate of bisphenol A matrix embedding clusters of these amidic monomers. We have emphasised the effect of the polymeric matrix on the properties of the synthesised monomers with the purpose to change the physical properties of the films (optical transmission, luminescence, electrical conduction, optical non-linear phenomena). The correlation between the morphology of the films and the optical and electrical properties has also been investigated. (C) 2011 Elsevier B.V. All rights reserved.

81. Optical and electrical properties of arylenevinylene compounds thin films prepared by vacuum evaporation

Authors: Rasoga, O; Vacareanu, L; Grigoras, M; Enculescu, M; Socol, M; Stanculescu, F; Ionita, I; Stanculescu, A

Published: JAN 2012, SYNTHETIC METALS, 161, 2617, DOI: 10.1016/j.synthmet.2011.10.001

This paper discusses the properties of two arylenevinylene oligomers thin films deposited by vacuum evaporation on different substrates. The morphology of the thin films was investigated by scanning electron microscopy and atomic force microscopy, and the optical properties by UV-Vis and fluorescence spectroscopy. The optical nonlinear phenomenon of two-photon absorption induced fluorescence has been evidenced in the thin films of these compounds. We have also investigated the electrical properties of semiconductor/insulator/semiconductor (ITO/oligomer/Si) heterostructures in correlation with the contact energetic barriers, morphological and structural properties of the layers. (C) 2011 Elsevier B.V. All rights reserved.

82. Influence of Al doping agents nature on the physical properties of Al:ZnO films deposited by spin-coating technique

Authors: Ghomrani, FZ; Iftimie, S; Gabouze, N; Serier, A; Socol, M; Stanculescu, A; Sanchez, F; Antohe, S; Girtan, M

Published: MAR 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 251, DOI:

In this paper we present the morphological, structural, optical and electrical properties of aluminium doped zinc oxide films prepared by spin coating technique from a zinc acetate dihydrate and 2-methoxyethanol (0.5M) solution. AlCl3 and Al(NO3)(3) were used as doping agents in different concentrations (1at%, 4at% and 6at% in starting solution). After deposition, films were dried at 100 degrees C and then annealed at temperatures between 400 degrees C and 500 degrees C. The characterization of deposited layer was performed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and UV-Vis spectroscopy. The results show that the optical and electrical properties of the structures strongly depend on the deposition conditions of ZnO:Al. In addition, the resistivity can be easily varied depending on ZnO:Al annealing temperatures and Al concentration.

83. Maple prepared organic heterostructures for photovoltaic applications

Authors: Stanculescu, A; Socol, M; Socol, G; Mihailescu, IN; Girtan, M; Stanculescu, F

Published: SEP 2011, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 104, 928, DOI: 10.1007/s00339-011-6440-y

In this study, we present the deposition of ZnPc, Alq3, and PTCDA thin films using Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. We also report the realisation of multilayer structures, made by the successive application of MAPLE. The films have been characterized by spectroscopic (UV-VIS and Photoluminescence) and microscopic (SEM and AFM) methods, and the effect of different deposition conditions such as fluence, number of pulses, and target concentration on the properties has been analysed. This paper also presents some investigations on the electrical conduction in sandwich type structures ITO or Si/organic layer/Au or Cu and ITO/double organic layer/Cu, emphasising the dominant effect of the height of the energetic barriers at the inorganic/organic and organic/organic interfaces.

84. Pulsed laser deposition of semiconducting crystalline double-doped barium titanate thin films on nickel substrates

Authors: Apostol, I; Stefan, N; Luculescu, CR; Birjega, R; Socol, M; Miroiu, M; Mihailescu, IN

Published: FEB 1 2011, APPLIED SURFACE SCIENCE, 257, 3576, DOI: 10.1016/j.apsusc.2010.11.078

We synthesized by pulsed laser deposition (Ba,Sr,Y)TiO3 and (Ba,Pb,Y)TiO3 thin films on mechanically polished nickel substrates. The synthesized thin films were analyzed for: crystalline structure by X-ray diffractometry, morphology and surface topography by atomic force microscopy, optical and scanning electron microscopy, and elemental composition by energy dispersive X-ray spectroscopy and electrical properties by electrical measurements. We have shown that film properties were determined by the dopants, target composition, and deposition parameters (oxygen pressure, substrate temperature and incident laser fluence). All films exhibited a semiconducting behavior, as proved by the decrease of electrical resistance with heating temperature. (C) 2010 Elsevier B. V. All rights reserved.

85. Thin films of arylenevinylene oligomers prepared by MAPLE for applications in non-linear optics

Authors: Stanculescu, A; Vacareanu, L; Grigoras, M; Socol, M; Socol, G; Stanculescu, F; Preda, N; Matei, E; Ionita, I; Girtan, M; Mihailescu, IN

Published: APR 1 2011, APPLIED SURFACE SCIENCE, 257, 5302, DOI: 10.1016/j.apsusc.2010.11.094

This paper discusses two arylenevinylene oligomers with optical nonlinear properties. Their trans molecular structure was confirmed by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. Second Harmonic Generation and two-photon fluorescence have been observed on Matrix Assisted Pulsed Laser Evaporation-deposited thin films. We have seen two local maxima in UV-Vis spectra and a red shift of the photoluminescence peak for carbazole-based oligomer, which can be correlated with a higher conformational flexibility and with strong polarization interactions in the solid state. Scanning Electron Microscopy and Atomic Force Microscopy images have revealed a grainy morphology of the film deposited on titanium and a higher roughness for carbazole-based oligomer. Second harmonic measurements have shown nearly equal values of the second-order nonlinear optical coefficient for the triphenylamine and carbazole-based oligomers for P-laser < 100 mW. z-Scan and x-scan representations of the carbazole-based oligomer film have shown strong two-photon fluorescence intensity inside the sample confirming a volume process, and a strong second harmonic at the surface of the sample determined by the surface morphology. (C) 2010 Elsevier B.V. All rights reserved.

86. Effect of maleic anhydride-aniline derivative buffer layer on the properties of flexible substrate heterostructures: Indium tin oxide/nucleic acid base/metal

Authors: Stanculescu, A; Socol, M; Socol, G; Mihailescu, IN; Girtan, M; Preda, N; Albu, AM; Stanculescu, F

Published: DEC 1 2011, THIN SOLID FILMS, 520, 1258, DOI: 10.1016/j.tsf.2011.04.204

This paper presents some investigations on the properties of guanine (G) and cytosine (C) based heterostructures deposited on flexible substrates. The effects of two types of maleic anhydride-aniline derivatives (maleic anhydride-cyano aniline or maleic anhydride-2,4 dinitroaniline) buffer layer, deposited between indium tin oxide and (G) or (C) layer, on the optical and electrical properties of the heterostructures have been identified. The heterostructures containing a film of maleic anhydride-2,4 dinitroaniline have shown a good transparency and low photoluminescence invisible range. This buffer layer has determined an increase in the conductance only in the heterostructures based on (G) and (C) deposited on biaxially-oriented polyethylene terephthalate substrate. (C) 2011 Elsevier B. V. All rights reserved.

87. TAILORING OF OPTICAL, COMPOSITIONAL AND ELECTRICAL PROPERTIES OF THE InxZn1-xO THIN FILMS OBTAINED BY COMBINATORIAL PULSED LASER DEPOSITION

Authors: Socol, G; Galca, AC; Luculescu, CR; Stanculescu, A; Socol, M; Stefan, N; Axente, E; Duta, L; Mihailescu, CM; Craciun, V; Craciun, D; Sava, V; Mihailescu, IN

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 115, DOI:

Indium Zinc Oxide compositional libraries were fabricated by combinatorial pulsed laser deposition technique on glass substrate at room temperature. Two pairs of targets with In atomic concentrations, In/(In+Zn), of 28 at.% and 56 at.% or 42 at.% and 70 at.% were employed. A high transparency was observed for all the coatings with transmittance values better than 95%. The maximum thicknesses of the samples, inferred by spectroscopic ellipsometry, were within the 174-310 nm range for the simple PLD films, whereas in case of combinatorial PLD coatings were 341 or 467 nm. Energy dispersive X-ray spectroscopy revealed that In content in the combinatorial films was in the 27-52 at. % range. From atomic force microscopy histograms we evidenced a decrease of the RMS roughness down to 1 nm with the increase of the In content. As a result of the compositional library studies two minimum values of the electrical resistivity were identified at 2.3x10(-3) Omega.cm and 8.6 x 10(-4) Omega.cm, which correspond to 28.8-29.5 at.% and 44-49 at% range of Indium content.

88. Tailoring immobilization of immunoglobulin by excimer laser for biosensor applications

Authors: Sima, F; Axente, E; Ristoscu, C; Mihailescu, IN; Kononenko, TV; Nagovitsin, IA; Chudinova, G; Konov, VI; Socol, M; Enculescu, I; Sima, LE; Petrescu, SM

Published: FEB 2011, JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 96A, 394, DOI: 10.1002/jbm.a.32991

The sheltered transfer and immobilization of rabbit anti-human antiserum immunoglobulin G (IgG) by matrix-assisted pulsed laser evaporation (MAPLE) are reported. The iced targets submitted to laser irradiation consisted of 0.2-2 mg/mL IgG blended or not with lipid (L-a-phosphatidylcholine dipalmitoyl) dissolved in distilled water-based saline buffer. Thin IgG coatings were obtained at room temperature onto glass, fused silica, or silicon substrates. Ten thousand subsequent laser pulses of 0.33, 0.5, or 0.67 J/cm(2) fluence were applied for the synthesis of each sample. Morphology and composition of the thin films were studied by optical, scanning, and atomic force microscopy and Fourier transformed infrared spectrometry. Optical labeling methods such as spectrofluorimetry and fluorescence microscopy were selected to verify the biosensor transduction principle because of their high sensitivity for detecting low amounts of antigen (IgG). Protein immobilization to the substrate surface was demonstrated for all obtained structures after immersion in the donkey anti-rabbit secondary antibody solution. The IgG transfer and immobilization onto substrates were improved by addition of lipid to MAPLE solutions. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 384-394, 2011.

89. Synthesis of ZnO thin films by 40 ps @ 532 nm laser pulses

Authors: Ristoscu, C; Socol, M; Socol, G; Mihailescu, IN; Jafer, R; Al-Hadeethi, Y; Batani, D

Published: SEP 2011, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 104, 876, DOI: 10.1007/s00339-011-6429-6

The synthesis by pulsed laser deposition of ZnO thin films with a Nd:YAG laser system delivering pulses of 40 ps @ 532 nm is reported. The laser beam irradiated the target placed inside a vacuum chamber evacuated down to 1.33x10(-1) Pa. The incident laser fluence was of 28 J/cm(2) in a spot of 0.1 mm(2). The ablated material was collected onto double face polished (111) Si or quartz wafers placed parallel at a separation distance of 7 mm. The AFM, SEM, UV-Vis, FT-IR and absorption ellipsometry results indicated that we obtained pure ZnO films with a rather uniform surface, having an average roughness of 37 nm. We observed by SEM that particulates are present on ZnO film surface or embedded into bulk. Their density and dimension were intermediary between particulates observed on similar structures deposited with fs or ns laser pulses. We noticed that the density of the particulates is increasing while their average size is decreasing when passing from ns to ps and fs laser pulses. The average transmission in the UV-Vis spectral region was found to be higher than 85%.

90. MAPLE deposited thin monomer films of maleimidic derivatives for photonics

Authors: Stanculescu, A; Albu, AM; Socol, G; Stanculescu, F; Socol, M; Preda, N; Rasoga, O; Girtan, M; Iulian, I

Published: MAR 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 739, DOI:

This paper presents a study of some thin monomer films deposited by MAPLE. These monomers have been synthesised from maleic anhydride and aniline derivatives and are characterized by a molecular structure adequate for the generation of optical non-linear phenomena. UV-VIS, FTIR, Raman and Photoluminescence spectroscopy have been used to investigate the influence of the experimental conditions on the properties of the films. X-Ray Diffraction has evidenced a certain degree of disorder in the thin films, which is correlated with the randomly orientated molecules and AFM images have revealed different roughness for different monomer layers and different substrates. Second harmonic measurements have shown a strong signal emitted by the thin film prepared from the monomer with one [-NH-NH-] donor and two [-NO(2)] acceptor groups. This thin film is characterized by good transparency and low photoluminescence emission at excitation with the wavelength of the second harmonic (lambda-400 nm).

91. On the structural, morphological, optical and electrical properties of sol-gel deposited ZnO In films

Authors: Girtan, M; Socol, M; Pattier, B; Sylla, M; Stanculescu, A

Published: NOV 1 2010, THIN SOLID FILMS, 519, 577, DOI: 10.1016/j.tsf.2010.07.006

Indium-doped zinc oxide thin films deposition was performed by the sol-gel technique using homogeneous and stable solutions of zinc acetate 2-hydrate and indium chloride in ethanol Films were spin coated onto glass substrates After drying and after a heat treatment at 450 degrees C highly transparent (80%-90%) films were obtained The effect on the structural morphological optical and electrical thin films properties of the dopant concentration was investigated The temperature dependencies of the electrical conductivity under vacuum and in open atmosphere were analysed and discussed (C) 2010 Elsevier B V All rights reserved

92. MAPLE preparation and characterization of benzil thin films

Authors: Socol, M; Socol, G; Rasoga, O; Stanculescu, F; Stanculescu, A; Mihailescu, I; Ionita, I; Preda, N; Enculescu, M; Antohe, S

Published: NOV 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1806, DOI:

In this study the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique was used to prepare thin films from a low melting point (< 100 degrees C) organic compound (benzil). Optical properties of the films have been investigated by UV-VIS, FTIR and PL spectroscopy. Details about crystallinity were obtained by XRD measurements. FTIR spectra have confirmed the preservation of the chemical structure of the compound during the deposition process. SEM and AFM investigation have evidenced a topography of the MAPLE deposited films characterized by different grain size depending on the deposition conditions. Second harmonic generation measurements have revealed that the MAPLE deposited benzil films have preserved the optical nonliniar properties of the bulk crystalline benzil.

93. Effect of the morphology on the optical and electrical properties of TPyP thin films deposited by vacuum evaporation

Authors: Socol, M; Rasoga, O; Stanculescu, F; Girtan, M; Stanculescu, A

Published: DEC 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 2038, DOI:

We have studied the effect of the morphology on the optical and electrical properties of the TPyP thin films deposited by vacuum evaporation on different substrates (Si with different characteristics, ITO, quartz and glass). The presence of some well-defined B and Q absorption bands has been evidenced. FTIR and photoluminescence measurements have been used to confirm the preservation of the chemical structure of the compound during the evaporation process. The contact Au/TPyP/Si(n) is rectifier, while a blocking behavior has been shown by Si(n)/TPyP/Si(n) and ITO/TPyP/Si(n) and an injector dominated behavior by Si(p)/TPyP/Si(p) and ITO/TPyP/Si(p) heterostructures. The best transmission was obtained on TPyP film deposited on ITO and the highest value of the current in heterostructures Si(n) electrode characterised by a large grain morphology and in consequence by a weak optical and charge carrier scattering at the grain boundaries.

94. Investigations of the Correlation Between the Preparation Method and the Properties of Anilinic Derivative Functionalised Polymer Thin Films for Non-Linear Optical Applications

Authors: Stanculescu, A; Socol, M; Albu, AM; Rasoga, O; Stanculescu, F; Ionita, I; Enculescu, I

Published: 2010, ADVANCED MATERIALS FORUM V, PT 1 AND 2, 636-637, +, DOI: 10.4028/www.scientific.net/MSF.636-637.798

This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.

95. MAPLE prepared polymeric thin films for non-linear optic applications

Authors: Socol, G; Mihailescu, IN; Albu, AM; Antohe, S; Stanculescu, F; Stanculescu, A; Mihut, L; Preda, N; Socol, M; Rasoga, O

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5614, DOI: 10.1016/j.apsusc.2008.07.206

This paper presents a study of some functionalised copolymers thin films prepared on silicon and quartz substrates by matrix assisted pulsed laser evaporation ( MAPLE) method. Two polymeric structures have been synthesised by the copolymerisation of maleic anhydride and methyl methacrylate, respectively, maleic anhydride and vinyl benzyl chloride and their subsequent functionalisation with 2,4-dinitroaniline. UV-Vis, FTIR, Raman and photoluminescence spectroscopy have been used to investigate the influence on the properties of the films of different substrate temperature ( 150 degrees C and 250 degrees C), background N-2 pressure (5-30 Pa) and polymer concentration in target (2% and 3%). We have evidenced that this deposition process does not damage the chemical structure of the polymers. SEM investigations revealed the droplets type morphology of the polymeric films with thickness between 41 nm and 105 nm calculated from ellipsometric measurements. (C) 2008 Elsevier B. V. All rights reserved.

96. Preparation and Characterization of Polar Aniline Functionalized Copolymers Thin Films for Optical Non-Linear Applications

Authors: Stanculescu, A; Rasoga, O; Preda, N; Socol, M; Stanculescu, F; Ionita, I; Albu, AM; Socol, G

Published: 2009, FERROELECTRICS, 389, 173, DOI: 10.1080/00150190902993291

This paper presents a study of two monomeric structures containing functional groups with different electronegativities [NH/NH-NH and NO2] and two different polymeric structures prepared by the copolymerisation of maleic anhydride and methylmethacrylate/maleic anhydride and vinyl benzyl chloride, and subsequent functionalization with 2,4 dinitroaniline. Thin films have been prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and UV-VIS, FTIR, Raman and Photoluminescence Spectroscopy have been used to comparatively investigate the properties of the synthesised compounds. We have evidenced the second harmonic emission (SHG), process sustained by the asymmetry of the chemical structure, which is correlated with the crystallization in non-centrosymmeric structures.

97. Charge carrier transport phenomena in some organic heterojunctions

Authors: Rasoga, OL; Socol, M; Stanculescu, F

Published: APR 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 514, DOI:

This paper presents investigations on the electrical transport phenomena in sandwich type inorganic/single (double) organic layer/inorganic such as silicon; ITO/TPyP, Alq3, alpha-NPD; ZnPc; perylene" PTCDA/silicon and inorganic (metal)/organic/metal such as silicon (A/)/ZnPc; alpha-NPD; TPyP/copper, Al, structures, prepared by vacuum evaporation. For most of these heterostructures the IN characteristics in the static regime have a near ohmic behaviour only at low voltages (<1 V) that changes in a power dependence with a coefficient n=2 or n=3 at higher voltages because of the space charge or trapped charge phenomena. For the same applied voltage, the n type Si electrode injects more charge carriers in TpyP than in Alq3. For higher voltages (>10V) an increased number of charge carriers are injected from n type Si in Alq3 compared to TpyP. The injection properties of the interface ITO, Cu, Al electrode/organic layer have also been investigated. The best injection has been obtained through ITO/ZnPc interface. For a grid configuration of the Al electrodes the transport phenomena are determined by the resistivity of the structure.

98. Electrical transport in crystalline perylene derivatives films for electronic devices

Authors: Stanculescu, A; Stanculescu, F; Socol, M; Grigorescu, O

Published: DEC 2008, SOLID STATE SCIENCES, 10, 1767, DOI: 10.1016/j.solidstatesciences.2008.03.023

This paper presents investigations on the electrical transport phenomena in perylene and PTCDA emphasising the particularities of the charge carrier injection at the contacts with inorganic semiconductors (Si) and metals (Cu, Al) and the effect of the supplementary organic layer (ZnPc, alpha-NPD) on the electrical conduction. The I-V characteristics for different delay and integration times, at forward and reverse bias, have evidenced a dominant ohmic behaviour of these SIS and MIS structures at low voltage (<0.1 V) and limitations of the current induced by the space charge and trap charge at voltages >1 V. An intermediate organic layer (ZnPc) with higher ionisation potential than PTCDA and lower electron affinity than perylene improves the charge carrier injection and the conduction properties of the Si/PTCDA/Si and forward biased Cu/perylene/Si heterostructures. No increase in the hole injection was obtained in Si(p)/perylene/Si(p) heterostructure introducing an a-NPD layer. (C) 2008 Elsevier Masson SAS. All rights reserved.

99. Effect of the metallic contact on the electrical properties of organic semiconductor film

Authors: Stanculescu, F; Stanculescu, A; Socol, M

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1357, DOI:

Sandwich type (MIS) heterostructures based on layers of organic semiconductors as meta-dinitrobenzene (m-DNB) and perylene or perylene derivative 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) have been prepared using alternative methods (rapid thermal directional solidification or two-steps, vacuum evaporation and deposition process) on different substrates (single crystal silicon wafer and textolite covered with copper film). Subsequently indium, gallium, aluminium of high purity (5N) and silver have been used for the preparations of the metallic contacts. This paper presents some investigations of the contact between different organic semiconductors and several metals: meta-dinitrobenzene/Cu, perylene/In, peryiene/Al, perylene/Ga, perylene/Ag, PTCDA/AI, PTCDA/Ga, and PTCDA/Ag. The comparative study of the electrical conduction properties of these organic semi conductor/metal contacts has emphasised significant differences depending on the metal type, metal/organic semiconductor interface properties and quality of the contact, which is determined by the preparation method (pressing, melting, vacuum evaporation, painting) and selected contact cinfiguration. The experimental data obtained using the 2 points contact geometry have evidenced linear or power IN dependences of the investigated metallic contacts emphasising the importance of the space-charge phenomenon and defects on the charge carriers' transport in these structures.

100. Photosensitization of ZnO nanostructured thin films with organic dyes

Authors: Tazlaoanu, C; Ion, L; Socol, G; Socol, M; Mihailescu, IN; Stanculescu, F; Enculescu, I; Ionescu, F; Magherusan, L; Antohe, S

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1346, DOI:

We report in this contribution on the photosensitization effect of ZnO nanostructured thin films with copper-phthalocyanine (CuPc). ZnO films were prepared by pulsed laser deposition (PLD), on optical glass substrates, covered with 300 nm thick ITO films. The structure and morphology of ZnO films were optimized for photovoltaic-cell applications by controlling the growing conditions. ZnO films (wurtzite type) were (001) preferentially oriented in the growth direction. Organic dyes were vacuum sublimated on ZnO films, and subsequently a 300 nm thick copper film was vacuum sublimated on top of the structure, acting as an ohmic contact. Action spectra of ITO/ZnO/CuPc/Cu photovoltaic structures were recorded and a well defined response was observed in the range of absorption bands of organic dyes. The dark IN characteristics were also recorded, and electrical characterizations of the photovoltaic structures are given. The measured fourth quadrant IN characteristics under integral illumination (photoelement regime), allowed us to extract the typical photovoltaic cells parameters.

101. Optical properties of 3,4,9,10-perylenetetracarboxylic dianhydride and 8-hydroxyquinoline aluminum salt films prepared by vacuum deposition

Authors: Stanculescu, A; Stanculescu, F; Tugulea, L; Socol, M

Published: 2006, ADVANCED MATERIALS FORUM III, PTS 1 AND 2, 514-516, 960, DOI: 10.4028/www.scientific.net/MSF.514-516.956

The main purpose of this paper is to investigate the optical properties of PTCDA and Alq3 films, prepared by two steps, vacuum evaporation and deposition processes on platelets of glass, quartz, and indium-tin-oxide (ITO) coated glass. We have emphasised the bands structure of the absorption spectra with peaks situated at 358 nm, 374 nm, 475 nm and 552 nm in PTCDA, respectively 232 nm, 261 nm and 380 nm in Alq3 that confirms the dominant presence of Alq3 meridianal molecular isomer. For PTCDA films deposited on glass coated with ITO, the structure of the weak double peak at low wavelength is partially modified, but the positions of the two important absorption peaks situated at 2.25 eV and 2.61 eV are unchanged. The two different luminescence emission peaks obtained in Alq3 for different excitation wavelengths (gimel=360 nm and gimel=520 nm) suggest the existence of the facial isomer beside the meridianal one. We have evidenced a significant Stocks shift in the spectra (Delta E-PTCDA=0.40 eV; Delta E-Alq3=0.9 eV) and a large Frank-Condon shift (0.40-2.3 eV), suggesting important effect associated respectively with the solid state structure and important conformational differences between the ground and excited state.

102. Optical properties of polycarbonate organic matrix/cadmium sulphide clusters composite material

Authors: Stanculescu, A; Stanculescu, F; Socol, M

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1061, DOI:

This paper presents the investigation of the optical properties of bisphenol A polycarbonate organic matrix/CdS clusters composite material in correlation with the method for the films' preparation using as precursors cadmium acetate (Cd(CH3COO)(2)), respectively ammonium thiocyanate (NH4CNS), and as general solvent for all the components, is dimethyformamide. The effect of the heat treatment temperature (90 degrees C or 150 degrees C) on the position and shape of the fundamental absorption edge was investigated for given substrate, drying conditions and duration (1.5 h or 0.5 h) of the heat treatment. A large blue shift of the absorption edge was evidenced in films prepared in vertical configuration and thermally treated at 90 degrees C for 1.5 h, which can be associated with a small dimension of the CdS crystallites and in consequence with quantum confinement effects. Using the effective mass theory we have deduced a crystallite dimension in the range 8.8-15 nm. We also have studied the interaction of the light with this composite material evaluating an optical band gap between 2.92 and 3.69 eV (depending on the preparation and annealing conditions) and an absorption mechanism in CdS clusters closer to an indirect transition and deviated from the normal direct absorption process in bulk CdS semiconductor.

103. Investigations of the nonhomogeneities in organic molecular crystalline materials using Kubelka-Munk theory

Authors: Socol, M; Stanculescu, A

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 190, DOI:

This paper presents a study of the nonhomogeneities in doped meta-dinitrobenzene (m-DNB) crystalline films. These growth defects lying in the film plane with dimensions smaller than the films thickness are correlated with the effect of the dopant on the crystallization regime in the dendritic growth conditions. To evaluate the dimension of the growth nonhomogeneities we have used a model based on the Kubelka-Munk theory, emphasising the general constraints imposed to the sample and the experimental set-up, and developing a more complex model through a step-by-step relaxation of these constraints, that ensures a better approximation for our experimental configuration. We have deduced higher scattering coefficients in m-DNB doped with 1,3 dihydroxybenzene (resorcinol) than in m-DNB doped with 8-hydroxyquinoline (oxine) films prepared by a rapid thermal solidification process. We also have emphasised that for the films of m-DNB doped with oxine the size of the scattering centers is larger than the wavelength of the radiation and in films of m-DNB doped with resorcinol the radiation scattering corresponds to a multiple scattering process leading to the superposition of different scattering mechanisms on centers with different dimensions.

104. Doped aromatic derivatives wide-gap crystalline semiconductor structured layers for electronic application

Authors: Stanculescu, A; Stanculescu, F; Alexandru, H; Socol, M

Published: JAN 20 2006, THIN SOLID FILMS, 495, 393, DOI: 10.1016/j.tsf.2005.08.243

We present some investigations on the electrical conductivity of two benzene substituted derivatives (m-DNB, benzil) emphasizing the correlation between the molecular structure, purity, structural defects and the particularities of the conduction mechanisms. The influence of inorganic/organic doping on the I-V plots of silicon/wide-gap organic semiconductor/silicon heterostructures has been analysed. The most significant increase in the conductance has been obtained for organic crystalline films of benzil doped with 3 wt.% m-DNB and m-DNB films doped with I wt.% oxine or 10 wt.% resorcinol. The influence of the silicon wafer's properties as resistivity, conduction type and surface processing on the carrier transport properties in these structures has been studied. We have remarked an increase in the conductance of the organic films of m-DNB doped with oxine or resorcinol in heterostructures realized with chemically polished, "n" type single crystal silicon wafers, compared to lapped ones. A special type of conduction mechanism given by a Poole-Frenkel dependence was evidenced in resorcinol doped m-DNB in the low voltages range. (c) 2005 Elsevier B.V. All rights reserved.

105. Light absorption in meta-dinitrobenzene and benzyl crystalline films

Authors: Stanculescu, F; Stanculescu, A; Socol, M

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1056, DOI:

This paper presents the optical absorption properties in crystalline meta-clinitrobenzene (m-DNB) and benzil. The optical band gap as an intrinsic property of these crystalline compounds has been studied using UV-VIS Spectroscopy on thin film. Analysing absorption near the fundamental absorption edge we have deduced the wide band gap semiconductor behaviour of these aromatic derivatives. Processing the experimental transmission data using a function obtained by the superposition of a linear function and a power function we have evaluated the band gap energy in m-DNB, E-g=2.90 eV and emphasised the same two edges patterns of the light absorption spectrum in benzil deposited on glass as for benzil deposited on quartz, with energetic thresholds slowly moved through lower energies, E-g1=2.79 eV and E-g2=3.49 eV. We have also remarked no significant change in the absorption spectrum in benzil induced by the dopant (organic and inorganic).

106. Molecular organic crystalline matrix for hybrid organic-inorganic (nano) composite materials

Authors: Stanculescu, A; Tugulea, L; Alexandru, HV; Stanculescu, F; Socol, M

Published: FEB 15 2005, JOURNAL OF CRYSTAL GROWTH, 275, E1786, DOI: 10.1016/j.jcrysgro.2004.11.210

Metal-doped benzil crystals have been grown by thermal gradient solidification in a vertical transparent growth configuration to investigate the effect of metallic guest on the ordered organic host. We have identified the conditions for growing homogeneous, optically good crystals of benzil doped with sodium and silver, limiting the effect of supercooling, low thermal conductivity and anisotropy of the growth speed (temperature gradient at the liquid-solid interface: 10-25 degrees C, moving speed of the growth interface 2.0 mm/h). The nature and concentration of the dopant are parameters affecting, through the growth process, the crystalline perfection and the optical properties of the organic matrix. Bulk optical characterisation, by spectrophotometrical methods, has offered details on some intrinsic properties of the system metal particles/benzil crystalline matrix. Analytical processing of the experimental data emphasised that benzil is a wide optical band gap organic semiconductor E-g = 2: 65 eV: We also have investigated the effect of sodium and silver on the properties of benzil crystal as potential transparent semiconductor matrix for (nano) composite metal/molecular organic material. With the increase of sodium concentration from c = 1 to 6 wt%, a small narrowing of the band gap has been remarked. The same behaviour has been found for benzil doped with silver (c = 2wt%) compared to pure benzil. (C) 2004 Elsevier B.V. All rights reserved.

107. Fluorescence of substituted aromatic derivatives crystalline materials for optical non-linear applications

Authors: Stanculescu, A; Tugulea, L; Stanculescu, F; Socol, M

Published: 2004, ROMOPTO 2003: SEVENTH CONFERENCE ON OPTICS, 5581, 607, DOI: 10.1117/12.583028

Our fluorescence study gave information on the presence of chemical defects and irregularities in crystal structure, offering a good tool for quality evaluation of organic crystalline materials. We have analysed the correlation between the bulk or thin film samples' quality determined by experimental parameters (thermal gradient, moving speed of the growth interface, crucible configuration, slow or fast solidification rates) and the fluorescence characteristics for pure meta-dinitrobenzene and meta-dinitrobenzene doped with 8 hydroxyquinoline or 1,3 dihydroxybenzene. The comparative study of the position and shape of the fluorescence emissions for pure and controlled doped materials nave us information on the chemical defects.

108. Effect of dopant on the intrinsic properties of some multifunctional aromatic compounds films for target applications

Authors: Stanculescu, A; Antohe, S; Alexandru, HV; Tugulea, L; Stanculescu, F; Socol, M

Published: DEC 7 2004, SYNTHETIC METALS, 147, 220, DOI: 10.1016/j.synthmet.2004.07.010

UV-VIS transmission and fluorescence spectroscopy have been used to study some intrinsic properties of crystalline films of pure metadinitrobenzene (m-DNB) and, pure and doped benzil. We have evaluated the band gap energy, E-g = 2.92 eV, emphasising the near classical semiconductor behaviour of m-DNB. The two bands split of the (n, pi*) level is assumed to be the origin the two edges absorption in benzil films with the energetic thresholds at E-g1 = 2.84 eV and E-g2 = 3.55 eV. The red shift of the emission peak in m-DNB films has been correlated with the process of self-absorption of the emitted radiation in the thicker film. The effect of the impurities on the shape and position of the emission peaks in benzil has been investigated and we have observed no significant shift of the absorption peak situated at 3.25 eV. We also have identified a three steps process for the relaxation of the excited crystalline lattice of benzil involving the geometrical change of the (S-1) excited state, the intersystem crossing and the radiative decay by phosphorescence with a peak at 2.30 eV. The small blue shift of this emission peak in benzil highly doped with sodium has been attributed to the modification of the molecular geometry of benzil as a result of the change in the trans-planar molecular configuration induced by the chemical reaction between the atoms of alkali metal and the carbonyl groups. (C) 2004 Elsevier B.V All rights reserved.

109. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

Authors: Petre, G; Stanculescu, A; Girtan, M; Socol, M; Breazu, C; Vacareanu, L; Preda, N; Rasoga, O; Stanculescu, F; Doroshkevich, AS

Published: DEC 2021 , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, DOI: 10.1002/pssa.202100521

110. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

Authors: Petre, G; Stanculescu, A; Girtan, M; Socol, M; Breazu, C; Vacareanu, L; Preda, N; Rasoga, O; Stanculescu, F; Doroshkevich, AS

Published: , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, DOI: 2100521

Dr. Marcela SOCOL

Scientific Researcher I

Expertize

Books

Patents

Projects

1. Photovoltaic cells with multilayer transparent conductive electrode developed on rigid and flexible substrates

2. Flexible hybrid photovoltaic cell structures

3. Metallic Electrode with 2D Photonic Crystal type Architecture for Bio(organic) Multilayer Structures

Publications

1. Composite Films Based on Poly(3-hexylthiophene):Perylene Diimide Derivative:Copper Sulfide Nanoparticles Deposited by Matrix Assisted Pulsed Laser Evaporation on Flexible Substrates for Photovoltaic Applications

2. Influence of flexible substrate nature covered with ITO on the characteristics of organic heterostructures fabricated by laser deposition techniques

3. Aluminum doped zinc oxide nanoplatelets based sensor with enhanced hydrogen sulfide detection

4. Induced Effects of Nano-Patterned Substrates on the Electrical and Photo-Electrical Properties of PTB7-Th:ICBA (1:1, wt.%) Bulk-Heterojunction Solar Cells

5. Reduced graphene oxide- based multilayer transparent conductive electrodes

6. ASSESSING THE COMBINED EFFECTS OF CHEMICAL AND MECHANICAL PARAMETERS ON SILAR-GROWN NANOSTRUCTURED ZnO THIN FILMS

7. Organic Heterostructures with Dendrimer Based Mixed Layer for Electronic Applications

8. Editorial for Special Issue: "Thin Films Based on Nanocomposites (2nd Edition)"

9. MAPLE deposition of hybrid PLGA-Fe3O4-Cypress-PEDOT: PSS coatings

10. MAPLE-Deposited Perylene Diimide Derivative Based Layers for Optoelectronic Applications

11. Organic heterostructures based on thermal evaporated phthalocyanine and porphyrin as mixed (ZnPc:TPyP) or stacked (ZnPc/TPyP) films

12. Macrocyclic Compounds: Metal Oxide Particles Nanocomposite Thin Films Deposited by MAPLE

13. Effects of Solvent Additive and Micro-Patterned Substrate on the Properties of Thin Films Based on P3HT:PC70BM Blends Deposited by MAPLE

14. Effect of dopants on the optical properties of benzil crystals

15. Editorial for Special Issue: "Thin Films Based on Nanocomposites"

16. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

17. Effect of Aluminum Nanostructured Electrode on the Properties of Bulk Heterojunction Based Heterostructures for Electronics

18. Thin Film Fabrication by Pulsed Laser Deposition from TiO2 Targets in O2, N2, He, or Ar for Dye-Sensitized Solar Cells

19. The effect of fullerene layer on the aggregates formation in amyloid beta Langmuir-Blodgett films

20. Electro-active properties of nanostructured films of cytosine and guanine nucleobases

21. Nucleobases thin films deposited on nanostructured transparent conductive electrodes for optoelectronic applications

22. Hybrid Nanocomposite Thin Films for Photovoltaic Applications: A Review

23. Organic Thin Films Deposited by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) for Photovoltaic Cell Applications: A Review

24. Silicon Metalens Fabrication from Electron Beam to UV-Nanoimprint Lithography

25. Arylenevinylene Oligomer-Based Heterostructures on Flexible AZO Electrodes

26. Hybrid organic-inorganic thin films based on zinc phthalocyanine and zinc oxide deposited by MAPLE

27. Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation

28. Organic Thin Films Based on DPP-DTT:C60 Blends Deposited by MAPLE

29. MAPLE Deposition of Binary and Ternary Organic Bulk Heterojunctions Based on Zinc Phthalocyanine

30. Long-Term Evaluation of Dip-Coated PCL-Blend-PEG Coatings in Simulated Conditions

31. EFFECTS OF ANNEALING ON THE PHYSICAL PROPERTIES OF ITO THIN FILMS GROWN BY RADIO FREQUENCY MAGNETRON SPUTTERING

32. Effect of ITO electrode patterning on the properties of organic heterostructures based on non-fullerene acceptor prepared by MAPLE

33. On the Physical Properties PEDOT:PSS Thin Films

34. Influence of Reduced Graphene Oxide on the Electropolymerization of 5-Amino-1-naphthol and the Interaction of 1,4-Phenylene Diisothiocyanate with the Poly(5-Amino-1-naphtol)/Reduced Graphene Oxide Composite

35. Reduced Graphene Oxide Sheets as Inhibitors of the Photochemical Reactions of α-Lipoic Acid in the Presence of Ag and Au Nanoparticles

36. Laser Processed Antimicrobial Nanocomposite Based on Polyaniline Grafted Lignin Loaded with Gentamicin-Functionalized Magnetite

37. Deposition temperature influence on the wear behaviour of carbon-based coatings deposited on hardened steel

38. Pulsed Laser Deposition of Indium Tin Oxide Thin Films on Nanopatterned Glass Substrates

39. ORGANIC HETEROSTRUCTURES DEPOSITED BY MAPLE ON PATTERNED AZO ELECTRODES

40. Flexible organic heterostructures obtained by MAPLE

41. On the properties of organic heterostructures prepared with nano-patterned metallic electrode

42. Organic heterostructures obtained on ZnO/Ag/ZnO electrode

43. Lincomycin-embedded PANI-based coatings for biomedical applications

44. Titanium implants' surface functionalization by pulsed laser deposition of TiN, ZrC and ZrN hard films

45. Biocomposite coatings based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/calcium phosphates obtained by MAPLE for bone tissue engineering

46. IZO deposited by PLD on flexible substrate for organic heterostructures

47. Effect of heavy ions irradiation on the properties of benzil crystals

48. Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study

49. Antimicrobial polycaprolactone/polyethylene glycol embedded lysozyme coatings of Ti implants for osteoblast functional properties in tissue engineering

50. MAPLE prepared heterostructures with oligoazomethine: Fullerene derivative mixed layer for photovoltaic applications

51. MEASUREMENT OF CHARGE CARRIER MOBILITY IN PEROVSKITE NANOWIRE FILMS BY PHOTO-CELIV METHOD

52. MAPLE DEPOSITION OF PLGA MICROSPHERES FOR MEDICAL APPLICATIONS

53. Organic heterostructures deposited by MAPLE on AZO substrate

54. Oxide/metal/oxide electrodes for solar cell applications

55. Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition

56. INVESTIGATIONS ON THE PROPERTIES OF A TWO-DIMENSIONAL NANOPATTERNED METALLIC FILM

57. Investigations of Ar ion irradiation effects on nanocrystalline SiC thin films

58. MAPLE preparation and characterization of mixed arylenevinylene based oligomers:C-60 layers

59. Flexible heterostructures based on metal phthalocyanines thin films obtained by MAPLE

60. Surface-enhanced Raman scattering activity of niobium surface after irradiation with femtosecond laser pulses

61. INVESTIGATIONS OF PULSED LASER DEPOSITED TiN THIN FILMS FOR TITANIUM IMPLANTS

62. HETEROSTRUCTURES BASED ON SMALL MOLECULES ORGANIC COMPOUNDS

63. MAPLE prepared heterostructures with arylene based polymer active layer for photovoltaic applications

64. Composite biodegradable biopolymer coatings of silk fibroin - Poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) for biomedical applications

65. EFFECT OF CHOLESTEROL ON THE DEPOSITION OF BETA-AMYLOID 1-40 AND 1-42 FILMS

66. Organic heterostructures based on arylenevinylene oligomers deposited by MAPLE

67. The Influence of the Microstructure and Morphology of CeO2 Buffer Layer on the Properties of YBCO Films PLD Grown on Ni Tape

68. Superhydrophobic ZnO networks with high water adhesion

69. Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates

70. Laser synthesis of nanometric iron oxide films for thermo-sensing applications