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Dr. Adam LORINCZI

Scientific Researcher II

Laboratory of Optical Processes in Nanostructured Materials

lorinczi[AT]infim[DOT]ro

Publications

1. Optical and Structural Properties of Composites Based on Poly(urethane) and TiO2 Nanowires
Authors: Stroe, M; Burlanescu, T; Paraschiv, M; Lorinczi, A; Matei, E; Ciobanu, R; Baibarac, M

Published: FEB 2023, MATERIALS, 16, 1742, DOI: 10.3390/ma16041742

This article's objective is the synthesis of new composites based on thermoplastic polyurethane (TPU) and TiO2 nanowires (NWs) as free-standing films, highlighting their structural and optical properties. The free-standing TPU-TiO2 NW films were prepared by a wet chemical method accompanied by a thermal treatment at 100 degrees C for 1 h, followed by air-drying for 2 h. X-ray diffraction (XRD) studies indicated that the starting commercial TiO2 NW sample contains TiO2 tetragonal anatase (A), cubic Ti0.91O (C), and orthorhombic Ti2O3 (OR), as well as monoclinic H2Ti3O7 (M). In the presence of TPU, an increase in the ratio between the intensities of the diffraction peaks at 43.4 degrees and 48 degrees belonging to the C and A phases of titanium dioxide, respectively, is reported. The increase in the intensity of the peak at 43.4 degrees is explained to be a consequence of the interaction of TiO2 NWs with PTU, which occurs when the formation of suboxides takes place. The variation in the ratio of the absorbance of the IR bands peaked at 765-771 cm(-1) and 3304-3315 cm(-1) from 4.68 to 4.21 and 3.83 for TPU and the TPU-TiO2 NW composites, respectively, with TiO2 NW concentration equal to 2 wt.% and 17 wt.%, indicated a decrease in the higher-order aggregates of TPU with a simultaneous increase in the hydrogen bonds established between the amide groups of TPU and the oxygen atoms of TiO2 NWs. The decrease in the ratio of the intensity of the Raman lines peaked at 658 cm(-1) and 635 cm(-1), which were assigned to the vibrational modes E-g in TiO2 A and E-g in H2Ti3O7 (ITiO2-A/I-H2Ti3O7), respectively, from 3.45 in TiO2 NWs to 0.94-0.96 in the TPU-TiO2 NW composites, which indicates that the adsorption of TPU onto TiO2 NWs involves an exchange reaction of TPU in the presence of TiO2 NWs, followed by the formation of new hydrogen bonds between the -NH- of the amide group and the oxygen atoms of TixO2x-mn, Ti2O3, and Ti0.91O. Photoluminescence (PL) studies highlighted a gradual decrease in the intensity of the TPU emission band, which is situated in the spectral range 380-650 nm, in the presence of TiO2 NW. After increasing the TiO2 NW concentration in the TPU-TiO2 NW composite mass from 0 wt.% to 2 wt.% and 17 wt.%, respectively, a change in the binding angle of the TPU onto the TiO2 NW surface from 12.6 degrees to 32 degrees and 45.9 degrees, respectively, took place.
2. Optical and Structural Properties of Composites Based on Poly(urethane) and TiO2 Nanowires
Authors: Stroe, M; Burlanescu, T; Paraschiv, M; Lorinczi, A; Matei, E; Ciobanu, R; Baibarac, M

Published: FEB 2023, MATERIALS, 16, 1742, DOI: 10.3390/ma16041742

This article's objective is the synthesis of new composites based on thermoplastic polyurethane (TPU) and TiO2 nanowires (NWs) as free-standing films, highlighting their structural and optical properties. The free-standing TPU-TiO2 NW films were prepared by a wet chemical method accompanied by a thermal treatment at 100 degrees C for 1 h, followed by air-drying for 2 h. X-ray diffraction (XRD) studies indicated that the starting commercial TiO2 NW sample contains TiO2 tetragonal anatase (A), cubic Ti0.91O (C), and orthorhombic Ti2O3 (OR), as well as monoclinic H2Ti3O7 (M). In the presence of TPU, an increase in the ratio between the intensities of the diffraction peaks at 43.4 degrees and 48 degrees belonging to the C and A phases of titanium dioxide, respectively, is reported. The increase in the intensity of the peak at 43.4 degrees is explained to be a consequence of the interaction of TiO2 NWs with PTU, which occurs when the formation of suboxides takes place. The variation in the ratio of the absorbance of the IR bands peaked at 765-771 cm(-1) and 3304-3315 cm(-1) from 4.68 to 4.21 and 3.83 for TPU and the TPU-TiO2 NW composites, respectively, with TiO2 NW concentration equal to 2 wt.% and 17 wt.%, indicated a decrease in the higher-order aggregates of TPU with a simultaneous increase in the hydrogen bonds established between the amide groups of TPU and the oxygen atoms of TiO2 NWs. The decrease in the ratio of the intensity of the Raman lines peaked at 658 cm(-1) and 635 cm(-1), which were assigned to the vibrational modes E-g in TiO2 A and E-g in H2Ti3O7 (ITiO2-A/I-H2Ti3O7), respectively, from 3.45 in TiO2 NWs to 0.94-0.96 in the TPU-TiO2 NW composites, which indicates that the adsorption of TPU onto TiO2 NWs involves an exchange reaction of TPU in the presence of TiO2 NWs, followed by the formation of new hydrogen bonds between the -NH- of the amide group and the oxygen atoms of TixO2x-mn, Ti2O3, and Ti0.91O. Photoluminescence (PL) studies highlighted a gradual decrease in the intensity of the TPU emission band, which is situated in the spectral range 380-650 nm, in the presence of TiO2 NW. After increasing the TiO2 NW concentration in the TPU-TiO2 NW composite mass from 0 wt.% to 2 wt.% and 17 wt.%, respectively, a change in the binding angle of the TPU onto the TiO2 NW surface from 12.6 degrees to 32 degrees and 45.9 degrees, respectively, took place.
3. Nanohybrid Composites Based on TiO2 and Single-Walled Carbon Nanohorns as Promising Catalysts for Photodegradation of Amoxicillin
Authors: Cercel, R; Androne, A; Florica, CS; Lorinczi, A; Serbschi, C; Baibarac, M

Published: OCT 2023, MOLECULES, 28, 6958, DOI: 10.3390/molecules28196958

In this work, applications of nanohybrid composites based on titanium dioxide (TiO2) with anatase crystallin phase and single-walled carbon nanohorns (SWCNHs) as promising catalysts for the photodegradation of amoxicillin (AMOX) are reported. In this order, TiO2/SWCNH composites were prepared by the solid-state interaction of the two chemical compounds. The increase in the SWCNH concentration in the TiO2/SWCNH composite mass, from 1 wt.% to 5 wt.% and 10 wt.% induces (i) a change in the relative intensity ratio of the Raman lines located at 145 and 1595 cm(-1), which are attributed to the E-g(1) vibrational mode of TiO2 and the graphitic structure of SWCNHs; and (ii) a gradual increase in the IR band absorbance at 1735 cm(-1) because of the formation of new carboxylic groups on the SWCNHs' surface. The best photocatalytic properties were obtained for the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.%, when approx. 92.4% of AMOX removal was achieved after 90 min of UV irradiation. The TiO2/SWCNH composite is a more efficient catalyst in AMOX photodegradation than TiO2 as a consequence of the SWCNHs' presence, which acts as a capture agent for the photogenerated electrons of TiO2 hindering the electron-hole recombination. The high stability of the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.% is proved by the reusing of the catalyst in six photodegradation cycles of the 98.5 mu M AMOX solution, when the efficiency decreases from 92.4% up to 78%.
4. Capacitive Photodetector Thin-Film Cells of Cu-As2S3-Cu as Revealed by Dielectric Spectroscopy
Authors: Ganea, P; Socol, G; Zamfira, S; Cretu, N; Matei, E; Lorinczi, A

Published: FEB 2022, SENSORS, 22, 1143, DOI: 10.3390/s22031143

The As2S3-Cu interface was studied by dielectric spectroscopy measurements on Cu-As2S3-Cu thin film heterostructure samples to assess the charge carriers' contribution to the electrical properties of such an interface. Three-dimensional printed masks ensured good reproducibility during the PLD deposition of heterostructure samples. The samples were tested for electrical conductivity and AC photoconductivity by dielectric spectroscopy measurements. DC bias voltages and light were applied to the samples. The electrical capacity of the thin film heterostructure can be modified electrically and optically. We observed long-term photoconductivity with a time dependency that was not exponential, and a quick change of the electrical capacity, indicating the potential of the heterostructure cells as photodetector candidates.
5. Design of highly transparent conductive optical coatings optimized for oblique angle light incidence
Authors: Nedelcu, N; Chiroiu, V; Munteanu, L; Girip, I; Rugina, C; Lorinczi, A; Matei, E; Sobetkii, A

Published: AUG 2021, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 127, DOI: 10.1007/s00339-021-04726-z

In this paper, three deposition techniques are combined to create a window material with high average transmission at oblique angles of incidence. Spectrophotometry and ellipsometry measurements, respectively, yield the optical constants n and k. In contrast with other analyses on the subject, a high average transmission, higher than 91% in the 450-900 nm spectral range, is obtained at incident angles of 20-25 degrees. The refractive index and extinction coefficient are determined by the Swanepoel method. The iterative optimization performed using the OpenFilters software leads to an antireflection (AR) multilayer with low reflection and high transmission. The surface quality of the films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which revealed compact, continuous, and smooth films.
6. Optical, Structural, and Dielectric Properties of Composites Based on Thermoplastic Polymers of the Polyolefin and Polyurethane Type and BaTiO3 Nanoparticles
Authors: Baibarac, M; Nila, A; Smaranda, I; Stroe, M; Stingescu, L; Cristea, M; Cercel, RC; Lorinczi, A; Ganea, P; Mercioniu, I; Ciobanu, R; Schreiner, C; Garcia, RG; Bartha, C

Published: FEB 2021, MATERIALS, 14, DOI: 10.3390/ma14040753

In this work, new films containing composite materials based on blends of thermoplastic polymers of the polyurethane (TPU) and polyolefin (TPO) type, in the absence and presence of BaTiO3 nanoparticles (NPs) with the size smaller 100 nm, were prepared. The vibrational properties of the free films depending on the weight ratio of the two thermoplastic polymers were studied. Our results demonstrate that these films are optically active, with strong, broad, and adjustable photoluminescence by varying the amount of TPU. The crystalline structure of BaTiO3 and the influence of thermoplastic polymers on the crystallization process of these inorganic NPs were determined by X-ray diffraction (XRD) studies. The vibrational changes induced in the thermoplastic polymer's matrix of the BaTiO3 NPs were showcased by Raman scattering and FTIR spectroscopy. The incorporation of BaTiO3 NPs in the matrix of thermoplastic elastomers revealed the shift dependence of the photoluminescence (PL) band depending on the BaTiO3 NP concentration, which was capable of covering a wide visible spectral range. The dependencies of the dielectric relaxation phenomena with the weight of BaTiO3 NPs in thermoplastic polymers blends were also demonstrated.
7. Photoluminescence as a Complementary Tool for UV-VIS Spectroscopy to Highlight the Photodegradation of Drugs: A Case Study on Melatonin
Authors: Daescu, M; Toulbe, N; Baibarac, M; Mogos, A; Lorinczi, A; Logofatu, C

Published: SEP 2020, MOLECULES, 25, DOI: 10.3390/molecules25173820

In this work, a complementary ultraviolet-visible (UV-VIS) spectroscopy and photoluminescence (PL) study on melatonin (MEL) hydrolysis in the presence of alkaline aqueous solutions and the photodegradation of MEL is reported. The UV-VIS spectrum of MEL is characterized by an absorption band with a peak at 278 nm. This peak shifts to 272 nm simultaneously with an increase in the band absorbance at 329 nm in the presence of an NaOH solution. The isosbestic point localized at 308 nm indicates the generation of some chemical compounds in addition to MEL and NaOH. The MEL PL spectrum is characterized by a band at 365 nm. There is a gradual decrease in the MEL PL intensity as the alkaline solution concentration added at the drug solution is increased. In the case of the MEL samples interacting with an alkaline solution, a new photoluminescence excitation (PLE) band at 335 nm appears when the exposure time to UV light reaches 310 min. A down-shift in the MEL PLE band, from 321 to 311 nm, as a consequence of the presence of excipients, is also shown. These changes are explained in reference to the MEL hydrolytic products.
8. Chalcogenide Science in Romania
Authors: Lorinczi, A; Badica, P; Botila, T; Ciurea, M; Velea, A; Popescu, A; Socol, G; Antohe, S; Nedelcu, N; Sobetkii, A

Published: NOV 2020, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 257, DOI: 10.1002/pssb.202000284

Almost six decades ago, in Romania a small group of physicists begun to study chalcogenide compositions, motivated primarily by the desire to understand the phase-change phenomenon in these materials, discovered recently, at that time, by Stanford R. Ovshinsky. It took not too long for them to realize the challenges these materials set to the research. With newcomers to the field, the research was broadened. In some cases just for basic research, to model, and to understand the chalcogenide materials, whereas in other cases, the applicative potential was revealed and used. Herein, the evolution of the field of these somewhat exotic materials is followed, listing the main contributions done in Romania, both in basic and applied research.
9. SnSe2-Zn-Porphyrin Nanocomposite Thin Films for Threshold Methane Concentration Detection at Room Temperature
Authors: Lorinczi, A; Fagadar-Cosma, E; Socol, G; Mihailescu, A; Matei, E; Sava, F; Stefan, M

Published: DEC 2020, CHEMOSENSORS, 8, DOI: 10.3390/chemosensors8040134

Nanocomposite thin films, sensitive to methane at the room temperature (25-30 degrees C), have been prepared, starting from SnSe2 powder and Zn(II)-5,10,15,20-tetrakis-(4-aminophenyl)- -porphyrin (ZnTAPP) powder, that were fully characterized by XRD, UV-VIS, FT-IR, Nuclear Magnetic Resonance (H-1-NMR and C-13-NMR), Atomic Force Microscopy (AFM), SEM and Electron Paramagnetic Resonance (EPR) techniques. Film deposition was made by drop casting from a suitable solvent for the two starting materials, after mixing them in an ultrasonic bath. The thickness of these films were estimated from SEM images, and found to be around 1.3 mu m. These thin films proved to be sensitive to a threshold methane (CH4) concentration as low as 1000 ppm, at a room temperature of about 25 degrees C, without the need for heating the sensing element. The nanocomposite material has a prompt and reproducible response to methane in the case of air, with 50% relative humidity (RH) as well. A comparison of the methane sensing performances of our new nanocomposite film with that of other recently reported methane sensitive materials is provided. It is suitable for signaling gas presence before reaching the critical lower explosion limit concentration of methane at 50,000 ppm.
10. In Memoriam Mihai Popescu (26 July 1942, Floresti-Soroca-14 July 2019, Bucharest)
Authors: Lorinczi, A

Published: NOV 2020, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 257, DOI: 10.1002/pssb.202000142

11. Thermal stability of phase change GaSb\GeTe, SnSe\GeTe and GaSb\SnSe double stacked films revealed by X-ray reflectometry and X-ray diffraction
Authors: Velea, A; Sava, F; Socol, G; Vlaicu, AM; Mihai, C; Lorinczi, A; Simandan, ID

Published: JUL 15 2018, JOURNAL OF NON-CRYSTALLINE SOLIDS, 492, 17, DOI: 10.1016/j.jnoncrysol.2018.02.033

We report a study related to the influence of heat treatment (up to 300 degrees C) on the structure of GaSb \GeTe, SnSe\GeTe and GaSb\SnSe stacked phase change memory films and of their counterparts with Hf thin film barrier between the layers. Samples were prepared by pulsed laser deposition and investigated by X-ray reflectometry and X-ray diffraction in order to evaluate the inter-films diffusion and the temperature threshold where this process is initiated. The thickness and mass density variations of films after each heat treatment, as well as the efficiency of hafnium barrier film, to eliminate potential atomic diffusion issues, were investigated.
12. Investigation of atmospheric corrosion by photon energy dependent luminescence and Raman spectroscopy in aged and freshly fractured g-,c-As2S3 with photosensitive realgar inclusions
Authors: Mitsa, V; Holomb, R; Marton, A; Veres, M; Toth, S; Himics, L; Lorinczi, A; Popescu, M

Published: DEC 1 2016, JOURNAL OF NON-CRYSTALLINE SOLIDS, 453, 27, DOI: 10.1016/j.jnoncrysol.2016.09.022

We have studied the light emission properties of aged glassy (g-) and crystalline (c-) As2S3 and freshly fractured glassy As2S3 with photosensitive realgar inclusions in the 1.5-4.5 eV spectral range and applying different excitation photon energies. Additionally, Raman scattering measurements were performed on g-As40S60 to investigate structural changes caused by corrosion of the glass in air. Major features in the luminescence spectra were observed at 1.65,1.87, 2.04, 226, 2.80 and 325 eV photon energies. The 1.65 eV band in photoluminescence spectra of g-As2S3 was identified to be related to the As side by comparison of the photoluminescence spectrum with literature data for As4S4 realgar crystal. A newly observed band at 1.87 eV was assigned to the As side in pararealgar occurring due to the light induced transformation from realgar to pararealgar phase. An oxidation process was found to take place during the aging and photo-aging accompanied with formation of As oxides, indicated by the emission bands at 2.04 and 226 eV. A rapid photo-oxidation process was observed in freshly fractured surfaces at room temperature which was connected with the light stimulated realgar-pararealgar transformation. (C) 2016 Elsevier B.V. All rights reserved.
13. Photoexpansion in amorphous As2S3: A new explanation
Authors: Lorinczi, A; Sava, F; Simandan, ID; Velea, A; Popescu, M

Published: SEP 1 2016, JOURNAL OF NON-CRYSTALLINE SOLIDS, 447, 125, DOI: 10.1016/j.jnoncrysol.2016.06.010

Thin amorphous As2S3 films show a giant photoexpansion of similar to 5% upon femtosecond laser illumination and this expansion remains after switching off the laser beam. To understand the structural modifications which occur during the photoexpansion process we assumed a molecular cluster structure of the amorphous As2S3. The focused femtosecond laser beam induces electrical charge redistribution on the sulfur atoms of each cluster, which increases the electrical repulsion between sulfur atoms, and thus induces an expansion of the clusters, by network reconfiguration, without breaking the bonds. An increase of the van der Waals distance between molecular clusters also takes place. (C) 2016 Elsevier B.V. All rights reserved.
14. Amorphous thin films in the gallium-chalcogen system
Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Galca, AC; Matei, E; Socol, G; Gherendi, F; Savastru, D; Miclos, S

Published: JUN 2016, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 253, 1037, DOI: 10.1002/pssb.201552551

Thin amorphous films based on gallium-chalcogen (Ga-Ch), namely Ga2S3, Ga2Se3, Ga2Te3, and GaTe have been prepared by pulsed laser deposition (PLD). The films were characterized by X-ray diffraction, extended X-ray absorption fine structure (EXAFS), energy-dispersive X-ray spectroscopy (EDX), optical transmission spectroscopy, ellipsometry, and electrical measurements. Structural measurements showed that Ga is threefold coordinated, except the Te-based alloys were, it seems, only twofold coordinated, while the chalcogen is usually twofold coordinated. In all the compositions, layered and chain-like structures are assumed. The bandgaps range between 1.09 eV for Ga2Te3 and 2.21 eV for Ga2Se3. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
15. Thin films of amorphous Ga2S3 and rare-earth sulphides
Authors: Popescu, M; Lorinczi, A; Sava, F; Velea, A; Simandan, ID; Badica, P; Burdusel, M; Galca, AC; Socol, G; Jipa, F; Zamfirescu, M

Published: MAR 1 2015, MATERIALS LETTERS, 142, 231, DOI: 10.1016/j.matlet.2014.12.028

The aim of this research is to prepare amorphous thin films of undoped gallium sulphide and doped with rare-earth sulphides, of rare-earth sulphides and to investigate their physical properties. We have prepared thin amorphous films of Ga2S3, EuS, Er2S3, Gd2S3, and Ga2S3 doped with rare-earth sulphides (Ga2S3:EuS, Ga2S3:Er2S3, Ga2S3:Gd2S3) by Pulsed laser Deposition (PLD). The corresponding targets for preparation of amorphous thin films were obtained by Spark Plasma Sintering (SPS) from commercially available powders of binary sulphides. The structural results for the undoped and doped Ga2S3 thin films indicate a packing of disordered layers similar to that of amorphous As2S3. Femtosecond laser irradiation of the Ga2S3 thin films shows a photoexpansion effect at low laser power (85-100 mW) and an ablation effect at higher laser power (above 105 mW). The threshold between low power and high power pulses is situated at higher value for Ga2S3 (100 mW) in comparison with the case of As2S3 thin films (20 mW). (C) 2014 Elsevier B.V. All rights reserved.
16. Ceramics and amorphous thin films based on gallium sulphide doped by rare-earth sulphides
Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Badica, P; Burdusel, M; Galca, AC; Matei, E; Preda, N; Secu, M; Socol, G; Jipa, F; Zamfirescu, M; Balan, A

Published: APR 2015, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 30, DOI: 10.1088/0268-1242/30/4/044001

Bulk ceramics of Ga2S3 and rare-earth sulfides (EuS, Gd2S3, Er2S3) as well as combinations thereof have been prepared by spark plasma sintering (SPS). The disk-shaped ceramics were used as targets for pulsed laser deposition (PLD) experiments to obtain amorphous thin films. The properties of these new bulks and amorphous thin films have been investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), optical transmission spectroscopy, and atomic force microscopy (AFM). In order to test the photoexpansion effect in Gd2S3 and the possibility to create planar arrays of microlenses, the film was irradiated with femtosecond laser pulses at different powers. For low laser power pulses (up to 100mW power per pulse) a photoexpansion effect was observed, which leads to formation of hillocks with a height of 40-50 nm. EuS doped Gd2S3 thin film shows luminescence properties, which recommend them for optoelectronic applications.
17. Chalcogenide systems at the border of the glass-formation domain: A key for understanding the memory-switching phenomena
Authors: Popescu, M; Velea, A; Sava, F; Lorinczi, A

Published: JUL 2014, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 251, 1339, DOI: 10.1002/pssb.201350104

The compositions in the ternary chalcogenide systems from the demarcation region between the glass-formation domain (GFD) and the partially or fully crystalline formation domain seem to exhibit outstanding properties. We have shown in this paper that the compositions with the best memory-switching properties are situated at the border of the GFD in many systems. One can use this correlation to find new phase-change materials with better switching properties or to discover GFDs that were not observed yet. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
18. Simulation of the structure of GeAs4Te7 chalcogenide materials during memory switching
Authors: Popescu, M; Sava, F; Velea, A; Lorinczi, A; Simandan, ID

Published: JUL 2014, CANADIAN JOURNAL OF PHYSICS, 92, 680, DOI: 10.1139/cjp-2013-0561

The complex chalcogenides with excellent memory switching properties are mainly situated close to the border of glass formation domain. The simulation of the structural changes occurring during the memory switching process of a ternary chalcogenide composition has been carried out. The transition of a high resistivity GeAs4Te7 amorphous cluster with 120 atoms to a low resistivity crystalline cluster was analyzed. The coordination of atoms changes from that corresponding to 8-N coordination rule (two for tellurium, three for arsenic, and four for germanium) in the amorphous phase to six (the same for all atoms) in metastable crystalline phase. Because of spatial constraints exercised by the amorphous matrix, the amorphous cluster cannot expand. In these circumstances Te atoms seem to be over-coordinated (up to sixfold-coordinated). During the switching process, the atoms are moving on distances up to 4.0 angstrom. The average displacement is of 2.36 angstrom.
19. EFFECT OF THERMAL ANNEALING ON THE STRUCTURAL AND OPTICAL PROPERTIES OF Ag/As2S3 MULTILAYERS
Authors: Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Preda, N; Socol, G; Mihailescu, IN; Zamfira, CS; Cretu, NC; Popescu, M

Published: NOV 2013, CHALCOGENIDE LETTERS, 10, 471, DOI:

A complex structure of four double layers of Ag / As2S3 has been deposited by Pulsed Laser Deposition method on a glass substrate. The effects of thermal annealing on the structural and optical properties were investigated. An effect of layer mixing has been evidenced.
20. Effect of broadband light on Ag/As2S3 multilayers
Authors: Sava, F; Velea, A; Popescu, M; Lorinczi, A; Simandan, ID; Vlaicu, AM; Socol, G; Mihailescu, IN; Stefan, N

Published: OCT 1 2013, JOURNAL OF NON-CRYSTALLINE SOLIDS, 377, 161, DOI: 10.1016/j.jnoncrysol.2013.02.023

A sandwich structure of four double layers of Ag (5 nm)/As2S3 (82.7 nm) has been prepared by Pulsed Laser Deposition (PLD) method. The effect of broadband light on the multilayer structure has been investigated. The X-ray reflectivity (XRR) patterns after different irradiation times have been measured. Although the fully intermixing of Ag and As2S3 layers should be expected during irradiation with visible light, however even after 5 h of irradiation the intermixing is not completed. The characteristic features of XRR diagrams for long irradiation times have been interpreted by scattering of X-ray radiation on clusters of Ag or Ag-As2S3. (c) 2013 Elsevier B.V. All rights reserved.
21. COMPLEX LANGMUIR-BLODGETT FILMS BASED ON BARIUM STEARATE MULTILAYERS WITH CARBON NANOTUBES AND As2S3 NANOPARTICLES
Authors: Simandan, ID; Sava, F; Popescu, M; Lorinczi, A

Published: NOV 2013, CHALCOGENIDE LETTERS, 10, 484, DOI:

We have prepared complex multilayer films based on Barium stearate. The multilayer samples have been deposited by the Langmuir-Blodgett technique. The complex multilayers were also deposited on body sensor. The sample was then subjected to the illumination with UV light. We observed changes in the resistivity of the multilayer during the illumination
22. Possible mechanism of Ag photodiffusion in a-As2S3 thin films
Authors: Sava, F; Popescu, M; Lorinczi, A; Velea, A

Published: MAY 2013, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 1003, DOI: 10.1002/pssb.201248517

Monitoring the silver photodiffusion in thin amorphous As2S3 film is addressed with a new experimental setup. A possible photo-diffusion mechanism of silver into the a-As2S3 thin film under green laser diode light (=532nm) irradiation is proposed. The proposed mechanism is based on a gradual filling of the structural voids existing in the network of the thin chalcogenide layer. This mechanism is supported by XRD measurements, optical absorption, and modeling data.
23. Disorder in order: silicon versus graphene
Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A

Published: MAY 2013, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 1010, DOI: 10.1002/pssb.201248516

The topological transition from order to disorder in crystalline silicon was investigated by a computer simulation procedure. The gradually introduction of topological WootenWinerWeaire defect states makes the crystal change in a more and more disordered assembly of atoms. The characterization of deformation energy around a single defect state is analyzed. The topological transition from graphene structure to an amorphous carbon layer, by introduction of a high number of StoneWales defect-type states was evidenced. The comparison of the disordered structure in tetrahedrally bonded semiconductors (silicon) and a two-dimensional network based on graphene structure was made.
24. LUMINESCENCE OF EUROPIUM IN ARSENIC SULPHIDE MATRIX
Authors: Popescu, M; Lorinczi, A; Velea, A; Simandan, ID; Sava, F; Pavelescu, G; Niciu, GH; Niciu, DO; Mihailescu, IN; Socol, G; Stefan, N

Published: NOV 2011, CHALCOGENIDE LETTERS, 8, 702, DOI:

Thin films of arsenic sulphide have been obtained by Pulsed Laser Deposition from bulk As(2)S(3). A very thin layer of Eu(2)O(3) was deposited by PLD from a different target in the next deposition process. After a heat treatment at 180 degrees C for 45 minutes in inert atmosphere a structural transformation of the amorphous As(2)S(3) to realgar (As(2)S(2)) occurred and the film develops a strong luminescence effect.
25. Optical properties of phase change memory Ge1Sb2Te4 glasses
Authors: Iovu, MS; Colomeico, EP; Benea, VG; Popescu, M; Lorinczi, A; Velea, A

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1486, DOI:

Phase change memory materials are promising for the next-generation of non-volatile flash memory that will serve in new mobile computing, entertainment and other handheld electronics. Among them are chalcogenide glasses Ge-Sb-Te (GST) which can exist in two separates structural states - amorphous and cristalline. Switching of the material from one to another state can be done by heating applying an electrical pulse or by exposure to intense laser beam. We report the changes of optical parameters of amorphous Ge1Sb2Te4 films under heat treatment and light exposure.
26. Nanocarbon embedded chalcogenides. Onion-like model
Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1453, DOI:

We modeled the equilibrium structure, at 0 K temperature, of some spherical As(2)S(3) molecules with only 12 rings of ten member (alternating As and S atoms) and 20 triangular faces: As(60)S(90) (like C(60)), As(140)S(210) (like C(140)), As(320)S(480) (like C(320)), grown on carbon fullerene and As(20)S(30) (like C(20)). We used a Monte-Carlo relaxation procedure in the frame of valence force fields theory. The onion-like configurations of the arsenic sulphide was demonstrated as possible. The deposited films of As(2)S(3) seen in the cross-section prove the presence of onion-like configurations even in pure As(2)S(3) material.
27. Silver doped As2S3 chalcogenide films: A diffusion study
Authors: Lorinczi, A; Popescu, M; Sava, F; Velea, A; Simandan, ID

Published: 2011, PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 9, 8, 2620, DOI: 10.1002/pssc.201084096

Photo-diffusion of silver across an As2S3 thin film layer is studied, as continuing some earlier work about surface morphology modifications in double-layer structures of Ag and As2S3, and some qualitative preliminary results on lateral Ag diffusion in As2S3 thin films. An estimation of the Ag film's dissolution rate and the diffusion front's advancement rate in As,S3 is given based on crosssection measurements. In order to understand better the diffusion mechanism of Ag in As2S3, a structural model of the As2S3 matrix is used to estimate the amount of silver which might be hosted by an As2S3 layer in terms of molar ratio, and an interaction mechanism of the Ag with the chalcogenide matrix is proposed. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
28. NON-LINEAR BEHAVIOUR IN SILVER - ARSENIC SULFIDE SYSTEM
Authors: Popescu, M; Lorinczi, A; Gherendi, F; Nistor, M; Velea, A; Simandan, ID; Sava, F

Published: NOV-DEC 2011, JOURNAL OF OVONIC RESEARCH, 7, 133, DOI:

Non-linear phenomena have been observed in the Ag(paint)-As2S3 system. This behaviour is useful in rectifier devices and in dynamical switching devices based on chalcogenides.
29. LUMINESCENCE OF ARSENIC SULPHIDE DOTS DOPED WITH EUROPIUM, PREPARED BY THERMAL EVAPORATION AND PULSED LASER DEPOSITION METHODS
Authors: Popescu, M; Velea, A; Simandan, ID; Sava, F; Lorinczi, A; Ghervase, L; Pavelescu, G; Mihailescu, IN; Socol, G; Georgescu, S

Published: DEC 2011, CHALCOGENIDE LETTERS, 8, 724, DOI:

Networks of dots made of As2S3 chalcogenide has been obtained by Vacuum Evaporation and Pulsed Laser Deposition from bulk glassy As2S3 by the adapted method of SCEV (screen evaporation method). A very thin layer of Eu2O3 was deposited from a different target in the final deposition process. After a heat treatment at 180 degrees C for 90 minutes in nitrogen atmosphere a structural transformation of the amorphous As2S3 to realgar (AsS) occurred in the PLD deposited dots and the network of dots develops a luminescence effect. (Received November 25, 2011; accepted December 2, 2011)
30. DEPENDENCE OF OPTICAL RESPONSE ON pH OF A WATER-SOLUBLE Zn(II)-METALLOPORPHYRIN
Authors: Fagadar-Cosma, E; Creanga, I; Maranescu, B; Palade, A; Lorinczi, A; Fagadar-Cosma, G; Popescu, M

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 80, DOI:

Nowadays, porphyrin derivatives are extensively used as analytical reagents. This work put the basis for a rapid, simple and inexpensive method developed for pH determination. It was demonstrated the potential for a water soluble metalloporphyrin, 5,10,15,20-tetrakis(N-methyl-4-pyridyl) porphyrin-Zn(II) tetrachloride (Zn-TNMPyP) to be a potential optical pH sensor in the 5.5-10.5 domain. Monitoring of the variations in the absorption spectra of the Zn-TNMPyP, both regarding the Soret and the Q(0,1) band, generated by the exposure to different base concentrations allowed us to notice the linearity of the response at different pH values.
31. Influence of defects on the switching speed of Ge2Sb2Te5
Authors: Velea, A; Popescu, M; Lorinczi, A; Sava, F; Simandan, ID; Mihai, C

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1596, DOI:

Chalcogenide phase change materials are one of the major contenders for the new non-volatile memory applications. Here is reported that the switching speed of Ge2Sb2Te5 is strongly dependent on the percent of defects in the material. Using cellular automata simulations it was shown that the size of the percolation cluster is minimum, thus the switching speed is maximum, for a percent of around 25% defects in the material. This is a property of the Ge2Sb2Te5 that can be useful for new phase change materials and devices design with better switching properties.
32. TWO DIMENSIONAL PHOTONIC STRUCTURES BASED ON As-S CHALCOGENIDE GLASS
Authors: Popescu, M; Velea, A; Lorinczi, A; Zamfirescu, M; Jipa, F; Miclos, S; Popescu, A; Ciobanu, M; Savastru, D

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1105, DOI:

Two-dimensional photonic structure has been imprinted on the surface of arsenic sulphide glass using the pulses of a femtosecond laser. Due to the interaction of the laser beam with the glass, the laser traces were obtained as hillocks of around 150-200 nanometer in height, or holes of depth around 100-300 nm, without the need for a later etching stage as in the usual practice. The calculation of the band structure shows a photonic band gap between 0.9 and 1.0 c/a. By varying the energy of the laser pulse we have the possibility to choose between the two possibilities to produce a photonic structure made-up of hillocks or a photonic structure consisting of holes. The value of the threshold pulse power which controls the resulting surface morphology and the obtained photonic structure has found to be around 15 mW. The surface topography of the structures obtained has been investigated by atomic force microscopy (AFM).
33. SYNTHESIS AND LUMINESCENCE PROPERTIES OF Nd-DOPED CHALCOGENIDE GLASS (Ge5As2S13) (NdCl3) x (x=0.3%, 0.5%)
Authors: Georgescu, S; Voiculescu, AM; Salamu, S; Niciu, H; Niciu, D; Popescu, M; Lorinczi, A; Velea, A; Simandan, ID

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 624, DOI:

The synthesis of the chalcogenide glass (Ge5As2S13) doped by Nd3+ has been carried out. The bulk glass develops a small amount of Nd2O3 and As2O3 crystallites besides some amount of (NdCl3)*6H(2)O crystalline phase initially introduced during synthesis. The optical absorption spectra demonstrate the presence of the Nd3+ both in the amorphous phase and in crystalline combinations. The formation of Nd2O3 crystallites was explained by the reaction of water with neodymium chloride. The presence of As2O3 is due to the oxidation of As from the glass during preparation.
34. STRUCTURAL DETAILS OF THE Ag-As2S3 INTERFACE OBTAINED BY VACUUM THERMAL EVAPORATION FOLLOWED BY GREEN LASER IRRADIATION
Authors: Lorinczi, A; Velea, A; Matei, E; Simandan, ID; Popescu, M

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 612, DOI:

As2S3 on Ag heterostructures deposited onto microscope glass substrates have been prepared. The quality of the hetero-structures has been investigated by careful analysis of the scanning electron microscope pictures taken on the native cross-sections, produced after the vacuum deposition sequence and various green laser irradiation times. The As2S3 layer is not uniformly grown, but reveals a columnar-like structure and multi-scale aggregation.
35. PREPARATION AND PROPERTIES OF BARIUM STEARATE MULTILAYERS WITH CARBON NANOTUBES, MANGANESE PORPHYRIN AND SILVER NITRATE
Authors: Simandan, ID; Popescu, M; Lorinczi, A; Velea, A; Fagadar-Cosma, E

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1033, DOI:

Barium stearate multilayer samples have been deposited by the Langmuir-Blodgett technique. Carbon nanotubes have been added in the deposition solution. The structural properties have been studied. The effect of the doped multilayers has been tested against the solution of ammonium nitrate in water. The effect of (5,10,15,20-tetraphenyl)-porphinato manganese (III) chloride, (MnTPP)Cl, on the multilayer sample has been tested. The change of resistivity of the multilayer samples modified by manganese porphyrin, as a function of the ultraviolet radiation has been discovered and investigated. The increase of the resistance during irradiation is a reversible process, although a slow one. This effect could give a basis for applications in UV sensors and switches. Finally, a photo-resistive effect (induced by UV light) has been discovered in Barium stearate layers doped by silver nitrate.
36. Langmuir and Langmuir-Blodgett films based on stearic acid, barium stearate and carbon nanotubes
Authors: Simandan, ID; Sava, F; Velea, A; Lorinczi, A; Popescu, M

Published: AUG 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1181, DOI:

Langmuir films and Langmuir-Blodgett multilayers based on fatty acid (stearic acid, barium stearate) mixed with carbon nanotubes have been prepared and investigated by isothermal compression (for Langmuir films) and X-ray diffraction (for Langmuir-Blodgett multilayers). An irreversible modification has been observed in the case of Langmuir films doped by carbon nanotubes, due to reordering of the nanotubes in the film matrix.
37. Structure and Mossbauer measurements on SnSe2 bulk and thin films
Authors: Bibicu, I; Lorinczi, A; Velea, A; Sava, F; Popescu, M

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1571, DOI:

Thin films samples of SnSe2 deposited by PLD and PED have been prepared and studied by XRD and Mossbauer spectroscopy. The films are crystalline with a major phase of SnSe2 and minor phase of amorphous SnSe2. An oxidation process lead to the appearance of a thin layer of SnO2 on the surface of the PLD samples.
38. MOULDING PROCEDURE FOR THE PREPARATION OF INFRARED GLASSY MICROLENSES AND PRISMS BASED ON ARSENIC SULPHIDE CHALCOGENIDE GLASS
Authors: Niciu, H; Popescu, M; Velea, A; Lorinczi, A; Manea, A; Niciu, D; Lazarescu, M

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 629, DOI:

A new procedure for the production of infrared lenses and prisms based on As(2)S(3) chalcogeniude glass has been devised. Infrared components are obtained with the size in the range 100-1500 micrometers. The procedure allows for getting various curvature radii of the micrometer lenses, ranging from planno-convex to spherical ones.
39. Mossbauer measurements on SnSe2
Authors: Bibicu, I; Lorinczi, A; Popescu, M

Published: 2010, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS, AND NANOTECHNOLOGIES V, 7821, DOI: 10.1117/12.881773

Tin chalcogenides SnX2 and SnX, where X = S, Se and Te present a particularly interest for their electronic properties and applications in gas sensors. The state of tin in these materials is important for understanding of the sensing effect and improvement of the sensor performances. Mossbauer spectroscopy is a widely used technique for the analysis of the local electronic structure or chemical bonding in solids. In this paper we applied Mossbauer technique for the investigation of bulk and thin films of SnSe2 chalcogenide. The films of SnSe2 chalcogenide were obtained by the methods: PLD ("Pulsed laser deposition") and PED ("Pulsed electron deposition"). Mossbauer measurements were performed by transmission (TMS), respectively conversion electron spectroscopy (CEMS). By CEMS spectroscopy surfaces, coatings and thin films containing Sn can be studied on substrates and to various depths up to 1000 nanometers.
40. Structure and properties of silver doped SnSe2 and Ge2Sb2Te5 thin films prepared by pulsed laser deposition
Authors: Popescu, M; Velea, A; Sava, F; Lorinczi, A; Tomescu, A; Simion, C; Matei, E; Socol, G; Mihailescu, IN; Andonie, A; Stamatin, I

Published: MAR 2010, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 207, 520, DOI: 10.1002/pssa.200982900

Amorphous thin films of SnSe2 and Ge2Sb2Te5 doped by different amount of silver (0.1, 0.2, 0.5 and 1 Ag atoms per formula unit) have been prepared by pulsed laser deposition (PLD) starting from solid polycrystalline targets. The films were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The good gas sensing properties for CO, as well as the sensitivity for CH4 and NO of the Ag; doped SnSe2 films have been demonstrated in the composition SnSe2Ag0.2. The structural effect of silver introduced in Ge2Sb2Te5 matrix has been investigated. The freshly deposited thin films doped by various amount of Ag develop three phases: an amorphous one, and two crystalline phases consisting of a major fcc cubic phase of AgSbTe2 and a minor cubic phase of composition Ag2Te. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
41. BIOGENIC PRODUCTION OF NANOPARTICLES
Authors: Popescu, M; Velea, A; Lorinczi, A

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1040, DOI:

Nanoparticles of interest in nanotechnology (design of nanodevices) and medicine (controlled-release of drugs) can be produced both by anorganic and organic synthesis. The biogenetic production is now of high interest due to simplicity of the procedures and their versatility. Several species of bacteria and plants are able to synthesize nanoparticles or to help in the process of their production. The paper gives an overview on the biogenetic production of nanomaterials.
42. Mossbauer measurements on SnSe(2)
Authors: Bibicu, I; Lorinczi, A; Popescu, M

Published: 2010, , DOI: 10.1117/12.881773

Tin chalcogenides SnX(2) and SnX, where X = S, Se and Te present a particularly interest for their electronic properties and applications in gas sensors. The state of tin in these materials is important for understanding of the sensing effect and improvement of the sensor performances. Mossbauer spectroscopy is a widely used technique for the analysis of the local electronic structure or chemical bonding in solids. In this paper we applied Mossbauer technique for the investigation of bulk and thin films of SnSe(2) chalcogenide. The films of SnSe2 chalcogenide were obtained by the methods: PLD ("Pulsed laser deposition") and PED ("Pulsed electron deposition"). Mossbauer measurements were performed by transmission (TMS), respectively conversion electron spectroscopy (CEMS). By CEMS spectroscopy surfaces, coatings and thin films containing Sn can be studied on substrates and to various depths up to 1000 nanometers.
43. Direct laser writing of two-dimensional photonic structures in amorphous As2S3 thin films
Authors: Popescu, A; Miclos, S; Savastru, D; Savastru, R; Ciobanu, M; Popescu, M; Lorinczi, A; Sava, F; Velea, A; Jipa, F; Zamfirescu, M

Published: NOV 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1880, DOI:

A method for building photonic structures in As2S3 amorphous chalcogenide films has been developed. 2-D photonic configurations characterized by a regular assembly of rods (triangular lattice) or gratings with traces of micrometer period have been obtained. A femto-second laser has been used in photonic crystal registration. The simulation performed on these photonic configuration shows that the obtained chalcogenide structures could be efficient for operation in the infrared range around several micrometers wavelength.
44. Crystalline-amorphous and amorphous-amorphous transitions in phase-change materials
Authors: Popescu, M; Sava, F; Velea, A; Lorinczi, A

Published: OCT 1 2009, JOURNAL OF NON-CRYSTALLINE SOLIDS, 355, 1823, DOI: 10.1016/j.jnoncrysol.2009.04.053

The transition from the crystalline state to amorphous state and back has been studied in the particular case of the GeSb2Te4 phase-change material by a computer simulation procedure. Modelling at the nanoscale indicates specific structural characteristics, especially the multiplicity of the amorphous phase as opposite to the uniqueness of the crystalline phase. in the particular case of the Si(12)Ge(10)AS(30)Te(48) switching glass two types of ordering have been pointed out and characterized. (C) 2009 Elsevier B.V. All rights reserved.
45. Silver/amorphous As2S3 heterostructure
Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Leonovici, M; Zamfira, S

Published: NOV 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1594, DOI:

The heterostructure Ag/As2S3 was deposited on glass substrate in two configurations: Ag/As2S3/glass and As2S3/Ag/glass. The effect of light emitted by a halogen lamp has been investigated by optical microscopy and X-ray diffraction. Particular morphological and structural aspects were revealed. Lateral diffusion rate of Ag has been determined.
46. Fabrication of submicrometer periodic structures using interference lithography and two-layer chalcogenide photoresist
Authors: Indutnyi, IZ; Popescu, M; Lorinczi, A; Sava, F; Min'ko, VI; Shepeliavyi, PE; Dan'ko, VA

Published: DEC 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1971, DOI:

Technological process of interference lithography using two-layer chalcogenide photoresist were investigated. Top As(40)S(30)Se(30) layer is photoresist with a high selectivity and can be used for recording of interference pattern and formation of first lithographic mask. Second, more thick As(4)Ge(30)S(66) layer, almost is not sensitive to light, but dissolves in weak (0.05%) water solution of KOH. That, optimizing the etchant solutions for both layers, exposure and time of etching it is possible to carry out the technological process of formation of the lithographic mask with high modulation and with the groove form close to rectangular. This technology has been used for the fabrication of one- and two-dimensional periodic structures. Using two layer As(40)S(30)Se(30)-As(4)Ge(30)S(66) photoresist, we have fabricated the diffraction gratings and two-dimensional periodic structures with elements of submicron size. Relief parameters and diffractions properties of the obtained structures and their dependence on etching time are studied.
47. Modelling of dissolution kinetics of thin amorphous chalcogenide films
Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Vlcek, M; Jain, H

Published: 2009, PHILOSOPHICAL MAGAZINE LETTERS, 89, 376, DOI: 10.1080/09500830902960117

A theoretical relationship for the dissolution kinetics of thin chalcogenide films is proposed. The influence of light irradiation on the film dissolution is taken into account. The theoretical curves are in good agreement with the experimental dissolution results obtained for As2S3 thin amorphous films.
48. Matrix-assisted photo-amorphization effect in As40S30Se30 films with silver
Authors: Popescu, M; Petkov, K; Sava, F; Taseeva, J; Lorinczi, A; Velea, A

Published: DEC 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 2003, DOI:

Matrix assisted photo-amorphization effect has been observed in thin chalcogenide films of composition As40S30Se30 deposited by thermal evaporation on silicon wafer substrate covered by silver. The initial films contain Ag2S and Ag4SeS crystallites embedded in an amorphous matrix. Illumination by a cold light halogen lamp induces the disappearance of the crystalline fraction and leads to significant changes in the diffraction pattern of the amorphous films.
49. COMMUTON - A NEW CONCEPT IN SWITCHING MATERIALS
Authors: Popescu, M; Velea, A; Lorinczi, A; Sava, F

Published: MAR-APR 2009, JOURNAL OF OVONIC RESEARCH, 5, 34, DOI:

A switching unit can be defined as the smallest unit that preserves the property of switching in memory materials. Atomic switching unit is discussed, molecular switching units are described and supramolecular units in phase change materials are evidenced and discussed. The "commuton", as basic switching unit, could give more insight into the particular properties of the switching phenomena in various solid materials.
50. A new model for the structure of chalcogenide glasses: The closed cluster model
Authors: Popescu, M; Sava, F; Lorinczi, A

Published: OCT 1 2009, JOURNAL OF NON-CRYSTALLINE SOLIDS, 355, 1819, DOI: 10.1016/j.jnoncrysol.2009.05.066

A new model is proposed for the structure of low atomic coordination chalcogenide glasses. The closed clusters model is based on the various types of clusters, packed by van der Waals forces in a molecular-type packing. Arguments are given to support the new model, taken as example the typical chalcogenide glass As2S3. (C) 2009 Elsevier B.V. All rights reserved.
51. Chalcogenide photonic structures
Authors: Popescu, M; Savastru, D; Popescu, A; Miclos, S; Lorinczi, A; Sava, F; Velea, A; Baschir, L; Ciobanu, M; Matei, E; Socol, G; Mihailescu, IN; Niciu, H

Published: SEP 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 859, DOI:

Chalcogenide glasses can be tailored for getting special configurations with photonic crystal properties A review on the advances in chalcogenide glass photonics is given Several methods to prepare two-dimensional photonic As-S glass and three-dimensional packing have been developed, and the photonic structures have been characterized Numerical simulations have also been performed The chalcogenide photonic structures fabricated by micro-technological procedures are described and tuned to work in the far infrared region of the electromagnetic spectrum
52. Optical properties of pulsed-laser deposited ZnO thin films
Authors: Bazavan, R; Ion, L; Socol, G; Enculescu, I; Bazavan, D; Tazlaoanu, C; Lorinczi, A; Mihailescu, IN; Popescu, M; Antohe, S

Published: APR 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 428, DOI:

ZnO thin films were deposited by pulsed laser deposition (PLD) technique on optical glass substrate. Structural analysis by X-ray diffraction revealed a wurtzite phase ZnO, highly textured, with (002) planes perpendicular to the growth direction. They were optically characterized by absorption and transmission spectrometry. The wavelength dependence of the refractive index was extracted from transmission data by using a numerical fitting procedure.
53. Interference lithography using chalcogenide inorganic photoresist
Authors: Indutnyy, IZ; Popescu, M; Lorinczi, A; Sava, F; Min'ko, VI; Shepeliavyi, PE

Published: DEC 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3192, DOI:

There was investigated the application of inorganic photo-resist based on three-component chalcogenide films for fabrication of submicrometer periodic relief on silicon wafers using interference lithography. For this purpose. technological process of resistive two-layer chalcogenide-Cr mask formation on a silicon surface was developed, and silicon anisotropic etching was optimized, too. This technology has been used for the fabrication of diffraction gratings and two-dimensional periodic structures on Si (100) surface. The obtained relief patterns were used to form photonic structures by oblique deposition of silicon monoxide in vacuum.
54. The effects of thermal treatments on microwave dielectric properties of Ba(Zn1/3Ta2/3.)O-3 ceramics
Authors: Ioachim, A; Nedelcu, L; Andronescu, E; Jinga, S; Toacsan, MI; Banciu, MG; Lorinczi, A; Popescu, M

Published: JAN 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 212, DOI:

Ba(Zn1/3Ta2/3)O-3 (BZT) dielectric materials were prepared by solid state reaction. The samples were sintered at temperatures in the range 1550 divided by 1650 degrees C for 2 h. XRD, SEM and EDX were employed for compositional, structural and morphological characterization. An additional annealing at 410 degrees C for 10 hours was performed in order to improve the dielectric parameters. The dielectric constant and quality factor of BZT dielectric resonators measured by using Hakki-Coleman method around 6 GHz was between 25 and 29. The temperature coefficient of the resonance frequency exhibits positive values less than 6 ppm/degrees C. The best parameters of BZT dielectric resonators were achieved for the samples sintered at 1650 degrees C with additional thermal treatment (square(r) = 29, Q x f = 100 THz).
55. Phase-change electrical memory elements and devices
Authors: Popescu, M; Lorinczi, A; Sava, F; Velea, A; Matei, E; Socol, G; Mihailescu, IN

Published: OCT 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2621, DOI:

Electrical memory elements based on Ge-Sb-Te pure and doped by Sn-Se have been obtained by pulsed laser deposition on special substrates covered by gold as well as on common glass. A set of electrical memory elements in a 4x4 matrix structure on the glass substrate has been produced. Devices with 3 and 10 memory elements have been constructed and tested for their memory properties. The special features of the voltage-current characteristics have been revealed.
56. Alternating barium stearate and copper stearate LB thin films
Authors: Popescu, M; Lorinczi, A; Velea, A; Sava, F

Published: DEC 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3415, DOI:

Alternating layers based on copper and barium stearate have been prepared. The interlayer distance for both type of stearates have been determined by X-ray diffraction. It was found that the interlayer distance for an alternating assembly depends on the actual type of the stearate layer. Thus we demonstrated the possibility to control the inter-layer distance by choosing an appropriate sequency of layers. It is suggested that such layers may serve as high precision thickness standard at the angstrom level.
57. Structure, properties and gas sensing effect of SnSe2 films prepared by pulsed laser deposition method
Authors: Popescu, M; Sava, F; Lorinczi, A; Socol, G; Mihailescu, IN; Tomescu, A; Simion, C

Published: JUN 15 2007, JOURNAL OF NON-CRYSTALLINE SOLIDS, 353, 1869, DOI: 10.1016/j.jnoncrysol.2007.02.055

Amorphous SnSe, films were prepared by pulsed laser deposition (PLD) from solid polycrystalline targets. The atomic scale structure has been revealed by X-ray diffraction. Hardness and electrical properties were measured. Strong gas sensing properties have been evidenced for the first time in heat treated films. (c) 2007 Elsevier B.V. All rights reserved.
58. FSDP-related correlations in chalcogenide glasses
Authors: Kavetskyy, T; Shpotyuk, O; Popescu, M; Lorinczi, A; Sava, F

Published: OCT 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3081, DOI:

A first sharp diffraction peak (FSDP) is the most sensitive characteristic to medium range order in non-crystalline solids with speculative origin up to now. The compositional trends in the FSDP position and full width at half maximum are tested on the example of pseudo-binary Sb2S3-As2S3 and Sb2S3-GeS2 systems of chalcogenide glasses. The FSDP-related correlations are found for the investigated materials and considered in terms of packing factor of amorphous layers and experimental density of glass.
59. Structural transition and intermediate (Boolchand) phase in amorphous thin films of the AS(2)S(3)-GeS2 system
Authors: Petkov, K; Popescu, M; Lorinczi, A; Sava, F; Zamfira, S; Leonovici, M

Published: OCT 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3092, DOI:

The structure of the chalcogenide glass films of composition As2S3-GeS2 has been investigated bu X-ray diffraction. The relation between the quasi-distance as evidenced from the first sharp diffraction peak, and the composition ration has been estabilished. The Boolchand (intermediate) phase was found ro be characterized by large structuro-compositional fluctuations.
60. Resistive sensor for water salinity
Authors: Popescu, M; Lorinczi, A; Sava, F; Savu, V; Savastru, D

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3956, DOI:

A simple electrical resistance sensor for monitoring of the coastal marine waters has been developed. The good sensitivity and reproducibility of the measurements make this sensor attractive for using in the research of the mixing of sweet (river) waters with the marine water, as well as the variation in the depth of the sea of the water salinity. Another advantage of the sensor is the possibility to monitor the water salinity by simply tracing the electrical resistance when the sensor is drawn at the surface or vertically in the sea and ocean waters.
61. (Te/SnSe2)(3) multilayers deposited by pulsed laser deposition. Structure and gas sensing properties
Authors: Lorinczi, A; Sava, F; Tomescu, A; Simion, C; Socol, G; Mihailescu, IN; Popescu, M

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3492, DOI:

Multilayers made of alternative layers of composition SnSe2 and tellurium (three pairs) have been prepared by pulsed laser deposition (PLD). The complex films have been investigated by X-ray diffraction. After a special annealing in oxygen fluence at various temperatures, up to 620 degrees C, the films were investigated both by X-ray diffraction and for gas sensing. Gas sensing properties were tested for water vapours, carbon monoxide (CO) and methane (CH4). After annealing at high temperature, the structure of the multilayer samples show oxide phases like TeO2, SnO2 and a mixed oxide ternary phase SnTe3O8. The annealed multilayers show good sensing properties to water vapours and CO gas.
62. DC conductivity in GeSb2Te4 and (GeSb2Te4)(90)(SnSe2)(10) phase change materials
Authors: Popescu, M; Kubliha, M; Kaluzny, J; Velea, A; Lorinczi, A

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3953, DOI:

The dc electrical conductivity of the bulk amorphous GeSb2Te4 material has been investigated. Pure and samples doped by 10 at. % SnSe2 have been measured. The conductivity in the samples has been compared with that of SnSe2 bulk sample. The activation energy of the doped sample is 0.165 eV. During heating the conductivity of doped material increases, reaches a maximum and then decreases. The comparison with the pure SnSe2 samples allows to explain this behavior by the release above 148 degrees C of a small amount of selenium not bonded in the network.
63. Crystallization of PLD deposited ITO thin films by thermal treating in various gaseous environments
Authors: Viespe, C; Grigoriu, C; Popescua, M; Sava, F; Lorinczi, A; Velea, A; Zamfira, S

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3566, DOI:

ITO films of composition (In2O3)(0.9) - (SnO2)(0.1) have been prepared by pulsed laser deposition (PLD).The films were found to be amorphous. The structure and evolution of the films during annealing in air, oxygen atmosphere and reducing atmosphere (CO2) have been investigated by X-ray diffraction. The films annealed in ambient atmosphere start to crystallize under 250 degrees C annealing temperature. The films treated in oxygen atmosphere crystallize at higher temperature (similar to 300 degrees C).
64. Preparation, properties and electrical switching effects in GeSb2Te4 and (GeSb2Te4)(90)(SnSe2)(10) amorphous films
Authors: Lorinczi, A

Published: SEP 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2972, DOI:

Thin films of composition GeSb2Te4 and (GeSb2Te4)(90)(SnSe2)to have been prepared by pulsed laser deposition and characterized by X-ray diffraction and scanning electron microscopy. The electrical switching was revealed in both compositions.
65. Nanostructural configurations in As2S3 glass
Authors: Popescu, M; Sava, F; Lorinczi, A; Anghel, A

Published: APR 2006, PHYSICS AND CHEMISTRY OF GLASSES-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART B, 47, 157, DOI:

Various closed nanocluster configurations based on the stoichiometric arsenic-chalcogen composition have been built and relaxed by a computer Monte Carlo procedure. They can be used in the construction of the glass network. A model with random packing of various large, closed nano-clusters has been devised and fairly good agreement with experimental data for As2S3 has been obtained.
66. Self-organization and anisotropy in amorphous chalcogenides
Authors: Popescu, M; Sava, F; Lorinczi, A

Published: JUN 15 2006, JOURNAL OF NON-CRYSTALLINE SOLIDS, 352, 1509, DOI: 10.1016/j.jnoncrysol.2005.11.140

The intermediate, self-organized phase, in the As-Se system has been modeled on the basis of clusters with one or more selenium-selenium bridges. The X-ray diffraction patterns of the glass models at the limits of the 'floppy phase-stressed rigid phase' window have been calculated. The structural and optical anisotropy in a matrix of clusters containing Se-Se bonds is supposed to be a consequence of breaking and re-linking the broken clusters in the direction of the polarized light beam that acts upon the chalcogenide material. (c) 2006 Elsevier B.V. All rights reserved.
67. Amorphous SnSe2 films
Authors: Sava, F; Lorinczi, A; Popescu, M; Socol, G; Axente, E; Mihailescu, IN; Nistor, M

Published: AUG 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1371, DOI:

Amorphous SnSe2 films were prepared by pulsed laser deposition (PLD) and pulsed electron deposition (PED) from solid polycrystalline targets. The atomic scale structure has been revealed by X-ray diffraction. Hardness properties and electrical properties were measured. The peculiarities of the structures of the films prepared by PLD and PED methods were investigated discussed.
68. Interstitial void structure in Cu-Sn liquid alloy as revealed from reverse Monte Carlo modelling
Authors: Hoyer, W; Kleinhempel, R; Lorinczi, A; Pohlers, A; Popescu, M; Sava, F

Published: FEB 9 2005, JOURNAL OF PHYSICS-CONDENSED MATTER, 17, S36, DOI: 10.1088/0953-8984/17/5/004

A model for the structure of copper-tin liquid alloy has been developed using the standard reverse Monte Carlo method. The interstitial void structure (size distribution) was analysed. The effects of various kinds of voids (small size and large size) on the interference function and radial distribution function were investigated. Predictions related to the formation of some ternary alloys by filling the interstices of the basic alloy were advanced.
69. Microspheres, planoconvex microlenses and optical fibres based on glassy As2S3
Authors: Popescu, M; Sava, F; Lorinczi, A; Savastru, D; Miclos, S; Savastru, R

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1106, DOI:

Microspheres and planoconvex lenses (50 divided by 400 mu m in diameter) based on glassy As2S3, an important infrared material, have been produced by a special flame melting technique. Glassy fibres of 45 mu m in diameter, with the length of 10-20 cm have been drawn from melt. The morphological properties of these optical elements have been investigated.
70. Preparation and properties of langasite and YAG amorphous films
Authors: Popescu, M; Sava, F; Lorinczi, A; Stegarescu, M; Georgescu, S; Mihailescu, IN; Socol, G; Stanoi, D; Daroczi, L; Kokenyesi, A; Leonovici, M; Wagner, D

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 966, DOI:

Amorphous thin films of langasite and YAG have been prepared from crystals targets by pulsed laser deposition, at room temperature, in vacuum, on silicon wafers. Bulges of micrometer size are formed on the film surface. Larger size bulges (10-50 micrometers in diameter) are characteristic to the annealed langasite films. Annealing at high temperatures leads to the crystallization of the films. The annealed langasite films (850 degrees C) are polycrystalline and partially oriented with the plane (001) parallel to the surface of the silicon wafer. The bulges break easily in the heat treated films. Their empty structure was remarked on the electron microscope images. The YAG films annealed at 1100 degrees C shows a crystalline YAG phase depleted in Y and traces of Y2O3. An interesting feature is the presence of silver particles spread along the macrodefects (fracture lines) of the film.
71. Amorphous thin films based on paraffin doped chalcogenides, prepared by pulsed laser deposition
Authors: Popescu, M; Sava, F; Lorinczi, A; Mihailescu, IN; Socol, G; Axente, E; Kaban, I; Hoyer, W

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 167, DOI:

A chalcogenide material of composition Se42S58, doped by 10 wt.% paraffins has been prepared as thin films by pulsed laser deposition. The structural properties of the films have been investigated by X-ray diffraction. Sample stabilization was carried out by annealing at temperatures around 100degreesC.
72. Modelling of large molecular clusters in the non-crystalline As2S3
Authors: Popescu, M; Sava, F; Lorinczi, A

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 890, DOI:

Modelling of several large molecular clusters possible to be formed in non-crystalline arsenic chalcogenides (As2S3, As2Se3 or mixed compositions) during cooling down of the melts has been performed. The structure of minimum free energy was calculated in the frame of valence force field theory using a Monte-Carlo-Metropolis method. The structural characteristics of the clusters were computed after energy relaxation. There was demonstrated that specific cluster configurations of the type nano-hat, nano-pie and nanotube are crystallo-chemically compatible with the non-crystalline structure of the arsenic chalcogenides.
73. Possible nano-tube configurations in arsenic chalcogenides
Authors: Lorinczi, A; Popescu, M; Sava, F

Published: JUN 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 492, DOI:

Modeling of nano-tube clusters based on As,S(Se)(3) has been performed. The structural data were calculated on a single nano-tube model of As2S3. For the first time electron microscope images of nanometer size objects in As2Se3 and AS(5.5)Se(4.5) glass have been observed and discussed.
74. Modelling of the complex carbon structure: Fullerene-nanotubule
Authors: Lorinczi, A; Popescu, M; Sava, F; Anghel, A

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 352, DOI:

The complex structure fullerene(C-60)-nanotubule has been built from special plastic units and relaxed by a computer Monte-Carlo - Metropolis procedure. The purpose was to show that interconnection fullerene-nanotubule is possible from the energetical point of view. The results open the way towards the assessing the possibility to create nano-conductors and connections between different parts of nano-devices, using nano-carbon configurations filled by metal atoms.
75. Optical recording in sulfur-selenium layers
Authors: Popescu, M; Sava, F; Lorinczi, A; Savastru, R; Savastru, D; Radvan, R; Mihailescu, IN

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 886, DOI:

Selenium-sulphur layers prepared by warm pressing or deposited by pulsed laser deposition (PLD) on silicon wafers were subjected to laser pulses in order to test the possibility of recording the optical information in these glassy materials. There was demonstrated that the contrast of reflectivity between the irradiated places and the amorphous matrix could be used for storage of information at a reasonable density.
76. Structure and properties of As25Te35Si40 glass
Authors: Lorinczi, A; Sava, F; Iovu, M; Leonovici, M; Halm, T; Popescu, M; Hoyer, W

Published: NOV 2003, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 240, 36, DOI: 10.1002/pssb.200301850

The glassy composition As25Te35Si40 was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), Raman spectroscopy, and infrared absorption (IR) measurements. X-ray diffraction patterns at room temperature and at temperatures around T-g were recorded and the radial distribution functions have been calculated. A continuous random network model for the ideal homogeneous glass structure has been proposed.
77. Structure and properties of As25Te35Si40 glass
Authors: Popescu, M; Lorinczi, A; Sava, F; Stegarescu, M; Iovu, M; Leonovici, M; Halm, T; Hoyer, W

Published: OCT 1 2003, JOURNAL OF NON-CRYSTALLINE SOLIDS, 326, 393, DOI: 10.1016/S0022-3093(03)00444-7

The glassy composition As25Te35Si40 was investigated by microhardness, differential scanning calorimetry, X-ray diffraction, electrical conductivity and Raman spectroscopy measurements. A continuous random network model of the glass structure has been developed. (C) 2003 Elsevier B.V. All rights reserved.
78. Pulsed laser deposition of selenium-sulfur doped by paraffins
Authors: Lorinczi, A

Published: 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 1084, DOI:

Hybrid polymer based on selenium-sulphur doped by paraffins has been deposited by pulsed laser deposition. The properties of the thin films were investigated. Sample stabilization was carried out by annealing. A nano-crystalline fraction was obtained in the films annealed at 100degreesC. The structure of the nanocrystals corresponds to the Se3S5 crystallographic form. The films exhibit optical memory properties and are suggested for use in optical phase change memories.
79. Substrate influence on the X-ray diffraction patterns of amorphous chalcogenide thin films deposited on silicon wafers
Authors: Lorinczi, A

Published: APR 3 2002, THIN SOLID FILMS, 408, 285, DOI: 10.1016/S0040-6090(02)00065-2

In the case of AsSe:Sn and Ge27Sb13Se60 amorphous thin films deposited on Si(100) wafer, it was observed that the diffraction pattern is distorted by the escape-peak, which is very sensitive in intensity to the wafer's position in its own plane, This peak was found to be superimposed on the first sharp diffraction peak, which characterises the medium range order in the amorphous materials. A method for the minimisation of the escape-peak effect is presented. A different method is suggested to avoid this peak. (C) 2002 Elsevier Science B.V. All rights reserved.
80. Structure, properties and modelling of As25Te35Si40 glass
Authors: Popescu, MA; Lorinczi, AA; Sava, FA; Iovu, MB; Leonovici, MC; Stegarescu, MA; Halm, TD; Hoyer, WD

Published: 2002, XIIITH INTERNATIONAL SYMPOSIUM ON NON-OXIDE GLASSES AND NEW OPTICAL GLASSES PTS 1 AND 2, 84, DOI:

Glassy composition As25Te35Si40 was investigated by microhardness, differential scanning calorimetry, X-ray diffraction, electrical conductivity and Raman spectroscopy measurements. A continuous random network model of the glass structure has been developed.
81. UV irradiation effects in pure and tin-doped amorphous AsSe films
Authors: Popescu, M; Iovu, M; Hoyer, W; Shpotyuk, O; Sava, F; Lorinczi, A

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 306, DOI:

Pure and tin-doped AsSe amorphous films were investigated. The changes in the MRO induced by Sn were analysed be accurate profiling the first sharp diffraction peak (FSDP) in the X-ray diffraction diagram. A shift of FSDP as a function of tin concentration was observed. The structural changes induced by ultraviolet rays (lambda = 336 nm) for various time intervals of irradiation were revealed by small angle X-ray diffraction. It was revealed the formation of a special layer at the surface of the films. whose thickness increases during UV irradiation.
82. Effect of ultraviolet radiation on Ge27Sb13Se60 amorphous films
Authors: Lorinczi, A

Published: MAR 1999, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 1, 42, DOI:

The photo-structural transformations induced by ultraviolet (UV) radiation in Ge27Sb13Se60 amorphous thin films prepared by thermal evaporation method have been investigated. The mechanical, optical and structural data were investigated before and after irradiation of the fresh and annealed films. The modifications of the film structure and properties depend essentially on the state of the films: fresh or annealed below glass transition temperature.
83. Amorphous Se/CdSe and SiOx/CdSe multilayers
Authors: Popescu, M; Sava, F; Lorinczi, A; Vateva, E; Nesheva, D; Tchaushev, G; Mihailescu, IN; Koch, PJ; Obst, S; Bradaczek, H

Published: 1998, FIFTH CONFERENCE ON OPTICS (ROMOPTO '97), PTS 1 AND 2, 3405, 964, DOI: 10.1117/12.312698

Amorphous multilayers based on Se and CdSe alternated sublayers were succesfully prepared by thermal vacuum evaporation and laser ablation with the periodicity of 22 nm. The multilayer structure is stable up to similar to 70 degrees C. In the samples prepared by laser ablation a large contraction of the multilayer stacking occurs by annealing. Amorphous SiOx/CdSe multilayers with the periodicity of similar to 15 nm were successfully prepared by thermal vacuum evaporation. The structure is stable up to 400 degrees C annealing temperature. Pulse excimer laser irradiation of the SiOx based multilayer produces an expansion of the interlayer distance with similar to 0.33%.
84. X-ray diffraction analysis of porous silicon
Authors: Popescu, M; Sava, F; Lorinczi, A; Mihailescu, IN; Cojocaru, I; Mihailova, G

Published: OCT 1998, JOURNAL DE PHYSIQUE IV, 8, 37, DOI: 10.1051/jp4:1998505

The modification of the ideal lattice parameter in porous silicon has been determined by X-ray diffraction. A contraction effect has been detected in several samples. There was shown that the position of the photoluminescence band is related to the modification of the lattice parameter. The quantum theory of confinement in wires was used for the interpretation of the experimental data.
85. Photo-induced softening and hardening in Ge-As-S amorphous films
Authors: Popescu, M; Sava, F; Lorinczi, A; Skordeva, E; Koch, PJ; Bradaczek, H

Published: 1998, JOURNAL OF NON-CRYSTALLINE SOLIDS, 227, 722, DOI: 10.1016/S0022-3093(98)00236-1

Hardness, X-ray diffraction and transmission as well as infrared reflection measurements on virgin and ultraviolet (UV)-irradiated amorphous films of the GexAs40-xS60 system have been performed. The UV light induces film softening for x < 19 and film hardening for x > 19. The structure remains amorphous but the distance characteristic of medium range order decreases for x < 19 and increases for x > 19. Photo-contraction of the films (up to similar to 12%) has been revealed from IR spectra and X-ray transmission experiments. A main effect of UV light is the release of sulphur. (C) 1998 Elsevier Science B.V. All rights reserved.
86. Modeling of photostructural effects in chalcogenide glasses
Authors: Popescu, M; Lorinczi, A; Sava, F

Published: OCT 1998, JOURNAL DE PHYSIQUE IV, 8, 14, DOI: 10.1051/jp4:1998502

The reversible photostructural effects observed in the amorphous thin films and in chalcogenide glasses based on arsenic have been explained with the help of computer relaxed models. Two photostructural mechanisms have been established: the incorporation of the chalcogenide molecular fraction into the disordered layers and the change of the relative positions of the atoms in the layers without destroying the bonding network. In the frame of this atomic scale mechanisms it is possible to explain the reversible photodarkening and the photoanisotropy observed in the chalcogenide thin Alms and bulk glasses.
87. Structure and hardness modifications induced by UV light in Ge-As-S amorphous chalcogenide films
Authors: Popescu, M; Skordeva, E; Arsova, D; Vateva, E; Sava, F; Lorinczi, A

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 470, DOI:

X-ray diffraction and transmission experiments as well as hardness measurements on virgin and ultra violet (UV)-irradiated amorphous films in the system GexAs40-xS60 have been performed. The W-light determines the plm softening for x<19 and film hardening for x>19. The structure remains amorphous but the distance characteristic to medium range order (MRO) shows variations as a function of composition and irradiation time. The main effect of the UV light is the release of a significant amount of sulphur.
88. Thermal stability of amorphous Se/CdSe multilayers
Authors: Popescu, M; Sava, F; Lorinczi, A; Vateva, E; Nesheva, D; Koch, PJ; Gutberlet, T; Uebach, W; Bradaczek, H

Published: AUG 1997, SOLID STATE COMMUNICATIONS, 103, 434, DOI: 10.1016/S0038-1098(97)00207-X

The thermal stability of amorphous Se/CdSe multilayers has been investigated by X-ray diffraction. The multilayer structure is stable up to similar to 60 degrees C. After annealing at higher temperatures hexagonal selenium and hexagonal CdSe phases with nanometric crystallite size were revealed. (C) 1997 Elsevier Science Ltd.
89. Thermal stability of Se/CdSe multilayers
Authors: Popescu, M; Sava, F; Lorinczi, A; Koch, PJ; Gutberlet, T; Uebach, W; Bradaczek, H; Vateva, E; Nesheva, D

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 304, DOI:

90. In Memoriam Mihai Popescu (26 July 1942, Floresti-Soroca-14 July 2019, Bucharest)
Authors: Lorinczi, A

Published: , , DOI: 10.1002/pssb.202000142

91. Chalcogenide Science in Romania
Authors: Lorinczi, A; Badica, P; Botila, T; Ciurea, M; Velea, A; Popescu, A; Socol, G; Antohe, S; Nedelcu, N; Sobetkii, A

Published: , , DOI: 10.1002/pssb.202000284

Almost six decades ago, in Romania a small group of physicists begun to study chalcogenide compositions, motivated primarily by the desire to understand the phase-change phenomenon in these materials, discovered recently, at that time, by Stanford R. Ovshinsky. It took not too long for them to realize the challenges these materials set to the research. With newcomers to the field, the research was broadened. In some cases just for basic research, to model, and to understand the chalcogenide materials, whereas in other cases, the applicative potential was revealed and used. Herein, the evolution of the field of these somewhat exotic materials is followed, listing the main contributions done in Romania, both in basic and applied research.
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