NIMP| Marius HUSANU, Author at NIMP

Resume

Dr. Marius-Adrian Hușanu (41 years)

Sythetic information:

Name: Marius-Adrian Hușanu

Age: 41

Studies: PhD in Physics (since 2011)

Employer: National Institute of Materials Physics (www.infim.ro)

Position: Researcher I.

ORCID: 0000-0003-4510-6653

Email: ahusanu@infim.ro

I graduated from the Univeristy of Bucharest in 2004, majoring in Theoretical and Condensed Matter Physics. After completing his MSc in Theroetical Phyics, I enrolled in the Graduate School of the Bucharest University in 2006. Under the guidance of Prof. Ioan Baltog, I received my PhD in Phyics in 2011 with a thesis focusing on the nonlinear optical properties of nanostructures.

Since 2006 I work at the National Institute of Materials Physics, focusing on understanding the interplay between the crystalline structure, local environment and functionality of materials, with a particular emphasis on the quantum mechanisms accompanying the reduced dimensionality (2D: surfaces and interfaces, 1D systems and 0D: quantum dots).

During 2015-2016 period I worked at the Swiss Light Source synchrotron in Switzerland with a Swiss Excellence Grant.

My approach combines preparation of materials by molecular beam epitaxy or pulsed laser deposition with their study using electron spectroscopies (X-ray photoelectron spectroscopy – XPS, angle resolved photoemssion – ARPES, Auger electron scpetroscopy - AES) and X-ray absorption spectroscopies performed at NIMP or at synchrotron facilities, with additional theoretical understanding from first-principles calculations.

Publications

1. Spin asymmetry of O 2p-related states in SrTiO₃(001)

Authors: Popescu, DG; Nicolaev, A; Costescu, RM; Borcan, LE; Lungu, GA; Tache, CA; Husanu, MA; Teodorescu, CM

Published: OCT 1 2024, PHYSICA SCRIPTA, 99, 105925, DOI: 10.1088/1402-4896/ad732c

Atomically clean SrTiO3(001) is characterized by low energy electron diffraction, core level and valence band photoelectron spectroscopy, the latter also with spin resolution. Samples prepared by a sputtering-annealing procedure exhibited in-gap states in the valence band spectra, Ti3+ components in Ti 2p core level spectra and a noticeable spin asymmetry in the 3-9 eV binding energy range, which corresponds to valence states of mainly O 2p character. Upon annealing in oxygen, the spin asymmetry vanishes, accompanied by the intensity decrease of the contribution of titanium low ionization states and of in-gap states, indicating that these three phenomena are mutually connected. The observed spin asymmetry may be generated by indirect exchange mediated by the in-gap states between O 2p orbitals, or by the partial Ti 3d character of these states, which acquire non-zero spin in case of incomplete oxygen coordination.

2. Enhancement of SrTiO₃ photocatalytic efficiency by Al doping: Answers from the structure, morphology and electronic properties contributions

Authors: Radu, I; Borhan, AI; Gherca, D; Popescu, DG; Borca, CN; Huthwelker, T; Bulai, G; Stoian, G; Husanu, MA; Pui, A

Published: JUN 1 2024, CERAMICS INTERNATIONAL, 50, DOI: 10.1016/j.ceramint.2024.03.188

Our study focuses on disclosing the mechanisms standing behind the improved photocatalytic performance of SrTiO3, where Al modification of the perovskite structure boosts the photocatalytic O2 evolution activity of the Al:SrTiO3 system. By adapting the synthesis method that produces well-crystallized materials with low defect density and employing surface modification techniques, we aim to enhance the photocatalytic efficiency of SrTiO3 via Al2O3 nanoceramic oxide doping at concentrations ranging from 0 to 10% and further examining of the relationship between doping process and the changes in the electronic and crystalline structure of SrTiO3. The prepared Al-based SrTiO3 perovskite samples (Al3%:SrTiO3, Al7%:SrTiO3, Al10%:SrTiO3) were thoroughly characterized to understand their structural, electronic, and morphological properties. Complementary X-ray techniques were employed to assess the stoichiometry (X-ray photoelectron spectroscopy - XPS), local environment, and chemical state (X-ray absorption spectroscopy - XAS in both total electron yield (TEY) and fluorescence yield (TFY). The comprehensive characterization enables us to understand the changes in the electronic properties and morphological features of the modified samples elucidating the surface formation mechanism while providing insights into the structural modifications induced by Al doping in the SrTiO3 perovskite lattice. Our findings give new perspectives for the development of Al-modified SrTiO3 perovskite materials with enhanced photocatalytic performance providing rich insights into the optimization of photocatalytic processes for applications in environmental remediation and sustainable energy production.

3. Experimental Band Structure of Pb(Zr,Ti)O-3: Mechanism of Ferroelectric Stabilization

Authors: Popescu, DG; Husanu, MA; Constantinou, PC; Filip, LD; Trupina, L; Bucur, CI; Pasuk, I; Chirila, C; Hrib, LM; Stancu, V; Pintilie, L; Schmitt, T; Teodorescu, CM; Strocov, VN

Published: FEB 2023, ADVANCED SCIENCE, 10, DOI: 10.1002/advs.202205476

Pb(Zr,Ti)O-3 (PZT) is the most common ferroelectric (FE) material widely used in solid-state technology. Despite intense studies of PZT over decades, its intrinsic band structure, electron energy depending on 3D momentum k, is still unknown. Here, Pb(Zr0.2Ti0.8)O-3 using soft-X-ray angle-resolved photoelectron spectroscopy (ARPES) is explored. The enhanced photoelectron escape depth in this photon energy range allows sharp intrinsic definition of the out-of-plane momentum k and thereby of the full 3D band structure. Furthermore, the problem of sample charging due to the inherently insulating nature of PZT is solved by using thin-film PZT samples, where a thickness-induced self-doping results in their heavy doping. For the first time, the soft-X-ray ARPES experiments deliver the intrinsic 3D band structure of PZT as well as the FE-polarization dependent electrostatic potential profile across the PZT film deposited on SrTiO3 and LaxSrMn1-xO3 substrates. The negative charges near the surface, required to stabilize the FE state pointing away from the sample (P+), are identified as oxygen vacancies creating localized in-gap states below the Fermi energy. For the opposite polarization state (P-), the positive charges near the surface are identified as cation vacancies resulting from non-ideal stoichiometry of the PZT film as deduced from quantitative XPS measurements.

4. Experimental Band Structure of Pb(Zr,Ti)O-3: Mechanism of Ferroelectric Stabilization

Authors: Popescu, DG; Husanu, MA; Constantinou, PC; Filip, LD; Trupina, L; Bucur, CI; Pasuk, I; Chirila, C; Hrib, LM; Stancu, V; Pintilie, L; Schmitt, T; Teodorescu, CM; Strocov, VN

Published: JAN 2023, ADVANCED SCIENCE, DOI: 10.1002/advs.202205476

5. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe-0@Ni-0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)

Authors: Borhan, AI; Ghemes, IA; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUL 1 2023, APPLIED SURFACE SCIENCE, 624, 157067, DOI: 10.1016/j.apsusc.2023.157067

6. Experimental Band Structure of Pb(Zr,Ti)O₃: Mechanism of Ferroelectric Stabilization

Authors: Popescu, DG; Husanu, MA; Constantinou, PC; Filip, LD; Trupina, L; Bucur, CI; Pasuk, I; Chirila, C; Hrib, LM; Stancu, V; Pintilie, L; Schmitt, T; Teodorescu, CM; Strocov, VN

Published: FEB 2023, ADVANCED SCIENCE, 10, DOI: 10.1002/advs.202205476

7. Surface charge dynamics on air-exposed ferroelectric Pb(Zr,Ti)O₃(001) thin films

Authors: Abramiuc, LE; Tanase, LC; Prieto, MJ; Caldas, LD; Tiwari, A; Apostol, NG; Husanu, MA; Chirila, CF; Trupina, L; Schmidt, T; Pintilie, L; Teodorescu, CM

Published: AUG 10 2023, NANOSCALE, 15, DOI: 10.1039/d3nr02690f

Probing of the free surface ferroelectric properties of thin polar films can be achieved either by estimating the band bending variance under the top-most layer or by studying the extent of the extrinsic charge accumulated outside the surface. Photoemitted or incoming low-energy electrons can be used to characterize locally both properties in a spectromicroscopic approach. Thin ferroelectric lead zirco-titanate (PZT) is investigated by combining low energy/mirror electron microscopy (LEEM/MEM) with photoemission electron microscopy (PEEM) and high-resolution photoelectron spectroscopy (XPS). Significant extrinsic negative compensation charge is proven to accumulate on the surface of the outward polarized thin film, indicated by high MEM-LEEM transition values, up to 15.3 eV, and is correlated with the surface electrostatic potential, which can be partially screened either by electrons interacting with the sample or by soft X-rays through the ejection of secondary electrons and generation of positive charge under the surface. A radiation-induced surface charge compensation effect is observed. The study indicates that air-exposed high quality ferroelectric thin films show large negative surface potentials, determined locally on the surface, which are nevertheless sensitive to beam damage and molecular desorption. These values represent a confirmation of previously estimated surface potential energy values determined from the LEED data on clean surfaces.

8. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics

Authors: Borhan, AI; Ghemes, AI; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUN 15 2023, APPLIED SURFACE SCIENCE, 622, 156987, DOI: 10.1016/j.apsusc.2023.156987

We reported on the sequential development of a high-operative photocatalyst with penta-component inorganic bulk heterojunction for improved charge trapping characteristics at particle-particle interfaces for enhanced solar light-driven photocatalytic degradation of active tetracycline antibiotic. Structural, morphological, optical, and electronic properties of the synthesized samples were investigated using a series of complementary char-acterization techniques, such as XRD, FE-SEM, HR-TEM, XPS, as well as hard and soft XAS in both total electron yield (TEY) and fluorescence yield (TFY). For the case of the carbon composite material, SrTiO3@NiFe2O4@-Fe0@Ni0@CNTs, a reduced crystallinity when compared to the starting support material was noticed, although this translated into a significant improvement of the morphology and the photocatalytic performance. The SrTiO3@NiFe2O4@Fe0@Ni0@CNTs fibrous photocatalyst can efficiently achieve a high-to-total degradation of tetracycline antibiotic under visible light irradiation in less than two hours, following a non-linear PFO kinetic model with an apparent reaction rate of about 0.0606 min-1 and an 98% photodegradation activity. The XPS and XAS analysis demonstrated unequivocally the appearance of nanoscale zero-valent iron (Fe0) and zero-valent nickel (Ni0) on the photocatalyst surface, which facilitates the separation of photogenerated e+ and h+ pairs, and the appearance of more active sites.

9. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO₃@NiFe₂O₄@Fe⁰@Ni⁰@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)

Authors: Borhan, AI; Ghemes, IA; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUL 1 2023, APPLIED SURFACE SCIENCE, 624, 157067, DOI: 10.1016/j.apsusc.2023.157067

10. Robust Electronic Structure of Manganite-Buffered Oxide Interfaces with Extreme Mobility Enhancement

Authors: Li, H; Gan, YL; Husanu, MA; Dahm, RT; Christensen, DV; Radovic, M; Sun, JR; Shi, M; Shen, BG; Pryds, N; Chen, YZ

Published: APR 26 2022, ACS NANO, 16, DOI: 10.1021/acsnano.2c00609

The electronic structure as well as the mechanism underlying the high-mobility two-dimensional electron gases (2DEGs) at complex oxide interfaces remain elusive. Herein, using soft X-ray angle-resolved photoemission spectroscopy (ARPES), we present the band dispersion of metallic states at buffered LaAlO3/SrTiO3 (LAO/STO) heterointerfaces where a single-unit-cell LaMnO3 (LMO) spacer not only enhances the electron mobility but also renders the electronic structure robust toward X-ray radiation. By tracing the evolution of band dispersion, orbital occupation, and electron-phonon interaction of the interfacial 2DEG, we find unambiguous evidence that the insertion of the LMO buffer strongly suppresses both the formation of oxygen vacancies as well as the electron-phonon interaction on the STO side. The latter effect makes the buffered sample different from any other STO-based interfaces and may explain the maximum mobility enhancement achieved at buffered oxide interfaces.

11. Ferroelectricity modulates polaronic coupling at multiferroic interfaces

Authors: Husanu, MA; Popescu, DG; Bisti, F; Hrib, LM; Filip, LD; Pasuk, I; Negrea, R; Istrate, MC; Lev, L; Schmitt, T; Pintilie, L; Mishchenko, A; Teodorescu, CM; Strocov, VN

Published: AUG 15 2022, COMMUNICATIONS PHYSICS, 5, 209, DOI: 10.1038/s42005-022-00983-3

A deeper understanding of the coupling at the interface of multiferroics heterostructures is being achieved by the use of synchrotron radiation techniques. Here, the authors use k-resolved soft X-ray photoemission spectroscopy and first principles calculations to investigate the band structure of several multiferroic heterostructures, isolating the distinct signature of the interface. Physics of the multiferroic interfaces is currently understood mostly within a phenomenological framework based on screening of the polarization field and depolarizing charges. Additional effects still unexplored are the band dependence of the interfacial charge modulation and the associated changes of the electron-phonon interaction, coupling the charge and lattice degrees of freedom. Here, multiferroic heterostructures of the colossal-magnetoresistance manganite La1-xSrxMnO3 buried under ferroelectric BaTiO3 and PbZrxTi1-xO3 are investigated using soft-X-ray angle-resolved photoemission. The experimental band dispersions from the buried La1-xSrxMnO3 identify coexisting two-dimensional hole and three-dimensional electron charge carriers. The ferroelectric polarization modulates their charge density, affecting the coupling of the 2D holes and 3D electrons with the lattice which forms large Frohlich polarons inherently reducing mobility of the charge carriers. Our k-resolved results on the orbital occupancy, band filling and electron-lattice interaction in multiferroic oxide heterostructures modulated by the ferroelectric polarization disclose most fundamental physics of these systems needed for further progress of beyond-CMOS ferro-functional electronics.

12. Impact of band-bending on the k-resolved electronic structure of Si-doped GaN

Authors: Lev, LL; Maiboroda, IO; Grichuk, ES; Chumakov, NK; Schroter, NBM; Husanu, MA; Schmitt, T; Aeppli, G; Zanaveskin, ML; Valeyev, VG; Strocov, VN

Published: MAR 4 2022, PHYSICAL REVIEW RESEARCH, 4, 013183, DOI: 10.1103/PhysRevResearch.4.013183

Band bending at semiconductor surfaces and interfaces is the key to applications ranging from classical transistors to topological quantum computing. A semiconductor particularly important for optical as well as microwave devices is GaN. What makes the material useful is not only its large bandgap but also that it can be heavily doped to become metallic. Here, we apply soft-x-ray angle-resolved photoelectron spectroscopy (ARPES) to metallic Si-doped GaN to explore the electron density and momentum-resolved band dispersions of the valence and conduction electrons varying through the surface band-bending region. We find an upward band bending, where the measured band occupation reduces toward the surface, as probed with low photon energies <0.5 keV. The band occupation approaches the bulk value, matching Hall effect measurements, as the photon energy increases to >1.4 keV, where the photoelectron mean free path exceeds the spatial extent of the band-bending region. Our quantitative analysis of the experimental data describes the potential variation in the band-bending region via self-consistent Poisson-Schrodinger equations. We put forward an insightful model to simulate the ARPES spectra from this region through summing up the contribution from all atomic layers, weighted by the photoelectron mean free path, under in-phase conditions achieved at particular values of the photoelectron out-of-plane momentum. The model adequately describes the peculiarities of the ARPES spectra caused by the surface band bending, including the photon-energy dependence of the apparent band occupation and Fermi-surface area, and allows accurate determination of the band-bending profile and values of the photoelectron mean free path. Finally, comparison of our data with supercell density functional theory calculations reveals the preferential location of Si atoms as substitutional for Ga, with the doped electrons entering the GaN conduction bands without formation of separate impurity states as would occur for Si interstitials. Our theoretical and experimental results resolve fundamental questions underpinning device performance of the GaN-based and other semiconductor materials in general and demonstrate a general methodology for quantitative studies of electron states in the band-bending region.

13. Re-entrant ferromagnetism at ultrahigh temperatures in epsilon-iron as possible origin of the geomagnetic field

Authors: Teodorescu, CMM; Husanu, MAA

Published: MAY 2022, PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 326, 106856, DOI: 10.1016/j.pepi.2022.106856

A recent theory of band ferromagnetism in 3d metals predicts 're-entrant' ferromagnetism at temperatures far above the boiling point of these metals in normal conditions (Teodorescu, C.M., 2021. Spin asymmetry originating from densities of states: Criterion for ferromagnetism, structures and magnetic properties of 3d metals from crystal field based DOSs. Results in Physics 25, 104,241). Metals, and in particular iron rich alloys, are still solid at such extremal temperatures in the Earth's inner solid core. It follows that this piece of the Earth may become ferromagnetic. This hypothesis is investigated in this work in more details, by using densities of states derived by ab initio density functional theory calculations for hexagonal close-packed iron and applying the basic theory of band ferromagnetism derived in the above Reference. The temperature for 're-entrant' ferromagnetism increases with the pressure, ranging between about 6530 and 6640 K for pressures between 330 and 360 GPa; these temperatures are in the range of most estimates for the temperature of the inner solid core of our planet. The dimension of the ferromagnetic "innermost inner core" (IMIC) derived from the estimated Fe magnetic moment are within the dimensions of a IMIC with different anisotropy in the propagation of seismic waves. For body centered cubic Fe no 're-entrant' ferromagnetism is predicted based on the actual model. It follows that the Earth's inner solid core with hexagonal close-packed structure is the main responsible for the geomagnetic field, and also most probably the reversal of this field proceeds by simple rotation of the magnetization of this core, while keeping a non-vanishing magnetic field during the reversal. This might prevent the Earth's surface bombardment with energetic charged particles during the reversals, with beneficial effects for complex lifeforms and for mankind civilization.

14. Band-Order Anomaly at the gamma-Al2O3/SrTiO3 Interface Drives the Electron-Mobility Boost

Authors: Chikina, A; Christensen, DV; Borisov, V; Husanu, MA; Chen, YZ; Wang, XQ; Schmitt, T; Radovic, M; Nagaosa, N; Mishchenko, AS; Valenti, R; Pryds, N; Strocov, VN

Published: MAR 23 2021, ACS NANO, 15, 4356, DOI: 10.1021/acsnano.0c07609

The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel-perovskite gamma-Al2O3/SrTiO3 interface compared to the paradigm perovskite-perovskite LaAlO3/SrTiO3 interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in gamma-Al2O3/SrTiO3 which depopulates electron states in the top SrTiO3 layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel gamma-Al2O3 and perovskite SrTiO3. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.

15. Effect of strain and stoichiometry on the ferroelectric and pyroelectric properties of the epitaxial Pb(Zr0.2Ti0.8)O-3 films deposited on Si wafers

Authors: Chirila, C; Boni, GA; Filip, LD; Husanu, M; Neatu, S; Istrate, CM; Le Rhun, G; Vilquin, B; Trupina, L; Pasuk, I; Botea, M; Pintilie, I; Pintilie, L

Published: APR 2021, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 266, DOI: 10.1016/j.mseb.2021.115042

Properties of epitaxial PbZr0.2Ti0.8O3 (PZT) films deposited on Si substrates were investigated for integration in the present CMOS technology. Polarization is downward oriented, in association with the presence of an internal electric field, and has a lower value compared to the PZT films deposited on single crystal perovskite SrTiO3 (STO) substrates (40 mu C/cm(2) versus 80 mu C/cm(2)), while the dielectric constant is larger (180 versus 120). Large value for the pyroelectric coefficient was also found, 1.22 x 10(-3)C/m(2)K, as for PZT grown on single crystal STO. The macroscopic ferroelectric and pyroelectric properties appear to be affected by the structural quality and stoichiometry of the PZT film. The changes in the electric properties are an effect of the strain gradients induced by the large difference between the thermal expansion coefficients of PZT and Si substrate, leading in turn to Pb oxidation and antisite defect formation compared to PZT films deposited on STO substrates.

16. CO adsorption, reduction and oxidation on Pb(Zr,Ti)O-3(001) surfaces associated with negatively charged gold nanoparticles

Authors: Apostol, NG; Husanu, MA; Lizzit, D; Hristea, IA; Chirila, CF; Trupina, L; Teodorescu, CM

Published: APR 15 2021, CATALYSIS TODAY, 366, 154, DOI: 10.1016/j.cattod.2020.02.042

Gold is deposited on atomically clean, inwards polarized, ferroelectric lead zirco-titanate deposited by pulsed laser deposition on strontium titanate (001) single crystal, then carbon monoxide adsorption and desorption experiments are investigated by in situ fast photoelectron spectroscopy using synchrotron radiation. Atomic force microscopy and high resolution photoelectron spectroscopy are consistent with the formation of 50?100 nm nanoparticles, and their Au 4f core levels point to a negative charge state of gold. As compared with a similar experiment performed on ferroelectric lead zirco-titanate with similar polarization state and without gold, the saturation coverage after exposure to carbon monoxide increases by about 68 %, and also most of the additional carbon is found in oxidized state. Desorption experiments with in situ follow-up by photoelectron spectroscopy are performed as function of temperature, and the neutral carbon intensity decreases when the ferroelectric polarization decreases, while the components corresponding to oxidized carbon remain unchanged. It looks that neutral carbon adsorption is strictly related to the polarization of the ferroelectric film, while carbon still found in molecular form is related to its carbonyl bonding on metal nanoparticles, independent of the polarization state of the substrate. Desorbed carbon at higher temperature uptakes oxygen from the substrate.

17. Electron-polaron dichotomy of charge carriers in perovskite oxides

Authors: Husanu, MA; Vistoli, L; Verdi, C; Sander, A; Garcia, V; Rault, J; Bisti, F; Lev, LL; Schmitt, T; Giustino, F; Mishchenko, AS; Bibes, M; Strocov, VN

Published: APR 2 2020, COMMUNICATIONS PHYSICS, 3, DOI: 10.1038/s42005-020-0330-6

The underlying mechanisms of the metal-insulator transition in correlated oxides are a rich source of interesting physics and a topic of long-standing investigation. Here, the authors use angle-resolved photoelectron spectroscopy to investigate changes in charge carrier properties and electron-phonon interactions as a function of Ce-doping across the metal-insulator transition in CaMnO3. Many transition metal oxides (TMOs) are Mott insulators due to strong Coulomb repulsion between electrons, and exhibit metal-insulator transitions (MITs) whose mechanisms are not always fully understood. Unlike most TMOs, minute doping in CaMnO3 induces a metallic state without any structural transformations. This material is thus an ideal platform to explore band formation through the MIT. Here, we use angle-resolved photoemission spectroscopy to visualize how electrons delocalize and couple to phonons in CaMnO3. We show the development of a Fermi surface where mobile electrons coexist with heavier carriers, strongly coupled polarons. The latter originate from a boost of the electron-phonon interaction (EPI). This finding brings to light the role that the EPI can play in MITs even caused by purely electronic mechanisms. Our discovery of the EPI-induced dichotomy of the charge carriers explains the transport response of Ce-doped CaMnO3 and suggests strategies to engineer quantum matter from TMOs.

18. Polarization-dependent magnetism of the Ni/BaTiO3 interface

Authors: Bocirnea, AE; Popescu, DG; Chirila, C; Costescu, RM; Kuncser, V; Stancu, V; Trupina, L; Pasuk, I; Vlaicu, AM; Husanu, MA

Published: MAR 4 2020, PHYSICAL REVIEW MATERIALS, 4, DOI: 10.1103/PhysRevMaterials.4.034402

We explore the cross coupling between the ferroelectric and ferromagnetic phases in Ni/BaTiO3(001) heterostructures and demonstrate the modulation of the magnetism and incidence of exchange bias in the ultrathin metallic Ni overlayer, depending on the ferroelectric state of the bottom layer. We establish that 5-nm-thick monocrystalline Ni film deposited on BaTiO3 with ferroelectric polarization pointing towards the surface (P+) favors the organization of Ni into uniform ferromagnetic domains. Ni grown on BaTiO3 with opposite ferroelectric polarization is featured by emerging exchange-bias coupling between the ferromagnetic Ni top layers and the antiferromagnetic reacted interface, as theoretically explained by first-principles calculations. We explicitly obtain the morphology of the magnetic domains of the crystalline Ni layer in atomic and magnetic force microscopy measurements (AFM/MFM). The resemblance of AFM and MFM images indicate that, although with radically different morphologies, in both cases all spins orient in the Ni plane. Consequently, the distinct signature of the ferroelectric-ferromagnetic coupling extracted from the magneto-optical Kerr effect measurements encodes all the information of sample magnetism. The peculiar magnetic coupling depending on the ferroelectric state indicates new ways of engineering the functionality of metal/ferroelectric interfaces.

19. The interplay of work function and polarization state at the Schottky barriers height for Cu/BaTiO3 interface

Authors: Popescu, DG; Husanu, MA; Chirila, C; Pintilie, L; Teodorescu, CM

Published: FEB 1 2020, APPLIED SURFACE SCIENCE, 502, DOI: 10.1016/j.apsusc.2019.144101

The emerging field of electronics based on ferro-functional materials relies on driving effectively and predictably a ferroelectric system between different polarization states through bias applied to metallic contacts. This requires detailed understanding of the growth mechanisms and electronic properties of the interface, including ferroelectric and material - dependent band alignment and Schottky barrier heights. Whether the major contribution at the interface band alignment comes from the work function difference or from the ferroelectric state is still under debate. Here, using X-ray photoemsion and ab-initio calculations, we derive the complex microscopic picture of metal/ferroelectric interface formation, including growth mechanism, valence alteration, ferroelectric-dependent electrostatic potential and thickness - dependent compensation mechanisms of ferroelectricity, starting from the ultrathin growth of Cu up to 100 angstrom on BaTiO3. One establishes the evolution of the band bending and of the build-in potential from the initial probed thickness of the ferroelectric in the range of 3 lambda (lambda - the inelastic mean free path) while gradually approaching the contact region with the metal at higher thickness of the top layer. We find that the well-defined orientation of the ferroelectric polarization lead to a band bending at the interface, which add at the bending expected from the work function difference of the two joining materials.

20. Probing single-unit-cell resolved electronic structure modulations in oxide superlattices with standing-wave photoemission

Authors: Yang, W; Chandrasena, RU; Gu, M; dos Reis, RMS; Moon, EJ; Arab, A; Husanu, MA; Nemsak, S; Gullikson, EM; Ciston, J; Strocov, VN; Rondinelli, JM; May, SJ; Gray, AX

Published: SEP 9 2019, PHYSICAL REVIEW B, 100, DOI: 10.1103/PhysRevB.100.125119

Control of structural coupling at complex-oxide interfaces is a powerful platform for creating ultrathin layers with electronic and magnetic properties unattainable in the bulk. However, with the capability to design and control the electronic structure of such buried layers and interfaces at a unit-cell level, a new challenge emerges to be able to probe these engineered emergent phenomena with depth-dependent atomic resolution as well as element- and orbital selectivity. Here, we utilize a combination of core-level and valence-band soft x-ray standing-wave photoemission spectroscopy, in conjunction with scanning transmission electron microscopy, to probe the depth-dependent and single-unit-cell resolved electronic structure of an isovalent manganite superlattice [Eu0.7Sr0.3MnO3/La0.7Sr0.3MnO3] x 15 wherein the electronic-structural properties are intentionally modulated with depth via engineered oxygen octahedra rotations/tilts and A-site displacements. Our unit-cell resolved measurements reveal significant transformations in the local chemical and electronic valence-band states, which are consistent with the layer-resolved first-principles theoretical calculations, thus opening the door for future depth-resolved studies of a wide variety of heteroengineered material systems.

21. k-resolved electronic structure of buried heterostructure and impurity systems by soft-X-ray ARPES

Authors: Strocov, VN; Lev, LL; Kobayashi, M; Cancellieri, C; Husanu, MA; Chikina, A; Schroter, NBM; Wang, X; Krieger, JA; Salman, Z

Published: OCT 2019, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 236, 8, DOI: 10.1016/j.elspec.2019.06.009

Angle-resolved photoelectron spectroscopy (ARPES) is the main experimental tool to explore electronic structure of solids resolved in the electron momentum k. Soft-X-ray ARPES (SX-ARPES), operating in a photon energy range around 1 keV, benefits from enhanced probing depth compared to the conventional VUV-range ARPES, and elemental/chemical state specificity achieved with resonant photoemission. These advantages make SX-ARPES ideally suited for buried heterostructure and impurity systems, which are at the heart of current and future electronics. These applications are illustrated here with a few pioneering results, including buried quantum-well states in semiconductor and oxide heterostructures, their bosonic coupling critically affecting electron transport, magnetic impurities in diluted magnetic semiconductors and topological materials, etc. High photon flux and detection efficiency are crucial for pushing the SX-ARPES experiment to these most photon-hungry cases.

22. Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3

Authors: Popescu, DG; Husanu, MA; Chirila, C; Pintilie, L; Teodorescu, CM

Published: JUL 2019, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 13, DOI: 10.1002/pssr.201900077

The competition between interface barrier in the Schottky-Mott limit and polarization driven mechanism is established during gradual formation of metal (Au) - ferroelectric (BaTiO3) interface. X-ray photoelectron spectroscopy provides core level energies and valence band positions in the contact region, to monitor the band alignment from the very first stages of metal deposition on BaTiO3. The band bending at metal/ferroelectric (FE) interface is extracted from the shift of core levels (Ba 3d, Ti 2p) as a function of the metal thickness. It is shown that the interface band alignment mechanism involves a well-defined polarization orientation washing out the bending expected from the work function difference. The sudden modification of the binding energies within ferroelectric at the first 2 angstrom Au indicates that the ferroelectric compensation mechanism triggered by the metal overlayer initiates already at ultrathin top layer, while subsequent growth contributes only at a gradual correction of the potential in the FE. The emerging picture is confirmed in first-principle calculation indicating the preferences of Au to grow preferentially to different terminated regions and to stabilize distinct ferroelectric polarization.

23. Electronic Structure of a Graphene-like Artificial Crystal of NdNiO3

Authors: Arab, A; Liu, XR; Koksal, O; Yang, WB; Chandrasena, RU; Middey, S; Kareev, M; Kumar, S; Husanu, MA; Yang, ZZ; Gu, L; Strocov, VN; Lee, TL; Minar, J; Pentcheva, R; Chakhalian, J; Gray, AX

Published: NOV 2019, NANO LETTERS, 19, 8317, DOI: 10.1021/acs.nanolett.9b03962

Artificial complex-oxide heterostructures containing ultrathin buried layers grown along the pseudocubic [111] direction have been predicted to host a plethora of exotic quantum states arising from the graphene-like lattice geometry and the interplay between strong electronic correlations and band topology. To date, however, electronic-structural investigations of such atomic layers remain an immense challenge due to the shortcomings of conventional surface-sensitive probes with typical information depths of a few angstroms. Here, we use a combination of bulk-sensitive soft X-ray angle-resolved photoelectron spectroscopy (SX-ARPES), hard X-ray photoelectron spectroscopy (HAXPES), and state-of-the-art first-principles calculations to demonstrate a direct and robust method for extracting momentum-resolved and angle-integrated valence-band electronic structure of an ultrathin buckled graphene-like layer of NdNiO3 confined between two 4-unit cell-thick layers of insulating LaAlO3. The momentum-resolved dispersion of the buried Ni d states near the Fermi level obtained via SX-ARPES is in excellent agreement with the first-principles calculations and establishes the realization of an antiferro-orbital order in this artificial lattice. The HAXPES measurements reveal the presence of a valence-band bandgap of 265 meV. Our findings open a promising avenue for designing and investigating quantum states of matter with exotic order and topology in a few buried layers.

24. Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Authors: Strocov, VN; Chikina, A; Caputo, M; Husanu, MA; Bisti, F; Bracher, D; Schmitt, T; Granozio, FM; Vaz, CAF; Lechermann, F

Published: OCT 7 2019, PHYSICAL REVIEW MATERIALS, 3, DOI: 10.1103/PhysRevMaterials.3.106001

Electronic phase separation is crucial for the fascinating macroscopic properties of the LaAlO3/SrTiO3 (LAO/STO) paradigm oxide interface, including the coexistence of superconductivity and ferromagnetism. We investigate this phenomenon using angle-resolved photoelectron spectroscopy (ARPES) in the soft-x-ray energy range, where the enhanced probing depth combined with resonant photoexcitation allow us access to fundamental electronic structure characteristics - momentum-resolved spectral function, dispersions and ordering of energy bands, Fermi surface - of buried interfaces. Our experiment uses x-ray irradiation of the LAO/STO interface to tune its oxygen deficiency, building up a dichotomic system where mobile weakly correlated Ti t(2g) electrons coexist with localized strongly correlated Ti e(g) ones. The ARPES spectra dynamics under x-ray irradiation shows a gradual intensity increase under constant Luttinger count of the Fermi surface. This fact identifies electronic phase separation (EPS) where the mobile electrons accumulate in conducting puddles with fixed electronic structure embedded in an insulating host phase, and allows us to estimate the lateral fraction of these puddles. We discuss the physics of EPS invoking a theoretical picture of oxygen-vacancy clustering, promoted by the magnetism of the localized Ti e(g) electrons, and repelling of the mobile t(2g) electrons from these clusters. Our results on the irradiation-tuned EPS elucidate the intrinsic one taking place at the stoichiometric LAO/STO interfaces.

25. Do topology and ferromagnetism cooperate at the EuS/Bi2Se3 interface?

Authors: Krieger, JA; Ou, Y; Caputo, M; Chikina, A; Dobeli, M; Husanu, MA; Keren, I; Prokscha, T; Suter, A; Chang, CZ; Moodera, JS; Strocov, VN; Salman, Z

Published: FEB 19 2019, PHYSICAL REVIEW B, 99, DOI: 10.1103/PhysRevB.99.064423

We probe the local magnetic properties of interfaces between the insulating ferromagnet EuS and the topological insulator Bi2Se3 using low energy muon spin rotation (LE-mu SR). We compare these to the interface between EuS and the topologically trivial metal, titanium. Below the magnetic transition of EuS, we detect strong local magnetic fields which extend several nm into the adjacent layer and cause a complete depolarization of the muons. However, in both Bi(2)Se(3 )and titanium we measure similar local magnetic fields, implying that their origin is mostly independent of the topological properties of the interface electronic states. In addition, we use resonant soft x-ray angle resolved photoemission spectroscopy (SX-ARPES) to probe the electronic band structure at the interface between EuS and Bi2Se3. By tuning the photon energy to the Eu antiresonance at the Eu M-5 pre-edge we are able to detect the Bi2Se3 conduction band, through a protective Al2O3 capping layer and the EuS layer. Moreover, we observe a signature of an interface-induced modification of the buried Bi2Se3 wave functions and/or the presence of interface states.

26. k-space imaging of anisotropic 2D electron gas in GaN/GaAlN high-electron-mobility transistor heterostructures

Authors: Lev, LL; Maiboroda, IO; Husanu, MA; Grichuk, ES; Chumakov, NK; Ezubchenko, IS; Chernykh, IA; Wang, X; Tobler, B; Schmitt, T; Zanaveskin, ML; Valeyev, VG; Strocov, VN

Published: JUL 11 2018, NATURE COMMUNICATIONS, 9, DOI: 10.1038/s41467-018-04354-x

Nanostructures based on buried interfaces and heterostructures are at the heart of modern semiconductor electronics as well as future devices utilizing spintronics, multiferroics, topological effects, and other novel operational principles. Knowledge of electronic structure of these systems resolved in electron momentum k delivers unprecedented insights into their physics. Here we explore 2D electron gas formed in GaN/AlGaN high-electron-mobility transistor heterostructures with an ultrathin barrier layer, key elements in current high-frequency and high-power electronics. Its electronic structure is accessed with angle-resolved photoelectron spectroscopy whose probing depth is pushed to a few nanometers using soft-X-ray synchrotron radiation. The experiment yields direct k-space images of the electronic structure fundamentals of this system-the Fermi surface, band dispersions and occupancy, and the Fourier composition of wavefunctions encoded in the k-dependent photoemission intensity. We discover significant planar anisotropy of the electron Fermi surface and effective mass connected with relaxation of the interfacial atomic positions, which translates into nonlinear (high-field) transport properties of the GaN/AlGaN heterostructures as an anisotropy of the saturation drift velocity of the 2D electrons.

27. Large positive linear magnetoresistance in the two-dimensional t(2g) electron gas at the EuO/SrTiO3 interface

Authors: Kormondy, KJ; Gao, LY; Li, X; Lu, SR; Posadas, AB; Shen, SD; Tsoi, M; McCartney, MR; Smith, DJ; Zhou, JS; Lev, LL; Husanu, MA; Strocov, VN; Demkov, AA

Published: MAY 16 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-26017-z

The development of novel nano-oxide spintronic devices would benefit greatly from interfacing with emergent phenomena at oxide interfaces. In this paper, we integrate highly spin-split ferromagnetic semiconductor EuO onto perovskite SrTiO3 (001). A careful deposition of Eu metal by molecular beam epitaxy results in EuO growth via oxygen out-diffusion from SrTiO3. This in turn leaves behind a highly conductive interfacial layer through generation of oxygen vacancies. Below the Curie temperature of 70 K of EuO, this spin-polarized two- dimensional t(2g) electron gas at the EuO/SrTiO3 interface displays very large positive linear magnetoresistance (MR). Soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) reveals the t(2g) nature of the carriers. First principles calculations strongly suggest that Zeeman splitting, caused by proximity magnetism and oxygen vacancies in SrTiO3, is responsible for the MR. This system offers an as-yet-unexplored route to pursue proximity-induced effects in the oxide two- dimensional t(2g) electron gas.

28. New bio-active, antimicrobial and adherent coatings of nanostructured carbon double-reinforced with silver and silicon by Matrix-Assisted Pulsed Laser Evaporation for medical applications

Authors: Duta, L; Ristoscu, C; Stan, GE; Husanu, MA; Besleaga, C; Chifiriuc, MC; Lazar, V; Bleotu, C; Miculescu, F; Mihailescu, N; Axente, E; Badiceanu, M; Bociaga, D; Mihailescu, IN

Published: MAY 31 2018, APPLIED SURFACE SCIENCE, 441, 883, DOI: 10.1016/j.apsusc.2018.02.047

We report on Matrix-Assisted Pulsed Laser Evaporation (MAPLE) deposition of Carbon thin films, simple or reinforced with intended concentrations of Ag and Si. A KrF* (lambda = 248 nm, tau(FWHM) < 25 ns, v = 10 Hz) excimer laser was used for irradiation. The effect of a post-deposition thermal treatment in vacuum was studied. Besides detailed morphological, compositional, structural and pull-out adherence characterizations, the potential of the carbonaceous films for medical applications was investigated in vitro by anti-biofilm and cytocompatibility assays. The microscopic images evidenced no delaminations. Micro-Raman spectroscopy revealed a graphitization tendency depending on preparation conditions, thermal treatment and reinforcing agents' presence. Adherence values improved considerably after thermal treatment. In vitro biological evaluation showed that the films containing similar to 1.85 at.% Ag were non-cytotoxic for MG63 cells, while eliciting a limited antimicrobial activity. The increase of Ag content to 3.6 at.% results in a significant enhancement of antimicrobial activity, whilst maintaining the cytotoxic action and adherence characteristics at acceptable levels. We propose a new class of metamaterials based on C reinforced with Ag and Si obtained by MAPLE for medical applications, i.e. the prevention and treatment of various infections associated with biofilms developed on implants and other medical equipments. (C) 2018 Elsevier B.V. All rights reserved.

29. Spectroscopic Characterisation of Multiferroic Interfaces

Authors: Husanu, MA; Vaz, CAF

Published: 2018, SPECTROSCOPY OF COMPLEX OXIDE INTERFACES: PHOTOEMISSION AND RELATED SPECTROSCOPIES, 266, 281, DOI: 10.1007/978-3-319-74989-1_10

In this chapter we discuss the capabilities of X-ray photoemission and absorption spectroscopies for the investigation of the electronic, magnetic and electric properties of multiferroic materials and heterostructures. As complementary techniques providing element selective information on both occupied and empty states, their combination delivers a comprehensive picture of the chemical state of individual species, magnetic moments, bulk and surface band structure, and local atomic environment at the interface between dissimilar materials. By directly probing the electronic structure at the atomic level, unique insights can be learned about the mechanisms responsible for the magnetoelectric couplings in this fascinating class of materials.

30. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO3/SrTiO3 If Interfaces

Authors: Chikina, A; Lechermann, F; Husanu, MA; Caputo, M; Cancellieri, C; Wang, XQ; Schmitt, T; Radovic, M; Strocov, VN

Published: AUG 2018, ACS NANO, 12, 7935, DOI: 10.1021/acsnano.8b02335

Interfacing different transition-metal oxides opens a route to functionalizing their rich interplay of electron, spin, orbital, and lattice degrees of freedom for electronic and spintronic devices. Electronic and magnetic properties of SrTiO3-based interfaces hosting a mobile two-dimensional electron system (2DES) are strongly influenced by oxygen vacancies, which form an electronic dichotomy, where strongly correlated localized electrons in the in-gap states (IGSs) coexist with noncorrelated delocalized 2DES. Here, we use resonant soft-X-ray photoelectron spectroscopy to prove the e(g) character of the IGSs, as opposed to the t(2g) character of the 2DES in the paradigmatic LaAlO3/SrTiO3 interface. We furthermore separate the d(xy) and d(xz)/d(xz) orbital contributions based on deeper consideration of the resonant photoexcitation process in terms of orbital and momentum selectivity. Supported by a self-consistent combination of density functional theory and dynamical mean field theory calculations, this experiment identifies local orbital reconstruction that goes beyond the conventional e(g)-vs-t(2g) band ordering. A hallmark of oxygen-deficient LaAlO3/SrTiO3 is a significant hybridization of the e(g) and t(2g) orbitals. Our findings provide routes for tuning the electronic and magnetic properties of oxide interfaces through "defect engineering" with oxygen vacancies.

31. Optimized silicon reinforcement of carbon coatings by pulsed laser technique for superior functional biomedical surfaces fabrication

Authors: Mihailescu, IN; Bociaga, D; Popescu-Pelin, G; Stan, GE; Duta, L; Socol, G; Chifiriuc, MC; Bleotu, C; Lazar, V; Husanu, MA; Zgura, I; Miculescu, F; Negut, I; Hapenciuc, C

Published: JUN 1 2017, BIOFABRICATION, 9, DOI: 10.1088/1758-5090/aa7076

We report on the fabrication of silicon-reinforced carbon (C: Si) structures by combinatorial pulsed laser deposition to search for the best design for a new generation of multi-functional coated implants. The synthesized films were characterized from the morphological, structural, compositional, mechanical and microbiological points of view. Scanning electron microscopy revealed the presence, on top of the deposited layers, of spheroid particulates with sizes in the micron range. No microcracks or delaminations were observed. Energy dispersive x-ray spectroscopy and grazing incidence x-ray diffraction pointed to the existence of aC to Si compositional gradient from one end of the film to the other. Raman investigation revealed a relatively high sp(3) hybridization of up to 80% at 40-48 mm a part from the edge with higher Ccontent. Si addition was demonstrated to significantly increase C: Si film bonding to the substrate, with values above the ISO threshold for coatings to be used in high-loading biomedical applications. Surface energy studies pointed to an increase in the hydrophilic character of the deposited structures along with Si content up to 52 m Nm(-1'). In certain cases, the Si-reinforced Ccoatings elicited an antimicrobial biofilm action. The presence of Si was proven to be benign to HEp-2 cells of human origin, without interfering with their cellular cycle. On this basis, reliable C: Si structures with good adherence to the substrate and high efficiency against microbial biofilms can be developed for implant coatings and other advanced medical devices.

32. Double band inversion in alpha-Sn: Appearance of topological surface states and the role of orbital composition

Authors: Rogalev, VA; Rauch, T; Scholz, MR; Reis, F; Dudy, L; Fleszar, A; Husanu, MA; Strocov, VN; Henk, J; Mertig, I; Schafer, J; Claessen, R

Published: APR 27 2017, PHYSICAL REVIEW B, 95, DOI: 10.1103/PhysRevB.95.161117

The electronic structure of alpha-Sn (001) thin films strained compressively in-plane was studied both experimentally and theoretically. A new topological surface state (TSS) located entirely within the gapless projected bulk bands is revealed by ab initio-based tight-binding calculations as well as directly accessed by soft x-ray angle-resolved photoemission. The topological character of this state, which is a surface resonance, is confirmed by unravelling the band inversion and by calculating the topological invariants. In agreement with experiment, electronic structure calculations show the maximum density of states in the subsurface region, while the already established TSS near the Fermi level is strongly localized at the surface. Such varied behavior is explained by the differences in orbital composition between the specific TSS and its associated bulk states, i.e., their hybridization, respectively.

33. Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

Authors: Schutz, P; Di Sante, D; Dudy, L; Gabel, J; Stubinger, M; Kamp, M; Huang, Y; Capone, M; Husanu, MA; Strocov, VN; Sangiovanni, G; Sing, M; Claessen, R

Published: DEC 22 2017, PHYSICAL REVIEW LETTERS, 119, DOI: 10.1103/PhysRevLett.119.256404

Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO3 ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading microscopic mechanisms, i.e., a dimensionality-induced readjustment of octahedral rotations, magnetism, and electronic correlations. The astonishing resemblance of the band structure in the two-dimensional limit to that of bulk Sr2IrO4 opens new avenues to unconventional superconductivity by "clean" electron doping through electric field gating.

34. Bioglass implant-coating interactions in synthetic physiological fluids with varying degrees of biomimicry

Authors: Popa, AC; Stan, GE; Husanu, MA; Mercioniu, I; Santos, LF; Fernandes, HR; Ferreira, JMF

Published: 2017, INTERNATIONAL JOURNAL OF NANOMEDICINE, 12, 707, DOI: 10.2147/IJN.S123236

Synthetic physiological fluids are currently used as a first in vitro bioactivity assessment for bone grafts. Our understanding about the interactions taking place at the fluid-implant interface has evolved remarkably during the last decade, and does not comply with the traditional International Organization for Standardization/final draft International Standard 23317 protocol in purely inorganic simulated body fluid. The advances in our knowledge point to the need of a true paradigm shift toward testing physiological fluids with enhanced biomimicry and a better understanding of the materials' structure-dissolution behavior. This will contribute to "upgrade" our vision of entire cascades of events taking place at the implant surfaces upon immersion in the testing media or after implantation. Starting from an osteoinductive bioglass composition with the ability to alleviate the oxidative stress, thin bioglass films with different degrees of polymerization were deposited onto titanium substrates. Their biomineralization activity in simulated body fluid and in a series of new inorganic-organic media with increasing biomimicry that more closely simulated the human intercellular environment was compared. A comprehensive range of advanced characterization tools (scanning electron microscopy; grazing-incidence X-ray diffraction; Fourier-transform infrared, micro-Raman, energy-dispersive, X-ray photoelectron, and surface-enhanced laser desorption/ionization time-of-flight mass spectroscopies; and cytocompatibility assays using mesenchymal stem cells) were used. The information gathered is very useful to biologists, biophysicists, clinicians, and material scientists with special interest in teaching and research. By combining all the analyses, we propose herein a step forward toward establishing an improved unified protocol for testing the bioactivity of implant materials.

35. Electronic band structure of the buried SiO2/SiC interface investigated by soft x-ray ARPES

Authors: Woerle, J; Bisti, F; Husanu, MA; Strocov, VN; Schneider, CW; Sigg, H; Gobrecht, J; Grossner, U; Camarda, M

Published: MAR 27 2017, APPLIED PHYSICS LETTERS, 110, DOI: 10.1063/1.4979102

The electronic structure of the SiO2/SiC (0001) interface, buried below SiO2 layers with a thickness from 2 to 4 nm, was explored using soft X-ray angle-resolved photoemission spectroscopy with photon energies between 350 and 1000 eV. The measurements have detected the characteristic k-dispersive energy bands of bulk Silicon Carbide (SiC) below the SiO2 layer without any sign of additional dispersive states, up to an estimated instrumental sensitivity of approximate to 5 x 10(9) cm 2 eV. This experimental result supports the physical picture that the large density of interface traps observed in macroscopic measurements results from dangling bonds randomized by the SiO2 rather than from Shockley-Tamm surface derived states extending into the bulk SiC. Published by AIP Publishing.

36. Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators

Authors: Krieger, JA; Chang, CZ; Husanu, MA; Sostina, D; Ernst, A; Otrokov, MM; Prokscha, T; Schmitt, T; Suter, A; Vergniory, MG; Chulkov, EV; Moodera, JS; Strocov, VN; Salman, Z

Published: NOV 2 2017, PHYSICAL REVIEW B, 96, DOI: 10.1103/PhysRevB.96.184402

We combine low energy muon spin rotation (LE-mu SR) and soft-x-ray angle-resolved photoemission spectroscopy (SX-ARPES) to study the magnetic and electronic properties of magnetically doped topological insulators, (Bi, Sb)(2)Te-3. We find that one achieves a full magnetic volume fraction in samples of (V/Cr)(x)(Bi, Sb)(2-x)Te-3 at doping levels x greater than or similar to 0.16. The observed magnetic transition is not sharp in temperature indicating a gradual magnetic ordering. We find that the evolution of magnetic ordering is consistent with formation of ferromagnetic islands which increase in number and/or volume with decreasing temperature. Resonant ARPES at the V L-3 edge reveals a nondispersing impurity band close to the Fermi level as well as V weight integrated into the host band structure. Calculations within the coherent potential approximation of the V contribution to the spectral function confirm that this impurity band is caused by V in substitutional sites. The implications of our results on the observation of the quantum anomalous Hall effect at mK temperatures are discussed.

37. Discovery of Lorentz-violating type II Weyl fermions in LaAlGe

Authors: Xu, SY; Alidoust, N; Chang, GQ; Lu, H; Singh, B; Belopolski, I; Sanchez, DS; Zhang, X; Bian, G; Zheng, H; Husanu, MA; Bian, Y; Huang, SM; Hsu, CH; Chang, TR; Jeng, HT; Bansil, A; Neupert, T; Strocov, VN; Lin, H; Jia, SA; Hasan, MZ

Published: JUN 2017, SCIENCE ADVANCES, 3, DOI: 10.1126/sciadv.1603266

In quantum field theory, Weyl fermions are relativistic particles that travel at the speed of light and strictly obey the celebrated Lorentz symmetry. Their low-energy condensed matter analogs are Weyl semimetals, which are conductors whose electronic excitations mimic the Weyl fermion equation of motion. Although the traditional (type I) emergent Weyl fermions observed in TaAs still approximately respect Lorentz symmetry, recently, the so-called type II Weyl semimetal has been proposed, where the emergent Weyl quasiparticles break the Lorentz symmetry so strongly that they cannot be smoothly connected to Lorentz symmetric Weyl particles. Despite some evidence of nontrivial surface states, the direct observation of the type II bulk Weyl fermions remains elusive. We present the direct observation of the type II Weyl fermions in crystalline solid lanthanum aluminum germanide (LaAlGe) based on our photoemission data alone, without reliance on band structure calculations. Moreover, our systematic data agree with the theoretical calculations, providing further support on our experimental results.

38. Aging phenomena and wettability control of plasma deposited carbon nanowall layers

Authors: Vizireanu, S; Ionita, MD; Ionita, ER; Stoica, SD; Teodorescu, CM; Husanu, MA; Apostol, NG; Baibarac, M; Panaitescu, D; Dinescu, G

Published: NOV 2017, PLASMA PROCESSES AND POLYMERS, 14, DOI: 10.1002/ppap.201700023

This paper reports on the aging of carbon nanowalls (CNW) and modification of their wettability by the storage time, growth conditions, and post-fabrication plasma treatments. The as-deposited CNW initially exhibit marked hydrophilic behavior (fresh CNW), but within a few days they become highly hydrophobic (aged CNW). Their final hydrophobicity is closely related to their topography which is controlled by the deposition parameters. In addition, subsequent fluorinated plasma treatments result in super-hydrophobic CNW layers, irrespective of the hydrophilic or hydrophobic character of the pre-treated samples. To explain this, we show that the CNW edges contain many defects initially, but such defects become passivated in time. As a result, the surfaces become highly hydrophobic after aging or fluorination, having inert stable terminations.

39. 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.

40. Fabrication of antimicrobial silver-doped carbon structures by combinatorial pulsed laser deposition

Authors: Mihailescu, IN; Bociaga, D; Socol, G; Stan, GE; Chifiriuc, MC; Bleotu, C; Husanu, MA; Popescu-Pelin, G; Duta, L; Luculescu, CR; Negut, I; Hapenciuc, C; Besleaga, C; Zgura, I; Miculescu, F

Published: DEC 30 2016, INTERNATIONAL JOURNAL OF PHARMACEUTICS, 515, 606, DOI: 10.1016/j.ijpharm.2016.10.041

We report on the selection by combinatorial pulsed laser deposition of Silver-doped Carbon structures with reliable physical-chemical characteristics and high efficiency against microbial biofilms. The investigation of the films was performed by scanning electron microscopy, high resolution atomic force microscopy, energy dispersive X-Ray Spectroscopy, X-ray diffraction, Raman spectroscopy, bonding strength "pull-out" tests, and surface energy measurements. In vitro biological assays were carried out using a large spectrum of bacterial and fungal strains, i.e., Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Enterococcus faecalis and Candida albicans. The biocompatibility of the films obtained was evaluated on MG63 mammalian cell cultures. The optimal combination with reasonable physical-chemical properties, efficient protection against microbial colonization and beneficial effects on human cells was found for Silver-doped Carbon films containing 2 to 7 at.% silver. These mixtures can be used to fabricate safe and efficient coatings of metallic implants, with the goal to decrease the risk of implant associated biofilm infections which are difficult to treat and often responsible for implant failure. (C) 2016 Elsevier B.V. All rights reserved.

41. Structural and biological evaluation of lignin addition to simple and silver-doped hydroxyapatite thin films synthesized by matrix-assisted pulsed laser evaporation

Authors: Jankovic, A; Erakovic, S; Ristoscu, C; Mihailescu, N; Duta, L; Visan, A; Stan, GE; Popa, AC; Husanu, MA; Luculescu, CR; Srdic, VV; Janackovic, D; Miskovic-Stankovic, V; Bleotu, C; Chifiriuc, MC; Mihailescu, IN

Published: JAN 2015, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 26, DOI: 10.1007/s10856-014-5333-y

We report on thin film deposition by matrix-assisted pulsed laser evaporation of simple hydroxyapatite (HA) or silver (Ag) doped HA combined with the natural biopolymer organosolv lignin (Lig) (Ag:HA-Lig). Solid cryogenic target of aqueous dispersions of Ag:HA-Lig composite and its counterpart without silver (HA-Lig) were prepared for evaporation using a KrF* excimer laser source. The expulsed material was assembled onto TiO2/Ti substrata or silicon wafers and subjected to physical-chemical investigations. Smooth, uniform films adherent to substratum were observed. The chemical analyses confirmed the presence of the HA components, but also evidenced traces of Ag and Lig. Deposited HA was Ca deficient, which is indicative of a film with increased solubility. Recorded X-ray Diffraction patterns were characteristic for amorphous films. Lig presence in thin films was undoubtedly proved by both X-ray Photoelectron and Fourier Transform Infra-Red Spectroscopy analyses. The microbiological evaluation showed that the newly assembled surfaces exhibited an inhibitory activity both on the initial steps of biofilm forming, and on mature bacterial and fungal biofilm development. The intensity of the antibiofilm activity was positively influenced by the presence of the Lig and/or Ag, in the case of Staphylococcus aureus, Pseudomonas aeruginosa and Candida famata biofilms. The obtained surfaces exhibited a low cytotoxicity toward human mesenchymal stem cells, being therefore promising candidates for fabricating implantable biomaterials with increased biocompatibility and resistance to microbial colonization and further biofilm development.

42. Spectro-microscopic photoemission evidence of charge uncompensated areas in Pb(Zr,Ti)O-3(001) layers

Authors: Popescu, DG; Husanu, MA; Trupina, L; Hrib, L; Pintilie, L; Barinov, A; Lizzit, S; Lacovig, P; Teodorescu, CM

Published: 2015, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17, 520, DOI: 10.1039/c4cp04546g

Photoelectron spectroscopy studies of (001) oriented PbTi0.8Zr0.2O3 (PZT) single crystal layers with submicron resolution revealed areas with different Pb 5d binding energies, attributed to the different charge and polarization states of the film surface. Two novel effects are evidenced by using intense synchrotron radiation beam experiments: (i) the progressive increase of a low binding energy component for the Pb core levels (evidenced for both 5d and 4f, on two different measurement setups), which can be attributed to a partial decomposition of the PZT film at its surface and promoting the growth of metallic Pb during the photoemission process, with the eventuality of the progressive formation of areas with downwards ferroelectric polarization; (ii) for films annealed in oxygen under clean conditions (in an ultrahigh vacuum installation) a huge shift of the Pb 5d core levels (by 8-9 eV) towards higher binding energies is attributed to the formation of areas with depleted mobile charge carriers, whose surface density is insufficient to screen the depolarization field. This shift is attenuated progressively with time, as the sample is irradiated with high flux soft X-rays. The formation of these areas with strong internal electric field promotes these films as good candidates for photocatalysis and solar cells, since in the operation of these devices the ability to perform charge separation and to avoid electron-hole recombination is crucial.

43. Correlation of optical reflectivity with numerical calculations for a two-dimensional photonic crystal designed in Ge

Authors: Husanu, MA; Popescu, DG; Ganea, CP; Anghel, I; Florica, C

Published: DEC 10 2015, EUROPEAN PHYSICAL JOURNAL D, 69, DOI: 10.1140/epjd/e2015-60478-7

A two dimensional photonic crystal (2DPhC) with triangular symmetry is investigated using optical reflectivity measurements and numerical calculations. The system has been obtained by direct laser writing, using a pulsed laser (lambda = 775 nm), perforating an In-doped Ge wafer. A lattice of holes with well-defined symmetry has been designed. Analyzing the spectral signature of PBGs recorded experimentaly with finite difference time domain theoretical calculations one was able to prove the relation between the geometric parameters (hole format, lattice constant) of the system and its ability to trap and guide the radiation in specific energy range. It was shown that at low frequency and telecommunication ranges of transvelsal electric modes photonic band gap occur. This structure may have potential aplications in designing photonic devices with applications in energy storage and conversion as potential alternative to Si-based technology.

44. Photoelectron spectroscopy and spectro-microscopy of Pb(Zr,Ti)O-3 (111) thin layers: Imaging ferroelectric domains with binding energy contrast

Authors: Husanu, MA; Popescu, DG; Tache, CA; Apostol, NG; Barinov, A; Lizzit, S; Lacovig, P; Teodorescu, CM

Published: OCT 15 2015, APPLIED SURFACE SCIENCE, 352, 81, DOI: 10.1016/j.apsusc.2015.01.153

The ability of photoelectron spectro-microscopy with sub-micrometer lateral resolution to identify ferroelectric domains by analysis of surface band bendings is demonstrated on lead zirco-titanate PZT(1 1 1) thin films grown by pulsed laser deposition. Conventional synchrotron radiation X-ray photoelectron spectroscopy allowed one to derive the surface composition of the sample and evidenced shifts toward higher binding energy when the sample is subject to intense soft X-ray beam. A basic model is developed which supposes that photogenerated carriers reduce the depolarization field, yielding a lower torque applied to the ferroelectric polarization. As a consequence, the out-of-plane component of the polarization increases. Domain migration during irradiation with soft X-ray is inferred from the relative amplitude of the components with different binding energy. When the flux density of soft X-ray is on the order of 1011 photons/(s mu m(2)), metal Pb clusters are formed at the surface on areas with the out-of-plane component of the polarization pointing outwards only. (C) 2015 Elsevier B.V. All rights reserved.

45. Surface topography to reflectivity mapping in two-dimensional photonic crystals designed in germanium

Authors: Husanu, MA; Ganea, CP; Anghel, I; Florica, C; Rasoga, O; Popescu, DG

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1191, DOI: 10.1016/j.apsusc.2015.07.218

Light confinement in a two dimensional photonic crystal (2D PhC) with hexagonal symmetry is studied using infra-red reflectance spectromicroscopy and numerical calculations. The structure has been realized by laser ablation, using a pulsed laser (lambda = 775 nm), perforating an In-doped Ge wafer and creating a lattice of holes with well-defined symmetry. Correlating the spectral signature of the photonic gaps recorded experimentally with the results obtained in the finite difference time domain and finite difference frequency domain calculations, we established the relationship between the geometric parameters of the structure (lattice constants, shape of the hole) and its efficiency in trapping and guiding the radiation in a well-defined frequency range. Besides the gap in the low energy range of transversal electric modes, a second one is identified in the telecommunication range, originating in the localization of the leaky modes within the radiation continuum. The emerging picture is of a device with promising characteristics as an alternative to Si-based technology in photonic device fabrication with special emphasize in energy storage and conversion. (C) 2015 Elsevier B.V. All rights reserved.

46. Influence of hole depletion and depolarizing field on the BaTiO3/La0.6Sr0.4MnO3 interface electronic structure revealed by photoelectron spectroscopy and first-principles calculations

Authors: Popescu, DG; Barrett, N; Chirila, C; Pasuk, I; Husanu, MA

Published: DEC 28 2015, PHYSICAL REVIEW B, 92, DOI: 10.1103/PhysRevB.92.235442

The effects of the bonding mechanism and band alignment in a ferroelectric (FE) BaTiO3/ferromagnetic La0.6Sr0.4MnO3 heterostructure are studied using x-ray photoelectron spectroscopy and first-principles calculations. The band lineup at the interface is determined by a combination of band bending and polarization-induced modification of core-hole screening. A Schottky barrier height for electrons of 1.22 +/- 0.17 eV is obtained in the case of downwards FE polarization of the top layer. The symmetry of the bonding states is emphasized by integrating the local density of states +/- 0.2 eV around the Fermi level, and strong dependence on the FE polarization is found: upwards, polarization stabilizes Ti t(2g) (xy) orbitals, while downwards, polarization favors Ti t(2g) (yz) symmetry. It is predicted that the abrupt (La, Sr)vertical bar TiO2 interface is magnetoelectrically active, leading to a A-type antiferromagnetic coupling of the first TiO2 interface layer with the underlying manganite layer through a superexchange mechanism.

47. The Role of Ambient Gas and Pressure on the Structuring of Hard Diamond-Like Carbon Films Synthesized by Pulsed Laser Deposition

Authors: Popescu, AC; Stan, GE; Duta, L; Nita, C; Popescu, C; Surdu, VA; Husanu, MA; Bita, B; Ghisleni, R; Himcinschi, C; Craciun, V

Published: JUN 2015, MATERIALS, 8, 3305, DOI: 10.3390/ma8063284

Hard carbon thin films were synthesized on Si (100) and quartz substrates by the Pulsed Laser Deposition (PLD) technique in vacuum or methane ambient to study their suitability for applications requiring high mechanical resistance. The deposited films' surface morphology was investigated by scanning electron microscopy, crystalline status by X-ray diffraction, packing and density by X-ray reflectivity, chemical bonding by Raman and X-ray photoelectron spectroscopy, adherence by pull-out measurements and mechanical properties by nanoindentation tests. Films synthesized in vacuum were a-C DLC type, while films synthesized in methane were categorized as a-C:H. The majority of PLD films consisted of two layers: one low density layer towards the surface and a higher density layer in contact with the substrate. The deposition gas pressure played a crucial role on films thickness, component layers thickness ratio, structure and mechanical properties. The films were smooth, amorphous and composed of a mixture of sp(3)-sp(2) carbon, with sp(3) content ranging between 50% and 90%. The thickness and density of the two constituent layers of a film directly determined its mechanical properties.

48. Epitaxial growth of Au on Ge(001) surface: Photoelectron spectroscopy measurements and first-principles calculations

Authors: Popescu, DG; Husanu, MA

Published: FEB 3 2014, THIN SOLID FILMS, 552, 249, DOI: 10.1016/j.tsf.2013.12.049

A single atomic Au layer is grown epitaxially on a Ge(001) surface featured by (2 x 1) reconstruction. The low energy electron diffraction pattern of the Au/Ge(001) surface indicates the formation of a square structure with the length of crystalline domains of similar to 3 nm. Ab-initio calculations show that Au growth stabilizes the Ge surface in symmetric dimers and angle-resolved photoelectron spectroscopy measurements reveal its metallic character. The modifications in the electronic properties of the Ge surface as a result of annealing are discussed and the consequences as reflected in X-ray photoelectron spectroscopy (XPS) measurements are underlined. The deformation density indicates the regions with covalent Au-Ge bonds. These bonds are identified from Au 4f and Ge 3d XPS data. (C) 2013 Elsevier B.V. All rights reserved.

49. Nanomechanical characterization of bioglass films synthesized by magnetron sputtering

Authors: Popa, AC; Marques, VMF; Stan, GE; Husanu, MA; Galca, AC; Ghica, C; Tulyaganov, DU; Lemos, AF; Ferreira, JMF

Published: FEB 28 2014, THIN SOLID FILMS, 553, 172, DOI: 10.1016/j.tsf.2013.10.104

Bioactive glasses are osteoproductive-type inorganic materials possessing the highest indices of bioactivity in both bulk and thin film forms. The prerequisites for reliable implant-type coatings are both their biological and mechanical performances. Whilst the bioglass films' structural, chemical and biological properties have been studied extensively, information about their mechanical performance is scarce. Here, transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nanoindentation and pull-out measurements were employed to assess the morphological, chemical, structural and mechanical properties of the bioglass films deposited onto Ti substrates by radio-frequency magnetron sputtering (RF-MS). The biological safety of the thin bioglass films was evaluated preliminarily in vitro by investigating the adherence, proliferation and cytotoxicity of fibroblast cells cultivated on their surface. Our study emphasize the versatility of RF-MS, showing how bioglass films' features such as composition, structure, bonding strength, hardness, elastic modulus and biological response can be conveniently adapted by tuning the RF-MS working conditions, and therefore demonstrating the unexplored potential of this deposition technique for preparing quality biomimetic glass coatings. (C) 2013 Elsevier B. V. All rights reserved.

50. Gold nano-island arrays on silicon as SERS active substrate for organic molecule detection

Authors: Ignat, T; Husanu, MA; Munoz, R; Kusko, M; Danila, M; Teodorescu, CM

Published: JAN 1 2014, THIN SOLID FILMS, 550, 360, DOI: 10.1016/j.tsf.2013.10.151

Gold islands forming highly controlled arrays have been fabricated by two potential step electrochemical deposition method using nanopatterned Si surface templates. In the present work, the Raman scattering studies realized using 11-mercaptoundecanoic probe molecule showed that such structures exhibit an enhanced Raman signal compared with nanostructured physical deposited thin gold film on flat silicon substrate and can be valued as surface-enhanced Raman scattering substrates. Besides the more appropriate management of nano-island arrays distribution, the high ratio of their Raman signals can be explain by the epitaxial-like growth mechanism of themetallic nano-islands, clearly showed by X-ray diffraction studies. Furthermore, the substrates enabled reproducibility and stability detection due to the chemically assembling of organothiol molecules, the X-ray photoelectron spectroscopy studies confirming formation of the thiolate species which corresponds to Au - S bonds, and also, the unwanted 'hot-spots' are missing, which make them suitable for high sensitivity biosensing applications. (C) 2013 Published by Elsevier B.V.

51. Structure, reactivity, electronic configuration and magnetism of samarium atomic layers deposited on Si(001) by molecular beam epitaxy

Authors: Gheorghe, NG; Lungu, GA; Husanu, MA; Costescu, RM; Macovei, D; Teodorescu, CM

Published: FEB 15 2013, APPLIED SURFACE SCIENCE, 267, DOI: 10.1016/j.apsusc.2012.08.016

The surface structure, interface reactivity, electron configuration and magnetic properties of Sm layers deposited on Si(0 0 1) at various temperatures are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and magneto-optical Kerr effect (MOKE). It is found that metal Sm is present on samples prepared at low temperature, with an interface layer containing SmSi2 and Sm4Si3. When samples are prepared at high temperature, much less metal Sm is found, with an increasing amount of SmSi2. Room temperature ferromagnetism is observed for all prepared layers, with a decrease of the saturation magnetization when samples are prepared at high temperature. It is found that ferromagnetism implies mostly a compound with approximate stoichiometry Sm4Si3. Also, the decrease in the intensity of the XAS 2p(3/2) -> 3d white lines with the corresponding increasing amount of SmSi2 may be explained by assuming a higher occupancy of Sm 5d orbitals (5d(2) configuration), most probably due to hybridation effects. (C) 2012 Elsevier B. V. All rights reserved.

52. Multi-layer haemocompatible diamond-like carbon coatings obtained by combined radio frequency plasma enhanced chemical vapor deposition and magnetron sputtering

Authors: Popa, AC; Stan, GE; Husanu, MA; Pasuk, I; Popescu, ID; Popescu, AC; Mihailescu, IN

Published: DEC 2013, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 24, 2707, DOI: 10.1007/s10856-013-5026-y

Radio-frequency Plasma Enhanced Chemical Vapour Deposition (in different methane dilutions) was used to synthesize adherent and haemocompatible diamond-like carbon (DLC) films on medical grade titanium substrates. The improvement of the adherence has been achieved by interposing a functional buffer layer with graded composition TixTiC1-x (x = 0-1) synthesized by magnetron co-sputtering. Bonding strength values of up to similar to 67 MPa have been measured by pull-out tests. Films with different sp(3)/sp(2) ratio have been obtained by changing the methane concentration in the deposition chamber. Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed for the physical-chemical characterization of the samples. The highest concentration of sp(3)-C (similar to 87 %), corresponding to a lower DLC surface energy (28.7 mJ/m(2) ), was deposited in a pure methane atmosphere. The biological response of the DLC films was assayed by a state-of-the-art biological analysis method (surface enhanced laser desorption/ionization-time of flight mass spectroscopy), in conjunction with other dedicated testing techniques: Western blot and partial thromboplastin time. The data support a cause-effect relationship between sp(3)-C content, surface energy and coagulation time, as well as between platelet-surface adherence properties and protein adsorption profiles.

53. Au-Ge bonding on a uniformly Au-covered Ge(001) surface

Authors: Popescu, DG; Husanu, MA

Published: APR 2013, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 7, 277, DOI: 10.1002/pssr.201307029

The structure and electronic properties of the system resulted by epitaxial growth of a single atomic Au layer on a heated Ge(001) surface featured by (2 x 1) reconstruction are studied. The deposition at similar to 750 K results in a well-ordered Au surface featured by ripples separated by four times the theoretical distance between two neighboring Au atoms. As revealed by valence-band photoemission studies, the Au/Ge(001) system has metallic character. Correlating X-ray photoelectron spectroscopy results with first-principles calculations we derive the implications on the covalent bonding of Au on the Ge dimer surface. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

54. Epitaxial ferromagnetic samarium and samarium silicide synthesized on Si(001)

Authors: Costescu, RM; Gheorghe, NG; Husanu, MA; Lungu, GA; Macovei, D; Pintilie, I; Popescu, DG; Teodorescu, CM

Published: OCT 2012, JOURNAL OF MATERIALS SCIENCE, 47, DOI: 10.1007/s10853-012-6672-z

Samarium is deposited on Si(001) at various temperatures (room temperature to 400 A degrees C), and the surface structure, interface reactivity, electron configuration, and magnetic properties are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and magneto-optical Kerr effect (MOKE), respectively. It is found that metal Sm is present on samples prepared at room temperature with an interface layer containing mostly Sm2+ and a lower amount of Sm3+. When samples are prepared at high temperature, much less Sm-0 is found with an increasing amount of Sm2+. Freshly prepared Sm-0 and SmSi2 layers react strongly with oxygen from the residual gas, promoting formation of Sm2O3 at the expense of both metal Sm and SmSi2. Room temperature ferromagnetism is observed for all prepared layers with a decrease of the saturation magnetisation when samples are prepared at high temperature. It is found that ferromagnetism implies mostly Sm3+ and Sm metal. In addition to these findings, this work proposes a new assignment of the Sm 3d chemically shifted components. Also, a noticeable variation of the XPS Sm 3d spin-orbit splitting is found as a function of the Sm ionization state.

55. Atomic structure and reactivity of ferromagnetic Fe deposited on Si(001)

Authors: Gheorghe, NG; Husanu, MA; Lungu, GA; Costescu, RM; Macovei, D; Teodorescu, CM

Published: FEB 2012, JOURNAL OF MATERIALS SCIENCE, 47, DOI: 10.1007/s10853-011-5963-0

This study presents a correlated study of structural, reactivity, and magnetic properties of ultrathin Fe layers grown on Si(001) by molecular beam epitaxy in ultrahigh vacuum. The interface reactivity is characterized by Auger electron spectroscopy. The surface structure is characterized by low electron energy diffraction with spot profile analysis. The magnetism of the synthesized layers is investigated by magneto-optical Kerr effect. At room temperature, metal Fe layers with poor long-range order are synthesized; these layers are ferromagnetic with an extremely low coercitive field (below 1 Oe). The reactivity with Si is low in this case, with formation of an interface layer of about 8 angstrom Fe equivalent thickness with about 7 at.% Si diffused. Samples synthesized at higher temperatures (500 degrees C) exhibit better long-range order, though the Fe reactivity with Si is higher and leads to the formation of an interface compound whose approximate stoichiometry is very close to Fe(3)Si. Once this compound is formed (for an equivalent Fe thickness of about 14 monolayers), disordered metal Fe islands are developing with subsequent Fe deposition, which contain also about 8 at.% Si diffused. These structures exhibit a much lower ferrimagnetism, with saturation magnetization about one order of magnitude lower than in the case of the room temperature synthesis. In this case of high temperature synthesis, two phases are observed, a ferrimagnetic one and a superparamagnetic one.

56. ATOMIC STRUCTURE AND MAGNETISM OF PLD DEPOSITED Tio(2):Fe

Authors: Costescu, RM; Lungu, GA; Socol, G; Gheorghe, NG; Macovei, D; Negrila, CC; Logofatu, C; Husanu, MA; Popescu, DG; Tache, CA; Teodorescu, CM

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, DOI:

TiO2:Fe thin films prepared by pulsed laser deposition exhibit in some case light dependent saturation magnetization, as determined from Kerr magnetometry measurements performed in dark or by illuminating the sample. This phenomenon is studied in correlation with local atomic structure investigated by extended X-ray absorption fine structure, composition and chemical state analyzed by X-ray photoelectron spectroscopy and by X-ray absorption near-edge structure. It is found that light-controllable magnetism is a property of a mixture of Fe and oxidized Fe clusters embedded in the anatase TiO2 matrix.

57. REACTIVITY, MAGNETISM AND LOCAL ATOMIC STRUCTURE IN FERROMAGNETIC FE LAYERS DEPOSITED ON SI(001)

Authors: Gheorghe, NG; Husanu, MA; Lungu, GA; Costescu, RM; Macovei, D; Popescu, DG; Teodorescu, CM

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, DOI:

This work presents recent studies concerning the synthesis of ultrathin ferromagnetic Fe layers on Si(001) and the correlated follow-up measurement of their structural properties, interface reactivity, and magnetism. This study is undertaken as function of the amount of Fe deposited and of substrate temperature. The interface reactivity is characterized by Auger electron spectroscopy. The surface structure is characterized by low electron energy diffraction (LEED). The local order of Fe atoms is investigated by X-ray absorption fine structure (XAFS) and the magnetism by magneto-optical Kerr effect (MOKE). A general trend established is that a higher deposition temperature stabilizes a better surface ordering, but also enhances Fe and Si interdiffusion and therefore decreases the magnetism. A surprising effect obtained by Fe deposition at room temperature is that, despite the rapid disappearance of the long range order with Fe deposition (no LEED pattern is observed for Fe coverage exceeding one monolayer), the material exhibits a significant uniaxial in-plane magnetic anisotropy. When the deposition is performed at high temperature (500 degrees C), a weak ferromagnetism is still observed, with saturation magnetization of about 10 % of the value obtained for room temperature deposition. The combined MOKE and EXAFS studies allowed inferring consistent values for the range of Fe thicknesses where the reaction takes place and the main properties of the distinct formed layers.

58. Successful Cleaning and Study of Contamination of Si(001) in Ultrahigh Vacuum

Authors: Gheorghe, NG; Lungu, GA; Husanu, MA; Costescu, RM

Published: 2011, PHYSICS CONFERENCE (TIM-10), 1387, DOI: 10.1063/1.3647078

This paper presents the very first surface physics experiment performed in ultrahigh vacuum (UHV) in Romania, using a new molecular beam epitaxy (MBE) installation. Cleaning of a Si(001) wafer was achieved by using a very simple technique: sequences of annealing at 900-1000 degrees C in ultrahigh vacuum: low 10(-8) mbar, with a base pressure of 1.5 x 10(-10) mbar. The preparation procedure is quite reproducible and allows repeated cleaning of the Si(001) after contamination in ultrahigh vacuum. The Si(001) single crystal surface is characterized by low energy electron diffraction (LEED), reflection high energy electron diffraction (RHEED), and Auger electron spectroscopy (AES). The latter technique is utilized in order to investigate the sample contamination by the residual gas in the UHV chamber, as determined by a residual gas analyzer (RGA). Unambiguous assignment of oxidized and unoxidized silicon is provided; also, an important feature is that the LVV Auger peak at 90-92 eV cannot be solely attributed to clean Si (i.e. Si surrounded only by Si), but also to silicon atoms bounded with carbon. Even with a sum of partial pressures of oxygen and carbon containing molecules in the range of 5 x 10(-10) mbar, the sample is contaminated very quickly, having a (1/e) lifetime of about 76 minutes.

59. Substrate-target distance dependence of structural and optical properties in case of Pb(Zr,Ti)O-3 films obtained by pulsed laser deposition

Authors: Galca, AC; Stancu, V; Husanu, MA; Dragoi, C; Gheorghe, NG; Trupina, L; Enculescu, M; Vasile, E

Published: MAR 1 2011, APPLIED SURFACE SCIENCE, 257, 5943, DOI: 10.1016/j.apsusc.2011.01.056

The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance. (C) 2011 Elsevier B.V. All rights reserved.

60. Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature

Authors: Stan, GE; Pasuk, I; Husanu, MA; Enculescu, I; Pina, S; Lemos, AF; Tulyaganov, DU; El Mabrouk, K; Ferreira, JMF

Published: DEC 2011, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 22, 2710, DOI: 10.1007/s10856-011-4441-1

Thin (380-510 nm) films of a low silica content bioglass with MgO, B2O3, and CaF2 as additives were deposited at low-temperature (150A degrees C) by radio-frequency magnetron sputtering onto titanium substrates. The influence of sputtering conditions on morphology, structure, composition, bonding strength and in vitro bioactivity of sputtered bioglass films was investigated. Excellent pull-out adherence (similar to 73 MPa) was obtained when using a 0.3 Pa argon sputtering pressure (BG-a). The adherence declined (similar to 46 MPa) upon increasing the working pressure to 0.4 Pa (BG-b) or when using a reactive gas mixture (similar to 50 MPa). The SBF tests clearly demonstrated strong biomineralization features for all bioglass sputtered films. The biomineralization rate increased from BG-a to BG-b, and yet more for BG-c. A well-crystallized calcium hydrogen phosphate-like phase was observed after 3 and 15 days of immersion in SBF in all bioglass layers, which transformed monotonously into hydroxyapatite under prolonged SBF immersion. Alkali and alkali-earth salts (NaCl, KCl and CaCO3) were also found at the surface of samples soaked in SBF for 30 days. The study indicated that features such as composition, structure, adherence and bioactivity of bioglass films can be tailored simply by altering the magnetron sputtering working conditions, proving that this less explored technique is a promising alternative for preparing implant-type coatings.

61. POLYMER-LIKE AND DIAMOND-LIKE CARBON COATINGS PREPARED BY RF-PECVD FOR BIOMEDICAL APPLICATIONS

Authors: Stan, GE; Marcov, DA; Popa, AC; Husanu, MA

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 718, DOI:

Hydrogenated amorphous carbon (a-C: H) films were grown by radio-frequency (1.78 MHz) plasma enhanced chemical vapour deposition technique onto medical grade Ti6Al4V substrates. By varying the deposition pressure (13.33 Pa and 53.33 Pa, respectively) and methane dilution (20% and 60%, respectively) several types of carbonic films were obtained, presenting different bonding structures, surface energies and morphological features reflected in their biological behaviour. FTIR, Raman, UV-Vis, XPS and AFM measurements were used for characterizing these structures. The surface energy was determined by contact angle measurements, and their thrombogenicity was tested by the activated partial thromboplastin time (aPTT) method. We have noticed that at the same values of methane in argon dilution but at different pressure values, the film structure was totally changed: soft polymer-like carbon (PLC) type at the higher pressure and hard diamond-like carbon (DLC) type at the lower pressure. Raman spectroscopy and XPS suggested that the highest sp(3) ratio (similar to 52%), was found for DLC films prepared in a 60% methane dilution in argon. It has been found that for both PLC and DLC structures the surface energy has a decreasing tendency with the methane concentration increase in the deposition atmosphere. Excellent aPTT results were obtained for the DLC-60 (18.6.+/- 0.3 min) and PLC-20 (17.4 +/- 0.5 min) structures, superior to those recorded for Ti6Al4V and PMMA commercial materials. These values recommend the prepared carbonic structures for medical applications: harder coatings (DLC) for metal prostheses (heart valves, acetabular cups etc.), while softer and flexible coatings (PLC) for the textile vessels or stents biofunctionalization.

62. Radiofrequency plasma beam deposition of various forms of carbon based thin films and their characterization

Authors: Vizireanu, S; Stoica, SD; Mitu, B; Husanu, MA; Galca, A; Nistor, L; Dinescu, G

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5381, DOI: 10.1016/j.apsusc.2008.08.042

The characteristics of carbonic materials obtained by downstream deposition in a low pressure argon plasma beam injected with acetylene are reported. The influence of substrate temperature, presence of Ni catalyst and hydrogen in gas composition on the material properties is described. By increasing the substrate temperature, an enhanced order in the material is revealed by Raman spectroscopy, while FTIR measurements show a decreasing of the hydrogen content and the disappearing of sp(1) hybridized carbon in the deposit. The SEM and Raman investigation show a clear tendency of crystalline phases formation when hydrogen is assisting the deposition. (C) 2008 Elsevier B. V. All rights reserved.

63. THE INTERCALATION OF PbI2 WITH 2,2 '-BIPYRIDINE EVIDENCED BY PHOTOLUMINESCENCE. FT-IR AND RAMAN SPECTROSCOPY

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I; Husanu, M; Bucur, C; Velula, T

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 675, DOI:

Hybrid material based on PbI2 intercalated with 2,2'-bypiridine (BIPY) was investigated by correlated studies of photoluminescence. infrared absorption and Raman spectroscopy. The PbI2(BIPY) intercalated compound has been synthesized by the chemical reaction of K1 and Pb(NO3)(2) in aqueous BIPY solution The optical studies reveal different properties for the hybrid material in comparison with those of pure PbI2 and BIPY. In the photoluminescence spectrum of the intercalated compound. recorded at liquid nitrogen temperature a new intense hand emission with maximum at 2 07 eV is observed. The excitation spectrum reveals it broad hand featured by several maxima at 2.77, 3.34 and 3 70 eV. New absorption bands at about 1589, 1489, 1435, 1312, 1009 cm(-1) are observed in the IR spectrum of PbI2(BIPY). The Raman spectrum of intercalated compound discloses new lines at 67, 83, 127 cm(-1) and the shift of two Raman lines from 994 cm(-1) to 1010 cm(-1) and from 1045 cm(-1) to 1060 cm(-1). A charge transfer process, leading to the formation of lead-BIPY coordination complexes. is considered its responsible for the strong host-guest interaction revealed by almost all experimental data

64. VIBRATIONAL PROPERTIES OF POLYANILINE FUNCTIONALIZED PbI2

Authors: Baltog, I; Baibarac, M; Mihut, L; Preda, N; Velula, T; Bucur, C; Husanu, M

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 688, DOI:

Functionalization of PbI2 with polyaniline-emeraldine base (PANI-EB) or polyaniline-emeraldine salt (PANI-ES) is demonstrated by Raman spectroscopy. Two functionalization methods were used: electrochemical polymerization of aniline onto the PbI2 modified Pt electrode and the mechanico-chemical reaction between PANI and PbI2. The functionalization induces changes in the Raman spectrum of PbI2 that consist in the appearance of new Raman lines with the peaks at 80, 144 and 170 cm(-1) The first line is the signature of the "stacking faults" that disrupt the stacking sequence of layers I-Pb-I atomic layers along the c crystalline axis by the intercalation of polymer molecules The bands at 144 and 170 cm(-1) are attributed to a vibrational mode associated to the Pb-NHR"(2) (R" = C6H4) bond.

65. Photoluminescence properties of composites based on zinc oxyde and single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Husanu, M; Velula, T; Bucur, C; Mihut, L; Preda, N

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 293, DOI:

Photoluminescence (PL) properties of the composites based on zinc oxide (ZnO) and single-walled carbon nanotubes (SWNTs) prepared by hydrothermal synthesis are studied in this paper. The emission and excitation spectra of nanometric ZnO powder are dramatically influenced by the adsorption of different molecules coming from the environment. Therefore, a special attention is given to reveal the influences of adsorption/de-sorption process on photoluminescence properties of zinc oxide nanoparticles. A quenching effect of the intrinsic PL is observed regularly when the ZnO is synthesized in the presence of SWNTs, i.e. when a ZnO/SWNTs composite is formed. A distinct feature of the ZnO/SWNTs composite, is an emission band with a maximum at 405-450 nm.

66. Particular signature of isolated and bundled carbon nanotubes in their Raman spectra

Authors: Husanu, M; Baibarac, M; Baltog, I

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, 699, DOI:

The efficiency of different surfactants (anionic, cationic, neutral) as chemical agents favoring in the unbinding of nanotube bundles in isolated entities is investigated by Raman and UV-VIS-NIR spectroscopy. ne neutral surfactants Tween 20 - polyoxyethylene sorbitan monolaurate (T-20-PSM) and Tween 80 - polyoxyethylene (80) sorbitan monooleate (T-80-PSM) have been found the most efficient. The isolated single walled carbon nanotubes (SWNTs) nanotubes are apprised at lambda(exc) = 1064 nm by two simultaneous modifications of the Raman spectra: i) narrowing of the band associated to the transversal vibration modes, i.e., G band (similar to 1592 cm(-1)); ii) change of shape of the complex band associated to the radial vibration modes (RBM) consequent on the decrease of the intensity of the components associated with the bundled nanotubes. The individualization of nanotubes is evidenced also in the UV-VIS-NIR absorption spectra by the appearance of a fine structure in the wide absorption band (similar to 1400-1750 nm) that is associated with the transitions E-S(11) of semiconducting SWNTs. The fine structure grows gradually with the separation degree in isolated nanotubes entities.

67. Non-covalent functionalization of carbon nanotubes: Experimental evidence for isolated and bundled tubes

Authors: Husanu, M; Baibarac, M; Baltog, I

Published: OCT 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 41, 69, DOI: 10.1016/j.physe.2008.06.001

Single-walled carbon nanotubes (SWNTs) may be used in technological applications as individual entities instead of bundled tubes. The Raman signature of these two forms is still a controversial subject. The profile, peak position and relative intensity of the Raman band associated with the tangential vibration modes (G band similar to 1600cm(-1)) and radial vibration modes (RBM similar to 100-200cm(-1)) are the main parameters which can reveal the dispersion state of nanotubes. Resonant Raman scattering and absorption spectroscopy on SWNTs furnish complementary information concerning the efficiency of the nanotube dispersion in individual entities. (C) 2008 Elsevier B.V. All rights reserved.

68. Vibrational and photoluminescence properties of composites based on zinc oxide and single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Lefrant, S; Mevellec, JY; Husanu, M

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2564, DOI: 10.1016/j.physe.2007.09.034

Composites based on zinc oxide (ZnO) nanoparticles and single-walled carbon nanotubes (SWNTs) were investigated by photoluminescence (PL) and Raman scattering. The room temperature PL spectrum of ZnO at the excitation wavelength of 335 nm displays a narrow excitonic band, peaking at 368 nm (3.36eV), and a wide one, disclosing two components with maxima at about 444 nm (2.79eV) and 560 nm (2.21eV) which are associated to the local oxygen vacancies and oxygen excess, respectively. Regardless the preparation method of the ZnO/SWNTs compound (electrochemical, mechanicochemical and hydrothermal synthesis), PL spectra reveal an increased quenching tendency with the concentration of nanotubes in the composite mass. As distinct feature in the PL spectra of ZnO/SWNTs composites are two bands, one at 450 nm (2.75 nm) and another one attributed to the formation of a donor-acceptor complex at 680 nm (1.82eV). The role of the dispersion of carbon nanotubes in the ZnO/SWNTs composite is observed by Raman scattering with the excitation wavelength of 676 nm. (C) 2007 Elsevier B.V. All rights reserved.

69. Raman and photoluminescence studies on intercalated lead iodide with pyridine and iodine

Authors: Preda, N; Mihut, L; Baibarac, M; Husanu, M; Bucur, C; Baltog, I

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 322, DOI:

Intercalated PbI2 compounds were prepared by exposing crystalline films and crystalline powders of lead iodide to pyridine or iodine vapor at room temperature. Correlated studies of optical absorption, Raman scattering and low temperature photoluminescence (PL) reveal different properties in comparison with those of pure crystalline PbI2 powder. Depending of the nature of intercalated molecules (organic or inorganic) the basic semiconducting properties of PbI2 are dramatically modified. The main signature of iodine intercalated PbI2 consists in a luminescence band peaking at 2.24 eV appearing at 77 K under 350 nm excitation light. In the case of pyridine intercalated PbI2 a new intense band at about 3.3 eV in the absorption spectrum is observed. The the PL spectra of pyridine intercalated PbI2 at 77 K change substantially when the excitation wavelength. The Raman spectra confirm the presence of pyridine between the PbI2 layers.

70. Resonant Raman scattering and absorption spectroscopy studies on individual carbon nanotubes in surfactant solutions

Authors: Husanu, M; Baibarac, M; Preda, N; Baltog, I

Published: JUL 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 1726, DOI:

Carbon Nanotubes are exotic low-dimensional systems, and due to their remarkable properties, are promising components for technological applications. The electronic and vibrational signatures raising from their existence as individual entities or associated in bundles, is still a controversed subject. A careful analysis of the G (similar to 1600 cm(-1)) and RBM (100-200 cm(-1)) band features as: profile, peak position and intensity in the Raman spectra may be a valuable indication about their dispersion state. The UV-VIS-NIR absorption spectrum comes to support this assumption. Observing the absorption spectra associated to resonant excitation of semiconducting and metallic nanotubes, may reveal complementary informations concerning the individualization procedure efficiency.

Dr. Marius HUSANU

Scientific Researcher I

Resume

Publications

1. Spin asymmetry of O 2p-related states in SrTiO3(001)

2. Enhancement of SrTiO3 photocatalytic efficiency by Al doping: Answers from the structure, morphology and electronic properties contributions

3. Experimental Band Structure of Pb(Zr,Ti)O-3: Mechanism of Ferroelectric Stabilization

4. Experimental Band Structure of Pb(Zr,Ti)O-3: Mechanism of Ferroelectric Stabilization

5. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe-0@Ni-0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)

6. Experimental Band Structure of Pb(Zr,Ti)O3: Mechanism of Ferroelectric Stabilization

7. Surface charge dynamics on air-exposed ferroelectric Pb(Zr,Ti)O3(001) thin films

8. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics

9. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)

10. Robust Electronic Structure of Manganite-Buffered Oxide Interfaces with Extreme Mobility Enhancement

11. Ferroelectricity modulates polaronic coupling at multiferroic interfaces

12. Impact of band-bending on the k-resolved electronic structure of Si-doped GaN

13. Re-entrant ferromagnetism at ultrahigh temperatures in epsilon-iron as possible origin of the geomagnetic field

14. Band-Order Anomaly at the gamma-Al2O3/SrTiO3 Interface Drives the Electron-Mobility Boost

15. Effect of strain and stoichiometry on the ferroelectric and pyroelectric properties of the epitaxial Pb(Zr0.2Ti0.8)O-3 films deposited on Si wafers

16. CO adsorption, reduction and oxidation on Pb(Zr,Ti)O-3(001) surfaces associated with negatively charged gold nanoparticles

17. Electron-polaron dichotomy of charge carriers in perovskite oxides

18. Polarization-dependent magnetism of the Ni/BaTiO3 interface

19. The interplay of work function and polarization state at the Schottky barriers height for Cu/BaTiO3 interface

20. Probing single-unit-cell resolved electronic structure modulations in oxide superlattices with standing-wave photoemission

21. k-resolved electronic structure of buried heterostructure and impurity systems by soft-X-ray ARPES

22. Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3

23. Electronic Structure of a Graphene-like Artificial Crystal of NdNiO3

24. Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

25. Do topology and ferromagnetism cooperate at the EuS/Bi2Se3 interface?

26. k-space imaging of anisotropic 2D electron gas in GaN/GaAlN high-electron-mobility transistor heterostructures

27. Large positive linear magnetoresistance in the two-dimensional t(2g) electron gas at the EuO/SrTiO3 interface

28. New bio-active, antimicrobial and adherent coatings of nanostructured carbon double-reinforced with silver and silicon by Matrix-Assisted Pulsed Laser Evaporation for medical applications

29. Spectroscopic Characterisation of Multiferroic Interfaces

30. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO3/SrTiO3 If Interfaces

31. Optimized silicon reinforcement of carbon coatings by pulsed laser technique for superior functional biomedical surfaces fabrication

32. Double band inversion in alpha-Sn: Appearance of topological surface states and the role of orbital composition

33. Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

34. Bioglass implant-coating interactions in synthetic physiological fluids with varying degrees of biomimicry

35. Electronic band structure of the buried SiO2/SiC interface investigated by soft x-ray ARPES

36. Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators

37. Discovery of Lorentz-violating type II Weyl fermions in LaAlGe

38. Aging phenomena and wettability control of plasma deposited carbon nanowall layers

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

40. Fabrication of antimicrobial silver-doped carbon structures by combinatorial pulsed laser deposition

41. Structural and biological evaluation of lignin addition to simple and silver-doped hydroxyapatite thin films synthesized by matrix-assisted pulsed laser evaporation

42. Spectro-microscopic photoemission evidence of charge uncompensated areas in Pb(Zr,Ti)O-3(001) layers

43. Correlation of optical reflectivity with numerical calculations for a two-dimensional photonic crystal designed in Ge

44. Photoelectron spectroscopy and spectro-microscopy of Pb(Zr,Ti)O-3 (111) thin layers: Imaging ferroelectric domains with binding energy contrast

45. Surface topography to reflectivity mapping in two-dimensional photonic crystals designed in germanium

46. Influence of hole depletion and depolarizing field on the BaTiO3/La0.6Sr0.4MnO3 interface electronic structure revealed by photoelectron spectroscopy and first-principles calculations

47. The Role of Ambient Gas and Pressure on the Structuring of Hard Diamond-Like Carbon Films Synthesized by Pulsed Laser Deposition

48. Epitaxial growth of Au on Ge(001) surface: Photoelectron spectroscopy measurements and first-principles calculations

49. Nanomechanical characterization of bioglass films synthesized by magnetron sputtering

50. Gold nano-island arrays on silicon as SERS active substrate for organic molecule detection

51. Structure, reactivity, electronic configuration and magnetism of samarium atomic layers deposited on Si(001) by molecular beam epitaxy

52. Multi-layer haemocompatible diamond-like carbon coatings obtained by combined radio frequency plasma enhanced chemical vapor deposition and magnetron sputtering

53. Au-Ge bonding on a uniformly Au-covered Ge(001) surface

54. Epitaxial ferromagnetic samarium and samarium silicide synthesized on Si(001)

55. Atomic structure and reactivity of ferromagnetic Fe deposited on Si(001)

56. ATOMIC STRUCTURE AND MAGNETISM OF PLD DEPOSITED Tio(2):Fe

57. REACTIVITY, MAGNETISM AND LOCAL ATOMIC STRUCTURE IN FERROMAGNETIC FE LAYERS DEPOSITED ON SI(001)

58. Successful Cleaning and Study of Contamination of Si(001) in Ultrahigh Vacuum

59. Substrate-target distance dependence of structural and optical properties in case of Pb(Zr,Ti)O-3 films obtained by pulsed laser deposition

60. Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature

61. POLYMER-LIKE AND DIAMOND-LIKE CARBON COATINGS PREPARED BY RF-PECVD FOR BIOMEDICAL APPLICATIONS

62. Radiofrequency plasma beam deposition of various forms of carbon based thin films and their characterization

63. THE INTERCALATION OF PbI2 WITH 2,2 '-BIPYRIDINE EVIDENCED BY PHOTOLUMINESCENCE. FT-IR AND RAMAN SPECTROSCOPY

64. VIBRATIONAL PROPERTIES OF POLYANILINE FUNCTIONALIZED PbI2

65. Photoluminescence properties of composites based on zinc oxyde and single-walled carbon nanotubes

66. Particular signature of isolated and bundled carbon nanotubes in their Raman spectra

67. Non-covalent functionalization of carbon nanotubes: Experimental evidence for isolated and bundled tubes

68. Vibrational and photoluminescence properties of composites based on zinc oxide and single-walled carbon nanotubes

69. Raman and photoluminescence studies on intercalated lead iodide with pyridine and iodine

70. Resonant Raman scattering and absorption spectroscopy studies on individual carbon nanotubes in surfactant solutions

1. Spin asymmetry of O 2p-related states in SrTiO₃(001)

2. Enhancement of SrTiO₃ photocatalytic efficiency by Al doping: Answers from the structure, morphology and electronic properties contributions

6. Experimental Band Structure of Pb(Zr,Ti)O₃: Mechanism of Ferroelectric Stabilization

7. Surface charge dynamics on air-exposed ferroelectric Pb(Zr,Ti)O₃(001) thin films

9. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO₃@NiFe₂O₄@Fe⁰@Ni⁰@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)