National Institute Of Materials Physics - Romania

Publications

5781 articles found

2211. Red blood cells interaction with vanadium and its oxides based nanocomposite structures

Authors: Prilepov, V; Gasin, P; Prilepov, I; Midoni, V; Chirita, A; Spoiala, D; Ketrush, P

Published: JAN-FEB 2014, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 8, 167, DOI:

The results of the investigation of vanadium and its oxides based nanocomposite structures interaction with the water are brought in this paper. It was established, that at the non-contact interaction of the nanocomposite structures with the water, its activation occurs, which is revealed in a change in the sign of the redox potential of the water from the initial positive to the negative one. Besides, the activation effect is interconnected, i.e. the activation both of the water as well as of nanocomposite structures occurs. The observed effect is explained in the frame of the resonance interaction of the oscillating dipoles theory (the conductive clusters uniformly distributed in V2O5 dielectric matrix with the water molecule dipoles. On the basis of the experimental results, one can affirm that the vanadium and its oxides based nanocomposite structures are a biologic activators and can be used in a modern biomedicine.

2212. ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE ACETABULAR CUPS FUNCTIONALIZED WITH BIOACTIVE GLASS COATINGS SYNTHESIZED BY PULSED LASER DEPOSITION

Authors: Duta, L; Popa, AC; Miculescu, F; Mihailescu, IN

Published: 2014, ROMANIAN REPORTS IN PHYSICS, 66, 800, DOI:

We report on the synthesis by PLD of bioactive glass (BG) films onto ultra high molecular weight polyethylene acetabular cups, and their preliminarily characterization after immersion in simulated body fluid. Fourier Transform Infrared spectra evidenced the strong depolymerization of the BG coatings. Scanning Electron Microscopy evidenced that the typical PLD film surface was converted after soaking in SBF to a rough one consisting of acicular crystals. Energy Dispersive Spectroscopy analysis demonstrated a remarkable conservation of the targets stoichiometry. The functionalization of acetabular cups with BG films by PLD should allow for the fabrication of implant coatings with improved osteoinductive characteristics.

2213. Surface Reactivity and Magnetism at Metal-Semiconductor Interfaces

Authors: Apostol, NG; Teodorescu, CM

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 292, DOI: 10.1007/978-3-662-44479-5_8

The interplay between magnetic properties and structure and interdifussion at interfaces is analyzed mainly by surface science methods and by core level spectroscopies (based on X-ray absorption XAS and X-ray photoelectron spectroscopy XPS) on model systems implying deposition of magnetic metals (Fe, Co, Sm) on usual semiconductors (Si, GaAs, InAs). The Chapters begins with a review of the core level spectroscopies and of derived techniques, such as X-ray photoelectron diffraction (XPD) from XPS and X-ray magnetic circular dichroism (XMCD) from XAS, together with a brief description of other surface science techniques employed, such as low energy electron diffraction (LEED), reflection high energy electron diffraction (RHEED), magneto-optical Kerr effect (MOKE), and with some basics of the molecular beam epitaxy (MBE) method. The examples are organized in pairs, namely one analyzes comparatively (i) interfaces formed by Fe or by Sm on Si(001), (ii) by Fe on GaAs(001) and on InAs(001), (iii) and by Co on bare GaAs(011) and on GaAs(011) passivated with Sb, in order to outline how small changes of the nature of the metal deposited, of the substrate (though identical from the chemical point of view) and of its initial state may result in strong deviations concerning both the quality of structures obtained and their magnetic properties. For instance, it is shown that Sb/Si(001) yields better properties than Fe/Si(001), Fe/InAs(001) exhibits lower reactivity and enhanced Fe magnetic moments than Fe/GaAs(001), and that passivation with antimony of GaAs(011) substrates yields to a reduced As out-diffusion into the metal layer, yielding lower tetragonal distortion and enhanced Co magnetic moments.

2214. Study of high-dose X-ray radiation damage of silicon sensors

Authors: Klanner, R; Fretwurst, E; Pintilie, I; Schwandt, J; Zhang, JG

Published: DEC 21 2013, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 732, 121, DOI: 10.1016/j.nima.2013.05.131

The high intensity and high repetition rate of the European X-Ray Free Electron Laser, presently under construction in Hamburg, will require pixel sensors which can stand X-ray doses up to 1 GGy for 3 years of operation. Within the AGIPD Collaboration the Hamburg group has systematically studied X-ray damage in silicon sensors for the dose range between 1 kGy and 1 GGy using strip sensors and test structures fabricated on high-ohmic n-type silicon from four different vendors. The densities of oxide charges, interface traps and surface current as function of dose and annealing conditions have been determined. The results have been implemented in TCAD simulations, and the radiation performance of strip sensors and guard-ring structures has been simulated and compared to experimental results. Finally, with the help of detailed TCAD simulations, the layout and technological parameters of the AGIPD pixel sensor have been optimized. It is found that the optimization for silicon sensors exposed to high X-ray doses is significantly different from that for non-irradiated sensors, and that the specifications of the AGIPD sensor can be met. (C) 2013 Elsevier B.V. All rights reserved.

2215. Study of the deposition of graphene oxide by matrix-assisted pulsed laser evaporation

Authors: del Pino, AP; Gyorgy, E; Logofatu, C; Duta, A

Published: DEC 18 2013, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 46, DOI: 10.1088/0022-3727/46/50/505309

Thin films composed of graphene-based materials exhibit promising functional properties for the development of high-performance devices in a wealth of applications. However, there are significant technological challenges which force one to search for alternative pathways of materials production and deposition. This paper reports the deposition of graphene oxide (GO) flakes on quartz substrates by using the ultraviolet matrix-assisted pulsed laser evaporation (MAPLE) technique in vacuum or controlled nitrogen gas environment. Water, which is highly transparent to UV radiation, was used as matrix solvent for the preparation of the MAPLE targets. The results reveal that GO platelets can be successfully transferred by MAPLE technique. Besides, the GO material experiences a significant deoxygenating process during deposition, leading to the formation of reduced GO. Numerical simulations also show that the thickness of GO platelets highly influences the deposition process and the structure of the immobilized material. Thick enough aggregates can reach temperatures of thousands of degrees and undergo a large degradation in their structure.

2216. Phenylboronic-Acid-Modified Nanoparticles: Potential Antiviral Therapeutics

Authors: Khanal, M; Vausselin, T; Barras, A; Bande, O; Turcheniuk, K; Benazza, M; Zaitsev, V; Teodorescu, CM; Boukherroub, R; Siriwardena, A; Dubuisson, J; Szunerits, S

Published: DEC 11 2013, ACS APPLIED MATERIALS & INTERFACES, 5, 12498, DOI: 10.1021/am403770q

Phenylboronic-acid-modified nanoparticles (NPs) are attracting considerable attention for biological and biomedical applications. We describe here a convenient and general protocol for attaching multiple copies of para-substituted phenylboronic acid moieties onto either iron-oxide-, silica-or diamond-derived NPs. The boronic acid fiinctionalized NPs are all fabricated by first modifying the surface of each particle type with 4-azidobenzoic ester functions. These azide-terminated nanostructures were then reacted with 4-[1-ozo-4-pentyn-1-yl) amino]phenylboronic acid units via a Cu(I) catalyzed Huisgen cycloaddition to furnish, conveniently, the corresponding boronic-acid modified NPs (or "borono-lectins") targeted in this work. The potential of these novel "borono-lectins" as antiviral inhibitors was investigated against the Hepatitis C virus (HCV) exploiting a bioassay that measures the potential of drugs to interfere with the ability of cell-culture-derived JFH1 virus particles to infect healthy hepatocytes. As far as we are aware, this is the first report that describes NP-derived viral entry inhibitors and thus serves as a "proof-of-concept" study. The novel viral entry activity demonstrated, and the fact that the described boronic-acid-functionalized NPs all display much reduced cellular toxicities compared with alternate NPs, sets the stage for their further investigation. The data supports that NP-derived borono-lectins should be pursued as a potential therapeutic strategy for blocking viral entry of HCV.

2217. Synthesis and properties of Ba(Zn1/3Ta2/3) O-3 for microwave and millimeter-wave applications (vol 516, pg 1558 , 2008)

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Alexandru, HV; Antohe, S; Andronescu, E; Jinga, S; Nita, P

Published: DEC 2 2013, THIN SOLID FILMS, 548, 663, DOI: 10.1016/j.tsf.2013.10.132

2218. Giant pyroelectric coefficient determined from the frequency dependence of the pyroelectric signal generated by epitaxial Pb(Zr0.2Ti0.8)O-3 layers grown on single crystal SrTiO3 substrates

Authors: Botea, M; Iuga, A; Pintilie, L

Published: DEC 2 2013, APPLIED PHYSICS LETTERS, 103, DOI: 10.1063/1.4838035

Epitaxial Pb(Zr0.2Ti0.8)O-3 layers of good structural quality were grown on single crystal SrTiO3 substrates. The pyroelectric coefficient was estimated from the signal generated by the ferroelectric film working as a pyroelectric detector in the voltage mode, without pre-poling procedure. The obtained value is as high as 1.9 x 10(-3) C/m(2) K. The large value is attributed to the presence of 90 degrees ferroelectric domains and to the compressive misfit strain, leading to an enhanced ferroelectric polarization. (C) 2013 AIP Publishing LLC.

2219. Challenges for silicon pixel sensors at the European XFEL

Authors: Klanner, R; Becker, J; Fretwurst, E; Pintilie, I; Pohlsen, T; Schwandt, J; Zhang, JG

Published: DEC 1 2013, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 730, 7, DOI: 10.1016/j.nima.2013.05.166

A systematic experimental study of the main challenges for silicon-pixel sensors at the European XFEL is presented. The high instantaneous density of X-rays and the high repetition rate of the XFEL pulses result in signal distortions due to the plasma effect and in severe radiation damage. The main parameters of X-ray-radiation damage have been determined and their impacton p(+)n sensors is investigated. These studies form the basis of the optimized design of a pixel-sensor for experimentation at the European XFEL. (C) 2013 Elsevier B.V. All rights reserved.

2220. Radiation damage in n-type silicon diodes after electron irradiation with energies between 1.5 MeV and 15 MeV

Authors: Radu, R; Fretwurst, E; Klanner, R; Lindstroem, G; Pintilie, I

Published: DEC 1 2013, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 730, 90, DOI: 10.1016/j.nima.2013.04.080

Radiation damage in silicon, caused by the creation of point and cluster defects due to energetic charged hadrons and neutrons, results in a serious degradation of silicon-sensor performance and limits their lifetime. So far not all the defects are understood. The work presented here focuses on the study of radiation damage by electrons of different kinetic energies, from 1.5 MeV to 15 MeV, in order to study the differences between point- and cluster-related defects. The introduction rate of vacancy-related point defects and of so-called clustered regions was investigated as a function of electron energy. It is shown that the ratio between cluster dominated and point defect formation increases with increasing electron energy. 1.5 MeV electrons create only point defects, and the formation of cluster defects starts already at 3.5 MeV. To study the defect kinetics, isothermal annealing at 80 degrees C and isochronal annealing measurements were performed. (C) 2013 Elsevier B.V. All rights reserved.