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ABSTRACT Atomic Force Microscopy (AFM) measurements have been performed for Fe doped SrTiO3 thin films with an Fe concentration of 2 and 5 at%. Thin films with a thickness of about 20 nm were grown by pulsed laser deposition on single... more
ABSTRACT Atomic Force Microscopy (AFM) measurements have been performed for Fe doped SrTiO3 thin films with an Fe concentration of 2 and 5 at%. Thin films with a thickness of about 20 nm were grown by pulsed laser deposition on single crystalline SrTi0.99Nb0.01O3 substrates. Low-energy electron diffraction examination showed that the films are single crystalline. The regions treated with the AFM tip (applied dc voltage up to 6V) showed inhomogeneity of the electrical conductivity.
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ABSTRACT Sulphur passivation effects on the performance of LPE-grown GaSb/InGaAsSb/AlGaAsSb photodiodes designed for TPV applications have been monitored within the period of 3 years. The applicability of (NH4)2S, Na2S, and (NH2)2CS... more
ABSTRACT Sulphur passivation effects on the performance of LPE-grown GaSb/InGaAsSb/AlGaAsSb photodiodes designed for TPV applications have been monitored within the period of 3 years. The applicability of (NH4)2S, Na2S, and (NH2)2CS solutions have been compared by measuring of electro-optical characteristics (I-V, RGammalambda, eta-lambda) and investigating surface properties (X-ray photoelectron spectroscopy and variable angle spectroscopic ellipsometry). We show that electrochemical passivation enables to reduce photodiodes dark current, to increase their differential resistance by a factor of 4 and detectivity up to 2 times 1010 cmHz1/2 W1 and assures long-term stability of passivated surfaces.
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ABSTRACTSulfur passivation effects on the performance of LPE-grown GaSb/InGaAsSb/AlGaAsSb mesatype photodiodes operating in wavelengths range 1.9 – 2.3 μm have been investigated. (NH4)2S, Na2S, and (NH2)2CS have been chosen as sulfur... more
ABSTRACTSulfur passivation effects on the performance of LPE-grown GaSb/InGaAsSb/AlGaAsSb mesatype photodiodes operating in wavelengths range 1.9 – 2.3 μm have been investigated. (NH4)2S, Na2S, and (NH2)2CS have been chosen as sulfur sources in either aqueous or C3H7OH solutions. Electrochemical passivation of mesa side walls was proven to reduce photodiodes dark current and increasing their differential resistance by a factor of 4. As a result devices characterized by the detectivity of 1.5–2×1010 cmHz1/2/W and dark current density of 20 mA/cm2 at –0.5V bias have been fabricated and their long-term stability has been proven.
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The critical temperatures of superconducting phases of nominal composition YBa2(Cu1-xTix)3O7-delta were investigated for x in the range from 0 to 0.33. Measurements of the electrical resistivity, the magnetic susceptibility and the powder... more
The critical temperatures of superconducting phases of nominal composition YBa2(Cu1-xTix)3O7-delta were investigated for x in the range from 0 to 0.33. Measurements of the electrical resistivity, the magnetic susceptibility and the powder X-ray diffraction were performed. An enhancement of both Tc(chiAC) and Tc(varrho = 0) was found although the X-ray patterns and chiAC runs indicated that the samples were multiphase.
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ABSTRACT X-ray photoelectron spectroscopy has been applied to study the electronic structure of the epitaxial Fe-doped SrTiO3 thin films with an Fe concentration of 1 and 2 at%. The results were compared to undoped thin films and lightly... more
ABSTRACT X-ray photoelectron spectroscopy has been applied to study the electronic structure of the epitaxial Fe-doped SrTiO3 thin films with an Fe concentration of 1 and 2 at%. The results were compared to undoped thin films and lightly Fe-doped single crystal of SrTiO3. Fe doping was found to increase the amount of the in-gap states which can be related to the increased ability of Fe-doped thin films to exhibit resistive switching behaviour. Core level analysis indicates the mixed-valence character of Fe atoms in the films, with a divalent contribution situated on the surface.
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Materials Science, Biomedical Engineering, Biomineralization, Atomic Force Microscopy, Medicine, and 15 moreCorrosion, Surface Chemistry, Stainless Steel, Chromium, Current Density, Nickel, Implant, Spectrum analysis, Chemical Composition, Materials Testing, Biocompatible Materials, Corrosion Resistance, Pectus Excavatum, Paper, and Bone Plates
High nickel content is believed to reduce the number of biomedical applications of nickel–titanium alloy due to the reported toxicity of nickel. The reduction in nickel release and minimized exposure of the cell to nickel can optimize the... more
High nickel content is believed to reduce the number of biomedical applications of nickel–titanium alloy due to the reported toxicity of nickel. The reduction in nickel release and minimized exposure of the cell to nickel can optimize the biocompatibility of the alloy and increase its use in the application where its shape memory effects and pseudoelasticity are particularly useful, e.g., spinal implants. Many treatments have been tried to improve the biocompatibility of Ni–Ti, and results suggest that a native, smooth surface could provide sufficient tolerance, biologically. We hypothesized that the native surface of nickel–titanium supports cell differentiation and insures good biocompatibility. Three types of surface modifications were investigated: thermal oxidation, alkali treatment, and plasma sputtering, and compared with smooth, ground surface. Thermal oxidation caused a drop in surface nickel content, while negligible chemistry changes were observed for plasma-modified samp...
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Materials Science, Biomedical Engineering, Titanium, Medicine, Surface Roughness, and 15 moreBiocompatibility, Cell Differentiation, Humans, Surface modification, Sputtering, Nickel, Surface Properties, Shape Memory Effect, Cell Proliferation, Osteoblasts, Materials Testing, Biocompatible Materials, Biomedical Application, Cell Growth, and Titanium alloy
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Abstract PHELIX is a new beamline at National Synchrotron Radiation Centre SOLARIS in Krakow using soft X-rays. The source of radiation is an Elliptically Polarizing Undulator APPLE II type with permanent magnets producing a variable... more
Abstract PHELIX is a new beamline at National Synchrotron Radiation Centre SOLARIS in Krakow using soft X-rays. The source of radiation is an Elliptically Polarizing Undulator APPLE II type with permanent magnets producing a variable polarization of light. The maximum size of the excited area on the sample will be smaller than 100 µm × 100 µm with the resolving power (RP) of at least 10 000 over the entire energy range (available range 50–1500 eV) and for all polarizations. The PHELIX end-station enables a wide range of spectroscopic methods including angle integrated and angle resolved photoemission, spin resolved photoemission and x-ray absorption studies under UHV conditions. The VLEED spin detector allows to determine all three components of photoelectron spin. The beamline is perfectly suited for investigations of new electronic materials, topological insulators, thin films and multilayers systems, surface of bulk compounds, surface magnetism, spin polarized surface states, biomaterials, etc.
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We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO)... more
We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced ...
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ABSTRACT GdFeSi silicide is a strong ferromagnet with Curie temperature (Tc) equal to 118 K. The substitution of cobalt for iron continuously suppresses ferromagnetism of the former compound, while it changes magnetic transition... more
ABSTRACT GdFeSi silicide is a strong ferromagnet with Curie temperature (Tc) equal to 118 K. The substitution of cobalt for iron continuously suppresses ferromagnetism of the former compound, while it changes magnetic transition temperature nonlinearly. When the molar amount of cobalt reaches 0.4, the temperature of magnetic transition reaches minimal value i.e, 70 K. For larger amount of cobalt, magnetic transformation temperature rises well above 200 K and the antiferromagnetic interactions become dominant. In the present work we have found that the magnetic transformation temperature can be strictly correlated with the lattice constant c, which determines the distance between gadolinium layers as well as distance between neighboring gadolinium atoms in one layer. These results correspond to the change of amplitude of magnetocaloric effect which is being suppressed when the amount of cobalt increases. Adiabatic temperature change is equal to 2 K during the magnetic field cycle 0–1.7 T for pure GdFeSi, while no temperature change is observed during the same cycle for pure GdCoSi because of its antiferromagnetic character.
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ABSTRACT X-ray Photoelectron Spectroscopy was used to investigate Eu valence in the following EuF3 samples: single crystal, buried MBE layers (Au/EuF3/Fe/GaAs and Au/EuF3/Fe/Ag/GaAs) and amorphous thin films. Evidence was found for a... more
ABSTRACT X-ray Photoelectron Spectroscopy was used to investigate Eu valence in the following EuF3 samples: single crystal, buried MBE layers (Au/EuF3/Fe/GaAs and Au/EuF3/Fe/Ag/GaAs) and amorphous thin films. Evidence was found for a surface divalent Eu state present on single crystal and amorphous films, while the MBE ultra thin buried layers only exhibited a trivalent Eu state. (© 2004 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim)
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ABSTRACT The effect of thermal reduction in ultra-high vacuum was studied in films of tantalum and niobium oxides obtained by oxidation of deposited metallic layers. The obtained films appeared to be amorphous and their stoichiometry was... more
ABSTRACT The effect of thermal reduction in ultra-high vacuum was studied in films of tantalum and niobium oxides obtained by oxidation of deposited metallic layers. The obtained films appeared to be amorphous and their stoichiometry was not uniform. For the Ta based film the main component was Ta 2 O 5 while for the oxidized Nb film the pentoxide was present in the topmost part of the film and the thickest layer had the electron density assigned to NbO 2 . Thermal reduction was studied with the use of in situ photoelectron spectroscopy which revealed for the Nb–O film a strong effect for temperature as low as 300 °C. The Nb–O film reduced at 600 °C exhibited dominating metallic-like electronic states assigned to NbO. For the Ta–O film the significant reduction process started above 600 °C. At 900 °C the film showed metallic-like states which can be attributed to Ta 2 O. A single crystal of Nb 2 O 5 showed no effect of reduction for temperatures up to 500 °C. A test performed with the use of local conductivity atomic force microscopy showed the most interesting bipolar-like resistive switching properties for the films reduced at temperatures up to 300 °C.
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ABSTRACT
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The paper reports a new route for the fabrication and determination of physicochemical properties and biological activity, of metallic silica-based nanostructure (Ag/SiO2, Cu/SiO2).
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Gd3Co single crystals were grown by the Czochralski technique from a levitated sample in an argon atmosphere. The starting materials of high purity (Gd - 99.9 %, spectroscopically pure Co) were placed in a conic-shaped water cooled... more
Gd3Co single crystals were grown by the Czochralski technique from a levitated sample in an argon atmosphere. The starting materials of high purity (Gd - 99.9 %, spectroscopically pure Co) were placed in a conic-shaped water cooled crucible. The crucible was placed in a quartz tube inside a RF induction coil. The temperature was controlled by a phototransistor. The crystals were pulled up from the levitated molten sample with the speed of about 10 mm per hour. The crystals were up to 50 mm long with a diameter of about 1.5 mm. The growth direction was close to the [110]. The crystals were studied by X-ray reflection topography and with the use of Auleytner’s spectrometer with an oscillating film1. X-ray reflection topographies of “as-grown” crystals usually showed the crystals without mosaic spread. However, low-angle boundaries in some crystals were revealed. In this case, the crystals consisted of blocks elongated along the growth direction. The surface of growing crystals was not smooth but some roughnesses occurred. Therefore black spots and lines appeared in topographies of the “as-grown” crystals (Fig. 1).
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Cell activity on an implant surface can be modulated by cues such as topography, chemistry or stiffness(1,2). For Ni-Ti alloy this is achieved mainly by alteration in chemistry. However, high nickel concentrations may be a concern in the... more
Cell activity on an implant surface can be modulated by cues such as topography, chemistry or stiffness(1,2). For Ni-Ti alloy this is achieved mainly by alteration in chemistry. However, high nickel concentrations may be a concern in the use Nitinol on a larger scale. Current reports on Nitinol bring contradictory data(3-5) suggesting that high nickel content is not particularly dangerous and nickel-titanium alloys are safe to be used. On the other hand it was shown that nickel has a toxic effects on cells(6). Nevertheless, shape memory effects and pseudo-elasticity could support different treatments (e.g. scoliosis) and currently, Nitinol is used to produce porous foams and coatings (Actipore™), pins, clamps and intramedullary nails. In this paper authors investigated a role for nickel surface concentration on influencing cell behaviour e.g. cytoskeleton formation and organization in vitro.
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Ultrafast lattice dynamics of few quintuple layers of topological insulator (TI) Bi2Te3 is studied with time-resolved optical pump-probe spectroscopy. Both optical and acoustic phonons are photogenerated and detected. Contrary to previous... more
Ultrafast lattice dynamics of few quintuple layers of topological insulator (TI) Bi2Te3 is studied with time-resolved optical pump-probe spectroscopy. Both optical and acoustic phonons are photogenerated and detected. Contrary to previous studies performed on confined systems like thin films, we show that there is no existing restriction to photogenerate the A1g(I) coherent longitudinal optical phonon in confined Bi2Te3 and that the photoinduced stress appears to be efficient even for nanostructures containing 10 quintuple layers (QLs). Remarkably, we also show that whatever the nanostructure of the film (single or polycrystalline arrangement), the A1g(I) optical phonon features are similar while clear differences exist between coherent acoustic phonons spectra. These latter spectra provide direct informations on the elastic properties of these few QLs assemblies
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We have investigated two approaches for the fabrication of thin ZnO films: sputter deposition from the ZnO target and thermal oxidation of vacuum deposited Zn. The microstructure and electronic properties after consecutive steps of the... more
We have investigated two approaches for the fabrication of thin ZnO films: sputter deposition from the ZnO target and thermal oxidation of vacuum deposited Zn. The microstructure and electronic properties after consecutive steps of the formation of n-ZnO/pGaN contacts have been studied using electron transmission microscopy and x-ray photoelectron spectrometry. We have achieved ohmic contacts by Zn oxidation and explain their ohmic behaviour in terms of a tunnel n + -ZnO -p-GaN junction.
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ABSTRACT In the paper the full sol-gel process of KNbO3 powder preparation, using KOH, Nb2O5 and K2CO3 as initial substrates as well as oxalic and citric acid as a chelating agent is presented. It was also confirmed that a mixture of... more
ABSTRACT In the paper the full sol-gel process of KNbO3 powder preparation, using KOH, Nb2O5 and K2CO3 as initial substrates as well as oxalic and citric acid as a chelating agent is presented. It was also confirmed that a mixture of compounds obtained during calcination of KOH and Nb2O5, mixed in adequate proportions, could be source of Nb ions in the sol-gel process. The crystal and electronic structure parameters of the manufactured powder proper for KNbO3 compound were established using XRD, XPS and UV-VIS techniques.