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EN
Experimental evidence for unidirectional microcracking in semi-bulk AlGaAs layers grown on (001) GaAs substrates is presented. The asymmetrical microcracking leads to anisotropic lattice misfit relaxation in the AlGaAs/GaAs structure and is explained in terms of higher mobility of [-110]-oriented α-type dislocations than that of β-type dislocations oriented in [110] direction.
EN
Reactive magnetron sputtering of austenitic stainless steel in nitrogen containing atmosphere was used to deposit coatings composed of S-phase. The process was conducted at constant temperature (200°C). The influence of total and partial nitrogen pressure on coating characteristics was investigated. It was observed that both total and nitrogen partial pressures have influence on coating composition and microstructure. Increasing nitrogen content in the S-phase coating can have a beneficial effect on its corrosion characteristics. It was also found that coatings deposited in the ambient of high nitrogen contents are composed of S-phase and the additional high-nitrogen phase, which is of crucial influence on mechanical properties of the coatings. It was also found that partial argon pressure can contribute to the changes in mechanical properties of the coatings.
EN
The thin layers of (Sn,Mn)Te solid solution were grown by molecular beam epitaxy onto (111)-oriented BaF₂ substrates and characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectrometry, and X-ray diffraction methods. The epitaxial character of the growth was confirmed. All the layers exhibited a regular (fcc) structure of the rock-salt type and were (111)-oriented, their thickness was close to about 1 μm. The layers contained up to 8% of Mn. The microhardness and the Young modulus values were determined by the nanoindentation measurements. The Berkovich type of the intender was applied, the maximum applied load was equal to 1 mN. The results of measurements demonstrated a lack of the composition dependence of the Young modulus value. A slight increase of the microhardness value with an increasing Mn content in the (Sn,Mn)Te solid solution was observed.
EN
The anodic oxide films were prepared on the niobium and tantalum in aqueous electrolyte mixtures containing 1 M CH₃COOH + 1 M H₃PO₄ or 1 M CH₃COOH + 1 vol.% HF or 1 M CH₃COOH + 1 M H₃PO₄ + 1 vol.% HF at 30 V for 30 min. The barrier films were obtained on both niobium and tantalum surfaces in all electrolyte mixtures except niobium oxide film formed in 1 M CH₃COOH + 1 vol.% HF which is porous in nature. The anodic oxide films were characterized by FESEM. Also, electrochemical impedance spectroscopy at open-circuit potential on Nb and Ta was applied and obtained data were analyzed by fitting with four different equivalent circuits.
EN
The paper presents the results of investigations of carbon doped austenitic stainless steel coatings (carbon S-phase) obtained by the reactive magnetron sputtering in the reactive atmosphere composed of argon and methane as a carbon source. Stainless steel targets were sputtered under different conditions. During the experiments the argon to methane proportion varied within a range 11/2-7/6. The other parameters such as temperature, pressure, sputtering power, etc. were kept constant. The phase composition was determined using the X-ray diffraction. Electron probe microanalysis (energy dispersive spectroscopy and wavelength dispersive spectroscopy) and glow discharge optical emission spectrometry techniques were used to study element composition of the coatings. Microstructure was investigated by scanning electron microscopy. It was found that varying the methane volume in the reactive atmosphere, it is possible to control the lattice parameter of the carbon S-phase.
EN
Results on epitaxial lateral overgrowth of GaAs layers are reported. The methods of controlling the growth anisotropy, the effect of substrate defects filtration in epitaxial lateral overgrowth procedure and influence of the mask on properties of epitaxial lateral overgrowth layers will be discussed. The case of GaAs epitaxial lateral overgrowth layers grown by liquid phase epitaxy on heavily dislocated GaAs substrates was chosen as an example to illustrate the processes discussed. The similarities between our results and those reported recently for GaN layers grown laterally by metallorganic vapour phase epitaxy will be underlined.
EN
Ferromagnetic resonance spectra of the La_{0.67}Ca_{0.33}MnO_3 ferromagnetic film deposited onto the x-cut LiNbO_3 substrate were investigated in a wide temperature range. The strain was mechanically introduced into the film using a special holder configuration. This leads to a shift of resonance field with respect to that of the as-grown sample. Analysis of the magnetic resonance shift, induced by a mechanical stress, allowed us to determine the magnetostriction constant λ_{100}. The magnetostriction determined in this way versus saturation magnetization could be well described by the Callen and Callen theory suggesting the domination of the single ion crystal field interaction in the sample being in the ferromagnetic state.
EN
In this work, the Au/Cu two-layer systems, with the total thickness equal to 30 nm are studied. The two-layer systems were deposited by thermal evaporation in a UHV system on the silicon substrate at room temperature. After deposition the samples were annealed. We examined samples subjected to thermal cycle with the different maximum temperature. The X-ray diffraction and X-ray reflectometry are performed for systems before and after annealing. It was found that during the cycle of annealing above 150°C starts process of penetration of the Au layer by Cu atoms results in alloying. In Au/Cu systems, the final layer is the ordered Au/Cu₃ phase.
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issue 5
803-807
EN
In this paper the results of investigations of pure and Ca-doped CoO thin films deposited by PLD technique are presented. The studies carried out for variable Ca content allowed to establish optimal conditions for good quality oxide films preparation. The microstructure, chemical/phase composition and morphology of obtained thin films were examined by means of diverse techniques (SEM, EDS, XPS and XRD). For estimation of deposited Ca-doped CoO films quality the nanohardness and scratch tests (adhesion) were performed. Obtained results confirm that using PLD technique it is possible to carry stoichiometric composition of (Co,Ca)O from target to single crystal substrate and allow to conclude that the calcium dopant concentration (chemical composition) influence on the morphology and measured properties of deposited (Co,Ca)O films.
EN
In a biomimetic approach for designing implants, both the physical properties (such as topography, elasticity, roughness, hydrophilicity, charges etc.) and the chemical structure of the artificial biomaterial should be considered, since they affect the adhesion of proteins in the nanometer-scale and of the cells in micro-scale at the interface. In this case, surface modification of biomaterials plays a major role because of the expectations from the material surface. These may be realized by changing the surface chemistry, physically or chemically, or by coating it with a material having a certain chemical composition. In this study, surface properties like topography and roughness, and mechanical properties like elastic modulus and hardness are determined for nanocoated materials.
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vol. 126
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issue 3
782-787
EN
Bismuth (Bi) doped zinc oxide (ZnO:Bi) thin films were prepared on glass substrates by sol-gel spin coating technique using homogeneous precursor solutions, and effects of Bi doping on the structural and optical properties of ZnO were investigated. The crystalline of ZnO films shifted from polycrystalline nature to amorphous nature with Bi doping. The plane stresses (σ) for hexagonal ZnO and ZnO:Bi crystals were calculated according to the biaxial strain model. The Urbach rule was studied as a function of non-thermal component to the disorder (defects in crystal structures) which is especially observed in the case of non-crystal semiconductors. The calculated Urbach energies and steepness parameters of undoped ZnO and ZnO:Bi films varied between 44.33 meV and 442.67 meV, and 58.3 × 10^{-2} and 5.8 × 10^{-2}, respectively. The Urbach energies of the films increased with an increase in the Bi doping concentration and a great difference was observed for 7.0 mol.% doping. The band gap values of the films exhibited a fluctuated behavior as a result of doping effect.
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