Effect of silicon doping on the elastic-plastic transition of GaAs crystal is demonstrated by results of nanoindentations and ab initio simulations. The performed experiments show that an increase of silicon concentration causes a decrease of the contact pressure at the onset of permanent nanodeformation of GaAs crystal. Ab initio calculations demonstrate that presence of Si atoms in the crystal lattice suppresses the shear modulus as well as the pressure of equilibrium between zinc-blende and rock-salt phases of GaAs. Furthermore, it is argued that the effect of dislocations pinning to Si dopants is essential for clarification of GaAs yielding.
Our finding of the current spike effect highlighted for the first time in 2009 offers an enhanced understanding of the link between nanoscale mechanical deformation and electrical behavior, and ultimately suggests key advances in unique phase-change applications in future electronics. Certainly, crystal imperfections affect the properties of the nanoparticles themselves, e.g., their biocompatibility and biodegradability. The potential role of dislocations having a profound impact on the use of Si nanoparticles was largely overlooked, since plastic deformation of bulk Si is dominated by amorphization and phase transformations. Here we show an effect of bulk → nanoparticle transition (deconfinement) on incipient plasticity of Si-nanovolume. Our results provide a fresh insight into the dilemma concerning dislocation or phase transformation origin of nanoscale plastic deformation of semiconductor nanoobjects.
This article presents the results of an experimental investigation of the energy spectra of charge carrier traps in undoped high-resistivity ZnSe single crystals. Fourteen peaks were found in the thermostimulated luminescence spectra of the ZnSe samples at temperatures between 8 K and 450 K, and the thermal activation energies of the charge carrier traps were estimated for the most intense peaks. It was found that the energy spectra of the charge carrier traps in ZnSe exhibit oscillatory regularity, and the energy of a vibrational quantum was estimated to be ħω = 206 cm¯¹, which is in good agreement with the vibrational mode in the Raman spectrum. Additionally, a linear relationship was observed between the thermal activation energies of the charge carrier traps and the temperature positions of the maxima in the thermostimulated luminescence of ZnSe.
In the paper, measurements of surface tension of solutions used for silicon etching and results of etching in the solutions are presented. Based on the obtained results, the analysis of interactions of surfactants with differently oriented silicon planes has been carried out.
The AuCl nanocrystals embedded in NaCl single crystals are elaborated using the Czochralski method. The X-ray diffraction has confirmed the formation of the AuCl nanocrystals with a tetragonal structure inside the NaCl matrix. The average radius of the AuCl nanocrystals is estimated using the Scherrer formula.
Thermal properties of glasses from the system Ag_x(As_{40}S_{30}Se_{30})_{100-x} for x=0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature T_{g} (onset temperature), crystallization temperature T_{p} (corresponding to the crystallization peak maximum), melting temperature T_{m}, crystallization enthalpy H_{c}, and melting enthalpy H_{m}. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed T_{g} shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria.
As a result of absorption of X-ray quantum in a semiconductor, the generation of electron-hole pairs takes place in a small volume (diameter < 0.5 μm). Their surplus energy is lost due to the scattering on phonons of the crystal lattice. Spatial distribution of the charge carriers makes the form of current pulse on electrodes of the crystal complicated when an external electric field is applied. We present a logical chart of construction of basic kinetic model of X-ray conductivity (XRC) in semiconductors that uses the successive in time calculation of the spatial distribution of free charge carriers and the diffusive-drift model of motion of free carriers in a solid. The basic form of current pulse in an external circle was obtained in the analytical kind for the case of an ideal semiconductor, e.g. that does not contain deep traps and recombination centers, as well as for the case of a crystal with dominant shallow or deep traps of electrons and holes.
The diagonal and non-diagonal parts for the Debye-Waller factor have been established using equation of motion technique of quantum dynamics and the Dyson equation approach. The double time temperature dependent phonon Green function has been taken to find the phonon linewidth and phonon shift. Renormalized mode frequency has been investigated in terms of electron-phonon coupling constant and temperature. The effect of electron-phonon interaction on the Debye-Waller factor has been studied in low temperature limit in low impurity concentration in semiconductor crystals.
Pure barium titanate BaTiO_3 (BT) and BT doped with two different transition elements Fe^{3+} and Ni^{2+} at 5 mol.% (BT5Fe and BT5Ni, respectively) as constant concentration in powder form have been prepared by sol-gel method using barium acetate, titanium(IV) n-butoxide, iron and nickel nitrates as precursor materials. The microstructure of BT and the influence of Fe and Ni dopants on it were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. X-ray diffraction shows that tetragonal phase is dominant for pure BT sintered for 4 h at 800°C. Scanning electron microscopy and transmission electron microscopy were used to study surface morphology and particle size distribution for BT5Fe and BT5Ni, respectively. The presence of hydroxyl defects were verified by Fourier transform infrared spectroscopy for (BaTi_{1-x}Fe_{x}O_{3-x/2}) (BT_xFe), where x=0.005, 0.01, 0.05, and 0.07 and (BaTi_{1-x}Ni_{x}O_{3-x/2}) (BT_xNi), where x=0.005, 0.01, 0.03, 0.05, and 0.07.
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