Исследование взаимосвязи механических напряжений, оптической неоднородности и концентрации кислорода в кристаллах германия

The radial distribution of mechanical stress, optical inhomogeneity and oxygen concentration in Sb-doped germanium crystals grown by the Czochralski method with diameter of 200 mm and resistivity from 10.5 to 18.5 Ω·cm were studied. It was found that residual stress calculated from the data of X-ray structural analysis correlates with results of numerical simulation of thermoelastic stress and interrelates with optical inhomogeneity and concentration of oxygen presented in the atomically dispersed state in germanium.

Growing of bulk β-(Al x Ga1-x )2O3 crystals from the melt by Czochralski method and investigation of their structural and optical properties

Bulk (Al x Ga1-x )2O3 crystals with an Al fraction x in the range from 0.0 to 0.23 were successfully grown by the Czochralski method. An increase in the band gap from 4.7 eV to 5.1 eV with the rise of the Al content was demonstrated by analyzing optical transmission spectra. The crystal quality of the obtained samples was controlled by X-ray diffractometry. The appearance of crystal`s mosaic blockness was found for the Al fraction x above 0.05.

Investigation of defect levels in Bi12SiO20 single crystals by thermally stimulated current measurements

Bi12SiO20 (BSO) single crystal belongs to the sillenite semiconducting family known as defective compounds. The present paper investigates the defect centers in BSO grown by Czochralski method by means of thermally stimulated current (TSC) measurements performed in the 10-260 K range. The TSC glow curve obtained at heating rate of β = 0.1 K/s presented several peaks associated with intrinsic defect centers. The activation energies of defect centers were revealed as 0.09, 0.15, 0.18, 0.22, 0.34, 0.70 and 0.82 eV accomplishing the curve fit analyses method. The peak maximum temperatures and orders of kinetics of each deconvoluted peak were also determined as an outcome of fitting process. TSC experiments were expanded by making the measurements at various heating rates between 0.1 and 0.3 K/s to get information about the heating rate dependent peak parameters.

Numerical and physical study of transitions to unsteady modes of melt flow with the Prandtl number 16 in the Czochralski method

The evolution of the flow structure and heat transfer with an increase in the characteristic temperature drop in the ranges of Grashof and Marangoni numbers 3558 ≤ Gr ≤ 7116 and 2970 ≤ Ma ≤ 5939 are investigated numerically. The boundary of the transition to unsteady flow and heat transfer regimes has been determined.

Anodic behaviour of manganese germanide Mn5Ge3 in a sodium sulphate aqueous solution

Germanides are an interesting class of two-component systems which consist of metal and germanium. They are similar in their structure with silicides but have the specific properties. The target of the investigation was finding the main anodic electrochemical behaviour mechanisms for magnesium germanide Mn5Ge3 in an Na2SO4 aqueous solution.Electrochemical behaviour of manganese germanide obtained by Czochralski method was investigated by polarization curves and electrochemical impedance spectroscopy methods and accomplished by microscopy data. Individual manganese and germanium were investigated in the same way for comparison. It was established that in the anodic oxidation process germanium is the potential-determining component. The passivation process associated with the formation of surface oxide films was accomplished by the current density oscillations appearing due to the bad adhesion of oxide film to the surface of the sample, its imperfection and discontinuity. The nature of oxide film formed in the polarization process waspartially established. The dependence of the anodic behaviour of the sample on the sulphate concentration was established: in the diluted solutions the passivation occurs at more positive potentials than in the concentrated. This phenomenon can be explained by the different mechanisms of anodic oxidation in the solutions of different concentrations.

Fluorescence quantum efficiency of Ti3+:Al2O3 at cryogenic temperatures and excitation by laser diodes

In this work the temperature dependences of the fluorescence of a titanium-sapphire crystal excited by radiation with λ=507 nm, λ=454 nm and λ=405 nm are measured. The quantum efficiency of fluorescence is determined. It was found for the first time that the quantum efficiency of fluorescence exceeds 100% in the cryogenic temperature range when the crystal is excited by radiation with λ = 454 nm. It is equal to (117 ± 5) % and (114 ± 5) % at T = 77 K for crystals grown by the Czochralski method and by gradient of temperature one, respectively.

Influence of the aluminum content on the luminescent and electronic properties of β-Ga2O3

In this work, we investigated bulk β-Ga2O3 samples grown by the Czochralski method on Al2O3 and β-Ga2O3 seeds. The elemental composition of the samples and its effect on the luminescent and electrophysical properties of the samples were determined. The Kelvin probe microscopy was used to study the processes of localization and dissipation of charges in the samples. It was shown that in a β-Ga2O3 sample grown on an Al2O3 seed, the characteristic charge dissipation time is 10 times longer.

Improving the Optical Properties of Potassium Chloride Crystals by Doping Diamond Nanoparticles

In this work, the growth and characterization of potassium chloride crystals containing diamond nanoparticles has been performed. The crystals were grown by the Czochralski method and the doped samples contained 0.5, 1 and 1.5% impurities of diamond nanoparticles. The crystals were characterized by X ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), etching and thermoluminesence (TL). The XRD analysis shows the most of the nanodiamonds are still in single crystal form. FTIR demonstrates the composed crystals are transparent in IR range (transmission ~ 87%). The etching analysis reveals a crystal dislocation in order of 105 for the samples. Examination of thermoluminescence properties of crystals by gamma irradiation with doses of 10, 80 and 300 Gy showed that the sample with 0.5% doped ND had the best glow curve, but for the dose of 1000 Gy, the sample with 1% doped had the best curve.