Formation and Characterization of Concentration Inhomogeneities in Melt-Grown Crystals

Crystallography Reports - The specific features of the formation of concentration inhomogeneities in crystals grown by the Czochralski method (GaSb:Te, Ge:Ga) and by the Bridgman method...     

Radiothermoluminescence of polycrystalline high-temperature superconducting YBa2Cu3O6.94, EuBa2Cu3O6.9, and SmBa2Cu3O6.9 samples

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1934, August, 1991.     

X-ray study of structural features of GaSb(Si) single crystals grown using a set of diffraction methods under various heat and mass transfer conditions

Structural features of GaSb(Si) single crystals grown under various heat and mass transfer conditions were studied by x-ray topography and by double- and triple-crystal diffractometry. It was shown that a decrease in the convective flow intensity during crystal growth by the vertical Bridgman method with axisymmetric upper heat supply in comparison with the Czochralski method eliminates growth striations (caused by microsegregation) and improves the uniformity of electrical parameters of materials. According to triple-crystal x-ray diffractometry data, the increased density of structural defects observed in some crystal regions causes significant lattice distortions, which makes an additional contribution to crystal inhomogeneity. Some specific features in x-ray topography images of growth striations, caused by a high silicon concentration and a dopant state deviation from an ideal substitutional solid solution, were revealed.     

Studying the potentials of secondary ion-mass spectrometry in the analysis of atmospheric water drop composition

The applicability of secondary ion-mass spectrometry to the qualitative and quantitative determination of atmospheric water drop composition was considered. Aqueous solutions of sulfuric acid with concentrations from 10^?1 to 10^?6 M were used as model solutions. It was shown that the composition of samples could be determined from the ion peaks in the positive and negative mass spectra. Quantification was successful down to 10^?6 M, which corresponded to the concentrations of the main trace components in rain water.     

Comparative studies of the features of the formation of impurity heterogeneity in GaSb:Te crystals in the case of directed crystallization under space and ground conditions

The results of comparative studies concerned with the formation of impurity heterogeneity in GaSb:Te crystals grown at the POLIZON facility by the Bridgman method under space and ground conditions are presented. Crystallization is carried out in the same temperature-time modes of the heaters: on board the Foton-M 3 spacecraft in space and by the vertical Bridgman method under conditions of weakened thermogravitational convection on Earth. In both cases, Marangoni convection is eliminated, and the effect of vibration microaccelerations on the ampoule that contains the melt is minimized. The microuniformity of the dopant distribution in the crystal areas that are recrystallized by the Bridgman method is higher than that in the seed grown by the Czochralski method. Microuniformity is higher under space conditions than under ground conditions with weakened thermogravitational convection. Spectral Fourier analysis of the spreading resistance distribution R _s reveals the characteristic periods of heat and mass transfer processes in the melts under ground and space conditions.     

Thermoluminescence of a polyethylene surface after plasma treatment with a high-frequency glow discharge

The plasma treatment of polyethylene (PE) gives a specific pattern of thermoluminescence (TL). The qualitative difference between the TL curves of PE after plasma treatment and the curves for radioluminescence appears to be due both to specific features of the plasma treatment (attack on the surface of the sample and the unavoidable effect of photobleaching) and to the particular structure of the surface of the polymer (the existence or formation in the surface layer of special low-molecular structures). TL after plasma treatment can therefore be used to investigate the surface structure of polymers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1742–1744, August, 1990.