Study of the Surface Processes in Vapor-Phase Epitaxial GaAs: Asymmetric Trapping of Atoms at the Step

Experimental proofs of asymmetric trapping of atoms at the growth step in vapor-phase epitaxy of gallium arsenide in the GaAs–AsCl₃–H₂ system are given. The data obtained confirm the important role of the surface diffusion mass transfer in the growth of epitaxial GaAs layers on vicinals in the neighborhood of (111)A. The effective diffusion length is estimated.     

Study of the Structure and Sorption Properties of Some Types of Cellulose

The pulsed NMR, isopiestic and pycnometric methods are applied to investigate the physicochemical properties of softwood [GOST (State Standard) 9571-89] and hardwood [GOST 28172-89] celluloses, as well as flax cellulose [GOST 10330-76, 9394-76], both in the initial state and subjected to chemical treatment. Possible changes occurring in the supramolecular structure of a polymer are analyzed. The structural and sorption characteristics of the investigated samples are calculated. Their water absorption capacities are determined.     

Laser-pulse fluctuations due to thermal self-action in a turbulent atmosphere

Conclusions Refractive-index fluctuations caused by heating alter the intensity and phase fluctuation spectra arising from the turbulence. The large-scale part of the spectra is weakened, whereas the small-scale part is strengthened, and the spatial-frequency range in which the fluctuations are attenuated becomes narrower as the beam energy increases. Correspondingly, the fluctuation structure functions alter. For values of the arguments in those functions less than the radius of the first Fresnel zone , the thermal nonlinearity causes increases in the structural functions D_, with the energy. For , the dependence of D_, on energy is nonmonotone, with the fluctuations at first weakened but then strengthened. The reduction in fluctuation variance and the improvement in coherence is less pronounced over long lines than on short ones. The range in which geometrical optics can be used to derive the fluctuations is independent of the nonlinearity and is defined by k₂z/2k /4. The trend to the diffraction asymptote becomes slower as the nonlinearity increases.Atmospheric Physics Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 9, pp. 1063–1071, September, 1989.     

Synthesis of some O,O-diethyl S-(β-acylaminoethyl) dithiophosphates

The ethyleneimides of N-phthalyl-D,L-valine, N-phthalyl-D,L-glycine, N-phthalyl-D,L-alanine, N-carbobenzoxy-D,L-valine, N-benzoyl-D,L-leucine, and of the -methyl ester of N-carbobenzoxy-L-glutamic acid and monomethyl succinate were synthesized. A number of O,O-diethyl S-(-acrylaminoethyl) dithiophosphates were obtained by opening the ethyleneimine ring in the ethyleneimides of N-acylated amino acids with diethyl dithiophosphoric acid. The -chloroethylamides of phthalyl-D,L-valine, N-acetyl-D,L-valine, and monomethyl succinate were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 479–482, April, 1972.     

Kinetics of the adsorptional deformation of zeolites

Adsorptional deformation in the Xe-CaA system has been studied at 303 K; the kinetics of adsorption and deformation has been investigated. A kinetic model of deformation is proposed based on the principle of the instantaneous establishment of local deformational equilibrium. Kinetic deformation curves based on this model are plotted that have local extrema above equilibrium values or in the negative region. It is shown that when Xe is adsorbed by CaA zeolite and trans-2-butene is adsorbed by NaA zeolite, the time required for deformational equilibrium to be established is negligibly small, and that deformation at any point of time at any point in the crystal is in equilibrium with respect to adsorption and temperature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1948–1951, September, 1990.     

Investigation of transitional layers in epitaxial gallium arsenide: Micromorphology and electron distribution in the layers,in dependence on the growth time in an iodine system

Layers of gallium arsenide with orientation 2° from (111) A in the (110) direction were grown by the open iodide method. A study was made of the morphology, (electron microscope) micromorphology, differential growth rate, and doping level of the layers in dependence on the growth time (1–180 min). The effect of special features of the growth mechanism on the appearance of transitional layers in the doping level is appraised.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 63–69, February, 1973.     

An infrared spectroscopic study of the reaction of alcohols and their decomposition products with yttrium oxide

This paper describes an infrared spectroscopic study of the adsorption of methanol, ethanol, acetaldehyde, ethylene, and water on two samples of yttrium oxide, one of which had dehydrating properties and the other, dehydrogenating properties. The occurrence of different surface compounds during the dehydration and dehydrogenation of alcohols is shown. Possible mechanisms for the decomposition of alcohols are discussed.