Silica film preparation by chemical vapour deposition

Silica film preparation by chemical vapour deposition

Classified abstracts 847-858 ture range. The system provides high rates of sample heating and cooling. V L Arbuzov et al, Prib Tekh Eksper, No 2, 1...

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ture range. The system provides high rates of sample heating and cooling. V L Arbuzov et al, Prib Tekh Eksper, No 2, 1971, 196-199 (in Russian). 847. Dependence of resistance frequency and current density.

of non-rectifying


30 to GaAs on

(USSR) Experimental data on the dependence of resistance of non-rectifying contacts to n- and p-type GaAs on current density in the range 80 to 3 x lo5 A/cm2 and on pulse repetition frequency from 50 to 10,ooO Hz are presented. The contacts were prepared by condensation of Au, Ag, Sn, In on GaAs from molecular beams in vacuum at 5 x lo-’ torr. V P Duraev et al, Prib Tekh Eksper, No 2, 1971, 243-244 (in Russian). 30 848. Crucible-less electron-beam


(USSR) A crucible-less electron-beam evaporator is described which possesses improved reliability due to bending of the electron beam by an angle of 90”. A special shape of magnet prism pole pieces enables deflection of the electron beam without violating its convergence. The evaporator represents a discrete assembly which can be mounted in laboratory or industrial evaporation equipment. The evaporator employs an accelerating voltage of 20 kV and emission current up to 25 mA. The diameter of the electron beam patch on the sample is not larger than 1 mm. At an electron beam power of 350 W the evaporation rate of Ge is 100, Si-200 and Al-50 mg/min. The time of continuous operation of the evaporator is determined by the life of the tantalum cathode and it is longer than 100 hours. L N Nemirovskiy and L A Seydman, Prib Tekh Eksper, No 6, 1971, 133-l 34 (in Russian). 30

and photoelectric characteristics of p-Si - n-Cd!3 (USSR) Electrical and photoelectric characteristics of p-Si- n-CdS heterojunctions prepared by evaporation of CdS on (111) silicon plates at 200°C in a quasi-closed volume are investigated. A G Rokakh and N M Tsukerman, Izv VUZ Fiz, No 10,1971,145-146 849. Electrical heterojunctions.

(in Russian).

30 850. Influence of crystallization temperature on degree of doping of gallium arsenide films and the impurity distribution. (USSR) Dependence of properties of epitaxial gallium arsenide films on conditions of their crystallization in an open iodide-hydrogen system is investigated. L G Lavrenteva et al, Izv VUZ Fiz, No 12, 1971, 144-146 (in Russian). 851. X-ray fluorescence method of determining (USSR) ness of two-component films.


30 and thick-

A method for determining thickness and composition of twocomponent films based on X-ray fluorescence is presented. The method was used for analysis of Pd-Ni films, and vacuum evaporated single-component Pd and Ni films were used as standards. V R Darashkevich et al, Zavodsk Lab, 37 (12), 1971, 1449-1452 (in Russian). 30 852. Condensation

of metals from an ionized beam.

(USSR) Influence of the ion current density and energy of ions present in an atom beam on the kinetics of condensation of metallic films is investigated for lead, bismuth and silver. A combined beam of atoms and ions was obtained with the aid of a capillary-arc source of metal ions. Ion acceleration voltage was up to 3 kV. Condensation is performed in vacuum of the order of 1OF torr on glass substrates initially covered by a 500 A copper layer. Substrate temperature was 80°C for bismuth and lead and 250°C for silver. Thicknesses of the condensed films, in the range of 1 to 3 x lo3 A, were determined by a two-beam interferometry method. It is shown that the processes associated with impact of ions on a substrate are analogous to the processes of cathode sputtering. B N Ilin and A K Krivtsov, Elektron Obrab Mater, No 5, 1971, 45-47 (in Russian).

30 853. Silica film preparation by chemical vapour deposition. (Hungary) Silica films were prepared by thermal decomposition of ethyl triethoxysilane in vertical quartz tube furnace. Oxygen was used as carrier gas at 7 m/hour flow rate, substrate temperature being 540600°C. Silica previously deposited on the wall of the tube furnace was

found to catalytically affect the pyrolytic process. A qualitative model was set up to describe this process. T Veszpremi, A Hiradastechnikai Ipari Kutatointezet Kozlemenyei, 11 (2), 1971,46-54

(in Hungarian). 30

854. Single crystal CdSe films.

(USSR) Single crystal CdSe films deposited in vacuum on mica substrates are studied. Evaporation was performed in a quasi-closed volume with a heated shield between the source and the substrate. Using this method, evaporating particles suffer multiple collisions with the walls and they lose part of their kinetic energy. Single crystal CdSe films with hexagonal and a mixture of hexagonal and cubic modifications are obtained. Investigation of the morphology of surface of growth of films showed that surface of growth of CdSe films is formed by hexagonal pyramids or triangles. A correlation between dimensions of growth figures and electrical conductivity is found. With increasing cross section of the pyramids, resistance and photosensitivity of the films increases. Single crystal films containing cubic and hexagonal modifications of CdSe possess higher photosensitivity than the films of only hexagonal modification. S V Svechnikov et al, Neorg Muter, 7 (12), 1971, 2146-2149 (in Russian). 30 855. Electron-beam

deposition source.

(Hungary) An electron-beam deposition source with 6 kV accelerating voltage, 6 kW power and 180” deflection is described. The equipment consists of the electron source constructed integrally with a water-coqled crucible containing the substance to be evaporated. T Szucs and Gy Vago, Finommechanika, 10 (5), 1971, 138-143 (in Hungarian). 30 856. Preparation group. (USSR)

of condensed films of chalcogenides

of metals of IV

A simple method for preparing condensed films of binary and more complex compounds is described, based on vacuum evaporation of a mechanical mixture of the constituents and characterized by accomplishment of two processes in one cycle: formation of the compound in the evaporator and evaporation of molecules of the produced compound. Thin films of Ge, Sn and Pb chalcogenides and solid solutions Sn,_,Pb,Te and PbSe,_,Te, have been prepared using this method. G M Gayduchok et al, Neorg Mater, 7 (ll), 1971, 2073-2074 (in Russian). 30 857. Preparation of single crystal gold films on GaAs.

(USSR) Structure of Au films deposited on GaAs is investigated with the aid of electron-graphical methods. The Au films were deposited from a molecular beam at 1O-5 torr with substrate temperatures between 20 and 250°C. Thickness and deposition rate were measured by a crystal film thickness monitor. Single crystal Au films on GaAs have been obtained at temperatures considerably lower than the eutectic temperature. The Au single crystal films replicate the substrate orientation regardless of large differences in lattice constants. It is shown that semiconductor surface oxide and substrate orientation influence the degree of perfection of films. The most perfect films are obtained for (111) orientation. The results can be used for analysis of the height of Schottky barriers on metal-GaAs contacts in dependence on the nature of the metal and conditions of contact preparation. VP Kloehkov et al, Neorg Muter, 7 (1 l), 1971,1953-1955 (in Russian). 30 858. Peculiarities in the growth of single crystal CdSe films on sapphire, (USSR) fluorite and mica.

The growth of single crystal CdSe films from the gaseous phase on to an insulating substrate is investigated. The method of chemical transport reaction in flowing system is used for the preparation of CdSe single crystal films. Purified hydrogen is used as reagent and transport gas and high purity CdS powder is used as starting material. It is found that in the open system CdSe-H,, epitaxial growth of CdSe on sapphire with orientation (0001) proceeds in the temperature range 610-815°C with a deposition rate of 1.2 to 3.1 pm/hour; on fluorite with orientation (ill), at 490 to 780°C with deposition rate 0.34 to 3.7 pm/hour; and on mica (001) at 415 to 500°C with a rate of 0.26 to 3.4 pm/hour. It is shown that the mechanism of growth of single crystal films of CdSe on sapphire, fluorite and mica agrees well with the theory of epitaxial growth. The influence of substrate surface