Synthesis of Silane and Silicon in a Non-Equilibrium Plasma Jet. Seventh Quarterly Report, February 1--April 30, 1978

摘要

The objective is to determine the feasibility of using a non-equilibrium hydrogen plasma jet as a chemical synthesis tool. The program has been narrowed down to determining the feasibility of preparing amorphous silicon photovoltaic surfaces from the reaction of SiCl sub 4 , SiHCl sub 3 , or SiH sub 4 with a non-equilibrium H/H sub 2 jet. The annular mixing nozzle has been characterized and found to give good mixing, while maintaining the integrity of the jet. The H-atom yields and efficiencies are similar to those for other nozzles. Further consideration of the NO sub 2 titration of H atoms indicates that the mass spectrometer sampling probe could be used to determine the titration endpoint and could also be used to determine the extent of mixing of the H/H sub 2 jet and the other reactant. The main effort has been on the preparation of amorphous silicon films. In experiments with SiCl sub 4 , SiHCl sub 3 , and SiH sub 4 where a cooled substrate holder was placed normal to the reacting jet, only polymeric powdery films were produced. When the substrate was placed on the bottom of a tube restricting recirculation of products back into the reacting jet, strongly adhering amorphous films were prepared from SiCl sub 4 on Vycor, Pyrex, aluminum and carbon substrates. These films became polycrystalline on heating to 500 exp 0 C for 24 hrs, by jet heating during long exposure times, or when high discharge power was used. The electrical resistivity of the films is between 1 to 20 x 10 exp 8 ohm cm with activation energies for electrical conductivity between 0.5 and 1.0 eV. These values are in the range for undoped amorphous silicon films prepared by the glow discharge technique and demonstrated to accept dopants to become photovoltaic. (ERA citation 04:007674)