THE KINETICS OF THE CATALYZED CVD OF MONOCRYSTALLINE ALPHA-SILICON NITRIDE FILAMENTS

Catalyzed chemical vapor deposition of alpha-silicon nitride filaments from silicon subhydrides and ammonia was studied using calculations o f nitrogen solubility in selected catalysts (silicon-containing iron a lloys), both in the solid and liquid-state, by filament deposition exp eriments with catalysts of various composition and size: and by variat ion of the flow rates and partial pressures of precursor gases, the si licon subhydrides and ammonia. The results show that neither nitrogen solubility in, nor nitrogen diffusion through the catalyst plays a det ermining role in the deposition kinetics, as has been previously sugge sted. Instead, the deposition rate is determined by the partial dissoc iation of ammonia, which can be accelerated by adding diluent gases wi th a sufficiently high collision cross section. The catalyst material has an additional, strongly accelerating effect. The present state of research suggests that nitrogen is the preferred diluent gas and chrom ium an optimum alloying element.