TRANSLATIONALLY ACTIVATED DISSOCIATIVE CHEMISORPTION OF SIH4 ON THE SI(100) AND SI(111) SURFACES

The reaction of SiH4 on clean Si(100) and Si(111) has been investigate d employing supersonic molecular beam scattering techniques. The proba bility of dissociative adsorption, S-R, Of SiH4 On both Surfaces depen ds strongly on incident kinetic energy, increasing nearly exponentiall y with increasing energy. On clean Si(100), S-R exhibits a weak depend ence on substrate temperature, T-S. On clean Si(111), however, a disti nct increase in S-R is evident at T-S > 800 degrees C; this increase c orresponds well to the (7 X 7)<---->(1 X 1) phase transition known to occur on this surface. Examination of the reaction of SiD4 reveals a m odest kinetic isotope effect, suggesting tunneling is not involved in this gas-surface reaction.