The adsorption of PH3 on the Si(111)-(7x7) surface: An example of autocatalytic dissociative chemisorption

[摘要] The dissociative chemisorption of phosphine, PH3, on the Si(111)-(7 X 7) surface has been examined employing supersonic molecular beam techniques. The initial probability of reaction, S-R,S-0, has been found to be sensitive to substrate temperature, T-s, where S-R,S-0 increases sharply by approximately a factor of 4-5 as T-s is increased above 800 degrees C, which corresponds well with the (7 X 7) <-> ''(1 X 1)'' phase transition. The reaction probability, S-R, measured as a function of dose for PH3 reacting on Si(111)-(7 X 7) at T-s < 800 degrees C, exhibits a dramatic increase as the surface is exposed to the PH3 molecular beam. This unique autocatalytic behavior is consistent with a mechanism in which submonolayer coverages of P(a) are capable of lifting the (7 x 7) reconstruction thus giving rise to a more reactive ''(1 X 1)-like'' phase. The reaction probability of Si2H6 on Si(111)-(7 x 7) is also observed to pass through a maximum with increasing P(a) coverages, and can be explained by considering similar changes in surface structure and reactivity.

[发布日期] 1995-12-30

[关键词] adsorption kinetics;chemisorption;hydrides;models of surface chemical reactions;molecule solid reactions;phosphine;phosphorus;silicon;solid-gas interfaces;surface chemical reaction;surface relaxation and reconstruction