Abstract

Deuterium and hydrogen adsorption, especially hydrogen adsorption, on Si(100) and also on Ge(100) have been studied quite extensively in the recent past. These studies reveal some fundamental differences between the way hydrogen reacts with these two surfaces. Different hydride phases have been found to form on Si(100) by hydrogen adsorption at different temperatures, i.e., chemisorption at 630 K yields only monohydride phase (2×1 phase), at 400±10 K, formation of both the monohydride and dihydride phases (3×1 phase) occur and at <400 K, the surface is a mixture of monohydride, dihydride and trihydride species (1×1 phase).¹ Since (1×1) phase involves trihydrides ie. SiH₃(a), which requires Si–Si bond breaking, substantial surface reconstruction and disordering become inevitable. Heating this phase results in SiH₄ desorption along with H₂, whereas almost only H₂ desorbs from both the (2×1) and (3×1) phases when heated. Hydrogen chemisorption on the Ge(100) surface, on the other hand, has widely been reported to yield only monohydrides (2x1 phase).²,³ Also only hydrogen has been found to desorb from the hydrogen–covered–Ge surface during temperature programmed desorption measurements. It, however, would be interesting to study the effect of hydrogen or deuterium on ultrathin Ge deposited over Si(100), a system of intense cunent research, where strains resulting from lattice mismatch between Si and Ge can open up new possibilities.

© 1997 Optical Society of America