PHOTOEMISSION-STUDY OF AU, GE, AND O2 DEPOSITION ON NH4F ETCHED SI(111)

We have studied the interaction of a metal Au, a semiconductor Ge, and a nonmetal O2, with the NH4F etched Si(111) surface with photoemissio n spectroscopy. Two components were present in Si 2p core-level spectr a from the H-terminated surface. We observed the flatband condition fr om the as-etched, n - type, Si(111) surface. We performed stepwise dep ositions of Au and measured the band bending with photoemission spectr oscopy. The Fermi level pinned near midgap as Au was deposited onto th e as-etched surface. After the deposition of 1 ML of Au, a Au-silicide layer formed. This interfacial component indicated that the passivati ng H layer was compromised. As the Au coverage was increased, layers o f pure Au formed between the bulk silicon and the Au-silicide layer. T he observed behavior was nearly identical to that of Au deposition on the Si(111) 7 X 7 surface [Phys. Rev. Lett. 67, 2187 (1991)]. Next, we tested the ability of the monohydride layer to sustain surfactant ass isted growth of Ge. Ge islanding was observed at 400-degrees-C indicat ing that good surfactant growth was not obtained. This was consistent with the recent results of Sakai and Tatsumi [Appl. Phys. Lett. 61, 52 (1994)] who reported that the surface roughness was nearly the same f or surfaces grown with or without H at this temperature. Although the monohydride layer was not a good surfactant for the Si(111) surface at this temperature, further study at different temperatures is needed t o determine the ability of the ideal monohydride layer to act as a sur factant. Finally, we observed no oxidation of the as-etched surface at room temperature upon exposure to molecular oxygen.