The adsorption of silicon on Cu(111) and the initial stages of oxidation of the silicon-copper interface

Abstract

We have used shallow-core level photoelectron spectroscopy from the Si 2p level to identify the presence of three silicon-containing species present when silane (SiH 4) is adsorbed onto the Cu(111) surface at 300 K. These species have binding energies of 98.84, 99.11 and 99.40 eV. Two species are assigned to elemental silicon on the surface, the other to SiH. We discuss the possible structural models for adsorption of silicon in three-fold hollow sites and in surface incorporation models. When the (√3 × √3)R30° silicon layer is exposed to oxygen at 300 K, a broad photoemission feature at 102.50 eV binding energy appears. Heating to 600 K results in a shift of the oxidised state binding energy to 103.80 eV, attributed to the Si 4+ state found in SiO 2. The width of this feature is ∼ 1.5 eV, larger than the feature observed for the Si SiO 2 interface, and the increased width is attributed to inhomogeneities in the silicon oxide layer. If silane is adsorbed in the presence of preadsorbed oxygen, the photoemission features corresponding to elemental silicon, the SiH species and oxidised silicon are observed. The binding energies are shifted to 99.11, 99.40 and 103.10 eV respectively. Heating to 800 K results in the complete extinction of any photoemission features from elemental silicon, while the oxidised silicon photoemission peak has a binding energy of 103.80 eV.