THE ADSORPTION OF SILICON ON CU(111) AND THE INITIAL-STAGES OF OXIDATION OF THE SILICON-COPPER INTERFACE

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 (SiH4) is adsorbed onto the Cu(111) surface at 30 0 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 oth er to -SiH. We discuss the possible structural models for adsorption o f silicon in three-fold hollow sires and in surface incorporation mode ls. When the (root 3 x root 3)R30 degrees silicon layer is exposed to oxygen at 300 K, a broad photoemission feature at 102.50 eV binding en ergy appears. Heating to 600 K results in a shift of the oxidised stal e binding energy to 103.80 eV, attributed to the Si4+ state found in S iO2. The width of this feature is similar to 1.5 eV, larger than the f eature observed for the Si/SiO2 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 fea tures corresponding to elemental silicon, the -SiH species and oxidise d 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 complet e extinction of any photoemission features from elemental silicon, whi le the oxidised silicon photoemission peak has a binding energy of 103 .80 eV. (C) 1997 Elsevier Science B.V.