Multiple-bonding configurations for oxygen on silicon surfaces

Using high-resolution core-level spectroscopy we show that up to four different oxidation states of silicon coexist even at monolayer oxygen coverage. This observation precludes current models with a single adsorption geometry. Below 0.2 monolayer coverage, a single oxidation state is seen but the (100) surface has an oxygen-bonding geometry different from the (111) surface evidenced by different valence states and work-function changes. © 1983 The American Physical Society.