Oxidized silicon surfaces studied by high resolution Si 2p core-level photoelectron spectroscopy using synchrotron radiation

The Si 2p soft X-ray photoemission study of various oxidized surfaces (thermal oxidation and room temperature (RT) oxidation) shows the benefit derived from the use of high-energy resolution (70 meV). Interesting structural information can be retrieved from an analysis of the line widths of the oxides, suboxides, and elemental Si peaks. In particular the binding energy (BE) of elemental silicon layers adjacent to the oxidized layer can be distinguished from that of deeper silicon layers (the two prominent `interfacialʹ elemental Si lines are shifted by about +0.2 and −0.2 eV). These new data show a possible effect of oxygen second neighbors on elemental Si 2p binding energies. Moreover, changes in the oxide/suboxide line widths – as seen in a comparative study of the Si(1 1 1)-7×7 surface thermally oxidized in O2 and exposed at RT to O2 or H2O – may be attributed to static disorder, i.e., variations in Si–O bond lengths.