The ST component in the Si 2p photoemission spectrum from H-terminated and oxidized Si (001) surfaces

One doublet is usually employed to fit the Si-0 substrate species in the Si 2p photoemission spectra from Si (001) H-terminated (after piranha treatment) and oxidized surfaces. However, there is a second substrate-top component (S-T) with a binding energy of 0.3 eV higher than the bulk component; its intensity varies from similar to 10% at normal emission (i.e., 90(o) from the surface) to similar to 20% at 35(o). It is present even for oxidized surfaces and does not correspond to any of the suboxide species. It corresponds to the first layers of the substrate and is responsible for the decrease in the signal dip between the two S-O branches of the Si 2p spectra for glancing electron takeoff angles. Although it is resolvable for monochromatized sources, the S-T component is absent in the literature on Si 2p spectra.

Automated summary

One doublet is typically used to fit the Si-0 substrate species in Si 2p photoemission spectra from Si (001) H-terminated and oxidized surfaces. However, there is a second substrate-top component (S-T) with a higher binding energy than the bulk component, varying in intensity depending on the emission angle. It exists even for oxidized surfaces and does not correspond to any suboxide species. The S-T component contributes to the signal dip between the two S-O branches of the Si 2p spectra for glancing electron takeoff angles, but it is not mentioned in the literature.