Effect of electrostatic screening on energy positions of electron spectra nearSiO2/Si interfaces

X-ray photoelectron spectra and Auger-electron spectra of thin ${\mathrm{SiO}}_2$ films grown on Si substrates show differences when compared to thick oxide films. In addition to ${\mathrm{SiO}}_{\mathrm{x}}$ spectral features, those associated with the ${\mathrm{SiO}}_2$ are shifted towards lower binding energies as the thickness of the film decreases. Calculations reported here indicate that a large part of these shifts can be accounted for by a model using electrostatic image charges. Any conclusions about the chemistry or the mechanical properties of the films based on these shifts is therefore suspect.