Band distortions and inversions in FTIR spectra of silicon dioxide on silicon

We report the FTIR spectra as a function of incident angle and polarization of a 307 Å layer of silicon dioxide on silicon substrate. Bands normally obscured in transmission spectra are revealed and can dominate the reflection spectra at incident angles away from normal. Strong band distortions were observed as the incident angle and polarization were varied. Our experimental results are in excellent agreement with calculations based on published optical constants. Thus, quantitative interpretations of IR spectra of silicon dioxide on silicon should be made with caution.