Structure of ultrathin silicon dioxide films

Abstract

Differential infrared spectroscopy has been used to study the silicon‐oxygen stretching band of thin silicon dioxide films thermally grown on single‐crystal silicon. We consistently observe an asymmetry in the spectra of films thicker than about 100 Å, of about 9 cm⁻¹. The peak position, width, and degree of asymmetry are also found to be sensitively dependent upon film thickness below 100–150 Å, while above this level these features are only very weakly dependent upon film thickness, indicating the presence of a thin layer of different structural or bonding properties. Our interpretation suggests that the infrared spectra of layers up to 100 Å thick are significantly affected by strain originating at the silicon‐oxide interface, in agreement with recent observations.