Infrared reflection spectroscopy of the SiO2-silicon interface

An infrared reflection technique, devised to study the structure of very thin films on substrates of high refractive index, yields an optical spectrum amplification of three orders of magnitude. With the aid of an infrared polarizer, an unanticipated peak at 1240 cm−1 in the internal reflection spectrum of thin (5–100 Å) thermal SiO2 films on silicon has been identified as a longitudinal optical phonon peak. The unambiguous identification of this peak supports a similar interpretation of the 1230-cm−1 peak in oxygen-containing silicon first proposed by Hu in 1980.