A study of thin silicon dioxide films using infrared absorption techniques

Infrared transmission spectra of a series of silicon dioxide (SiO2) films grown on silicon wafers from a HCl and O2 gas mixture at 850 °C, have been studied for film thicknesses down to 28 Å. The validity of Lambert‐Bouguer’s Law for such thin films has been confirmed, and the apparent absorption coefficient calculated for the absorption at 1065 cm^-1 is in good agreement with previously published data for thicker, vapor‐deposited, and thermally grown films. A continuous shift of the absorption near 1065 cm^-1 has been found, moving from an asymptotic limit maximum of ∼1070 cm^-1 for thick films towards smaller wave numbers for thinner films. Various possibilities for the origin of this shift are discussed.