Oxide phase determination in silicon using infrared spectroscopy and transmission electron microscopy techniques

Infrared absorption spectra of polyhedral and platelet oxygen precipitates in silicon are analyzed using a modified Day–Thorpe approach [J. Phys.: Condens. Matter 11, 2551 (1999)]. The aspect ratio of the precipitates is determined by transmission electron microscopy analysis. The reduced spectral function and the stoichiometry of the precipitate are extracted from the absorption spectra and the amount of precipitated interstitial oxygen. The experimental absorption spectra can be divided in a set with a Fröhlich frequency of around 1100 cm⁻¹ and in a set with a Fröhlich frequency between 1110 and 1120 cm⁻¹. It is shown that the shift in the Fröhlich frequency is not due to a differing stoichiometry, but to the detailed structure of the reduced spectral function. Inverse modeling of the spectra suggests that the oxide precipitates consist of substoichiometric $SiOγ$ with $γ=1.17±0.14.$