Computational study of interstitial oxygen and vacancy-oxygen complexes in silicon

Abstract

The formation and binding energies, the ionization levels, the structures, and the local vibrations of ${\mathrm{O}}_{i},$ ${\mathrm{O}}_{2i},$ ${\mathrm{O}}_{3i},$ $V\mathrm{O},$ $V{\mathrm{O}}_{2},$ and ${V}_{2}\mathrm{O}$ $(V$=vacancy) in silicon are calculated using a self-consistent total-energy pseudopotential method. The most important results are as follows: The ionization levels and associated structures are given for $V\mathrm{O}$ and ${V}_{2}\mathrm{O}$ as well as the local vibration modes for the negative charge states of $V\mathrm{O}.$ The experimental frequency of ${\mathrm{O}}_{i}$ at $517 {\mathrm{cm}}^{\ensuremath{-}1}$ is associated tentatively with an oxygen-induced silicon mode of weakly interacting ${\mathrm{O}}_{i}$'s. We find two competing structures for ${\mathrm{O}}_{2i}:$ the staggered configuration and the skewed ${\mathrm{O}}_{i}\ensuremath{-}{\mathrm{S}\mathrm{i}\ensuremath{-}\mathrm{S}\mathrm{i}\ensuremath{-}\mathrm{O}}_{i}$ configuration with the binding energies of 0.2 and 0.1 eV, respectively. The experimental frequencies of ${\mathrm{O}}_{2i}$ at 1060, 1012, 690, and $556 {\mathrm{cm}}^{\ensuremath{-}1}$ are found to originate from the staggered ${\mathrm{O}}_{2i}.$ The experimental frequency of ${\mathrm{O}}_{2i}$ at $1105 {\mathrm{cm}}^{\ensuremath{-}1}$ is found to originate from the skewed ${\mathrm{O}}_{i}\ensuremath{-}\mathrm{Si}\ensuremath{-}\mathrm{Si}\ensuremath{-}{\mathrm{O}}_{i}$ configuration of ${\mathrm{O}}_{2i}.$ The calculated effects of pressure on the structures and local vibration frequencies (Gr\"uneisen parameters) of ${\mathrm{O}}_{i}$ and ${\mathrm{O}}_{2i}$ are presented.