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 Oi, O2i, O3i, VO, VO2, and V2O (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 VO and V2O as well as the local vibration modes for the negative charge states of VO. The experimental frequency of Oi at 517 cm−1 is associated tentatively with an oxygen-induced silicon mode of weakly interacting Oi’s. We find two competing structures for O2i: the staggered configuration and the skewed Oi−Si−Si−Oi configuration with the binding energies of 0.2 and 0.1 eV, respectively. The experimental frequencies of O2i at 1060, 1012, 690, and 556 cm−1 are found to originate from the staggered O2i. The experimental frequency of O2i at 1105 cm−1 is found to originate from the skewed Oi−Si−Si−Oi configuration of O2i. The calculated effects of pressure on the structures and local vibration frequencies (Grüneisen parameters) of Oi and O2i are presented.