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

The formation and binding energies, the ionization levels, the structures, and the local vibrations of O-i, O-2i, O-3i, 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 O-i at 517 cm(-1) is associated tentatively with an oxygen-induced silicon mode of weakly interacting O-i's. We find two competing structures for O-2i : the staggered configuration and the skewed O-i-Si-Si-O-i configuration with the binding energies of 0.2 and 0.1 eV, respectively. The experimental frequencies of O-2i at 1060, 1012, 690, and 556 cm(-1) are found to originate from the staggered O-2i The experimental frequency of O-2i at 1105 cm(-1) is found to originate from the skewed O-i-Si-Si-O-i configuration of O-2i. The calculated effects of pressure on the structures and local vibration frequencies (Gruneisen parameters) of O-i and O-2i are presented. [S0163-1829(99)06535-2].