Computational study of interstitial oxygen and vacancy-oxygen complexes insilicon

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 pseudopoten tial method. The most important results are as follows: The ionization leve ls 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 freq uency 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 config uration with the binding energies of 0.2 and 0.1 eV, respectively. The expe rimental frequencies of O-2i at 1060, 1012, 690, and 556 cm(-1) are found t o originate from the staggered O-2i The experimental frequency of O-2i at 1 105 cm(-1) is found to originate from the skewed O-i-Si-Si-O-i configuratio n of O-2i. The calculated effects of pressure on the structures and local v ibration frequencies (Gruneisen parameters) of O-i and O-2i are presented. [S0163-1829(99)06535-2].