Various charged forms of substitutional O in diamond were examined by using ab initio plane-wave pseudopotential calculations. The results showed that 2 defect levels were associated with substitutional O and that the charged form of the defect depended sensitively upon the Fermi level. One of the defect states lay well within the energy gap, and the other was located near to the conduction-band edge. The positively charged form of the O defect was suggested to be responsible for an optical absorption band at 2.6eV. It was shown that O in the lattice vacancy exhibited an amphoteric behaviour in diamond.

Defect States of Substitutional Oxygen in Diamond. A.Gali, J.E.Lowther, P.Deák: Journal of Physics - Condensed Matter, 2001, 13[50], 11607-13