Defect states of substitutional oxygen in diamond

Different charged forms of substitutional oxygen in diamond are examined using ab initio plane-wave pseudopotential calculations. The results show that two defect levels are associated with substitutional oxygen and that the charged form of the defect depends sensitively on the Fermi level. One of the defect states lies well in the energy gap and the other is located near the conduction band edge. The positively charged form of the oxygen defect is suggested to be responsible for an optical absorption band occurring at 2.6 eV. It is shown that oxygen in the lattice vacancy exhibits an amphoteric behaviour in diamond. (author)