The implantation of noble-gas ions resulted in the appearance of photoluminescence centers that were closely related to an intrinsic-defect luminescence at 1.018eV. A theoretical study was made of the identification of these defects. The calculations were performed on molecular clusters, using first-principles Hartree-Fock methods. It was predicted that interstitial noble-gas impurities were not associated with the luminescence, and that the activation energies for their diffusion would be high. The noble gas atoms did not become substitutional, but were instead strongly repelled by vacancies. This suggested the operation of an unusual vacancy-enhanced diffusion mechanism. Noble-gas di-vacancy complexes were very stable, and their predicted properties suggested that they were excellent candidates for the defects which were responsible for noble gas-related photoluminescence. Larger vacancy aggregates (up to hexa-vacancies) were not thought to be responsible for the observed luminescence, although the formation of a hexa-vacancy plus noble-gas complex might easily the disappearance of this luminescence at higher temperatures. The results implied that the 1.018eV line was due to the neutral di-vacancy.

S.K.Estreicher, J.Weber, A.Derecskei-Kovacs, D.S.Marynick: Physical Review B, 1997, 55[8], 5037-44