The creation of Ge nano-crystals in oxide films was carried out by the precipitation from a supersaturated solid solution, of Ge in SiO2, which had been prepared by Ge ion implantation. The films exhibited a strong visible photoluminescence at room temperature. The measured photoluminescence peak energies and lifetimes exhibited a poor correlation with the nano-crystal size. Also, the photoluminescence spectra and lifetime measurements exhibited only a weak temperature dependence. The results strongly suggested that the observed visible luminescence was not due to the radiative recombination of quantum-confined excitons in Ge nano-crystals. Instead, observations of a similar luminescence in Xe+-implanted samples, and a reversible photoluminescence quenching by H or D, suggested that radiative defect centers in the oxide matrix were responsible for the luminescence.

K.S.Min, K.V.Shcheglov, C.M.Yang, H.A.Atwater, M.L.Brongersma, A.Polman: Applied Physics Letters, 1996, 68[18], 2511-3