Using first-principles calculations in a periodic amorphous silica super-cell, calculations were made of the energies and migration barriers of a positively charged O vacancy in pure and Ge-doped silica. The results showed that the puckered and dimer structures of the Si-E′ and of the Ge-E′ centers were quite similar. The puckered structure of the Si-E′ center was not affected by the presence of a Ge atom in its surroundings. Moreover, the calculation showed that, in the presence of a Ge atom as first-nearest neighbour of an O vacancy, Ge-E′ rather than Si-E′ were preferably created in silica.

A First Principles Study of Positively Charged Oxygen Vacancies Migration in Pure and Ge-Doped Amorphous Silica. N.Richard, S.Girard, L.Martin-Samos, A.Boukenter, Y.Ouerdane, J.P.Meunier: Nuclear Instruments and Methods in Physics Research B, 2008, 266[12-13], 2719-22