A first principles study of positively charged oxygen vacancies migration in pure and Ge-doped amorphous silica

Using first principles calculations in a periodic amorphous silica supercell, we calculated the energies and the migration barriers of a positively charged oxygen vacancy in pure and germanium-doped silica. The results show that the puckered and dimer structures of the Si-E′ and of the Ge-E′ centers are quite similar. The puckered structure of the Si-E′ center is not affected by the presence of a germanium atom in its surroundings. Moreover, our calculation shows that in the presence of a germanium atom as first neighbour of an oxygen vacancy, Ge-E′ rather than Si-E′ are preferably created in silica.