Effect of density of Ge nanocrystals on violet–blue photoluminescence of Ge+-implanted SiO2 film

Luminescent SiO2 films containing Ge nanocrystals (nc-Ge) are fabricated by Ge+ ion implantation and thermal annealing. The nc-Ge density is controlled by the implanted Ge+ dose. Under ultraviolet excitation, the films exhibit two photoluminescent (PL) bands simultaneously in the violet–blue region. With increasing annealing temperature (Tan) in the range of 1100 °C, the relative ratio of the intensities of the two PL bands increases slightly from 2.3 to 3 for the films with a dose of 1×1016 cm−2, whereas it increases remarkably from 2.8 to 4.5 for films with a dose of 1×1017 cm−2. On the other hand, the PL integrated intensities of the two kinds of films reach their maxima at Tan of 900 and 700 °C, respectively. It is proposed that the two PL bands are due to germanium-related oxygen-deficient centers. The annealing characteristics are explained well.