Blue and red photoluminescence from Ge+ implanted SiO2 films and its multiple mechanism

Under violet excitation, a strong blue band and a broad red band are emitted simultaneously from the Ge nanocrystal embedded SiO2 films fabricated by Ge+ implantation and annealing. The blue band exhibits a complex annealing behavior, and the photoluminescence excitation spectral analysis indicates that it results from a combination of several implantation-induced deficient centers. The peak position of the red band shifts from 600 to 640 nm when the mean size of Ge nanocrystals increases from 4.3 to 6.7 nm, suggesting that the red band comes from the radiative recombination of excitons confined in Ge nanocrystals.