Visible photoluminescence of Ge microcrystals embedded in SiO2 glassy matrices

Ge microcrystals embedded in SiO2 glassy matrices were formed by a radio-frequency magnetron cosputtering technique and then annealed at 800 °C for 30 min. The average radius of the Ge microcrystals in SiO2 was determined to be about 3 nm by means of Raman spectroscopy and high resolution electron microscope. The annealed sample showed a strong room temperature luminescence with a peak at 2.18 eV. This is consistent with quantum confinement of electrons and holes.