Structure and optical properties of SiO2 films containing Ge nanocrystallites

SiO2 thin films embedded with Ge nanocrystallines (nc-Ge) were prepared on p-type Si and optical quartz glasses substrates by RF-magnetron co-sputtering method from a composite target of Ge and SiO2. The as-deposited films were annealed in the temperature range of 300–1000 °C under nitrogen ambience. The structure of the films was evaluated by X-ray diffraction and X-ray photoemission spectroscopy. Results show that the average size of nc-Ge in the SiO2 matrix is in the range of 2–10 nm which can be controlled by the annealing temperature. Quantum confinement effect was observed in the films by the measurements of absorption spectrum. Photoluminescence (PL) spectra were observed in visible range at room temperature. Possible origins of the visible PL are discussed.