Enhanced formation of Ge nanocrystals in Ge : SiO2 layers by swift heavy ions

Abstract

In this paper we report the ability of swift heavy Xe ions with an energy of 480 MeV and a fluence of 1012 cm−2 to enhance the formation of Ge nanocrystals within SiO2 layers with variable Ge contents. These Ge-SiO2 films were fabricated by the co-sputtering of Ge and quartz sources which followed various annealing procedures. In particular, we found that the irradiation of the Ge : SiO2 films with subsequent annealing at 500 °C leads to the formation of a high concentration of nanocrystals (NCs) with a size of 2–5 nm, whereas without irradiation only amorphous inclusions were observed. This effect, as evidenced by Raman spectra, is enhanced by pre-irradiation at 550 °C and post-irradiation annealing at 600 °C, which also leads to the observation of room temperature visible photoluminescence.