Optical and structural properties of Ge-ion-implanted fused silica after annealing in different ambient conditions

Ge^ + ions are implanted into fused silica glass at room temperature and a fluence of 1× 10^17~cm^ - 2. The as-implanted samples are annealed in O₂, N₂ and Ar atmospheres separately. Ge^0, GeO and GeO₂ coexist in the as-implanted and annealed samples. Annealing in different atmospheres at 600~\du\ leads each composite to change its content. After annealing at 1000~\du, there remains some amount of Ge^0 in the substrates. However, the content of Ge decreases due to out-diffusion. After annealing in N₂, Si--N composite is formed. The absorption peak of GeO appears at 240~nm after annealing in O₂ atmosphere, and a new absorption peak occurs at 418~nm after annealing in N₂ atmosphere, which is attributed to the Si--N composite. There is no absorption peak appearing after annealing in Ar atmosphere. Transmission electron microscopic images confirm the formation of Ge nanoparticles in the as-implanted sample and GeO₂ nanoparticles in the annealed sample. In the present study, the GeO content and the GeO₂ content depend on annealing temperature and atmosphere. Three photoluminescence emission band peaks at 290, 385 and 415~nm appear after ion implantation and they become strong with the increase of annealing temperature below 700~\du, and their photoluminescences recover to the values of as-grown samples after annealing at 700~\du. Optical absorption and photoluminescence depend on the annealing temperature and atmosphere.