Photoluminescence (PL) and electroluminescence (EL) from Si+- and Ge+-implanted SiO2 layers thermally-grown on a Si substrate were studied. The PL spectra were recorded after annealing at temperatures in the range of 400° to 1200°C. Single-peak PL at 460 nm and doublepeak PL at 420 and 385 nm due to Si+-implanted and Ge+-implanted oxide layers, respectively, reached a maximum following heat treatment at 500°C for 30 min. The EL spectra from the Gerich oxides after annealing at 1000°C correlated very well with the PL signal, and showed a linear dependence on the injection current. The EL emission was strong enough to be readily seen with the naked eye, and the EL efficiency was estimated to be about 5×10−4. High-resolution transmission electron microscopy (HRTEM) analysis showed that the formation of nanocrystals in the implanted oxide layers occurred at annealing temperatures in excess of 800°C. The observed light emission is attributable to the presence of-≡Si-Si≡, ≡Si-Ge≡ and ≡Ge-Ge≡ centres in SiO2.