Abstract Thermally grown, 200 nm thick layers of SiO 2 were double implanted with Ge + and Sn + ions in turn and the resulting SiO 2(Ge+Sn)/Si structures were annealed at 400–900°C for 30 min. Using transmission electron microscopy (TEM) and electron diffraction (TED), clear evidence is found that the layers of SiO 2 contain Ge and Sn nano-clusters. Depending on the conditions of implantation and thermal treatment the average size and the density of the nano-clusters vary within 10–20 nm and 10 10–10 11 cm −2 respectively. Rutherford backscattering spectroscopy (RBS) demonstrated that no visible redistribution of Ge and Sn takes place after thermal treatment at 400–800 °C and only slow segregation of dopants at the SiO 2/Si interface occurs at 900 °C for the sample implanted with high ion fluence. The cathodoluminescence (CL) spectra obtained from the SiO 2(Ge+Sn)/Si structures contain intensive peaks in blue and near-infrared regions.