Halogen ions (Cl, Br and 1) and copper ions have been implanted in silica glass at the same dose and at energies of the order of MeV, sequentially. The coordination structure of implanted copper atoms has been studied by X-ray absorption fine structure spectroscopy. It was found that implanted Cu atoms were coordinated with two oxygen atoms in all the as-implanted glasses. Heat treatment in air caused the formation of copper-halogen bonds without the formation of halide crystals. Further heat-treatment caused the formation of halide crystals in the glasses. (C) 2003 Elsevier Science B.V. All rights reserved.