Defect-band-free luminescence from ZnO nanoparticles fabricated by ion implantation and thermal oxidation

Defect-band-free luminescence is observed from ZnO nanoparticles fabricated by implantation of 60 keV Zn+ ions in silica glass (SiO2) to 1.0 × 1017 ions/cm2 and subsequent oxidation at 600 °C for 1 h. To clarify the mechanism, the samples were evaluated by optical absorption spectroscopy, grazing incidence X-ray diffraction (GIXRD), photoluminescence (PL) spectroscopy and sputter depth profiling using X-ray excited Auger electron spectroscopy (XAES). Based on these observations, we discuss the possible origins of defect-band-free luminescence; i.e. the stoichiometric formation of ZnO nanoparticles due to the coexistence of metallic Zn nanoparticles, and the suppression of additional transformation of ZnO to Zn2SiO4 phase at the low oxidation temperature of 600 °C.