Effects of ion beam irradiation on self-trapped defects in single-crystal Lu 2SiO 5

Abstract

Ion irradiation effects on emission bands related to self-trapped defects in Czochralski-grown Lu 2SiO 5 (LSO) crystals has been investigated. Irradiation was carried out using 53 keV He + and 40 keV H + beams with doses of 1 and 2×10 16 atoms/cm 2, respectively, at room temperature. Post-irradiation radioluminescence measurements were carried out in the 5–300 K temperature range using Mo-target X-ray excitation. Two emission bands were observed at 256 and 315 nm and assigned to self-trapped excitons (STE) and self-trapped holes (STH), respectively. The intensity of the bands was determined by the ballistic damage induced by irradiation, and no effects due to the chemical nature of implanted species were observed. Thermal-quenching activation energies of these defects as a function of irradiation conditions were extracted by applying the Mott–Seitz two-level model. Each band presents strikingly different behavior following irradiation; activation energy of the STH increases two-fold whereas the STE decreases three-fold. The results indicate a major role of surface effects on the radioluminescence of LSO. For comparative purposes, irradiated Lu 2O 3 was also investigated.