Ion-Beam-induced Defects and Defects Interactions in Perovskite-Structure Titanates

摘要

Ion-beam irradiation of perovskite structures results in the production and accumulation of defects. Below a critical temperaur,e irradiation also leads to a crystalline-to-amorphous transformaiton. The critical temperature for amorphization under 800 keV Kr~+ ion irradiation is 425, 440 and 550 K for SrTiO_3, CaTiO_3 and BaTiO_3, respectively. The results of ion-channeling studies on SrTiO_3 irradiated with 1.0 MeV Au~2+ ions suggest that the crystalline-to-induced defects. In SrTiO_3 irradiated with He~+ and O~+ ions at 180 K, isochronal annealing studies indicate that there is significant recovery of defects on both the oxygen and cation sublattices between 200 and 400 K. these results suggest that defect recovery processes may control the kinetics of amorphization. A fit of the direct-impact/defect-stimulated model to the data for SrTiO_3 suggests that the kinetics of amorphization are controlled by both a nearly athermal irradiation-assisted recovery process with an activatio nenergy of 0.1+-0.05 eV and a thermal defect recovery process with an activation energy of 0.6+-0.1 eV. In SrTiO_3 implanted with 40 keV H~+ to 5.0 x 1016 and 1.0 x 1017 ions/cm2, annealing at 470 K increases the backscattering yield from Sr and Ti and is mostly likely due to hte coalescence of H_2 into bubble nuclei. Annealing at 570 K and higher results in the formation of blisters or large cleaved areas.