Damage structure evolution in Al 2O 3 irradiated with multiple ion beams of H, He and O and after annealing

Abstract

Damage structures in a single crystal Al 2O 3 sample irradiated at 923 K with simultaneous triple beams of H-, He- and O-ions with respective energies of 0.25, 0.9 and 4.7 MeV up to a fluence of 2.7, 3.5 and 5.5 × 10 20 m 2, were examined by cross-section electron microscopy. High density dislocation loops are formed to a depth of 2.4 μm and the loop density increases with increasing depth. Cavities are observed in bands with the swelling peaked at depths of 1.4, 1.9 and 2.3 μm for H-, He- and O-ion implanted regions, respectively. The growth of cavities is most pronounced in the O-ion damaged region with a maximum size of 13 nm and a density of 2–3 × 10 23m 3. In a sample annealed for 1 h at 1273 K after the irradiation, cavities grown to an average size 40 and 60 nm with a maximum of 70 nm were observed in He- and O-ion implanted regions, respectively, and the density was decreased by about two orders.