Cross-sectional observation of damage structures in Al2O3 irradiated with multiple beams of H,He, and O ions and after annealing at 1273 K

Damage structures in a single crystal α-Al2O3 sample irradiated with triple (0.25 MeV H+, 0.6 MeV He+ and 2.4 MeV O2+) ion beams at 923 K to a peak dose of 3.6 dpa were characterized by dislocation loops distributed from the region close to the incident surface to the region of 1.8 μm in depth, with cavities being formed in the restricted region of depths from 1.2 to 1.75 μm. A similar depth profile of damage structures was formed in a sample inradiated with dual (0.25 MeV H+ and 2.4 MeV O+) ion beams to a peak dose of 10.6 dpa, except that tiny cavities were formed down to the smaller depth of 0.5 μm. Depth profiles of implanted hydrogen atoms measured through a nuclear reaction analysis revaled that point defect mobilities were largely enhanced in the presence of hydrogen without helium. Upon annealing for 1 h at 1273 K, cavities grown to 70-80 nm at the maximum size were formed around peak damage regions in both the irradiated samples. Resultant cavity swellings were 6.2% and 18%, the ratio of which was found to be equal to that of accumulated damage. (orig.)