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 alpha-Al2O3 sample irradiated wi th 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 di stributed from the region close to the incident surface to the region of 1.8 mu m in depth, with cavities being formed in the restricted reg ion of depths from 1.2 to 1.75 mu m. A similar depth profile of damage structures was formed in a sample irradiated with dual (0.25 MeV H+ a nd 2.4 Me V 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 mu m. Depth pro files 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 12 73 K, cavities grown to 70-80 nm at the maximum size were formed aroun d 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. (C) 1998 Elsevier Science B.V.