Volume expansion and annealing compaction of ion-bombarded single-crystal and polycrystalline α-Al2O3

Radiation damage of α-Al2O3 was systematically investigated as a function of incident ion mass and energy partitioning into atomic and electronic processes by measuring the resulting stress in the ion-bombarded layer with a cantilever beam technique. Heavy-ion-bombardment-induced expansion in the implanted surface layer shows strong anisotropy which appears to be related to the higher defect production rate along the c axis. Stress relief is observed at fluences above 1×1015 Ar/cm2 for the [0001] orientation only and is attributed to basal slip. Hydrogen bombardment subsequent to heavy-ion bombardment results in compaction which is also anisotropic. The anisotropy of both the expansion and the compaction point to structure sensitive defects. Approximately 80% of the radiation damage is annealed at 900 °C for the [0001] orientation and 60% for the [011̄0] orientation. A similar expansion-compaction response is found in argon- and hydrogen-bombarded polycrystalline Al2O3.