Surface blistering and void swelling of α-Al 2 O 3 irradiated with H 2 + ions followed by 1000, 1200 °C annealing

Surface morphology and defect structures in α -Αl 2 O 3 irradiated with 106 keV H 2 + and post-irradiation-annealed at 1000, 1200 °C were investigated. The ion irradiations and annealing cause modifications to the Raman scattering peaks such as the peak disappearance and peak shifts. Surface blisters with several micrometers in diameter are visible. The mean blister sizes increase with increasing annealing temperatures and decrease with increasing irradiation fluences. Transmission electron microscopy characterizations reveal large numbers of spherical or oval shaped voids around the peak-damage zone. Faceted voids are also observed. The irradiation-induced dislocation loops are mostly annealed out with only some dislocation lines left inside. Nevertheless, small dislocation loops with sizes of ∼20–30 nm are characterized under different diffraction conditions, which are found to be associated with the void structures in the 1.5 × 10 17 H 2 + /cm 2 irradiated and annealed sample. These loop structures are considered to be induced through the ‘loop punching’ mechanism due to a high gas pressure inside during the bubble growth period.