On the threshold of damage formation in aluminum oxide via electronic excitations

This work is aimed to determine the threshold of dense ionization induced damage formation and their morphology in sapphire single crystals irradiated with 1.2 MeV/amu Xe ions. Cross-sectional TEM examination of r-oriented Al2O3 specimens irradiated to fluences of 2 × 1012 and 2 × 1013 cm−2 has revealed discontinuous ion tracks visible from the irradiated surface up to a depth of 7.6 ± 0.1 μm. According to the SRIM code calculation, the threshold electronic stopping power for track formation in Al2O3 is within the range 9.8 ÷ 10.5 keV/nm. This value agrees with those predicted by both inelastic and analytical thermal spike models.