Damage accumulation in Al2O3 during H2+ or He+ ion irradiation

The damage evolution in α-Al2O3 single crystals during He+ or H2+ ion irradiation was studied in an electron microscope. The irradiations were performed with 10 keV He+ions at a flux of 1x1013 ions/cm2 s and 15 keV H2+ ions at a flux of 1x1014 ions/cm2 s over the temperature range of room temperature to 1273 K. Dislocation loops and bubbles became larger in the specimens irradiated with hydrogen ions compared to those irradiated with helium ions. At higher temperature, bubbles were formed preferentially inside the planes of dislocation loops. This is observed at lower temperature under hydrogen ion irradiation than under helium ion irradiation. These differences may be caused by strong trapping of helium atoms at radiation-induced vacancies which retard the growth of loops or bubbles. In the case of hydrogen ion irradiation, enhanced point defect mobility due to hydrogen ions leads to the formation of large loops or bubbles