AMORPHIZATION IN ALUMINUM-OXIDE INDUCED BY ION IRRADIATION

Amorphization in sapphire induced by irradiation has been observed for years but it is still in discussion whether displacements or implante d ions have an important role for the amorphization. In this work, we perform irradiation with high-energy heavy ions in thin film alpha-alu mina below room temperature, so that the effects of atomic displacemen ts, especially of damage cascades, can be revealed. Amorphization was detected at temperatures from 90 K to 230 K under irradiation with 600 -900 keV xenon and krypton ions, while no amorphization was detected u nder irradiation with argon nor oxygen ions. The critical energy densi ty to induce amorphization is estimated. Four stages on the crystallin e-to-amorphous transformation was observed from the temperature depend ence of the dose-to-amorphization. The effect of damage cascades on th e irradiation-induced amorphization and defect kinetics resulting in a n increase of the dose-to-amorphization will be discussed.