DAMAGE STRUCTURE EVOLUTION IN AL2O3 IRRADIATED WITH MULTIPLE ION-BEAMS OF H, HE AND O AND AFTER ANNEALING

Damage structures in a single crystal Al2O3 sample irradiated at 923 K with simultaneous triple beams of H-, He- and O-ions with respective energies of 0.25, 0.9 and 4.7 MeV up to a fluence of 2.7, 3.5 and 5.5 x 10(20) m(2), were examined by cross-section electron microscopy. Hig h density dislocation loops are formed to a depth of 2.4 mu m and the loop density increases with increasing depth. Cavities are observed in bands with the swelling peaked at depths of 1.4. 1.9 and 2.3 mu m for H-, He- and O-ion implanted regions, respectively. The growth of cavi ties is most pronounced in the O-ion damaged region with a maximum siz e of 13 nm and a density of 2-3 x 10(23)m(3). In a sample annealed for 1 h at 1273 K after the irradiation, cavities grown to an average siz e 40 and 60 nm with a maximum of 70 nm were observed in He- and O-ion implanted regions, respectively, and the density was decreased by abou t two orders. (C) 1998 Elsevier Science B.V. All rights reserved.