ENHANCED OXYGEN VACANCY AGGREGATION AND COLLOID PRODUCTION IN AL2O3

Optical luminescence and absorption measurements on Al2O3 (sapphire) e lectron irradiated at temperatures between 200 and 270 degrees C with and without an applied electric field have been used to identify an ox ygen vacancy aggregation process leading to the formation of aluminium colloids. This process, which is only observed when an electric field is applied during irradiation, occurs within the volume and is consid ered as a possible precursor for RIED. The results help to clarify the observed similarity between RIED and colloid production, and help to provide an explanation for the observation of gamma alumina in sapphir e which has suffered RIED. (C) 1997 Elsevier Science B.V.