Electrical surface degradation of electron irradiated sapphire and silica

Two types of oxides, silica and sapphire have been irradiated with 1.8 MeV electron and 54 keV He(+) in order to study surface electrical and optical degradation processes. It has been found that both materials suffer severe surface degradation as a consequence of radiation induced oxygen removal for either 1.8 MeV electron irradiation or 54 keV He(+) implantation. Degradation is higher in the case of alpha particle bombardment, but the results strongly suggest that the fundamental processes taking place are basically the same. Ionizing radiation rather than knock-on displacements appears to be the origin of the severe oxygen removal from the irradiated surface. The possibility of such surface degradation in insulators for ITER and future fusion reactors needs to be fully assessed. (C) 2009 Elsevier B.V. All rights reserved.