TEM and SEM studies of radiation blistering in helium-implanted copper

Abstract

Nanoporous layers produced in metal surfaces by He implantation are of special interest for applications such as catalysis. At high doses nanoporous layer formation can be limited by the onset of radiation blistering. Research into the blistering of metals was stimulated originally by the need to find materials resistant to blistering for use in the first-wall of future nuclear fusion reactors. Blistering was the subject of intensive international study in the two decades centred on 1977. Despite this effort the bubble structures associated with blistering were never determined. In the present work TEM sections have been successfully prepared, by ultramicrotomy, perpendicular to the surface of high dose copper targets. For the first time, in any case of radiation blistering, the bubble structures directly associated with blistering are identified and their depth dependence determined. Local swellings, caused by a bimodal distribution of nanoscale bubbles, are estimated to exceed 150%. Probable answers can now be provided for some longstanding questions from earlier studies.