The effect of cascade damage upon vacancy cluster formation was investigated. No defect clusters were observed, using transmission electron microscopy, in thin foils of 2N8-purity material which had been bombarded with 200 or 400keV V+ ions to a dose of 1016/m2 at room temperature. Thin-foil specimens were also irradiated with Au+ or Xe+ ions to a dose of 1016/m2. The energy of the ions ranged from 50 to 400keV. In specimens which had been irradiated with Au+ ions, defect clusters with sizes of 2 to 2.5nm were detected by transmission electron microscopy. The areal density of the defect clusters increased with ion energy, and also depended upon the thickness of the specimen. In thin regions of the specimens, the density of defect clusters as a function of deposited damage energy increased with ion energy. It was concluded that vacancy clusters were produced by a high density of displacements in cascade damage.

Defect Cluster Formation in Vanadium Irradiated with Heavy Ions. N.Sekimura, Y.Shirao, H.Yamaguchi, S.Yonamine, Y.Arai: Journal of Nuclear Materials, 1999, 271-272, 63-7