Fabrication and annihilation of nanovoids in Cu nanoclusters by ion implantation into silica and subsequent annealing

Cu ions were implanted at $180keV$ into silica with doses ranging from $5×1016to2×1017ions∕cm2$⁠. Cross-sectional transmission electron microscopy and high-resolution transmission electron microscopy images showed that Cu nanoclusters containing nanovoids have been formed for doses higher than $1×1017ions∕cm2$⁠. The nanovoids grew when the samples were annealed in a reducing atmosphere at $900°C$ for $1h$ and then disappeared at $900°C$ for $4h$⁠. The mechanisms for the formation and disappearance of nanovoids are discussed.