Ion beam effects on the formation of Ge and Si nanoclusters in silica thin films

Abstract

We have observed that ion-beam-assisted deposition (IBAD) has important effects on the optical properties of nanoclusters of Si or Ge in silica thin films. Si or Ge nanocluster(nc)-containing, thin silica films were prepared both by evaporation (PVD) and ion-beam-assisted deposition (IBAD), along with post-deposition annealing. Ge-nc IBAD films contain smaller nanoclusters (3.8± 0.5 nm) with a much tighter size distribution than the PVD films (13±6 nm). The difference in cluster size leads to a shift of the peak position of photoluminescence (PL). Furthermore, X-ray diffraction (XRD) from Ge-nc containing silica films reveals that IBAD promotes the crystallization of semiconductor nc's at lower annealing temperatures and inhibits further growth with increasing annealing temperature. For the Si-system, a decreasing Si-nc size was observed for an increasing ion energy, which weakens the PL and produces an observable small blue shift in the peak of the PL.