Competing processes of clustering and mixing of noble metal films embeddedin silica under ion irradiation

Thin layers of noble metals (M = Cu, Ag, Pd, Pt, Au) embedded in silica wer e submitted to irradiation with increasing fluences Phi of 4.5 MeV Au ions. Concurrently to the mixing of metal and silica atoms, the irradiation prom otes the clustering of the metallic phase. Metallic particles were observed in transmission electron microscopy in order to determine if their size co ntributes fur a large part to the spreading of the M distribution measured by Rutherford Backscattering Spectrometry (RBS). The part of this spreading due to the recoil implantation of M atoms into the silica matrix and to th eir radiation-enhanced diffusion is yet larger. The variance of the distrib ution increases in proportion to Phi or to its square, depending on whether it is controlled by the diffusion (thin films) or the recoil implantation process (thicker films). (C) 2000 Elsevier Science S.A. All rights reserved .