FORMATION OF METALLIC NANOPHASES IN SILICA BY ION-BEAM MIXING PART II- CLUSTER FORMATION

The formation of Ag nanoclusters in a SiO2 matrix by ion-beam mixing o f SiO2/Ag multilayers is studied via Rutherford backscattering spectro metry, optical absorption, and transmission electron microscopy experi ments. In a first step, irradiation with MeV heavy ions transforms the continuous Ag layers into a string of micrometer-sized Ag inclusions. This mechanism can be attributed to lateral segregation of metallic a toms induced by irradiation. In a second step, the Ag inclusions are b roken up by incoming ions and Ag nanoclusters are formed by agglomerat ion of mobile Ag atoms. The latter mechanism is likely due to a combin ation of ballistic mixing and radiation-induced segregation or radiati on-enhanced diffusion processes. The size of the metallic nanoclusters formed depends also on the irradiation temperature.