Segregation effects in Ag-Si composites

Abstract Ag-Si composites prepared by co-sputtering the components onto sapphire substrates are found to result in the Ag rapidly segregating to the Si surface if both sputtering sources are shut off at the same time. If the Si source is allowed on for a period of time after shutting off the Ag source this segregation does not occur and the Ag is uniformly distributed throughout the Ag-Si composite. Though strain considerations or a “kick-out” mechanism may be used to explain this segregating effect, it is not clear why the Ag Si/Si interface prevents Ag segregation at the free Si-vacuum surface, though the αSi overlayer may provide a sufficient diffusion barrier to prevent the Ag from segregating.