Composite deposition of Co and Si clusters by rf/dc plasma-gas-codensation

Abstract

A double-glow discharge cluster source system has been made by modification of a conventional co-sputter-deposition apparatus. Using this equipment, we tried to produce Co clusters generated by a dc glow discharge mode, Si clusters by an rf glow discharge mode, and deposit them simultaneously on a substrate. Putting a separate plate between these two glow discharge rooms, we have obtained a mixture of Co and Si clusters. Here, the Co clusters are distributed rather at random, while the Si clusters are aggregated to form a larger group. Taking off the separate plate, we have obtained core–shell clusters, in which small Si clusters surround Co core clusters. These features are quite different from the instantaneous alloying and/or very rapid atom diffusion that has been expected at contact interfaces between nanometer-sized small Co and Si clusters. They suggest that this double-cluster source system is useful to fabricate various sorts of cluster composites that cannot be prepared by thermodynamical methods, such as co-evaporation and precipitation.