Production of hollow hemisphere shells by pure Kirkendall porosity formation in Au/Ag system

Abstract

Interdiffusion has been studied in Ag/Au hemispherical core-shell structures on sapphire substrate. In isothermal heat treatments first a relatively fast growth of nanovoids was observed, which was followed by a slower shrinkage process. The void formation is interpreted by pure Kirkendall-porosity formation since Ag-50%Au solid solution has been formed in the shell. In contrary, in all previous publications on hollow nanoshell formation a chemical reaction took place and the shell consisted of the reaction product (i.e., of sulphide or oxide). Furthermore, in these cases the shrinkage was observed at temperatures higher than the formation temperature. © 2010 American Institute of Physics.