Ion-beam mixing in pure and in immiscible copper bilayer systems

Abstract

Ion-beam mixing was measured in immiscible Cu bilayer systems after Kr irradiation at 6 K and at 295 K. It was observed that for the systems which form miscible liquids but which have limited solid solubility, Cu-Nb and Cu-Bi, mixing occurs at 6 but not at 295 K. For a system which is not miscible in either the solid or liquid state, mixing does not occur at either 6 or 295 K. Mixing was also measured in pure Cu isotope bilayer specimens,⁶³Cu–⁶⁵Cu, to provide a standard for the other measurements. The results are interpreted on the basis of an atomistic model of ion beam mixing. The model assumes that point defects are created in the initial phases of the cascade evolution, and that these defects migrate during the later ‘thermal spike’ phase.