Mechanical Properties of Multilayered Copper-Nickel thin films Measured by Indentation Techniques

Abstract

ABSTRACTArtificially multilayered copper/nickel thin films with bilayer repeat lengths between 1.6 and 12 nm were produced by ion beam sputtering. The mechanical properties of these films were investigated by low load microhardness and nanoindentation (force versus depth) techniques. It was found that none of the films displayed bilayer repeat length dependent enhanced elastic behavior (the supermodulus effect) as measured during unloading in the nanoindenter. However, enhancements in hardness, as measured by both the nanoindenter and the low load microhardness tester, were observed in films with small bilayer repeat lengths. These measurements displayed a Hall-Petch-type relationship, using the individual layer thickness (equal to half the bilayer repeat length) as the characteristic “grain size.” This hardness behavior can be understood in terms of a mechanism involving dislocation pinning at the interfaces analogous to the mechanism of grain boundary hardening.