Scratch behavior of multi-layered metallic thin films on Al2O3 substrates

Au/NiCr/Ta and Au/NiCr multi-layered metallic films were deposited on hard Al2O3 substrates by magnetron sputtering and a scratch test method was applied with both friction and acoustic emission modes to monitor changes of scratched response of the films. The characteristic curve in the scratch and the morphology of the films were compared with those of a TiN film. It is evident that both modes can eventually be used for conventionally critical load determination, but the friction mode can additionally reflect the changes at different metallic film layers. The critical characteristic load at each point corresponding to abrupt change of the coefficient of friction was not sensitive to deposition temperature and post-heating process, but sensitive to the number of layers and the thickness of films. It increases approximately linear with increasing the thickness of metallic films.