Piezoresistance and electrical resistivity of Pd, Au, and Cu films

Abstract Electrical resistivity and piezoresistance of some metal films, such as the Pd, Au, and Cu films, were measured. Surface features of a few characteristic films, used in this study, were revealed by using an atomic force microscope. The electrical resistivity ρ is plotted as a function of the film thickness t, and the strain gauge factor γ is plotted as a function of the sheet resistivity Rsq. Two parameters are found useful: i.e. h/λ and 2h/t, where h is the amplitude of undulations of the surface roughness and λ is the electron mean free path at room temperature. By taking the Cu film as an example, the area-distribution function of island-like humps on the specimen surface is also analyzed. Two models, namely the surface roughness and the electron tunneling models, are employed to explain the electrical resistivity and piezoresistance data observed. It is found that (1) if h/λ⩽0.3 and 2h/t