Size effects on the mechanical properties of thin metallic films studied by nanoindentation

The effects of the thickness and grain size on the mechanical properties of thin polycrystalline Cu and Ag films on silicon substrates are investigated by nanoindentation. At small indentation depths the results are affected by the tip radius of the Berkovich indenter and the response of indented films at first stages of loading is adequately represented by the dependence for the spherical indenter. The loading conditions are determined to remove the effects of the substrate and surface roughness on the hardness and the elastic modulus of the films. The hardness of the films is found to increase with decreasing the film thickness and the grain size. The yield stresses of the Cu and Ag films are estimated.