Hardness and elastic modulus of Au/NiCr/Ta multilayers on Al2O3 substrate by nanoindentation continuous stiffness measurement technique

Au/NiCr/Ta soft metallic multilayered films were deposited on hard Al2O3 substrate by magnetron sputtering. The distribution of hardness and elastic modulus was investigated by nanoindentation continuous stiffness measurement technique. The film hardness was constant for all samples at indentation depths 1/7 ≤ h/t ≤ 1/4, which can be considered as the true hardness. The hardness increased with increasing indentation depths at 1/4 ≤ h/t ≤ 1. The hardness was shown to be not regular at indentation depths h/t ≤ 1/7; this is due to the different surface roughness of films. Compared to the hardness, the measured elastic modulus was more sensitive to the substrate.