Mechanical behavior of hard amorphous Si-C-N thin films

Completely hard amorphous Si-C-N films were prepared by electron cyclotron resonance microwave plasma assisted chemical vapor deposition and characterized by atomic force microscopy and nanoindentation. In contrast to common findings of sink-in effects for hard films on soft substrates, anomalous pile-up effects were observed in such kinds of hard films. Inherently different from the traditional measurements of hardness, which are taken from the residual impression after unloading, load-displacement curves from nanoindentation measurements reveal the feature of a large elastic deformation based on the evaluation of the total work and the elastic work. The reduced modulus shows an approximately linear relationship with the measured hardness, while no linear relation can be extracted for the energy dissipation and the ratio of hardness and Young modulus, H/E. Mechanical behaviors of Si-C-N films measured by the Oliver and Pharr method match well with the fitted data from the modified King's model within the investigated range of the indentation depth.