Determination of intrinsic film properties from nanoindentation of film/substrate composites.

摘要

Determination of the mechanical properties of thin films on substrates by indentation has always been a problem because of the influence of the substrate on measured properties. The objective of the research described in this dissertation was to study the effect of substrate properties on the measurement of film properties by nanoindentation and to develop methods for extracting the intrinsic film properties from nanoindentation experiments.; Aluminum films and tungsten films with thicknesses varying from 0.5 μm to 2.0 μm were sputter deposited onto aluminum, glass, silicon, and sapphire substrates. Hardness and elastic modulus were first determined using the well-established Oliver-Pharr method. The Al films have a hardness of 0.6 GPa and a modulus of 65 GPa and the W films have a hardness of 13–14 GPa and a modulus of 400–440 GPa at small indentation depths. However, due to limitations in the Oliver-Pharr method, these measurements showed significant deviations from the expected value, especially at large indentation depths relative to the film thickness.; The true or intrinsic hardness of the Al films on glass and the W films on sapphire can be determined by utilizing the elastic homogeneity of the film and substrate and the P/S2 parameter, where P is the load and S is the contact stiffness. Two other hardness models, the Tsui-Pharr model and the Korsunsky model, were examined using the Al and W data. Finite element methods were also used to model the indentation response of the film/substrate system. The model permitted an estimate of the intrinsic film properties.; A model developed by King has been used to extract the intrinsic modulus of the films from the composite data. Although King developed the method for a flat punch indenting an elastic half space, his model works reasonably well for indentations made with the three-faced Berkovich indenter. A simple model for calculating pile-up height from the nanoindentation data is also presented. The pile-up height predicted by the model is compared with measurements made with AFM and found to agree reasonably well.