An Improved Indentation Method for Estimating Limits of Fracture Toughness in Brittle Films

We previously presented an energy method for predicting the bounds of fracture toughness of brittle films on a soft substrate from nanoindentation. The method is now further improved by minimizing elastic-plastic work from the measured energy during ring crack formation. Then, we applied this method to determine the limits of fracture toughness of alumina films with a thickness of 100 nm. It was found that fracture toughness of the films is in the range of 1.8-2.2 MPa.m0.5, which is consistent with those measured by the conventional method.