Nanoprobing fracture length scales

Historically fracture behavior has been measured and modeled from the largest structures of earthquakes and ships to the smallest components of semiconductor chips and magnetic recording media. Accompanying this is an evolutionary interest in scale effects partially due to advances in instrumentation and partially to expanded supercomputer simulations. We emphasize the former in this study using atomic force microscopy, nanoindentation and acoustic emission to probe volumes small in one, two and three dimensions. Predominant interest is on relatively ductile Cu and Au films and semi-brittle, silicon nanoparticles. Measured elastic and plastic properties in volumes having at least one dimension on the order of 10 - 1000 nm, are shown to be state of stress and length scale dependent. These in turn are shown to affect fracture properties. All properties can vary by a factor of three dependent upon scale. Analysis of fracture behavior with dislocation-based, crack-tip shielding is shown to model both scale and stress magnitude effects