Effect of Surface Steps on the Plastic Threshold in Nanoindentation

Abstract

Using interfacial force microscopy and passivated Au surfaces, we have investigated the effect of surface steps on the initiation of plastic yield by performing nanoindentations as a function of separation between the probe and neighboring steps. The mean stress at yield was $30\%$– $45\%$ lower at a step than in regions free of surface defects. In addition, the spatial extent of the step's influence was found to be approximately 3 times the contact radius at the yield threshold, suggesting that yield processes are not limited to the region in contact with the indenter.