Effect of surface steps on the plastic threshold in nanoindentation

Using interfacial force microscopy and passivated Au surfaces, we have investigated the effect of surface steps on the initiation of plastic yield by performing nanoindenrations 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 foe 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.