Gold vicinal surfaces (788), with a high density of steps, along with (111) flat surfaces taken as a reference, were nano-indented and their resulting penetration curves and related defect structure comparatively analyzed by atomic force microscopy and atomistic simulations. Stepped surfaces were shown to yield at smaller loads than (111) ones in agreement with calculations of the critical resolved shear stress needed to nucleate a dislocation. In the stepped surfaces, a novel intermediate state was identified in which the penetration curves depart from a Hertzian behavior prior to the appearance of pop-ins. This state was shown to result from heterogeneous nucleation at pre-existing surface steps of dislocation loops, most of which retracted and vanish when the indenter load was removed.

Uncommon Dislocation Processes at the Incipient Plasticity of Stepped Gold Surfaces. V.Navarro, O.Rodríguez de la Fuente, A.Mascaraque, J.M.Rojo: Physical Review Letters, 2008, 100[10], 105504 (4pp)