Atomic force microscopy captures quantized plastic deformation in gold nanowires

Scanning probe microscopy has become a powerful tool to detect structural c hanges in small clusters of atoms. Herein, we use an atomic force microscop e to measure the length of gold nanowire structures during extension and co mpression cycles. We have found that nanowires elongate under force in quan tized steps of up to three integer multiples of 1.76 Angstrom and that they shorten spontaneously in steps of 1.52 Angstrom. Our results can be explai ned by the sliding of crystal planes within the gold nanowires creating sta cking faults that change the local structure from face-centered cubic to he xagonal close packed. Our data also show that there can be up to three simu ltaneous slip events, in good agreement with the tetrahedral arrangement of slip planes in a gold crystal. These experiments provide direct evidence f or the mechanism underlying the plastic deformation of a nanowire. A simila r approach can be used to examine the atomic events underlying the plastic failure of other metals and their alloys.