Atomistic deformation mechanism of perfect crystal Au nanowires

Atomistic deformation mechanism of perfect crystal Au nanowires
Au nanowire; Dislocation; Twin propagation; HRTEM
Issue Date
MRS 2010 Fall
Metal nanowires are great of technological importance due to their potential applications in miniaturized electrical, thermal, and mechanical system because their structure and properties can be quite different than bulk materials. The recent molecular dynamics works predicted the existence of strong but ductile behavior of metal nanowires achieved by deformation twinning. However it has been not experimentally proven by the tensile test of metallic nanowires. Unfortunately, previous experiment only observed high strength but brittle fracture in nanowires. Thus, the presence of ductile deformation in nanowires by structural transformation is in question and the deformation mechanism of nanowire proposed by atomic scale simulations is still controversial. In this study, we report ultra-strong but ductile deformation behavior of gold nanowires by structural transformation through deformation twinning through the tensile test using Nanomanipulator (MM3A, Kleidiek) equipped in Focused Ion Beam (Quanta 3D, FEI) as well as the observation of the each deforming steps and fracture region using transmission electron microscope (Titan80-300, FEI). The single crystalline Au nanowires were synthesized with the growth direction of <110> on a sapphire substrate. For the uniaxial tensile test, the both sides of single Au nanowire were attached to the W nanomanipulator tip and TEM copper half grid by the Pt deposition of FIB. We observed real time twin nucleation and twin migration leading to the transformation of the entire shape and orientation of gold nanowires using our in-situ tensile test. The Au nanowire was governed by the multiple twin deformation of {111}<112> at initial stress state and by the growth of one twin boundary among them. As the result, the twin growth spontaneously leads to the orientation rotation from <110> to <100>. In the stress-strain curves measured from Au nanowires, the elongation of Au nanowire by tw
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