Effect of surface energy on size-dependent deformation twinning of defect-free Au nanowires

In this study, we report the size-dependent transition of deformation twinning studied using in situ SEM/TEM tensile testing of defect-free [110] Au nanowires/ribbons with controlled geometry. The critical dimension below which the ordinary plasticity transits to deformation twinning is experimentally determined to be similar to 170 nm for Au nanowires with equilateral cross-sections. Nanoribbons with a fixed thickness but increased width-to-thickness ratios (9 : 1) were also studied to show that an increase in the surface energy due to the crystal re-orientation suppresses the deformation twinning. Molecular dynamics simulations confirmed that the transition from partial dislocation mediated plasticity to perfect dislocation plasticity with increase in the width-to-thickness ratio is due to the effect of the surface energy.