Deformation of nanoporous nanopillars by ion beam-induced bending

We have applied a novel approach to the investigation of deformation of nanoporous metals at the nanoscale by exposing nanoporous nanopillars to a Ga+ ion beam. We will show the results that we have obtained with Au nanopillars, but we have also observed similar behaviors in Cu, Al, and Ni nanopillars, i.e., a gradual massive deformation effect of the pillar during Ga ion beam exposure, where the pillar bends toward the ion beam. We derive a relationship between the formation of defects due to ion collisions in the nanopillars and the pillar's deformations and find that the deflection is linearly related to ion fluence. Computational models have shown that the deflection rate can be varied through change in acceleration voltage. This occurs due to the dual influence of a decreasing bending arm which reduces the associated bending moment, as well as the decreasing ion concentration, and thus defect concentration at the peak stress point. The high degree of control over deflection and the variables that influence it open an opportunity for use of ion-induced bending as a characterization technique of mechanical performance.