The ion-beam bending of ZnO nanoneedles was studied in order to determine the dependence of their bending direction upon the ion-beam energy and to clarify the bending mechanism. Through gallium focused ion beam bending, the stems of the nanoneedles were found to be bent into the direction of the ion beam source for ion beam energies of 30keV whereas they were bent in the opposite direction at ion energies lower than 20keV. It was found, for the first time, that the bending direction of ZnO nanoneedles could be changed by repeated switching of the ion beam energy between lower and higher energy levels, and that the thin tip parts of the nanoneedles were bent toward to the ion beam source like the higher energy bending mode during the process of lower energy bending below 20keV. Through high resolution transmission electron microscopy observations of the microstructure of a nanoneedle, bent by 30keV higher energy ion beams, based on the atomic scale, It was found that more edge dislocations were created in the rear side, deeper than the central plane of the nanoneedle, than the front side and that each edge dislocation added an extra lattice plane in this region. These observations clearly showed that the bent nanoneedles were plastically deformed by the edge dislocations created by the ion beams.

Repeatable Switching of the Bending Direction of ZnO Nanoneedles by Ion Beams. D.H.Kim, H.J.Lee, G.C.Yi: Nanotechnology, 2012, 23[7], 075302