Effect of surface morphology on the mechanical properties of ZnO nanowires

Although studies of ZnO nanostructured materials have concentrated on the electric, optical, and magnetic properties, applicational devices with nanoscale moving parts usually suffer mechanical fatigue and failure for reasons that are less understood. Here, differing from vertical bending and tension measurements, conventional three-point bending tests are employed to study the elastic modulus and bending strength of ZnO nanowires (NWs) in an atomic force microscopy system. To shed new light on the extensive disagreement regarding the mechanical behavior of ZnO NWs, the effect of the surface morphology of the prepared NWs is mainly investigated. An average Young’s modulus of 148 GPa close to that of the bulk ZnO materials is obtained, and the size dependence is found to be unaffected by the detailed micro and macro surface morphology. On the other hand, the bending strain of 0.2–0.7% is one order of magnitude lower than that reported in the literature. It indicates that an irregular surface such as cracks, flaws, curved and neck-like surface, and body defects dominates the fracture properties of ZnO NWs, rather than the elastic behavior.