Diameter dependence of modulus in zinc oxide nanowires and the effect of loading mode: In situ experiments and universal core-shell approach

Abstract

Uniaxial tensile measurements have been performed on [0001]-oriented zinc oxide nanowires (NWs) with diameters ranging from 18 to 204 nm using a homemade in situ mechanical testing system. Diameter dependence of tensile modulus (TM) is further compared with that of bending modulus (BM, shown earlier). With diameters of NWs decreasing in an intermediate range (about 30–120 nm), TM increases slower than BM, while it gets close to the latter with diameters decreasing below 30 nm; for rather large diameters, they both tend to the bulk modulus. A core-shell model is developed based on diameter-dependent and radial-distributed elastic stiffening in NWs and well explains our experimental results.