Imaging the mechanical properties of nanowire arrays

Dimensional and contact resonance (CR) images of nanowire (NW) arrays (NWAs) are measured using our newly developed microprobe CR imaging (CRI) setup. Then a reference method is employed to calculate the indentation modulus of NWs (Mi,NW) representing the elasticity of NWs, by measuring NWAs and reference samples at the same static probing force. Furthermore, topography is imaged in combination with CR and Mi,NWseparately by software, in which the zvalues indicate the topography of the NWs and the color bars show its CR or Mi,NW. Then NWs’ topography relation to Mi,NWis visualized. As typical examples, 3D imaging of topography and measurement of Mi,NWis performed with Si<111> pillar arrays as well as Cu and ZnO NWAs. The novel method enables fast mechanical performance measurements of large-scale vertically-aligned NWAs without releasing them from their respective substrates. For instance, the diameter and pitch of the Si<111> pillars and the diameter of the Cu NWAs are in good agreement with the values measured by scanning electron microscopy (SEM). The position of ZnO NWs bunches grown at arbitrary sites on silicon can be identified with the help of combined topography and indentation modulus images. Furthermore, Mi,NWmeasured by our homemade CRI setup agrees well with bulk values. Differences between the measured Mi,NWand bulk Mivalues may be related to a size effect in NW elasticity.