Mechanical characterization of epitaxially grown zinc oxide nanorods

We performed a well controlled in situ bending test in a scanning electron microscope on individual ZnO nanorods to determine the bending modulus. The crystallographically aligned vertical nanocrystals were grown by wet epitaxial growth method through an electron beam generated pattern. They show good homogeneity, their length and top facet diameter vary in the range of 1.3–1.5 μm and 97–113 nm, respectively. The nanorods, which are fixed at their roots by the substrate, were bent at their free end along 〈11–20〉 and 〈10–10〉 crystallographic directions by a calibrated atomic force microscopy cantilever. The typical deflections, caused by ∼40–60 nN lateral loads, fall in the range of ∼50–100 nm. In order to take into the account the non-uniform cross section along the vertical axis, we propose a two-part mechanical model, which is built up from a lower truncated circular, and an upper truncated hexagonal cone. The obtained bending modulus is 36.0±8.3 GPa, which is significantly lower than that of the bulk ZnO (140 GPa).