Photoinduced stiffening in ZnO nanobelts.

We report the observation of remarkable photoinduced stiffening in a single ZnO nanobelt using nanoindentation and atomic force microscopy. The apparent elastic modulus of a ZnO nanobelt under illumination with a photon energy greater than the band gap becomes much larger than that under darkness. The physical mechanism for the observed phenomena is analyzed in terms of the surface effect and the electronic strain induced by the photogeneration of free carriers in a ZnO nanobelt.