Modifying optical properties of ZnO nanowires via strain-gradient

We conduct systematical cathodoluminescence study on red-shift of near-band-edge emission energy in elastic bent ZnO nanowires with diameters within the exciton diffusion length (~ 200 nm) in liquid nitrogen temperature (81 K). By charactering the emission spectra of the nanowires with different local curvatures, we find a linear relationship between strain-gradient and the red-shift of near-band-edge emission photon energy, an elastic strain-gradient effect in semiconductor similar to the famous flexoelectric effect in liquid crystals. Our results provide a new route to understand the inhomogeneous strain effect on the energy bands and optical properties of semiconductors and should be useful for designing advanced nano-optoelectronic devices