Local electronic structure and luminescence properties of Er doped ZnO nanowires

Using combined microscopy and optical characterizations, the authors demonstrate effective Er doping into freestanding ZnO nanowires via ion implantation. The Er atoms are observed to take the substitutional sites in ZnO without causing obvious distortion to the host lattice. While the band gap threshold of the Er doped ZnO nanowires remains similar to that of the undoped ZnO, band tail states are created in the band structure of the ZnO upon Er doping. Room temperature 1.54 mu m emission is achieved in the doped nanowire sample after oxygen annealing. In particular, the generation of the band tail state(s) in the band gap of the ZnO nanowire host is found to be responsible for the 1.54 mu m emission under the below-band-gap indirect excitation.