Room temperature excitonic emission in highly aligned ZnO nanostructures prepared by glancing angle Xe plus ion irradiation

Highly aligned ZnO nanostructures have been prepared using glancing angle ion irradiation technique. ZnO thin films were deposited on Si substrates using pulsed laser deposition method. These films were irradiated with 100 keV Xe+ ions of different fluencies ranging from 1 x 1016 to 1 x 1017 ions/cm2 at a glancing angle of 70 degrees with respect to the sample normal. The scanning electron and atomic force microscopy studies reveal a randomly oriented flower petal like structure in the pristine ZnO film. However after ion irradiation, these petals are aligned in the beam direction. Further, with the increase of the ion fluence the petals are transformed to the nanostripe, nanowire like structures and at highest fluence wrinkled structure are formed. Interestingly, on closer examination, these wrinkles consist of nanopillar like structures aligned in the beam direction. The X-ray diffraction analysis reveals that the formed ZnO nanostructures are of hexagonal wurtzite structure with preferred orientation along the c-axis. Further, the ion beam modified nanostructures exhibit interesting photoluminescence emissions in the UV regime. The exciton emission of these ion beam modified ZnO nanostructures has been discussed with the aid of X-ray absorption near edge spectroscopy at O K-edge.