A vertically aligned ZnO nanowall arrays have been synthesized on a patterned ZnO buffer layer using an interference laser beam. The average height and thickness of the ZnO nanowall were 4 μm and 200 nm, respectively. Room-temperature ultraviolet (UV) lasing was obtained from single piece of ZnO nanowall detached from the substrate. The threshold power density for lasing was estimated to be about 80 kW/cm2. In addition, UV lasing from vertically aligned ZnO nanowall was also observed owing to the presence of holes. The lasing spectra had no regularity in the mode spacing and many different spatial modes, suggesting that the action was supported by the random lasing mechanism. The threshold power density for lasing was about 300 kW/cm2, which was much higher than that of the single piece of ZnO nanowall because of the leakage of the light into buffer layer.
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