Aligned ZnO nanowires were grown by metal organic chemical vapor deposition on patterned silicon substrate. The shape of nanostructures was greatly influenced by the micropatterned surface. The aspect ratio, packing fraction and the number density of nanowires on top surface are around 10, 0.8 and 10(7) per mm(2), respectively, whereas the values are 20, 0.3 and 5 x 10(7) per mm(2), respectively, towards the bottom of the cavity. XRD patterns suggest that the nanostructures have good crystallinity. High-resolution transmission electron microscopy confirmed the single-crystal line growth of the ZnO nanowires along the [0 0 0 1] direction. Photosensitivity of the nanowires, grown on both top and bottom surface of the microchannel, was observed. However. the nanowires grown on bottom surface have shown better UV response with base line recovery at dark condition. (C) 2009 Elsevier B.V. All rights reserved.