Preparation and characterization of epitaxial growth of ZnO nanotip arrays are essential for field emission applications due to its high emission rate of electron and fast electron-transfer rate. At first, nanocrystalline ITO thin films were prepared on glass substrates by ion-beam sputter deposition (IBSD) method. ZnO seed layer was prepared on the ITO coated glass substrates by IBSD at room temperature, and then, ZnO nanotip arrays were epitaxially grown on the as-prepared ZnO seed layer coated ITO/Glass substrates by hydrothermal method. The surface morphology study confirmed that the ZnO nanotip array films were epitaxially grown on ITO/Glass substrates, and it clearly showed the formation of well-aligned ZnO nano-tip arrays on ITO/Glass substrate. The as-prepared samples were annealed at different temperatures (100, 150 and 270 degrees C). After annealing, the surface morphology of ZnO nanotip arrays did not show any remarkable change. X-ray diffraction pattern of ZnO nanotip array films prepared on ITO/Glass showed a main peak at 20 = 34.3 degrees, which corresponds to (002) plane. The photoluminescence spectra showed the strong intensity of UV emission and weak intensity of green emission. The J-V characteristic of Ag/NPB/PMMA/ZnO/ITO showed good rectification behavior. (C) 2012 Elsevier Inc. All rights reserved.