NiO films consisting of vertically aligned cone-shaped NiO rods

By thermally heating a nickel foil in a vacuum of similar to 5 x 10(-2) Torr, films consisting of vertically aligned cone-shaped NiO microrods were deposited on Si (001) substrates at a temperature of < 300 degrees C. The NiO rods were grown along < 001 > directions by stacking the NiO (001) nanoslices, and are similar to 10 mu m long with a sharp nanosized tip. Due to this morphology, the NiO film exhibited a threshold field of similar to 6.5 V/mu m in field emission and a field enhancement factor of 2130 that is sufficiently high for field emission applications. The optical band gap of the NiO film was estimated to be similar to 3.68 eV from the optical absorption measurement and was almost a constant upon heating. In addition, the NiO film exhibited a strong photoluminescence at similar to 674 nm when excited by a 514 nm Ar+ laser, which might be attributed to the oxygen vacancies. (c) 2006 American Institute of Physics.