ZnO nanopencils: Efficient field emitters

ZnO nanopencils were synthesized on a silicon wafer without catalysts at a low temperature of 550 degrees C through a simple two-step pressure controlled thermal evaporation. Penholders were well-hexagonal faceted and the diameter of pen tips on the nanopencils was in the range of 20-30 nm. High-resolution transmission electron microscopy shows that the nanopencils were single crystals growing along the [0001] direction and the pen tips subtend a small angle with multiple surface perturbations. Field-emission measurements on the nanopencils show a low turn-on field of 3.7 V/mu m at a current density of 10 mu A/cm(2). The emission current density reached 1.3 mA/cm(2) at an applied field of 4.6 V/mu m. The emission at the low field is attributed to the sharp tip and surface perturbations on the nanopencils. (c) 2005 American Institute of Physics.