AVS 49th International Symposium
    Plasma Science Wednesday Sessions
       Session PS+NT-WeM

Paper PS+NT-WeM7
Zinc Oxide Nanowires Grown by Plasma Assisted Chemical Vapor Deposition

Wednesday, November 6, 2002, 10:20 am, Room C-103

Session: Plasma Science and Technology for Nanostructures
Presenter: J.B. Baxter, University of California, Santa Barbara
Authors: J.B. Baxter, University of California, Santa Barbara
E.S. Aydil, University of California, Santa Barbara
Correspondent: Click to Email
Zinc Oxide is a wide band gap semiconductor (Eg=3.37eV) that can exhibit visible and UV luminescence, piezoelectricity, and high conductivity. ZnO nanowires and hexagonal columns have been grown using plasma assisted chemical vapor deposition, using either metallic zinc or metalorganic precursors. Nanowire growth is catalyzed by monodisperse gold nanoparticles (20 nm diameter) dispersed on a substrate from a colloidal solution. Transmission electron microscopy and electron diffraction show that single crystal ZnO nanowires grow from the gold particles in the <0001> direction. The nanowires have monodisperse diameters determined by the diameter of the gold particles (~ 20nm), and can grow to several microns in length. Energy dispersive x-ray spectroscopy confirms that the wires have a Zn:O ratio of 1:1. ZnO columns were formed by subliming metallic zinc in oxygen plasma, with the columns growing in the <0001> direction from the zinc surface. The columns are several 100 nm in diameter and are hexagonally faceted. Cathodoluminescence results show that both wires and columns emit photons upon excitation by electrons, with the columns emitting most light through the top face. This suggests that ZnO nanowires act as light pipes by internally reflecting the emitted light, making them good candidates for UV lasing. Because the gold particles from which the wires grow can be closely packed, the wires can be grown on a substrate in very dense, high surface area arrays. This property suggests that ZnO nanowires are also ideally suited toward application as the mesoporous semiconductor in dye sensitized (Gratzel) solar cells.