AVS 59th Annual International Symposium and Exhibition
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS+EN-TuM

Paper NS+EN-TuM3
Optical and Electrical Characteristics of Al-doped ZnO Nanowires Grown by Chemical Vapor Deposition

Tuesday, October 30, 2012, 8:40 am, Room 12

Session: One-Dimensional Nanowires and Nanotubes
Presenter: G. Shen, University of Alabama, Tuscaloosa
Authors: G. Shen, University of Alabama, Tuscaloosa
N. Dawahre, University of Alabama, Tuscaloosa
J. Waters, University of Alabama, Tuscaloosa
J. Krafcik, University of Alabama, Tuscaloosa
S.M. Kim, University of Alabama, Tuscaloosa
P. Kung, University of Alabama, Tuscaloosa
Correspondent: Click to Email
Zinc oxide (ZnO) is a well-known major semiconductor material for optoelectronic devices due to its wide bandgap (~3.3 eV) and large exciton binding energy (~60 meV). One dimensional ZnO nanowires have been successfully synthesized by various techniques ranging from as simple as thermal chemical vapor deposition and solution growth, to more complex such as metal organic chemical vapor deposition, with good structural, optical and electrical properties. These are promising as an alternative to indium tin oxide as a more abundant, lower cost transparent window for a number of optoelectronic devices, including photovoltaics, while at the same time offering potentially more efficient electron charge transport. ZnO is also capable of harvesting the short wavelength spectral bands more efficiently.

In this work, we present the growth, doping and characterization of vertical well-aligned ZnO nanowire arrays. The wires are synthesized without metal catalyst by thermal chemical vapor deposition on basal plane sapphire substrates following the carbo-thermal reduction of zinc oxide powder. Control of the aluminum doping is accomplished by adjusting the ratio of Al and ZnO in the source material. The effects of doping and synthesis conditions on the nanowire optical and electrical properties are investigated through a number of techniques. The concentration of Al in the crystal is determined by energy dispersive spectroscopy, while atom probe tomography enables us to investigate the distribution of aluminum within the ZnO matrix. Micro-Raman spectroscopy and micro-photoluminescence, including their temperature dependence, are used to probe the vibrational and optical properties of the nanowires as a function of doping. It is observed that a defect related radiative green emission in ZnO is significantly reduced after Al doping. The electrical characteristics of undoped and doped nanowires are compared by leading electrical nano-connections to individual nanowires, which show a more than 1 order of magnitude decrease in the resistivity after doping down to 1 ohm.cm.