The affect of reactant purity and specimen post-processing on the cathodoluminescence of ZnO nano-powders
|Katie E. McBean 1, Matthew R. Phillips 1, Dominique Drouin 2|
1. University of Technology (UTS), PO Box 123, Broadway, NSW 2007, Sydney, Australia
ZnO nano-powders were synthesised by mixing equal volumes of 0.05 M zinc chloride in ethanol and 0.20 M sodium hydroxide (either 97+% or semiconductor grade) in ethanol, for six hours at room temperature. The resulting cloudy solutions were centrifuged and the resulting powders rinsed before being dried under vacuum. The synthesised ZnO powders are referred to as: HP ZnO; made with the semiconductor grade NaOH, and ZnO; made with the 97+% NaOH.
Cathodoluminescence (CL) spectra and images were collected at 5 K of these as-prepared specimens, as well as specimens annealed at 700°C for 10 minutes in an atmosphere of 5% H2 / 95% Ar. The HP ZnO displayed a much more intense UV near band edge (NBE) emission compared with ZnO, and lacked the broad green defect related emission observed in the specimen prepared with 97+% NaOH. Annealing in H2 increased the intensity of the NBE emission in both powders although the HP ZnO NBE emission remained by far the most intense, while the intensity of the green defect emission of the ZnO was greatly reduced.
The NBE emission from H2 annealed HP ZnO contained recombination centres at 3.36 eV; attributed to I6/6a Aluminium donor and 3.32 eV; an unidentified acceptor-bound exciton emission with LO phonon replicas at 3.25 eV and 3.18 eV. The H2 annealed ZnO displayed weaker intensity emissions at the same energies in addition to a weak green defect emission at 2.40 eV.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Katie E. McBean
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-20 09:09 Revised: 2009-06-07 00:44