CL spectra from nano-granular and electronic grade bulk ZnO have been measured as a function of electron beam current, I_B, and specimen temperature (80K-300K). A power-law model (I_CL=k.I_B^m) was used to investigate the influence of particle size on the excitation power dependence of each of the observed ZnO CL emission bands. Bulk ZnO displayed a near band edge (NBE) emission peak at 3.28eV with no other CL emission. The intensity of the bulk ZnO NBE exhibited a superlinear dependence on I_B with a power law exponent of m = 2.2 at 300K, while its peak position remains fixed with increasing I_B. Conversely, the NBE in the nano-granular ZnO displayed a strong red shift with increasing I_B at 300K. Its position, however, did not change with I_B at low temperature. Power exponents of m = 0.9 and m = 1.4 were measured for the NBE in the nano-granular ZnO at 300K and 80K, respectively. CL emission from defect-related centres positioned at 1.8eV and 2.3eV was observed at 300K in the ZnO nano-particles but not in the bulk ZnO. The nano-granular ZnO also exhibited an intense featureless emission which steadily increased up to the IR detection limit at 0.75eV. Its intensity displayed a supralinear dependence on I_B with m > 9. This emission was completely quenched by a slight decrease in specimen temperature, and was not observed in the bulk ZnO under all excitation conditions. The IR emission is attributed to black-body radiation where the low thermal conductance of the ZnO nano-particles leads to significant electron beam heating. The observed red shift of the NBE peak position in nano-granular ZnO is therefore attributed to its dependence on temperature rather than carrier density. Variation in the NBE power law exponents between bulk and nano-granular ZnO is explained by the higher defect density of the ZnO nano-particles as well as their large surface-to-volume ratio.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/736 must be provided.

1. Cathodoluminescence spectroscopy of silica capped Li doped ZnO nanoparticles
2. Cathodoluminescence spectroscopy of Lithium in-diffusion in ZnO
3. The affect of reactant purity and specimen post-processing on the cathodoluminescence of ZnO nano-powders
4. Nanoscale Characterisation of Exciton and Carrier Diffusion in Wide Band Gap Semiconductors using Low Voltage Cathodoluminescence Microscopy and Spectroscopy
5. Quantized Electron Accumulation, Inversion Layers and Fermi Level-Stabilization in Indium Nitride
6. Cathodoluminescence centres in ZnO
7. Influence of n-type doping on light emission properties of GaN layers and GaN-based quantum well structures
8. In-depth and in-plane profiling of InGaN-based laser diodes and heterostructures
9. Cathodoluminescence study of n-type doped GaN epilayers and GaN/InGaN quantum well structures
10. Compensation mechanisms in magnesium doped GaN