The role of surface depletion layer effects on the enhancement of the UV emission in ZnO induced by a nanostructured Al surface coating

Saskia Fiedler*, Laurent O. Lee Cheong Lem, Cuong Ton-That, Matthew R. Phillips

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The UV enhancement of Al-coated ZnO single crystals with a wide range of carrier densities is systematically studied using depth-resolved cathodoluminescence and photoluminescence as well as valence band X-ray photoemission spectroscopy (VB-XPS). An up to 17-fold enhanced PL UV emission for Al-coated ZnO with the highest carrier density was measured, which falls to a 12-fold increase for the lowest carrier density. Depth-resolved cathodoluminescence measurements confirm that the enhancement is strongest near the Al-ZnO interface consistent with an increased UV emission due to an exciton-localized surface plasmon coupling mechanism. Correlative cathodoluminescence, photoluminescence and VB-XPS studies reveal that a number of additional effects related to the presence of the Al surface coating also contribute to the UV enhancement factor. These include increased UV enhancement due to the formation of a surface depletion layer induced by the Al coating, which also passivates competitive non-radiative surface recombination channels found in uncoated ZnO. Significantly, it was established that the magnitude of the emission enhancement factor can be raised in a controlled way by reducing the thickness of the depletion layer by increasing the carrier density. The contribution of these effects collectively provides an explanation for the large span of enhancement factors reported in the literature.

Original languageEnglish
Article number144409
JournalApplied Surface Science
Volume504
Number of pages7
ISSN0169-4332
DOIs
Publication statusPublished - 28. Feb 2020

Keywords

  • Aluminum nanoparticles
  • Cathodoluminescence
  • Localized surface plasmons
  • Photoluminescence
  • UV enhancement
  • ZnO

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