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

Date

2020

Authors

Fiedler, Saskia
Lee Cheong Lem, Olivier
Ton-That, Cuong
Phillips, Matthew

Journal Title

Journal ISSN

Volume Title

Publisher

Elsevier

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.

Description

Keywords

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

Citation

Source

Applied Surface Science

Type

Journal article

Book Title

Entity type

Access Statement

License Rights

DOI

10.1016/j.apsusc.2019.144409

Restricted until

2099-12-31