Giant defect emission enhancement from ZnO nanowires through desulfurization process

Junze Zhou,Komla Nomenyo,Alain Lusson,Chun-Chieh Yen,Gilles Lerondel,Adam Schwartzberg,Clotaire Chevalier Cesar,Wei-Yen Woon

doi:10.1038/s41598-020-61189-7

Abstract

Zinc oxide (ZnO) is a stable, direct bandgap semiconductor emitting in the UV with a multitude of technical applications. It is well known that ZnO emission can be shifted into the green for visible light applications through the introduction of defects. However, generating consistent and efficient green emission through this process is challenging, particularly given that the chemical or atomic origin of the green emission in ZnO is still under debate. In this work we present a new method, for which we coin term desulfurization, for creating green emitting ZnO with significantly enhanced quantum efficiency. Solution grown ZnO nanowires are partially converted to ZnS, then desulfurized back to ZnO, resulting in a highly controlled concentration of oxygen defects as determined by X-ray photoelectron spectroscopy and electron paramagnetic resonance. Using this controlled placement of oxygen vacancies we observe a greater than 40-fold enhancement of integrated emission intensity and explore the nature of this enhancement through low temperature photoluminescence experiments.

Highlights

Zinc oxide (ZnO) is a stable, direct bandgap semiconductor emitting in the UV with a multitude of technical applications
The defect structure investigations of ZnO by PL have been complemented by the aid of electron paramagnetic resonance (EPR) spectroscopy[20,21,22,23,24] and a core-shell model has been introduced for distinguishing the surface and core defects emission
For the as-grown ZnO nanowire thin film the simulated curve in Fig. 2(a) is calculated based on the following parameters: the thickness of ZnO is 450 nm, the roughness amplitude is 25 nm, and the volume fraction of ZnO is 70%. This optimized curve fit well with the measured curve, while the thickness is known from cross sectional SEM, and we found the volume fraction is fairly comparable to the density of ZnO nanowires

Summary

Introduction

Zinc oxide (ZnO) is a stable, direct bandgap semiconductor emitting in the UV with a multitude of technical applications. We describe a simple route to create a ZnO nanowire thin film via post growth sulfurization/desulfurization with significantly enhanced defect emission. The modified ZnO thin film exhibits significant green emission enhancement as compared with the as grown sample with a strong correlation between oxygen vacancies and green emission.

Results

Conclusion