Molecular nitrogen acceptors in ZnO nanowires induced by nitrogen plasma annealing

TL;DR

This study investigates nitrogen dopants in ZnO nanowires, revealing multiple nitrogen states and linking N2 molecules at Zn sites to shallow acceptor states, confirming theoretical predictions and ruling out NO complexes.

Contribution

It provides experimental evidence for nitrogen states in ZnO nanowires and confirms N2 at Zn sites as a shallow acceptor, advancing understanding of nitrogen doping effects.

Findings

N2 molecules at Zn sites act as shallow acceptors

Multiple nitrogen states identified: NO, NZn, N2

NO complexes are not responsible for shallow acceptor states

Abstract

X-ray absorption near-edge spectroscopy (XANES), photoluminescence, cathodoluminescence and Raman spectroscopy have been used to investigate the chemical states of nitrogen dopants in ZnO nanowires. It is found that nitrogen exists in multiple states: NO, NZn and loosely bound N2 molecule. The work establishes a direct link between a donor-acceptor pair (DAP) emission at 3.232 eV and the concentration of loosely bound N2. These results confirm that N2 at Zn site is a potential candidate for producing a shallow acceptor state in N-doped ZnO as theoretically predicted by Lambrecht and Boonchun [Phys. Rev. B 87, 195207 (2013)]. Additionally, shallow acceptor states arising from NO complexes have been ruled out in this study.