Noble gas as a functional dopant in ZnO

TL;DR

This study uses first-principles calculations to reveal that noble gases can act as functional dopants in ZnO, influencing vacancy stability and electronic properties despite their inert nature.

Contribution

It demonstrates that noble gases can modify electronic structures and vacancy behavior in ZnO, a novel role contrary to their usual inertness.

Findings

Noble gases destabilize local electron density in ZnO.

Noble gases can delocalize deep in-gap vacancy states.

Noble gases lift electrons to the conduction band.

Abstract

Owing to fully occupied orbitals, noble gases are considered to be chemically inert and to have limited effect on materials properties under standard conditions. However, using first-principles calculations, we demonstrate herein that the insertion of noble gas (i.e., He, Ne, or Ar) in ZnO results in local destabilization of electron density of the material driven by minimization of an unfavorable overlap of atomic orbitals of the noble gas and its surrounding atoms. Specifically, the noble gas defect (interstitial or substitutional) in ZnO pushes the electron density of its surrounding atoms away from the defect. Simultaneously, the host material confines the electron density of the noble gas. As a consequence, the interaction of He, Ne, or Ar with O vacancies of ZnO in different charge states q (ZnO:VOq) affects the vacancy stability and their electronic structures. Remarkably, we find that the noble gas is a functional dopant that can delocalize the deep in-gap VOq states and lift electrons associated with the vacancy to the conduction band.