Oxygen vacancy induced room temperature metal-insulator transition in nickelates films and its potential application in photovoltaics

TL;DR

This study demonstrates reversible control of oxygen vacancies in NdNiO3 films, inducing a room-temperature metal-insulator transition with significant resistance and optical changes, and explores its potential in photovoltaic applications.

Contribution

It reveals a universal method to reversibly induce a metal-insulator transition in nickelates via oxygen vacancies at room temperature, with potential for optoelectronic applications.

Findings

Achieved over six orders of magnitude resistance modulation.

Demonstrated large optical band gap change at room temperature.

Observed induced magnetization of ~50 emu/cm3 due to oxygen vacancies.

Abstract

Oxygen vacancy is intrinsically coupled with magnetic, electronic and transport properties of transition-metal oxide materials and directly determines their multifunctionality. Here, we demonstrate reversible control of oxygen content by post-annealing at temperature lower than 300 degree centigrade and realize the reversible metal-insulator transition in epitaxial NdNiO3 films. Importantly, over six orders of magnitude in the resistance modulation and a large change in optical band gap are demonstrated at room temperature without destroying the parent framework and changing the p-type conductive mechanism. Further study revealed that oxygen vacancies stabilized the insulating phase at room temperature is universal for perovskite nickelates films. Acting as electron donors, oxygen vacancies not only stabilize the insulating phase at room temperature, but also induce a large magnetization of ~50 emu/cm3 due to the formation of strongly correlated Ni2+ t2g6eg2 states. The band gap opening is an order of magnitude larger than that of the thermally driven metal-insulator transition and continuously tunable. Potential application of the newly found insulating phase in photovoltaics has been demonstrated in the nickelates-based heterojunctions. Our discovery opens up new possibilities for strongly correlated perovskite nickelates.