Realization of electron antidoping by modulating the breathing distortion in BaBiO$_3$

TL;DR

This study demonstrates that oxygen vacancies in BaBiO$_3$ can induce electron antidoping, increasing the band gap and suppressing breathing distortions, confirmed through theoretical calculations and spectroscopic experiments.

Contribution

It provides the first combined theoretical and experimental evidence of electron antidoping in a main group oxide via oxygen vacancies, highlighting bond disproportionation effects.

Findings

Band gap increases with oxygen vacancy concentration

Breathing distortions are suppressed by antidoping

Maximal band gap increase of 75% observed

Abstract

The recent proposal of antidoping scheme breaks new ground in conceiving conversely functional materials and devices, yet the few available examples belong to the correlated electron systems. Here we demonstrate both theoretically and experimentally that the main group oxide BaBiO$_3$ is a model system for antidoping using oxygen vacancies. The first principles calculations show that the band gap systematically increases due to the strongly enhanced BiO breathing distortions away from the vacancies and the annihilation of Bi 6s and O 2p hybridized conduction bands near the vacancies. The spectroscopic experiments confirm the band gap increasing systematically with electron doping, with a maximal gap enhancement of 75% when the film's stoichiometry is reduced to BaBiO$_{2.75}$. The Raman and diffraction experiments show the suppression of the overall breathing distortion. The study unambiguously demonstrates the remarkable antidoping effect in a material without strong electron correlations and underscores the importance of bond disproportionation in realizing such an effect.