Electronic signature of the vacancy ordering in NbO (Nb3O3)

TL;DR

This study uses advanced photoelectron spectroscopy to reveal the electronic structure and vacancy ordering in NbO, highlighting the importance of inter-Nb-4d hybridization for vacancy stability.

Contribution

It demonstrates that density-functional calculations with self-interaction corrections accurately describe NbO's spectral features and identifies the vacancy band related to vacancy ordering.

Findings

Identification of the vacancy band in angle-resolved spectra

Confirmation of the role of inter-Nb-4d hybridization in vacancy formation

Correlation between electronic structure and thermal stability of NbO

Abstract

We investigated the electronic structure of the vacancy-ordered 4d-transition metal monoxide NbO (Nb3O3) using angle-integrated soft- and hard-x-ray photoelectron spectroscopy as well as ultra-violet angle-resolved photoelectron spectroscopy. We found that density-functional-based band structure calculations can describe the spectral features accurately provided that self-interaction effects are taken into account. In the angle-resolved spectra we were able to identify the so-called vacancy band that characterizes the ordering of the vacancies. This together with the band structure results indicates the important role of the very large inter-Nb-4d hybridization for the formation of the ordered vacancies and the high thermal stability of the ordered structure of niobium monoxide.