Tuning the work function in transition metal oxides and their heterostructures

TL;DR

This paper systematically studies how various surface and interface factors influence the work function of transition metal oxides, providing reference data and insights for designing materials with tailored electronic properties.

Contribution

It offers the first comprehensive analysis of work function tunability in perovskite oxides considering surface termination, reconstructions, vacancies, and heterostructures.

Findings

Work function varies with surface termination and reconstruction

Oxygen vacancies significantly affect work function values

Heterostructuring enables tunability of electronic properties

Abstract

The development of novel functional materials in experimental labs combined with computer-based compound simulation brings the vision of materials design on a microscopic scale continuously closer to reality. For many applications interface and surface phenomena rather than bulk properties are key. One of the most fundamental qualities of a material-vacuum interface is the energy required to transfer an electron across this boundary, i.e. the work function. It is a crucial parameter for numerous applications, including organic electronics, field electron emitters, and thermionic energy converters. Being generally very resistant to degradation at high temperatures, transition metal oxides present a promising materials class for such devices. We have performed a systematic study for perovskite oxides that provides reference values and, equally important, reports on materials trends and the tunability of work functions. Our results identify and classify dependencies of the work function on several parameters including specific surface termination, surface reconstructions, oxygen vacancies, and heterostructuring.