Band alignment and charge transfer in complex oxide interfaces

TL;DR

This paper introduces a new scheme to predict band alignment and charge transfer in complex oxide interfaces, overcoming limitations of traditional models by using bulk properties and oxygen network continuity.

Contribution

The authors propose a novel scheme for predicting band alignment and charge transfer in oxide interfaces based on oxygen network continuity, supported by DFT simulations and experimental evidence.

Findings

Predicts sign and magnitude of charge transfer using bulk properties.

Supports predictions with density functional theory simulations.

Demonstrates applications in doping and magnetic ordering control.

Abstract

The synthesis of transition metal heterostructures is currently one of the most vivid fields in the design of novel functional materials. In this paper we propose a simple scheme to predict \emph{band alignment }and \emph{charge transfer} in complex oxide interfaces. For semiconductor heterostructures band alignment rules like the well known Anderson or Schottky-Mott rule are based on comparison of the work function or electron affinity of the bulk components. This scheme breaks down for oxides due to the invalidity of a single workfunction approximation as recently shown (Phys. Rev. B 93, 235116; Adv. Funct. Mater. 26, 5471). Here we propose a new scheme which is built on a continuity condition of valence states originating in the compounds' shared network of oxygen. It allows for the prediction of sign and relative amplitude of the intrinsic charge transfer, taking as input only information about the bulk properties of the components. We support our claims by numerical density functional theory simulations as well as (where available) experimental evidence. Specific applications include i) controlled doping of SrTiO$_3$ layers with the use of 4$d$ and 5$d$ transition metal oxides and ii) the control of magnetic ordering in manganites through tuned charge transfer.