Translating XPS Measurement Procedure for Band Alignment into Reliable Ab-initio Calculation Method

TL;DR

This paper introduces a new ab-initio calculation method for band alignment that aligns with XPS measurements by considering surface polarity and lattice deformation, resolving previous inconsistencies.

Contribution

A reliable ab-initio method for band alignment based on XPS procedure, accounting for surface and lattice effects, and distinguishing coupled and intrinsic alignments.

Findings

Method shows good agreement with experimental data for TiO2.

Can produce both coupled and intrinsic band alignments.

Explains discrepancies between XPS and electrochemical measurements.

Abstract

Band alignment between solids is a crucial issue in condensed matter physics and electronic devices. Although the XPS method has been used as a routine method for determination of the band alignment, the theoretical calculations by copying the XPS band alignment procedure usually fail to match the measured results. In this work, a reliable ab-initio calculation method for band alignment is proposed on the basis of the XPS procedure and in consideration of surface polarity and lattice deformation. Application of our method to anatase and rutile TiO2 shows well agreement between calculation and experiment. Furthermore, our method can produce two types of band alignment: the coupled and the intrinsic, depending on whether the solid/solid interface effect is involved or not. The coupled and intrinsic band alignments correspond to alignments measured by XPS and electrochemical impedance analysis, respectively, explaining why band alignments reported by these two experiments are rather inconsistent.