Surface Termination and Band Alignment in 2D Heterostructures

TL;DR

This paper presents a new computational method for accurately predicting band alignments in 2D heterostructures using DFT, closely matching experimental results and improving upon traditional approaches.

Contribution

The study introduces a novel approach that adjusts layer choices in DFT calculations to achieve more accurate band alignments in 2D heterostructures.

Findings

The method accurately predicts band alignments matching experimental data.

Alternative layer selection shifts band edges and changes heterojunction type.

The approach is versatile and applicable to various 2D systems.

Abstract

Heterostructures are ubiquitous in many optoelectronic devices and as photocatalysts. One of the key features of a heterojunction is the proper band alignment between the two materials. Estimation of the correct relative band positions with density functional theory (DFT) based electronic structure calculations is often constrained by the accuracy and cost associated with the various DFT functionals. In this study, we introduce a novel computational approach that achieves band alignments closely matching experimental results with the widely used PBE functional. We specifically examine the well-documented MoO3/MoS2 system, a type-II heterojunction. In our setup, the MoS2 layers are kept as it is but for MoO3 the individual layers are chosen differently. These alternative layers have higher surface energy, and hence, the band edges are higher than the conventional layers. This shift in band edges of the alternative MoO3 layers changes the band alignment in MoO3/MoS2 heterojunction from type-III to the experimentally observed type-II character. We also extend this computational strategy to additional systems, demonstrating its versatility and effectiveness.