Determination of band alignment in the single layer MoS2/WSe2 heterojunction

TL;DR

This paper measures the band offsets in MoS2/WSe2 heterostructures using experimental techniques and confirms the type-II alignment with theoretical calculations, advancing understanding of 2D TMD heterojunctions.

Contribution

It provides the first experimental determination of band offsets in MoS2/WSe2 heterostructures and compares these with first-principles calculations.

Findings

Type-II band alignment with VBO of 0.83 eV and CBO of 0.76 eV.

Experimental results are consistent with DFT calculations showing VBO of 0.94 eV.

Weak interlayer coupling preserves individual layer electronic structures.

Abstract

The emergence of transition metal dichalcogenides (TMDs) as 2D electronic materials has stimulated proposals of novel electronic and photonic devices based on TMD heterostructures. Here we report the determination of band offsets in TMD heterostructures by using microbeam X-ray photoelectron spectroscopy ({\mu}-XPS) and scanning tunneling microscopy/spectroscopy (STM/S). We determine a type-II alignment between $\textrm{MoS}_2$ and $\textrm{WSe}_2$ with a valence band offset (VBO) value of 0.83 eV and a conduction band offset (CBO) of 0.76 eV. First-principles calculations show that in this heterostructure with dissimilar chalcogen atoms, the electronic structures of $\textrm{WSe}_2$ and $\textrm{MoS}_2$ are well retained in their respective layers due to a weak interlayer coupling. Moreover, a VBO of 0.94 eV is obtained from density functional theory (DFT), consistent with the experimental determination.