Direct nanoscale mapping of band alignment in single-layer semiconducting lateral heterojunctions

TL;DR

This study uses nanoscale angle-resolved photoemission spectroscopy to directly map and understand the band alignment and electronic structure at single-layer TMDC heterojunctions, revealing mechanisms for band engineering.

Contribution

It introduces nanoARPES combined with photoluminescence to analyze band evolution at TMDC heterostructure interfaces with nanometer precision.

Findings

Type-II band alignment governed by composition and interstitials

Correlation of valence band and exciton features across interfaces

Agreement with density functional theory calculations

Abstract

Atomic-scale control over band alignment in single-layer lateral heterostructures (LHSs) of dissimilar transition metal dichalcogenides (TMDCs) is critical for nextgeneration electronic, optoelectronic, and quantum technologies. However, direct experimental access to interfacial electronic states with nanometer precision remains a significant challenge. Here, we employ angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES) to directly map the epitaxial alignment and valence band evolution across MoSe2-WSe2 LHSs. By combining nanoARPES with spatially resolved photoluminescence, we correlate the evolution of the valence band maximum and exciton features across both atomically sharp and compositionally graded diffusive interfaces. We identified type-II band alignments governed by both material composition and interstitial-induced modifications of band offsets, in close agreement with density functional theory calculations. These results reveal fundamental mechanisms of electronic structure modulation at 1D TMDC heterointerfaces and provide a robust platform for tailored band engineering in van der Waals materials.