Direct Nanoscale Mapping of Band Alignment in Single-Layer Semiconducting Lateral Heterojunctions.

Sahoo, Chakradhar; Chakraborty, Suman Kumar; Kousika, A; Jones, Alfred J H; Sharma, Manas; Nielsen, Thomas S; Jiang, Zhihao; Kolasseri, Ihsan A et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Atomic-scale control over band alignment in single-layer lateral heterostructures (LHSs) of dissimilar transition metal dichalcogenides (TMDCs) is critical for next-generation 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 the MoSe<sub>2</sub>-WSe<sub>2</sub> 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.