Spectroscopic Signatures of Interlayer Coupling in Janus MoSSe/MoS2 Heterostructures

TL;DR

This study investigates how the interlayer coupling in Janus MoSSe/MoS2 heterostructures can be tuned via twist angle and interface composition, revealing differences in optical properties and charge transfer mechanisms.

Contribution

It demonstrates the tunability of interlayer interactions in Janus heterostructures through interface engineering and twist angle control, supported by experimental and theoretical analysis.

Findings

S/S interfaces show stronger interlayer coupling than Se/S interfaces.

Interlayer distance differences are explained by density-functional theory calculations.

Charge transfer and PL quenching vary with interface composition, affecting optical properties.

Abstract

The interlayer coupling in van der Waals heterostructures governs a variety of optical and electronic properties. The intrinsic dipole moment of Janus transition metal dichalcogenides (TMDs) offers a simple and versatile approach to tune the interlayer interactions. In this work, we demonstrate how the van der Waals interlayer coupling and charge transfer of Janus MoSSe/MoS2 heterobilayers can be tuned by the twist angle and interface composition. Specifically, the Janus heterostructures with a sulfur/sulfur (S/S) interface display stronger interlayer coupling than the heterostructures with a selenium/sulfur (Se/S) interface as shown by the low-frequency Raman modes. The differences in interlayer interactions are explained by the interlayer distance computed by density-functional theory (DFT). More intriguingly, the built-in electric field contributed by the charge density redistribution and interlayer coupling also play important roles in the interfacial charge transfer. Namely, the S/S and Se/S interfaces exhibit different levels of PL quenching of MoS2 A exciton, suggesting the enhanced and reduced charge transfer at the S/S and Se/S interface, respectively. Our work demonstrates how the asymmetry of Janus TMDs can be used to tailor the interfacial interactions in van der Waals heterostructures.