Nanoscale optical imaging of multi-junction MoS2-WS2 lateral heterostructure

TL;DR

This study employs plasmonic near-field tip-enhanced technology to achieve nanoscale optical imaging of a monolayer WS2-MoS2 lateral heterostructure, revealing detailed interface properties crucial for advanced optoelectronic applications.

Contribution

It introduces a high-resolution nano-PL technique to analyze lateral heterostructure interfaces, improving spatial resolution and understanding of optical properties at the nanoscale.

Findings

Enhanced PL spatial resolution at heterojunctions

Pronounced nano-PL signals at interfaces

Insights into band gap properties of 2D heterostructures

Abstract

Two-dimensional monolayer transition metal dichalcogenides (TMDs) have unique optical and electronic properties for applications pertaining to field effect transistors, light emitting diodes, photodetectors, and solar cells. Vertical interfacing of WS2 and MoS2 layered materials in combination with other families of 2D materials were previously reported. On the other hand, lateral heterostructures are particularly promising for the spatial confinement of charged carriers, excitons and phonons within an atomically-thin layer. In the lateral geometry, the quality of the interface in terms of the crystallinity and optical properties is of paramount importance. Using plasmonic near-field tip-enhanced technology, we investigated the detailed nanoscale photoluminescence (nano-PL) characteristics of the hetero-interface in a monolayer WS2-MoS2 lateral heterostructure. Focusing the laser excitation spot at the apex of a plasmonic tip improved the PL spatial resolution by an order of magnitude compared to the conventional far-field PL. Nano-PL spatial line profiles were found to be more pronounced and enhanced at the interfaces. By analyzing the spectral signals of the heterojunctions, we obtained a better understanding of these direct band gap layered semiconductors, which may help to design next-generation smart optoelectronic devices.