Nano-optical imaging of monolayer MoSe2-WSe2 lateral heterostructure

TL;DR

This study employs tip-enhanced photoluminescence imaging to achieve nanoscale resolution in mapping charge carriers and photons in monolayer MoSe2-WSe2 heterostructures, revealing interface heterogeneities crucial for optoelectronic applications.

Contribution

It demonstrates the use of TEPL imaging to enhance nanoscale resolution in 2D heterostructures, enabling detailed analysis of interface properties.

Findings

Distinct crystalline boundaries identified

Heterogeneities across interfaces mapped

Enhanced resolution of PL emission near interfaces

Abstract

Near-field optical microscopy can be used as a viable route to understand the nanoscale material properties below the diffraction limit. On the other hand, atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) are the materials of recent interest to study the spatial confinement of charge carriers, photon, and phonons. Heterostructures based on Mo or W based monolayer TMDs form type-II band alignment, and hence the optically excited carriers can be easily separated for applications pertaining to photonics and electronics. Mapping these spatially confined carriers or photons in a heterostructure with nanoscale resolution as well as their recombination behavior at the interfaces are necessary for the effective use of these materials in future high performance optoelectronics. We performed tip-enhanced photoluminescence (TEPL) imaging to increase the spatial resolution on multi-junction monolayer MoSe2-WSe2 lateral heterostructures grown by chemical vapor deposition (CVD) method. The near-field nano-PL emission map was used to distinguish the presence of distinct crystalline boundaries and the heterogeneities across the interfaces. This method significantly improves the nanoscale resolution of 2D materials, especially for understanding the PL emission properties at the vicinity of hetero-interfaces.