Nanoscale Raman Characterization of a 2D Semiconductor Lateral Heterostructure Interface

TL;DR

This study employs tip-enhanced Raman scattering to analyze the nanoscale composition and heterogeneity of a MoS2/WS2 lateral heterostructure interface, revealing alloying and structural evolution at 50 nm resolution.

Contribution

It demonstrates the use of nanoscale TERS spectroscopy to characterize 2D heterostructure interfaces with high spatial resolution, providing insights into their composition and defect states.

Findings

The interface is alloyed with a size varying from 50 to 600 nm.

Nanoscale imaging reveals the evolution of vibrational spectra across the interface.

TERS spectroscopy can elucidate structure-property relationships in 2D materials.

Abstract

The nature of the interface in lateral heterostructures of 2D monolayer semiconductors including its composition, size, and heterogeneity critically impacts the functionalities it engenders on the 2D system for next-generation optoelectronics. Here, we use tip-enhanced Raman scattering (TERS) to characterize the interface in a single-layer MoS2/WS2 lateral heterostructure with a spatial resolution of 50 nm. Resonant and non-resonant TERS spectroscopies reveal that the interface is alloyed with a size that varies over an order of magnitude-from 50-600 nm-within a single crystallite. Nanoscale imaging of the continuous interfacial evolution of the resonant and non-resonant Raman spectra enables the deconvolution of defect-activation, resonant enhancement, and material composition for several vibrational modes in single-layer MoS2, MoxW1-xS2, and WS2. The results demonstrate the capabilities of nanoscale TERS spectroscopy to elucidate macroscopic structure-property relationships in 2D materials and to characterize lateral interfaces of 2D systems on length scales that are imperative for devices.