Thickness-Dependent Differential Reflectance Spectra of Monolayer and Few-Layer MoS2, MoSe2, WS2 and WSe2

TL;DR

This study analyzes how differential reflectance spectra of monolayer to six-layer TMDCs vary with thickness, aiding layer identification and understanding of band structure changes in 2D materials.

Contribution

It provides a comprehensive analysis of thickness-dependent optical spectra of TMDCs, enabling layer determination through differential reflectance spectroscopy.

Findings

Differential reflectance spectra change systematically with layer number.

Excitonic features shift with increasing layers, indicating band structure evolution.

Method offers a practical tool for layer identification in 2D TMDCs.

Abstract

The research field of two dimensional (2D) materials strongly relies on optical microscopy characterization tools to identify atomically thin materials and to determine their number of layers. Moreover, optical microscopy-based techniques opened the door to study the optical properties of these nanomaterials. We presented a comprehensive study of the differential reflectance spectra of 2D semiconducting transition metal dichalcogenides (TMDCs), MoS2, MoSe2, WS2, and WSe2, with thickness ranging from one layer up to six layers. We analyzed the thickness-dependent energy of the different excitonic features, indicating the change in the band structure of the different TMDC materials with the number of layers. Our work provided a route to employ differential reflectance spectroscopy for determining the number of layers of MoS2, MoSe2, WS2, and WSe2.