Complex Optical Conductivity of Two-Dimensional MoS₂: A Striking Layer Dependency

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Complex optical conductivities of 2D materials are crucial for optoelectronic devices.
• Understanding layer-dependent optical properties is key to material application.

Purpose of the Study:

• To systematically investigate the layer-dependent optical conductivity of 1-6 layer 2D MoS2.
• To analyze spectral features and their evolution with increasing layer number.
• To understand the underlying physical mechanisms driving these changes.

Main Methods:

• Spectroscopic ellipsometry was employed to measure optical conductivity.
• Measurements covered an ultrawide spectral range (0.73-6.42 eV).
• Analysis focused on identifying and characterizing spectral peaks (A-E).

Main Results:

• Five distinct feature peaks (A-E) were identified in the optical conductivity spectra.
• Peaks A and B showed minimal dependence on layer number.
• Peaks C and D exhibited redshifts with increasing layer number, indicating band shrinkage and changing exciton effects.

Conclusions:

• Layer-dependent optical conductivity in 2D MoS2 is governed by a interplay between exciton effects and band shrinkage.
• The study provides experimental insights into the optical properties of few-layer MoS2.
• The applicability of theoretical models for evaluating optical conductivity in 2D materials was discussed.