Layer Dependence of Complex Refractive Index in CrSBr.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Chromium sulfur bromide (CrSBr) is a novel 2D anti-ferromagnetic material.
• It exhibits promising properties for optoelectronic and spintronic devices.
• Layer-dependent optical properties, especially the complex refractive index, remain under-explored.

Purpose of the Study:

• To systematically investigate the room-temperature complex refractive indices of CrSBr flakes.
• To determine the layer-dependent band gap of few-layer CrSBr.
• To correlate optical properties with material thickness.

Main Methods:

• Micro-reflectance spectroscopy was employed to measure optical contrast.
• Fresnel equations were utilized to model optical contrast and extract complex refractive indices.
• Band gaps were determined for monolayer, bilayer, and trilayer CrSBr.

Main Results:

• The complex refractive indices of CrSBr flakes were successfully extracted.
• Band gaps were determined for monolayer (1.88 eV), bilayer (1.81 eV), and trilayer (1.77 eV) CrSBr.
• A decreasing band gap trend with increasing CrSBr thickness was observed.

Conclusions:

• The study provides crucial optical constants for CrSBr.
• Thickness-dependent band gap variations in CrSBr were quantitatively established.
• Findings offer insights for designing CrSBr-based optoelectronic and spintronic devices.