Optical determination of layered-materials InSe thickness via RGB contrast method and regression analysis

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Indium selenide (InSe) exhibits thickness-dependent optoelectronic properties crucial for its applications.
• Accurate and rapid thickness identification methods are vital for advancing InSe research.

Purpose of the Study:

• To develop a simple, precise, and quantitative method for determining InSe thickness.
• To correlate optical contrast in RGB channels with InSe thickness (1-35 nm).

Main Methods:

• Utilized a red, green, and blue (RGB) color contrast method combined with regression analysis.
• Employed Fresnel equations and numerical analysis to extract effective refractive indices.
• Validated thickness measurements against atomic force microscopy (AFM) data.
• Incorporated ab initio numerical calculations for complex refractive index spectra.

Main Results:

• Achieved improved accuracy in thickness estimation by refining refractive index considerations.
• Demonstrated a significant improvement in the regression line slope (from 1.59 ± 0.05 to 0.97 ± 0.02) after incorporating wavelength-dependent refractive indices.
• Showcased the utility of ab initio calculations for thickness identification, noting the band structure's minimal impact compared to dispersion.

Conclusions:

• The developed RGB color contrast method offers a reliable approach for precise InSe thickness determination.
• This technique facilitates the study of thickness-dependent properties in layered materials like InSe.
• The findings support the broader application of layered materials by enabling accurate characterization.