Versatile technique for assessing thickness of 2D layered materials by XPS

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Accurate thickness characterization is crucial for understanding and utilizing 2D materials.
• Traditional methods like transmission electron microscopy (TEM) offer limited sample area analysis.
• Developing rapid, large-area, non-destructive characterization techniques is essential for 2D material research and development.

Purpose of the Study:

• To establish and validate X-ray photoelectron spectroscopy (XPS) as a reliable method for determining the thickness of various 2D films.
• To demonstrate the applicability of XPS for 2D materials synthesized via different techniques.
• To highlight the advantages of XPS for large-area, non-destructive thickness assessment.

Main Methods:

• Utilized XPS to measure the intensity ratio of photoemission peaks from 2D films (few-layer graphene, MoS2, a-BN) and their substrates.
• Employed a proposed model incorporating atomic densities and electron attenuation lengths for thickness calculation.
• Validated XPS thickness measurements against cross-sectional transmission electron microscopy (TEM) data.

Main Results:

• XPS accurately measured the thickness of few-layer graphene, MoS2, and amorphous boron nitride films up to approximately 10 nm.
• Thickness calculations were validated through cross-sectional TEM measurements.
• The XPS method provides thickness values averaged over significantly larger areas compared to TEM.

Conclusions:

• X-ray photoelectron spectroscopy (XPS) is a versatile, rapid, and reliable technique for non-destructive thickness characterization of 2D materials over large areas.
• This method facilitates the optimization of growth conditions for producing thin 2D materials effectively.
• XPS analysis allows for subsequent processing or utilization of the same sample without special preparation.