# Thickness determination of MoS2, MoSe2, WS2 and WSe2 on transparent stamps used for deterministic transfer of 2D materials

## TL;DR

This paper introduces an optical microscopy-based method to accurately determine the thickness of common TMDCs on transparent stamps, facilitating easier identification of layer number for 2D material transfer processes.

## Contribution

The study presents a simple, robust optical transmittance technique focusing on the blue channel to determine TMDC thickness on transparent substrates, applicable to MoS2, MoSe2, WS2, and WSe2.

## Key findings

- Blue channel transmittance correlates monotonically with thickness.
- Method is insensitive to doping variations.
- Applicable to multiple TMDC materials.

## Abstract

Here, we propose a method to determine the thickness of the most common transition metal dichalcogenides (TMDCs) placed on the surface of transparent stamps, used for the deterministic placement of two-dimensional materials, by analyzing the red, green and blue channels of transmission-mode optical microscopy images of the samples. In particular, the blue channel transmittance shows a large and monotonic thickness dependence, making it a very convenient probe of the flake thickness. The method proved to be robust given the small flake-to-flake variation and the insensitivity to doping changes of MoS2. We also tested the method for MoSe2, WS2 and WSe2. These results provide a reference guide to identify the number of layers of this family of materials on transparent substrates only using optical microscopy.

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Source: https://tomesphere.com/paper/1907.07365