Optical-based thickness measurement of MoO$_3$ nanosheets

TL;DR

This paper introduces two rapid, non-destructive optical methods for measuring the thickness of MoO$_3$ nanosheets, enabling quick and accurate characterization crucial for research and applications involving 2D materials.

Contribution

It presents novel optical techniques combining color analysis and spectral fitting to determine MoO$_3$ flake thickness with high precision.

Findings

Color analysis estimates thickness within ±3 nm.

Spectral fitting achieves accuracy within ±2 nm.

Methods are fast and non-destructive.

Abstract

Considering that two-dimensional (2D) molybdenum trioxide has acquired more attention in the last few years, it is relevant to speed up thickness identification of this material. We provide two fast and non-destructive methods to evaluate the thickness of MoO$_3$ flakes on SiO$_2$/Si substrates. First, by means of quantitative analysis of the apparent color of the flakes in optical microscopy images, one can make a first approximation of the thickness with an uncertainty of $\pm3$ nm. The second method is based on the fit of optical contrast spectra, acquired with micro-reflectance measurements, to a Fresnel law-based model that provides an accurate measurement of the flake thickness with $\pm2$ nm of uncertainty.