Optical thickness determination of hexagonal Boron Nitride flakes

TL;DR

This paper demonstrates a rapid, noninvasive optical method to determine the thickness of hexagonal Boron Nitride flakes, enabling efficient characterization for nanodevice applications.

Contribution

It introduces a simple optical contrast technique for measuring hBN thickness, calibrated against atomic force microscopy, for the first time.

Findings

Optical contrast shows a strong negative peak at short wavelengths.

Contrast varies linearly with 1-80 layers of hBN.

Method allows quick calibration of hBN thickness.

Abstract

Optical reflectivity contrast provides a simple, fast and noninvasive method for characterization of few monolayer samples of two-dimensional materials. Here we apply this technique to measure the thickness of thin flakes of hexagonal Boron Nitride (hBN), which is a material of increasing interest in nanodevice fabrication. The optical contrast shows a strong negative peak at short wavelengths and zero contrast at a thickness dependent wavelength. The optical contrast varies linearly for 1-80 layers of hBN, which permits easy calibration of thickness. We demonstrate the applicability of this quick characterization method by comparing atomic force microscopy and optical contrast results.