Fast thickness mapping of large-area exfoliated two-dimensional transition metal dichalcogenides by imaging spectroscopic ellipsometry

¹ Dipartimento di Fisica, Università di Genova, via Dodecaneso 33, 16146 Genova, Italy
² Functional Nanosystems, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy
³ Molecular Foundry, Lawrence Berkeley National Laboratory, 67 Cyclotron Rd, Berkeley, CA 94720, United States
⁴ Laboratory for Transport at Nanoscale Interfaces, Empa – Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
⁵ Sezione di Genova, Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, 16146 Genova, Italy
⁶ Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Torino, Italy
⁷ CNR-SPIN, corso Perrone 24, 16152 Genova, Italy

^* Corresponding author: ermes.peci@edu.unige.it

Published online: 31 October 2024

Abstract

Two-dimensional transition metal dichalcogenides (2D TMDCs) have gained significant attention from the scientific community due to their exceptional properties, making them extremely attractive for optoelectronic and photonic applications. However, many exfoliation or synthesis techniques yield 2D crystals with limited crystalline quality and/or small lateral size. Here, we report a facile Au-assisted exfoliation method, yielding high-quality, large-area monolayers with lateral sizes of hundreds of micrometers. A self-assembled monolayer of (3-aminopropyl)triethoxysilane (APTES) is employed to improve the adhesion between the 2D material and the target substrate, dramatically improving the yield and reliability of the exfoliation process. The monolayer nature of the final sample is then assessed by means of Imaging Spectroscopic Ellipsometry (iSE), which enables a quick and reliable thickness mapping over millimeter-sized areas.