Atomically thin mica flakes and their application as ultrathin insulating substrates for graphene

TL;DR

This paper demonstrates the successful exfoliation of atomically thin mica flakes as ultrathin insulating substrates for graphene, providing a new method for high-quality, defect-free 2D material integration.

Contribution

It introduces a mechanical exfoliation technique for atomically thin mica flakes and a dry transfer method for graphene, improving quality over traditional wet procedures.

Findings

Atomically thin mica flakes can be deposited on SiO2/Si wafers.

Optical contrast depends on thickness and illumination, modeled by Fresnel law.

Dry transfer yields cleaner, higher quality graphene flakes.

Abstract

We show that it is possible to deposit, by mechanical exfoliation on SiO2/Si wafers, atomically thin mica flakes down to a single monolayer thickness. The optical contrast of these mica flakes on top of a SiO2/Si substrate, which depends on their thickness, the illumination wavelength and the SiO2 substrate thickness, can be quantitatively accounted for by a Fresnel law based model. The preparation of atomically thin insulating crystalline sheets will enable the fabrication of ultrathin defect-free insulating substrates, dielectric barriers or planar electron tunneling junctions. Additionally, we show that few-layer graphene flakes can be deposited on top of a previously transferred mica flake. Our transfer method relies on viscoelastic stamps, as those used for soft lithography. A Raman spectroscopy study shows that such an all-dry deposition technique yields cleaner and higher quality flakes than conventional wet-transfer procedures based on lithographic resists.