Scalable fabrication of edge contacts to 2D materials

TL;DR

This paper introduces a scalable, reliable fabrication method for creating electrical edge contacts to 2D materials like graphene and MoS2, enabling high-performance transistors and precise electrical measurements.

Contribution

The authors develop a tri-layer resist fabrication process that allows reproducible edge contact formation to 2D materials using thermal evaporation or sputtering.

Findings

Contact resistances follow the Landauer quantum limit in epigraphene.

MoS2 transistors achieve ON/OFF ratios > 10^6 at room temperature.

The method is compatible with various metallization techniques.

Abstract

We present a fabrication method for reliably and reproducibly forming electrical contacts to 2D materials, based on the tri-layer resist system. We demonstrate the applicability of this method for epitaxial graphene on silicon carbide (epigraphene) and the transition metal dichalcogenides (TMDCs) molybdenum disulfide ($MoS_2$). For epigraphene, the specific contact resistances are of the order of $\rho_c$ ~ $50$ $\Omega\mu m$, and follow the Landauer quantum limit, $\rho_c \propto n^{-1/2}$, with $n$ being the carrier density of graphene. For $MoS_2$ flakes, our edge contacts enable field effect transistors (FET) with ON/OFF ratio of $> 10^6$ at room temperature ( $> 10^9$ at cryogenic temperatures). The fabrication route here demonstrated allows for contact metallization using thermal evaporation and also by sputtering, giving an additional flexibility when designing electrical interfaces, which is key in practical devices and when exploring the electrical properties of emerging materials.