Towards barrier free contact to MoS2 using graphene electrodes

TL;DR

This paper introduces a graphene-based contact method for MoS2 that achieves barrier-free, transparent electrical contacts, enabling high mobility and observation of metal-insulator transition at cryogenic temperatures.

Contribution

The study demonstrates a novel graphene electrode strategy that creates nearly perfect Ohmic contacts to MoS2, significantly improving device performance and enabling new observations.

Findings

Achieved zero contact barrier with graphene electrodes on MoS2.

Observed metal-insulator transition in two-terminal devices.

Recorded high extrinsic mobility over 1300 cm2/Vs with passivation.

Abstract

The two-dimensional (2D) layered semiconductors such as MoS2 have attracted tremendous interest as a new class of electronic materials. However, there is considerable challenge in making reliable contacts to these atomically thin materials. Here we present a new strategy by using graphene as back electrodes to achieve Ohmic contact to MoS2. With a finite density of states, the Fermi level of graphene can be readily modified by gate potential to ensure a nearly perfect band alignment with MoS2. We demonstrate, for the first time, a transparent contact can be made to MoS2 with essentially zero contact barrier and linear output behaviour at cryogenic temperatures (down to 1.9 K) for both monolayer and multilayer MoS2. Benefiting from the barrier-free transparent contacts, we show that a metal-insulator-transition (MIT) can be observed in a two-terminal MoS2 device, a phenomenon that could be easily masked by Schottky barrier and only seen in four-terminal devices in conventional metal-contacted MoS2 system. With further passivation y born nitride encapsulation, we demonstrate a record high extrinsic (two-terminal) field effect mobility over 1300 cm2/Vs in MoS2.