Unexpected Electron Transport Suppression in a Heterostructures Graphene MoS2 Multiple Field-Effect Transistor Architecture

TL;DR

This study investigates electron transport in a graphene-MoS2 heterostructure with multiple FETs, revealing unexpected suppression of transport linked to sulfur vacancy trapping, despite the layered architecture.

Contribution

It provides new insights into electron transport suppression mechanisms in graphene-MoS2 heterostructures, combining experimental characterization with ab-initio modeling.

Findings

Transport suppression observed on the n-side of the transconductance curve.

Sulfur vacancies trap charge carriers, affecting conductance.

Field-effect influences trapping behavior despite device layering.

Abstract

We demonstrate a graphene-MoS2 architecture integrating multiple field-effect transistors and we independently probe and correlate the conducting properties of van der Waals coupled graphene-MoS2 contacts with the ones of the MoS2 channels. Devices are fabricated starting from high-quality single-crystal monolayers grown by chemical vapor deposition and characterized by scanning Raman and photoluminescence spectroscopies. Transconductance curves of MoS2 are compared with the current-voltage characteristics of graphene contact stripes, revealing a significant suppression of transport on the n-side of the transconductance curve. Based on ab-initio modeling, the effect is understood in terms of trapping by sulfur vacancies, which counter-intuitively depends on the field-effect, even though the graphene contact layer is positioned between the backgate and the MoS2 channel.