Electrically Tunable and Negative Schottky Barriers in Multi-layered Graphene/MoS2 Heterostructured Transistors.

Dongri Qiu,Eun Kyu Kim

doi:10.1038/srep13743

Abstract

We fabricated multi-layered graphene/MoS2 heterostructured devices by positioning mechanically exfoliated bulk graphite and single-crystalline 2H-MoS2 onto Au metal pads on a SiO2/Si substrate via a contamination-free dry transfer technique. We also studied the electrical transport properties of Au/MoS2 junction devices for systematic comparison. A previous work has demonstrated the existence of a positive Schottky barrier height (SBH) in the metal/MoS2 system. However, analysis of the SBH indicates that the contacts of the multi-layered graphene/MoS2 have tunable negative barriers in the range of 300 to −46 meV as a function of gate voltage. It is hypothesized that this tunable SBH is responsible for the modulation of the work function of the thick graphene in these devices. Despite the large number of graphene layers, it is possible to form ohmic contacts, which will provide new opportunities for the engineering of highly efficient contacts in flexible electronics and photonics.

Highlights

Among layered 2-dimensional (2D) materials, molybdenum disulfide (MoS2) is attracting attention as a semiconducting material in the transition metal dichalcogenide family[1,2]
The individual layers, which interact through the van der Waals force, can be readily exfoliated into atomically thin layers[7], and when this method is applied to combine MoS2 with other 2D materials, novel heterostructured devices can be constructed[8]. Examples of these types of structures that have been reported in the literature include vertical tunneling transistors[9,10], hybrid graphene/MoS2 photoresponsive devices[11], and memory devices that incorporate hexagonal boron nitride[12]
We present heterostructured MoS2 field-effect transistors (FETs) that contain approximately 20 layers of graphene to form bottom-up interconnections for source

Summary

Introduction

Among layered 2-dimensional (2D) materials, molybdenum disulfide (MoS2) is attracting attention as a semiconducting material in the transition metal dichalcogenide family[1,2]. The individual layers, which interact through the van der Waals force, can be readily exfoliated into atomically thin layers[7], and when this method is applied to combine MoS2 with other 2D materials, novel heterostructured devices can be constructed[8]. Examples of these types of structures that have been reported in the literature include vertical tunneling transistors[9,10], hybrid graphene/MoS2 photoresponsive devices[11], and memory devices that incorporate hexagonal boron nitride[12]. Ohmic contact has been rarely achieved with relatively thick graphene (or graphite), and few detailed studies on the back-gate tunability of negative barrier heights have been conducted

Methods

Results

Conclusion