The Nature of Electronic States in Atomically Thin MoS2 Field-Effect Transistors

TL;DR

This study investigates the electronic states in atomically thin MoS2 FETs, revealing localization phenomena and Coulomb disorder effects through low-temperature transport experiments on monolayer to trilayer films.

Contribution

It provides experimental evidence of localized electronic states and Coulomb disorder effects in atomically thin MoS2 FETs, highlighting the role of substrate charges.

Findings

Electronic states are localized up to room temperature.

2D variable range hopping dominates at high temperatures.

Resonant tunneling causes oscillations below 30 K.

Abstract

We present low temperature electrical transport experiments in five field effect transistor devices consisting of monolayer, bilayer and trilayer MoS2 films, mechanically exfoliated onto Si/SiO2 substrate. Our experiments reveal that the electronic states in all films are localized well up to the room temperature over the experimentally accessible range of gate voltage. This manifests in two dimensional (2D) variable range hopping (VRH) at high temperatures, while below \sim 30 K the conductivity displays oscillatory structures in gate voltage arising from resonant tunneling at the localized sites. From the correlation energy (T0) of VRH and gate voltage dependence of conductivity, we suggest that Coulomb potential from trapped charges in the substrate are the dominant source of disorder in MoS2 field effect devices, which leads to carrier localization as well.