Thickness-dependent electron mobility of single and few-layer MoS2 thin-film transistors

Ji Heon Kim,Hyunjea Lee,Tae Ho Kim,Woong Choi,Young Ran Park,Cheol Jin Lee

doi:10.1063/1.4953809

Abstract

We investigated the dependence of electron mobility on the thickness of MoS2 nanosheets by fabricating bottom-gate single and few-layer MoS2 thin-film transistors with SiO2 gate dielectrics and Au electrodes. All the fabricated MoS2 transistors showed on/off-current ratio of ∼107 and saturated output characteristics without high-k capping layers. As the MoS2 thickness increased from 1 to 6 layers, the field-effect mobility of the fabricated MoS2 transistors increased from ∼10 to ∼18 cm2V−1s−1. The increased subthreshold swing of the fabricated transistors with MoS2 thickness suggests that the increase of MoS2 mobility with thickness may be related to the dependence of the contact resistance and the dielectric constant of MoS2 layer on its thickness.

Highlights

A great interest has been given to two-dimensional transition metal dichalcogenides because of their interesting electronic and optical properties
We investigated the dependence of electron mobility on the thickness of MoS2 nanosheets by fabricating bottom-gate single and few-layer MoS2 thin-film transistors with SiO2 gate dielectrics and Au electrodes
The increased subthreshold swing of the fabricated transistors with MoS2 thickness suggests that the increase of MoS2 mobility with thickness may be related to the dependence of the contact resistance and the dielectric constant of MoS2 layer on its thickness

Summary

INTRODUCTION

A great interest has been given to two-dimensional transition metal dichalcogenides because of their interesting electronic and optical properties Among these layered semiconductors, molybdenum disulfide (MoS2) has been most extensively investigated as a channel material of a thin-film transistor (TFT).[1,2] Mono- or multilayer MoS2 TFTs exhibit intriguing characteristics including relatively large bandgap (1.2-1.9 eV), high mobility at room temperature (∼100 cm2V−1s−1), and low subthreshold swing (∼70 mV decade−1).[3,4,5,6] To harvest the promising potential of MoS2 TFTs requires comprehensive understanding on various topics such as the synthesis of large-area MoS2, the formation of low-resistance metal-MoS2 junctions, the formation of reliable interface between high-k dielectric and MoS2, and the transport in MoS2 channels. SiO2 gate dielectrics, Au contacts, and no high-k capping layers and investigate the dependence of electron mobility on channel thickness between 1 and 6 layers

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSIONS

CONCLUSION