Influence of Metal–MoS₂Interface on MoS₂Transistor Performance: Comparison of Ag and Ti Contacts

Abstract

In this work, we compare the electrical characteristics of MoS2 field-effect transistors (FETs) with Ag source/drain contacts with those with Ti and demonstrate that the metal-MoS2 interface is crucial to the device performance. MoS2 FETs with Ag contacts show more than 60 times higher ON-state current than those with Ti contacts. In order to better understand the mechanism of the better performance with Ag contacts, 5 nm Au/5 nm Ag (contact layer) or 5 nm Au/5 nm Ti film was deposited onto MoS2 monolayers and few layers, and the topography of metal films was characterized using scanning electron microscopy and atomic force microscopy. The surface morphology shows that, while there exist pinholes in Au/Ti film on MoS2, Au/Ag forms a smoother and denser film. Raman spectroscopy was carried out to investigate the metal-MoS2 interface. The Raman spectra from MoS2 covered with Au/Ag or Au/Ti film reveal that Ag or Ti is in direct contact with MoS2. Our findings show that the smoother and denser Au/Ag contacts lead to higher carrier transport efficiency.

First-principles study of van der Waals interactions and lattice mismatch atMoS2/metalinterfaces

“…In Ref. 64 it is found that MoS 2 /Ag gives a better contact than MoS 2 /Ti, due to a much smoother interface in the former case, suggesting to prefer physisorption over chemisorption.…”

Booming Development of Group IV–VI Semiconductors: Fresh Blood of 2D Family

“…and group III–VI nanomaterials (InSe,38, 39, 40, 41, 42 GaSe,43, 44, 45, 46, 47, 48 etc.) have been extensively investigated in many fields including photodetectors,49, 50, 51, 52, 53, 54, 55, 56, 57, 58 gas sensors,59, 60 field effect transistors (FETs),38, 61, 62, 63, 64, 65 and flexible devices 66, 67, 68…”

Making one‐dimensional electrical contacts to molybdenum disulfide‐based heterostructures through plasma etching

“…The first one is the phenomenon of Fermi‐level pinning , meaning that the carrier injection is always constrained, though, to different extent, by the Schottky barrier formed at metal–semiconductor (M–S) interface. Low work function metal such as Sc , Al , and Ag have been proved producing superior transistor performance than conventional high work function metal (like Ni and Au); the second limitation originates from the inherent surface defects found on natural MoS 2 crystal. High density of sulfur rich/deficient sites on a freshly exfoliated MoS 2 crystal render localized p‐ or n‐type conduction and variation of the electronic properties from sample to sample .…”