title: Influence of metal-MoS2 interface on MoS2 transistor 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.
authors.affiliation: Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20878, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Yuan
authors.forename: Guangjun
authors.initials: G
authors.lastname: Cheng
authors.forename: Lin
authors.initials: L
authors.lastname: You
authors.forename: Haitao
authors.initials: H
authors.lastname: Li
authors.forename: Hao
authors.initials: H
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Kopanski
authors.forename: Yaw S
authors.initials: YS
authors.lastname: Obeng
authors.forename: Angela R
authors.initials: AR
authors.lastname: Hight Walker
authors.forename: David J
authors.initials: DJ
authors.lastname: Gundlach
authors.forename: Curt A
authors.initials: CA
authors.lastname: Richter
authors.forename: Dimitris E
authors.initials: DE
authors.lastname: Ioannou
authors.forename: Qiliang
authors.initials: Q
authors.lastname: Li
keywords: 2D material; Raman spectroscopy; field-effect transistor; metal contact; molybdenum disulfide; transition-metal dichalcogenides