title: Spatially resolved photoexcited charge-carrier dynamics in phase-engineered monolayer MoS2.
abstract: A fundamental understanding of the intrinsic optoelectronic properties of atomically thin transition-metal dichalcogenides (TMDs) is crucial for its integration into high performance semiconductor devices. Here, we investigate the transport properties of chemical vapor deposition (CVD) grown monolayer molybdenum disulfide (MoS2) under photoexcitation using correlated scanning photocurrent microscopy and photoluminescence imaging. We examined the effect of local phase transformation underneath the metal electrodes on the generation of photocurrent across the channel length with diffraction-limited spatial resolution. While maximum photocurrent generation occurs at the Schottky contacts of semiconducting (2H-phase) MoS2, after the metallic phase transformation (1T-phase), the photocurrent peak is observed toward the center of the device channel, suggesting a strong reduction of native Schottky barriers. Analysis using the bias and position dependence of the photocurrent indicates that the Schottky barrier heights are a few millielectron volts for 1T- and ∼ 200 meV for 2H-contacted devices. We also demonstrate that a reduction of native Schottky barriers in a 1T device enhances the photoresponsivity by more than 1 order of magnitude, a crucial parameter in achieving high-performance optoelectronic devices. The obtained results pave a way for the fundamental understanding of intrinsic optoelectronic properties of atomically thin TMDs where ohmic contacts are necessary for achieving high-efficiency devices with low power consumption.
authors.affiliation: MPA-11 Materials Synthesis and Integrated Devices, Materials Physics and Applications Division and ‡C-PCS Physical Chemistry and Applied Spectroscopy, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Hisato
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Blancon
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kappera
authors.forename: Sidong
authors.initials: S
authors.lastname: Lei
authors.forename: Sina
authors.initials: S
authors.lastname: Najmaei
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Mangum
authors.forename: Gautam
authors.initials: G
authors.lastname: Gupta
authors.forename: Pulickel M
authors.initials: PM
authors.lastname: Ajayan
authors.forename: Jun
authors.initials: J
authors.lastname: Lou
authors.forename: Manish
authors.initials: M
authors.lastname: Chhowalla
authors.forename: Jared J
authors.initials: JJ
authors.lastname: Crochet
authors.forename: Aditya D
authors.initials: AD
authors.lastname: Mohite
keywords: MoS2; contact resistance; monolayer; optoelectronic; phase conversion; scanning photocurrent microscopy; transition-metal dichalcogenide