High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact

Dongjea Seo, Dong Yun Lee, Junyoung Kwon, Jea Jung Lee, Takashi Taniguchi, Kenji Watanabe, Gwan-Hyoung Lee, Keun Soo Kim, James Hone, Young Duck Kim, Heon-Jin Choi

Research output: Contribution to journalArticle

Abstract

A finite Schottky barrier and large contact resistance between monolayer MoS2 and electrodes are the major bottlenecks in developing high-performance field-effect transistors (FETs) that hinder the study of intrinsic quantum behaviors such as valley-spin transport at low temperature. A gate-tunable graphene electrode platform has been developed to improve the performance of MoS2 FETs. However, intrinsic misalignment between the work function of pristine graphene and the conduction band of MoS2 results in a large threshold voltage for the FETs, because of which Ohmic contact behaviors are observed only at very high gate voltages and carrier concentrations (∼1013 cm-2). Here, we present high-performance monolayer MoS2 FETs with Ohmic contact at a modest gate voltage by using a chemical-vapor-deposited (CVD) nitrogen-doped graphene with a high intrinsic electron carrier density. The CVD nitrogen-doped graphene and monolayer MoS2 hybrid FETs platform exhibited a large negative shifted threshold voltage of -54.2 V and barrier-free Ohmic contact under zero gate voltage. Transparent contact by nitrogen-doped graphene led to a 214% enhancement in the on-current and a fourfold improvement in the field-effect carrier mobility of monolayer MoS2 FETs compared with those of a pristine graphene electrode platform. The transport measurements, as well as Raman and X-ray photoelectron spectroscopy analyses before and after thermal annealing, reveal that the atomic C-N bonding in the CVD nitrogen-doped graphene is responsible for the dominant effects of electron doping. Large-scale nitrogen-doped graphene electrodes provide a promising device platform for the development of high-performance devices and the study of unique quantum behaviors.

Original languageEnglish
Article number012104
JournalApplied Physics Letters
Volume115
Issue number1
DOIs
Publication statusPublished - 2019 Jul 1

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electric contacts
graphene
field effect transistors
nitrogen
electrodes
platforms
vapors
threshold voltage
electric potential
carrier mobility
contact resistance
misalignment
valleys
conduction bands
electrons
photoelectron spectroscopy
annealing
augmentation
x rays

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

Cite this

Seo, Dongjea ; Lee, Dong Yun ; Kwon, Junyoung ; Lee, Jea Jung ; Taniguchi, Takashi ; Watanabe, Kenji ; Lee, Gwan-Hyoung ; Kim, Keun Soo ; Hone, James ; Kim, Young Duck ; Choi, Heon-Jin. / High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact. In: Applied Physics Letters. 2019 ; Vol. 115, No. 1.
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Seo, D, Lee, DY, Kwon, J, Lee, JJ, Taniguchi, T, Watanabe, K, Lee, G-H, Kim, KS, Hone, J, Kim, YD & Choi, H-J 2019, 'High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact', Applied Physics Letters, vol. 115, no. 1, 012104. https://doi.org/10.1063/1.5094682

High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact. / Seo, Dongjea; Lee, Dong Yun; Kwon, Junyoung; Lee, Jea Jung; Taniguchi, Takashi; Watanabe, Kenji; Lee, Gwan-Hyoung; Kim, Keun Soo; Hone, James; Kim, Young Duck; Choi, Heon-Jin.

In: Applied Physics Letters, Vol. 115, No. 1, 012104, 01.07.2019.

Research output: Contribution to journalArticle

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T1 - High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact

AU - Seo, Dongjea

AU - Lee, Dong Yun

AU - Kwon, Junyoung

AU - Lee, Jea Jung

AU - Taniguchi, Takashi

AU - Watanabe, Kenji

AU - Lee, Gwan-Hyoung

AU - Kim, Keun Soo

AU - Hone, James

AU - Kim, Young Duck

AU - Choi, Heon-Jin

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AB - A finite Schottky barrier and large contact resistance between monolayer MoS2 and electrodes are the major bottlenecks in developing high-performance field-effect transistors (FETs) that hinder the study of intrinsic quantum behaviors such as valley-spin transport at low temperature. A gate-tunable graphene electrode platform has been developed to improve the performance of MoS2 FETs. However, intrinsic misalignment between the work function of pristine graphene and the conduction band of MoS2 results in a large threshold voltage for the FETs, because of which Ohmic contact behaviors are observed only at very high gate voltages and carrier concentrations (∼1013 cm-2). Here, we present high-performance monolayer MoS2 FETs with Ohmic contact at a modest gate voltage by using a chemical-vapor-deposited (CVD) nitrogen-doped graphene with a high intrinsic electron carrier density. The CVD nitrogen-doped graphene and monolayer MoS2 hybrid FETs platform exhibited a large negative shifted threshold voltage of -54.2 V and barrier-free Ohmic contact under zero gate voltage. Transparent contact by nitrogen-doped graphene led to a 214% enhancement in the on-current and a fourfold improvement in the field-effect carrier mobility of monolayer MoS2 FETs compared with those of a pristine graphene electrode platform. The transport measurements, as well as Raman and X-ray photoelectron spectroscopy analyses before and after thermal annealing, reveal that the atomic C-N bonding in the CVD nitrogen-doped graphene is responsible for the dominant effects of electron doping. Large-scale nitrogen-doped graphene electrodes provide a promising device platform for the development of high-performance devices and the study of unique quantum behaviors.

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