Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors

Yan Wang, Jong Chan Kim, Ryan J. Wu, Jenny Martinez, Xiuju Song, Jieun Yang, Fang Zhao, Andre Mkhoyan, Hu Young Jeong, Manish Chhowalla

Research output: Contribution to journalLetter

5 Citations (Scopus)

Abstract

As the dimensions of the semiconducting channels in field-effect transistors decrease, the contact resistance of the metal–semiconductor interface at the source and drain electrodes increases, dominating the performance of devices 1–3 . Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS 2 ) have been demonstrated to be excellent semiconductors for ultrathin field-effect transistors 4,5 . However, unusually high contact resistance has been observed across the interface between the metal and the 2D transition-metal dichalcogenide 3,5–9 . Recent studies have shown that van der Waals contacts formed by transferred graphene 10,11 and metals 12 on few-layered transition-metal dichalcogenides produce good contact properties. However, van der Waals contacts between a three-dimensional metal and a monolayer 2D transition-metal dichalcogenide have yet to be demonstrated. Here we report the realization of ultraclean van der Waals contacts between 10-nanometre-thick indium metal capped with 100-nanometre-thick gold electrodes and monolayer MoS 2 . Using scanning transmission electron microscopy imaging, we show that the indium and gold layers form a solid solution after annealing at 200 degrees Celsius and that the interface between the gold-capped indium and the MoS 2 is atomically sharp with no detectable chemical interaction between the metal and the 2D transition-metal dichalcogenide, suggesting van-der-Waals-type bonding between the gold-capped indium and monolayer MoS 2 . The contact resistance of the indium/gold electrodes is 3,000 ± 300 ohm micrometres for monolayer MoS 2 and 800 ± 200 ohm micrometres for few-layered MoS 2 . These values are among the lowest observed for three-dimensional metal electrodes evaporated onto MoS 2 , enabling high-performance field-effect transistors with a mobility of 167 ± 20 square centimetres per volt per second. We also demonstrate a low contact resistance of 220 ± 50 ohm micrometres on ultrathin niobium disulfide (NbS 2 ) and near-ideal band offsets, indicative of defect-free interfaces, in tungsten disulfide (WS 2 ) and tungsten diselenide (WSe 2 ) contacted with indium alloy. Our work provides a simple method of making ultraclean van der Waals contacts using standard laboratory technology on monolayer 2D semiconductors.

Original languageEnglish
JournalNature
DOIs
Publication statusPublished - Jan 1 2019

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indium
contact resistance
transition metals
gold
metals
micrometers
field effect transistors
electrodes
disulfides
tungsten
molybdenum disulfides
trucks
niobium
graphene
solid solutions
transmission electron microscopy
scanning electron microscopy
annealing
defects
interactions

ASJC Scopus subject areas

  • General

Cite this

Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors. / Wang, Yan; Kim, Jong Chan; Wu, Ryan J.; Martinez, Jenny; Song, Xiuju; Yang, Jieun; Zhao, Fang; Mkhoyan, Andre; Jeong, Hu Young; Chhowalla, Manish.

In: Nature, 01.01.2019.

Research output: Contribution to journalLetter

Wang, Yan ; Kim, Jong Chan ; Wu, Ryan J. ; Martinez, Jenny ; Song, Xiuju ; Yang, Jieun ; Zhao, Fang ; Mkhoyan, Andre ; Jeong, Hu Young ; Chhowalla, Manish. / Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors. In: Nature. 2019.
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abstract = "As the dimensions of the semiconducting channels in field-effect transistors decrease, the contact resistance of the metal–semiconductor interface at the source and drain electrodes increases, dominating the performance of devices 1–3 . Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS 2 ) have been demonstrated to be excellent semiconductors for ultrathin field-effect transistors 4,5 . However, unusually high contact resistance has been observed across the interface between the metal and the 2D transition-metal dichalcogenide 3,5–9 . Recent studies have shown that van der Waals contacts formed by transferred graphene 10,11 and metals 12 on few-layered transition-metal dichalcogenides produce good contact properties. However, van der Waals contacts between a three-dimensional metal and a monolayer 2D transition-metal dichalcogenide have yet to be demonstrated. Here we report the realization of ultraclean van der Waals contacts between 10-nanometre-thick indium metal capped with 100-nanometre-thick gold electrodes and monolayer MoS 2 . Using scanning transmission electron microscopy imaging, we show that the indium and gold layers form a solid solution after annealing at 200 degrees Celsius and that the interface between the gold-capped indium and the MoS 2 is atomically sharp with no detectable chemical interaction between the metal and the 2D transition-metal dichalcogenide, suggesting van-der-Waals-type bonding between the gold-capped indium and monolayer MoS 2 . The contact resistance of the indium/gold electrodes is 3,000 ± 300 ohm micrometres for monolayer MoS 2 and 800 ± 200 ohm micrometres for few-layered MoS 2 . These values are among the lowest observed for three-dimensional metal electrodes evaporated onto MoS 2 , enabling high-performance field-effect transistors with a mobility of 167 ± 20 square centimetres per volt per second. We also demonstrate a low contact resistance of 220 ± 50 ohm micrometres on ultrathin niobium disulfide (NbS 2 ) and near-ideal band offsets, indicative of defect-free interfaces, in tungsten disulfide (WS 2 ) and tungsten diselenide (WSe 2 ) contacted with indium alloy. Our work provides a simple method of making ultraclean van der Waals contacts using standard laboratory technology on monolayer 2D semiconductors.",
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AU - Kim, Jong Chan

AU - Wu, Ryan J.

AU - Martinez, Jenny

AU - Song, Xiuju

AU - Yang, Jieun

AU - Zhao, Fang

AU - Mkhoyan, Andre

AU - Jeong, Hu Young

AU - Chhowalla, Manish

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N2 - As the dimensions of the semiconducting channels in field-effect transistors decrease, the contact resistance of the metal–semiconductor interface at the source and drain electrodes increases, dominating the performance of devices 1–3 . Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS 2 ) have been demonstrated to be excellent semiconductors for ultrathin field-effect transistors 4,5 . However, unusually high contact resistance has been observed across the interface between the metal and the 2D transition-metal dichalcogenide 3,5–9 . Recent studies have shown that van der Waals contacts formed by transferred graphene 10,11 and metals 12 on few-layered transition-metal dichalcogenides produce good contact properties. However, van der Waals contacts between a three-dimensional metal and a monolayer 2D transition-metal dichalcogenide have yet to be demonstrated. Here we report the realization of ultraclean van der Waals contacts between 10-nanometre-thick indium metal capped with 100-nanometre-thick gold electrodes and monolayer MoS 2 . Using scanning transmission electron microscopy imaging, we show that the indium and gold layers form a solid solution after annealing at 200 degrees Celsius and that the interface between the gold-capped indium and the MoS 2 is atomically sharp with no detectable chemical interaction between the metal and the 2D transition-metal dichalcogenide, suggesting van-der-Waals-type bonding between the gold-capped indium and monolayer MoS 2 . The contact resistance of the indium/gold electrodes is 3,000 ± 300 ohm micrometres for monolayer MoS 2 and 800 ± 200 ohm micrometres for few-layered MoS 2 . These values are among the lowest observed for three-dimensional metal electrodes evaporated onto MoS 2 , enabling high-performance field-effect transistors with a mobility of 167 ± 20 square centimetres per volt per second. We also demonstrate a low contact resistance of 220 ± 50 ohm micrometres on ultrathin niobium disulfide (NbS 2 ) and near-ideal band offsets, indicative of defect-free interfaces, in tungsten disulfide (WS 2 ) and tungsten diselenide (WSe 2 ) contacted with indium alloy. Our work provides a simple method of making ultraclean van der Waals contacts using standard laboratory technology on monolayer 2D semiconductors.

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