ALD-grown two-dimensional TiSx metal contacts for MoS2 field-effect transistors

Reyhaneh Mahlouji; W.M.M. Kessels; Abhay A. Sagade; Ageeth A. Bol

doi:10.1039/D3NA00387F

ALD-grown two-dimensional TiSx metal contacts for MoS2 field-effect transistors

Reyhaneh Mahlouji (Corresponding author), W.M.M. Kessels, Abhay A. Sagade (Corresponding author), Ageeth A. Bol (Corresponding author)

Research output: Contribution to journal › Article › Academic › peer-review

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Abstract

Metal contacts to MoS2 field-effect transistors (FETs) play a determinant role in the device electrical characteristics and need to be chosen carefully. Because of the Schottky barrier (SB) and the Fermi level pinning (FLP) effects that occur at the contact/MoS2 interface, MoS2 FETs often suffer from high contact resistance (Rc). One way to overcome this issue is to replace the conventional 3D bulk metal contacts with 2D counterparts. Herein, we investigate 2D metallic TiSx (x ∼ 1.8) as top contacts for MoS2 FETs. We employ atomic layer deposition (ALD) for the synthesis of both the MoS2 channels as well as the TiSx contacts and assess the electrical performance of the fabricated devices. Various thicknesses of TiSx are grown on MoS2, and the resultant devices are electrically compared to the ones with the conventional Ti metal contacts. Our findings show that the replacement of 5 nm Ti bulk contacts with only ∼1.2 nm of 2D TiSx is beneficial in improving the overall device metrics. With such ultrathin TiSx contacts, the ON-state current (ION) triples and increases to ∼35 μA μm−1. Rc also reduces by a factor of four and reaches ∼5 MΩ μm. Such performance enhancements were observed despite the SB formed at the TiSx/MoS2 interface is believed to be higher than the SB formed at the Ti/MoS2 interface. These device metric improvements could therefore be mainly associated with an increased level of electrostatic doping in MoS2, as a result of using 2D TiSx for contacting the 2D MoS2. Our findings are also well supported by TCAD device simulations.

Original language	English
Pages (from-to)	4718-4727
Number of pages	10
Journal	Nanoscale Advances
Volume	5
Issue number	18
DOIs	https://doi.org/10.1039/D3NA00387F
Publication status	Published - 21 Sept 2023

Funding

This work is funded by the European research council (ERC) under the grant Agreement No. 648787-ALDof2DTMDs. The authors would like to acknowledge the NanoLab TU/e for the cleanroom facilities as well as the technical support of E. J. Geluk, B. Krishnamoorthy, M. G. Dijstelbloem, P. P. P. Bax, T. de Vries, C. V. Helvoirt, J. J. A. Zeebregts and W. M. Dijkstra. Further, R. M. would like to express her special gratitude to Prof. Dr J. P. Hofmann and Y. Zhang from the laboratory of inorganic materials and catalysis (Department of Chemical Engineering and Chemistry, TU/e) for sulfurizing the MoO samples in their home-built tube furnace, Dr S. B. Basuvalingam and J. J. P. M. Schulpen for scientific and practical discussions, M. A. Taheri (founder of Cosmointel Inc.) for graciously enabling access to T-consciousness fields used in this work, Molecular Materials and Nano-systems (M2N) research group (Department of Applied Physics, TU/e) for supplying resources to conduct the electrical measurements as well as SMART Photonics to provide access to their glove box for sample storage. A. A. S. would also like to thank NWO, The Netherlands, SERB (SERB/2017/1562) India, and SRMIST for the financial support and research funding. x This work is funded by the European research council (ERC) under the grant Agreement No. 648787-ALDof2DTMDs. The authors would like to acknowledge the NanoLab TU/e for the cleanroom facilities as well as the technical support of E. J. Geluk, B. Krishnamoorthy, M. G. Dijstelbloem, P. P. P. Bax, T. de Vries, C. V. Helvoirt, J. J. A. Zeebregts and W. M. Dijkstra. Further, R. M. would like to express her special gratitude to Prof. Dr J. P. Hofmann and Y. Zhang from the laboratory of inorganic materials and catalysis (Department of Chemical Engineering and Chemistry, TU/e) for sulfurizing the MoOx samples in their home-built tube furnace, Dr S. B. Basuvalingam and J. J. P. M. Schulpen for scientific and practical discussions, M. A. Taheri (founder of Cosmointel Inc.) for graciously enabling access to T-consciousness fields used in this work, Molecular Materials and Nano-systems (M2N) research group (Department of Applied Physics, TU/e) for supplying resources to conduct the electrical measurements as well as SMART Photonics to provide access to their glove box for sample storage. A. A. S. would also like to thank NWO, The Netherlands, SERB (SERB/2017/1562) India, and SRMIST for the financial support and research funding.

Funders	Funder number
SRM Institute of Science and Technology
H2020 European Research Council	648787-ALDof2DTMDs
Nederlandse Organisatie voor Wetenschappelijk Onderzoek	SERB/2017/1562

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Cite this

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title = "ALD-grown two-dimensional TiSx metal contacts for MoS2 field-effect transistors",

abstract = "Metal contacts to MoS2 field-effect transistors (FETs) play a determinant role in the device electrical characteristics and need to be chosen carefully. Because of the Schottky barrier (SB) and the Fermi level pinning (FLP) effects that occur at the contact/MoS2 interface, MoS2 FETs often suffer from high contact resistance (Rc). One way to overcome this issue is to replace the conventional 3D bulk metal contacts with 2D counterparts. Herein, we investigate 2D metallic TiSx (x ∼ 1.8) as top contacts for MoS2 FETs. We employ atomic layer deposition (ALD) for the synthesis of both the MoS2 channels as well as the TiSx contacts and assess the electrical performance of the fabricated devices. Various thicknesses of TiSx are grown on MoS2, and the resultant devices are electrically compared to the ones with the conventional Ti metal contacts. Our findings show that the replacement of 5 nm Ti bulk contacts with only ∼1.2 nm of 2D TiSx is beneficial in improving the overall device metrics. With such ultrathin TiSx contacts, the ON-state current (ION) triples and increases to ∼35 μA μm−1. Rc also reduces by a factor of four and reaches ∼5 MΩ μm. Such performance enhancements were observed despite the SB formed at the TiSx/MoS2 interface is believed to be higher than the SB formed at the Ti/MoS2 interface. These device metric improvements could therefore be mainly associated with an increased level of electrostatic doping in MoS2, as a result of using 2D TiSx for contacting the 2D MoS2. Our findings are also well supported by TCAD device simulations.",

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AU - Mahlouji, Reyhaneh

AU - Kessels, W.M.M.

AU - Sagade, Abhay A.

AU - Bol, Ageeth A.

PY - 2023/9/21

Y1 - 2023/9/21

N2 - Metal contacts to MoS2 field-effect transistors (FETs) play a determinant role in the device electrical characteristics and need to be chosen carefully. Because of the Schottky barrier (SB) and the Fermi level pinning (FLP) effects that occur at the contact/MoS2 interface, MoS2 FETs often suffer from high contact resistance (Rc). One way to overcome this issue is to replace the conventional 3D bulk metal contacts with 2D counterparts. Herein, we investigate 2D metallic TiSx (x ∼ 1.8) as top contacts for MoS2 FETs. We employ atomic layer deposition (ALD) for the synthesis of both the MoS2 channels as well as the TiSx contacts and assess the electrical performance of the fabricated devices. Various thicknesses of TiSx are grown on MoS2, and the resultant devices are electrically compared to the ones with the conventional Ti metal contacts. Our findings show that the replacement of 5 nm Ti bulk contacts with only ∼1.2 nm of 2D TiSx is beneficial in improving the overall device metrics. With such ultrathin TiSx contacts, the ON-state current (ION) triples and increases to ∼35 μA μm−1. Rc also reduces by a factor of four and reaches ∼5 MΩ μm. Such performance enhancements were observed despite the SB formed at the TiSx/MoS2 interface is believed to be higher than the SB formed at the Ti/MoS2 interface. These device metric improvements could therefore be mainly associated with an increased level of electrostatic doping in MoS2, as a result of using 2D TiSx for contacting the 2D MoS2. Our findings are also well supported by TCAD device simulations.

AB - Metal contacts to MoS2 field-effect transistors (FETs) play a determinant role in the device electrical characteristics and need to be chosen carefully. Because of the Schottky barrier (SB) and the Fermi level pinning (FLP) effects that occur at the contact/MoS2 interface, MoS2 FETs often suffer from high contact resistance (Rc). One way to overcome this issue is to replace the conventional 3D bulk metal contacts with 2D counterparts. Herein, we investigate 2D metallic TiSx (x ∼ 1.8) as top contacts for MoS2 FETs. We employ atomic layer deposition (ALD) for the synthesis of both the MoS2 channels as well as the TiSx contacts and assess the electrical performance of the fabricated devices. Various thicknesses of TiSx are grown on MoS2, and the resultant devices are electrically compared to the ones with the conventional Ti metal contacts. Our findings show that the replacement of 5 nm Ti bulk contacts with only ∼1.2 nm of 2D TiSx is beneficial in improving the overall device metrics. With such ultrathin TiSx contacts, the ON-state current (ION) triples and increases to ∼35 μA μm−1. Rc also reduces by a factor of four and reaches ∼5 MΩ μm. Such performance enhancements were observed despite the SB formed at the TiSx/MoS2 interface is believed to be higher than the SB formed at the Ti/MoS2 interface. These device metric improvements could therefore be mainly associated with an increased level of electrostatic doping in MoS2, as a result of using 2D TiSx for contacting the 2D MoS2. Our findings are also well supported by TCAD device simulations.

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JO - Nanoscale Advances

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ALD-grown two-dimensional TiSx metal contacts for MoS2 field-effect transistors

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Reports from Eindhoven University of Technology Add New Data to Findings in Nanotechnology (Ald-grown Two-dimensional Tisx Metal Contacts for Mos2 Field-effect Transistors)

Researchers improve the performance of semiconductors using novel 2D metal

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ALD-grown two-dimensional TiSx metal contacts for MoS2 field-effect transistors

Abstract

Funding

Access to Document

Other files and links

Fingerprint

Press/Media

Reports from Eindhoven University of Technology Add New Data to Findings in Nanotechnology (Ald-grown Two-dimensional Tisx Metal Contacts for Mos2 Field-effect Transistors)

Researchers improve the performance of semiconductors using novel 2D metal

Cite this