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Juo JY, Kern K, Jung SJ. Investigation of Interface Interactions Between Monolayer MoS 2 and Metals: Implications on Strain and Surface Roughness. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:1277-1285. [PMID: 38171366 PMCID: PMC10795178 DOI: 10.1021/acs.langmuir.3c02740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/13/2023] [Accepted: 12/15/2023] [Indexed: 01/05/2024]
Abstract
Achieving a low contact resistance has been an important issue in the design of two-dimensional (2D) semiconductor-metal interfaces. The metal contact resistance is dominated by interfacial interactions. Here, we systematically investigate 2D semiconductor-metal interfaces formed by transferring monolayer MoS2 onto prefabricated metal surfaces, such as Au and Pd, using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and Raman spectroscopy. In contrast to the MoS2/HOPG interface, the interfaces of MoS2/Au and MoS2/Pd feature the formation of weak covalent bonds. The XPS spectra reveal distinct peak positions for S-Au and S-Pd, indicating a higher doping concentration at the S-Au interface. This difference is a key factor in understanding the electronic interactions at the metal-MoS2 interfaces. Additionally, we observe that the metal surface roughness is a critical determinant of the adhesion behavior of transferred monolayer MoS2, resulting in different strains and doping concentrations. The strain on transferred MoS2 increases with an increase in substrate roughness. However, the strain is released when the roughness of metal surface surpasses a certain threshold. The dependence of the contact material and the influence of the substrate roughness on the contact interface provide critical information for improving 2D semiconductor-metal contacts and device performance.
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Affiliation(s)
- Jz-Yuan Juo
- Max-Planck-Institut
Für Festkörperforschung, Heisenbergstraße 1, Stuttgart DE-70569, Germany
| | - Klaus Kern
- Max-Planck-Institut
Für Festkörperforschung, Heisenbergstraße 1, Stuttgart DE-70569, Germany
- École
Poly Technique Fédérale de Lausanne, Institut de Physique, Lausanne CH-1015, Switzerland
| | - Soon Jung Jung
- Max-Planck-Institut
Für Festkörperforschung, Heisenbergstraße 1, Stuttgart DE-70569, Germany
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Ahn W, Jeong HB, Oh J, Hong W, Cha JH, Jeong HY, Choi SY. A Highly Reliable Molybdenum Disulfide-Based Synaptic Memristor Using a Copper Migration-Controlled Structure. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2300223. [PMID: 37093184 DOI: 10.1002/smll.202300223] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 03/13/2023] [Indexed: 05/03/2023]
Abstract
Memristors are drawing attention as neuromorphic hardware components because of their non-volatility and analog programmability. In particular, electrochemical metallization (ECM) memristors are extensively researched because of their linear conductance controllability. Two-dimensional materials as switching medium of ECM memristors give advantages of fast speed, low power consumption, and high switching uniformity. However, the multistate retention in the switching conductance range for the long-term reliable neuromorphic system has not been achieved using two-dimensional materials-based ECM memristors. In this study, the copper migration-controlled ECM memristor showing excellent multistate retention characteristics in the switching conductance range using molybdenum disulfide (MoS2 ) and aluminum oxide (Al2 O3 ) is proposed. The fabricated device exhibits gradual resistive switching with low switching voltage (<0.5 V), uniform switching (σ/µ ∼ 0.07), and a wide switching range (>12). Importantly, excellent reliabilities with robustness to cycling stress and retention over 104 s for more than 5-bit states in the switching conductance range are achieved. Moreover, the contribution of the Al2 O3 layer to the retention characteristic is investigated through filament morphology observation using transmission electron microscopy (TEM) and copper migration component analysis. This study provides a practical approach to developing highly reliable memristors with exceptional switching performance.
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Affiliation(s)
- Wonbae Ahn
- Graphene/2D Materials Research Center, School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Han Beom Jeong
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Jungyeop Oh
- Graphene/2D Materials Research Center, School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Woonggi Hong
- Convergence Semiconductor Research Center, School of Electronics and Electrical Engineering, Dankook University, 152 Jukjeon-ro, Suji-gu, Yongin-si, Gyeonggi-do 16890, Republic of Korea
| | - Jun-Hwe Cha
- Graphene/2D Materials Research Center, School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Hu Young Jeong
- Graduate School of Semiconductor Materials and Devices Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, Republic of Korea
| | - Sung-Yool Choi
- Graphene/2D Materials Research Center, School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
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Wang C, Song Y, Huang H. Evolution Application of Two-Dimensional MoS 2-Based Field-Effect Transistors. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12183233. [PMID: 36145022 PMCID: PMC9504544 DOI: 10.3390/nano12183233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 09/12/2022] [Accepted: 09/15/2022] [Indexed: 06/12/2023]
Abstract
High-performance and low-power field-effect transistors (FETs) are the basis of integrated circuit fields, which undoubtedly require researchers to find better film channel layer materials and improve device structure technology. MoS2 has recently shown a special two-dimensional (2D) structure and superior photoelectric performance, and it has shown new potential for next-generation electronics. However, the natural atomic layer thickness and large specific surface area of MoS2 make the contact interface and dielectric interface have a great influence on the performance of MoS2 FET. Thus, we focus on its main performance improvement strategies, including optimizing the contact behavior, regulating the conductive channel, and rationalizing the dielectric layer. On this basis, we summarize the applications of 2D MoS2 FETs in key and emerging fields, specifically involving logic, RF circuits, optoelectronic devices, biosensors, piezoelectric devices, and synaptic transistors. As a whole, we discuss the state-of-the-art, key merits, and limitations of each of these 2D MoS2-based FET systems, and prospects in the future.
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Affiliation(s)
- Chunlan Wang
- School of Science, Xi’an Polytechnic University, Xi’an 710048, China
| | - Yongle Song
- School of Science, Xi’an Polytechnic University, Xi’an 710048, China
| | - Hao Huang
- Guangxi Key Laboratory of Processing for Nonferrous Metals and Featured Material, School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China
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Zou D, Zhao W, Xie W, Xu Y, Li X, Yang C. Surface functional group modification induced partial Fermi level pinning and ohmic contact at borophene-MoS 2 interfaces. Phys Chem Chem Phys 2020; 22:19202-19212. [PMID: 32812593 DOI: 10.1039/d0cp02663h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Large Schottky barrier at the electric contact interface drastically hinders the performance of two-dimensional (2D) semiconductor devices, because of which it is crucial to develop better methods to achieve the ohmic contact. Recently, a new field effect transistor (FET) device was constructed by the popular 2D channel material MoS2 and an electrode material borophene was detected theoretically, but the large Schottky barrier still existed. Hence, we used surface functional groups modification on the borophene surface to regulate this Schottky barrier, based on ab initio electronic structure calculations and quantum transport simulations. Our study shows that this method makes it possible to obtain tunable metal work functions in a wide range, and the ohmic contact can still be realized. Although van der Waals (vdW) contacts were observed at all the interfaces between the 2D borophene-based metals and the monolayer MoS2, the Fermi level pinning (FLP) effect was still obvious, and existed in our proposed system with the ohmic contact. Moreover, we also discuss the origin of the FLP with varying degrees. It was found that the interface dipole and metal-induced gap states (MIGS) would be responsible for the FLP of vertical and lateral directions, respectively. More precisely, we find that the size of MIGS is dependent on the relative orientation between the functional group and metal-MoS2 interface. This work not only suggests that surface functional group modification is effective in forming ohmic contact with MoS2, but also holds some implication in the fundamental research on metal-semiconductor contacts with the vdW type.
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Affiliation(s)
- Dongqing Zou
- School of Physics and Optoelectronics Engineering, Ludong University, Yantai, 264025, People's Republic of China.
| | - Wenkai Zhao
- School of Physics and Optoelectronics Engineering, Ludong University, Yantai, 264025, People's Republic of China.
| | - Wanfeng Xie
- School of Electronics & Information, Qingdao University, Qingdao, 266071, People's Republic of China
| | - Yuqing Xu
- School of Physics and Optoelectronics Engineering, Ludong University, Yantai, 264025, People's Republic of China.
| | - Xiaoteng Li
- School of Physics and Optoelectronics Engineering, Ludong University, Yantai, 264025, People's Republic of China.
| | - Chuanlu Yang
- School of Physics and Optoelectronics Engineering, Ludong University, Yantai, 264025, People's Republic of China.
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Giannazzo F, Schilirò E, Greco G, Roccaforte F. Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures. NANOMATERIALS 2020; 10:nano10040803. [PMID: 32331313 PMCID: PMC7221570 DOI: 10.3390/nano10040803] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/16/2020] [Accepted: 04/17/2020] [Indexed: 11/16/2022]
Abstract
Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materials or introduced during device fabrication processes. This paper reviews recent applications of conductive atomic force microscopy (C-AFM) to the investigation of nanoscale transport properties in TMDs, discussing the implications of the local phenomena in the overall behavior of TMD-based devices. Nanoscale resolution current spectroscopy and mapping by C-AFM provided information on the Schottky barrier uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at metal/TMD interfaces. Methods for nanoscale tailoring of the Schottky barrier in MoS2 for the realization of ambipolar transistors are also illustrated. Experiments on local conductivity mapping in monolayer MoS2 grown by chemical vapor deposition (CVD) on SiO2 substrates are discussed, providing a direct evidence of the resistance associated to the grain boundaries (GBs) between MoS2 domains. Finally, C-AFM provided an insight into the current transport phenomena in TMD-based heterostructures, including lateral heterojunctions observed within MoxW1-xSe2 alloys, and vertical heterostructures made by van der Waals stacking of different TMDs (e.g., MoS2/WSe2) or by CVD growth of TMDs on bulk semiconductors.
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