1
|
Kong L, Liu H, Wang X, Abbas A, Tang L, Han M, Li W, Lu Z, Lu D, Ma X, Liu Y, Liang Q. Precisely Tailoring WSe 2 Polarity via van der Waals Bismuth-Gold Modulated Contact. NANO LETTERS 2024; 24:10949-10956. [PMID: 39186014 DOI: 10.1021/acs.nanolett.4c02848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/27/2024]
Abstract
Creating high-quality contacts between high-melting-point metals and delicate two-dimensional (2D) semiconductors poses a critical challenge to polarity control due to inevitable chemical disorder and Fermi-level pinning observed in the contact regions. Here, we report a van der Waals (vdW) integration strategy to precisely tailor the WSe2 polarity by meticulously modulating metal contact compositions. Controlling the low-melting-point bismuth (Bi) thickness effectively modulates the Bi/Au dominant contact with WSe2. This facilitates the precise polarity transformation between n-type, ambipolar, and p-type, with exceptional field-effect mobilities of 200 cm2 V-1 s-1 for electrons and 136 cm2 V-1 s-1 for holes. Within this vdW geometry, we further demonstrate the fundamental electrical components such as diodes and complementary inverters with enhanced rectification ratios and voltage gains. Our results showcase an effective and compatible with mass manufacturing method for precise polarity modulation of 2D semiconductors, providing a promising pathway toward large-scale high-performance 2D electronics and integrated circuits.
Collapse
Affiliation(s)
- Lingan Kong
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Hao Liu
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Xiaowei Wang
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Aumber Abbas
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Lei Tang
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Mengjiao Han
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Wenbo Li
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Zheyi Lu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Donglin Lu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Xiuliang Ma
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| | - Yuan Liu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Qijie Liang
- Songshan Lake Materials Laboratory, University Innovation Park, Dongguan 523808, China
| |
Collapse
|
2
|
Cai J, Wu P, Tripathi R, Kong J, Chen Z, Appenzeller J. Ternary Content-Addressable Memory Based on a Single Two-Dimensional Transistor for Memory-Augmented Learning. ACS NANO 2024; 18:23489-23496. [PMID: 39137093 DOI: 10.1021/acsnano.4c07024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2024]
Abstract
Ternary content-addressable memory (TCAM) is promising for data-intensive artificial intelligence applications due to its large-scale parallel in-memory computing capabilities. However, it is still challenging to build a reliable TCAM cell from a single circuit component. Here, we demonstrate a single transistor TCAM based on a floating-gate two-dimensional (2D) ambipolar MoTe2 field-effect transistor with graphene contacts. Our bottom graphene contacts scheme enables gate modulation of the contact Schottky barrier heights, facilitating carrier injection for both electrons and holes. The 2D nature of our channel and contact materials provides device scaling potentials beyond silicon. By integration with a floating-gate stack, a highly reliable nonvolatile memory is achieved. Our TCAM cell exhibits a resistance ratio larger than 1000 and symmetrical complementary states, allowing the implementation of large-scale TCAM arrays. Finally, we show through circuit simulations that in-memory Hamming distance computation is readily achievable based on our TCAM with array sizes up to 128 cells.
Collapse
Affiliation(s)
- Jun Cai
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Peng Wu
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Rahul Tripathi
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jing Kong
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Zhihong Chen
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Joerg Appenzeller
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| |
Collapse
|
3
|
Cloninger JA, Harris R, Haley KL, Sterbentz RM, Taniguchi T, Watanabe K, Island JO. A back-to-back diode model applied to van der Waals Schottky diodes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:455301. [PMID: 39084637 DOI: 10.1088/1361-648x/ad69ef] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Accepted: 07/31/2024] [Indexed: 08/02/2024]
Abstract
The use of metal and semimetal van der Waals contacts for 2D semiconducting devices has led to remarkable device optimizations. In comparison with conventional thin-film metal deposition, a reduction in Fermi level pinning at the contact interface for van der Waals contacts results in, generally, lower contact resistances and higher mobilities. Van der Waals contacts also lead to Schottky barriers that follow the Schottky-Mott rule, allowing barrier estimates on material properties alone. In this study, we present a double Schottky barrier model and apply it to a barrier tunable all van der Waals transistor. In a molybdenum disulfide (MoS2) transistor with graphene and few-layer graphene contacts, we find that the model can be applied to extract Schottky barrier heights that agree with the Schottky-Mott rule from simple two-terminal current-voltage measurements at room temperature. Furthermore, we show tunability of the Schottky barrierin-situusing a regional contact gate. Our results highlight the utility of a basic back-to-back diode model in extracting device characteristics in all van der Waals transistors.
Collapse
Affiliation(s)
- Jeffrey A Cloninger
- Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154, United States of America
| | - Raine Harris
- Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154, United States of America
| | - Kristine L Haley
- Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154, United States of America
| | - Randy M Sterbentz
- Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154, United States of America
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Joshua O Island
- Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154, United States of America
| |
Collapse
|
4
|
Ma L, Wang Y, Liu Y. van der Waals Contact for Two-Dimensional Transition Metal Dichalcogenides. Chem Rev 2024; 124:2583-2616. [PMID: 38427801 DOI: 10.1021/acs.chemrev.3c00697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2024]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as highly promising candidates for next-generation electronics owing to their atomically thin structures and surfaces devoid of dangling bonds. However, establishing high-quality metal contacts with TMDs presents a critical challenge, primarily attributed to their ultrathin bodies and delicate lattices. These distinctive characteristics render them susceptible to physical damage and chemical reactions when conventional metallization approaches involving "high-energy" processes are implemented. To tackle this challenge, the concept of van der Waals (vdW) contacts has recently been proposed as a "low-energy" alternative. Within the vdW geometry, metal contacts can be physically laminated or gently deposited onto the 2D channel of TMDs, ensuring the formation of atomically clean and electronically sharp contact interfaces while preserving the inherent properties of the 2D TMDs. Consequently, a considerable number of vdW contact devices have been extensively investigated, revealing unprecedented transport physics or exceptional device performance that was previously unachievable. This review presents recent advancements in vdW contacts for TMD transistors, discussing the merits, limitations, and prospects associated with each device geometry. By doing so, our purpose is to offer a comprehensive understanding of the current research landscape and provide insights into future directions within this rapidly evolving field.
Collapse
Affiliation(s)
- Likuan Ma
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Yiliu Wang
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Yuan Liu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| |
Collapse
|
5
|
Wang X, Hu Y, Kim SY, Cho K, Wallace RM. Mechanism of Fermi Level Pinning for Metal Contacts on Molybdenum Dichalcogenide. ACS APPLIED MATERIALS & INTERFACES 2024; 16:13258-13266. [PMID: 38422472 DOI: 10.1021/acsami.3c18332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
The high contact resistance of transition metal dichalcogenide (TMD)-based devices is receiving considerable attention due to its limitation on electronic performance. The mechanism of Fermi level (EF) pinning, which causes the high contact resistance, is not thoroughly understood to date. In this study, the metal (Ni and Ag)/Mo-TMD surfaces and interfaces are characterized by X-ray photoelectron spectroscopy, atomic force microscopy, scanning tunneling microscopy and spectroscopy, and density functional theory systematically. Ni and Ag form covalent and van der Waals (vdW) interfaces on Mo-TMDs, respectively. Imperfections are detected on Mo-TMDs, which lead to electronic and spatial variations. Gap states appear after the adsorption of single and two metal atoms on Mo-TMDs. The combination of the interface reaction type (covalent or vdW), the imperfection variability of the TMD materials, and the gap states induced by contact metals with different weights are concluded to be the origins of EF pinning.
Collapse
Affiliation(s)
- Xinglu Wang
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States of America
| | - Yaoqiao Hu
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States of America
| | - Seong Yeoul Kim
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States of America
| | - Kyeongjae Cho
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States of America
| | - Robert M Wallace
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States of America
| |
Collapse
|
6
|
Wong H, Zhang J, Liu J. Contacts at the Nanoscale and for Nanomaterials. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:386. [PMID: 38392759 PMCID: PMC10893407 DOI: 10.3390/nano14040386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 02/06/2024] [Accepted: 02/16/2024] [Indexed: 02/24/2024]
Abstract
Contact scaling is a major challenge in nano complementary metal-oxide-semiconductor (CMOS) technology, as the surface roughness, contact size, film thicknesses, and undoped substrate become more problematic as the technology shrinks to the nanometer range. These factors increase the contact resistance and the nonlinearity of the current-voltage characteristics, which could limit the benefits of the further downsizing of CMOS devices. This review discusses issues related to the contact size reduction of nano CMOS technology and the validity of the Schottky junction model at the nanoscale. The difficulties, such as the limited doping level and choices of metal for band alignment, Fermi-level pinning, and van der Waals gap, in achieving transparent ohmic contacts with emerging two-dimensional materials are also examined. Finally, various methods for improving ohmic contacts' characteristics, such as two-dimensional/metal van der Waals contacts and hybrid contacts, junction doping technology, phase and bandgap modification effects, buffer layers, are highlighted.
Collapse
Affiliation(s)
- Hei Wong
- Department of Electrical Engineering, City University of Hong Kong, Hong Kong, China
| | - Jieqiong Zhang
- Hubei Jiu Feng Shan Laboratory, Wuhan 430074, China; (J.Z.); (J.L.)
| | - Jun Liu
- Hubei Jiu Feng Shan Laboratory, Wuhan 430074, China; (J.Z.); (J.L.)
| |
Collapse
|
7
|
Jeong BJ, Choi KH, Lee B, Cho S, Kang J, Zhang X, Kim Y, Jeon J, Bang HS, Oh HS, Lee JH, Yu HK, Choi JY. Tailoring Contacts for High-Performance 1D Ta 2Pt 3S 8 Field-Effect Transistors. ACS APPLIED MATERIALS & INTERFACES 2024; 16:7593-7603. [PMID: 38315799 DOI: 10.1021/acsami.3c17204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Materials with van der Waals (vdW) unit structures rely on weak interunit vdW forces, facilitating physical separation and advancing nanomaterial research with remarkable electrical properties. Recently, there has been growing interest in one-dimensional (1D) vdW materials, celebrated for their advantageous properties, characterized by reduced dimensionality and the absence of dangling bonds. In this context, we synthesize Ta2Pt3S8, a 1D vdW material, and assess its suitability for field-effect transistor (FET) applications. Spectroscopic analysis and electrical characterization confirmed that the band gap and work function of Ta2Pt3S8 are 1.18 and 4.77 eV, respectively. Leveraging various electrode materials, we fabricated n-type FETs based on Ta2Pt3S8 and identified Cr as the optimal electrode, exhibiting a high mobility of 57 cm2 V-1 s-1. In addition, we analyzed the electron transport mechanism in n-type FETs by investigating Schottky barrier height, Schottky barrier tunneling width, and contact resistance. Furthermore, we successfully fabricated p-type operating Ta2Pt3S8 FETs using a molybdenum trioxide (MoO3) layer as a high work function contact electrode. Finally, we achieved Ta2Pt3S8 nanowire rectifying diodes by creating a p-n junction with asymmetric contact electrodes of Cr and MoO3, demonstrating an ideality factor of 1.06. These findings highlight the electronic properties of Ta2Pt3S8, positioning it as a promising 1D vdW material for future nanoelectronics and functional vdW-based device applications.
Collapse
Affiliation(s)
- Byung Joo Jeong
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kyung Hwan Choi
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Bom Lee
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Sooheon Cho
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jinsu Kang
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Xiaojie Zhang
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Youngho Kim
- Department of Materials Science and Engineering & Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Jiho Jeon
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hyeon-Seok Bang
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - Hyung-Suk Oh
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- KIST-SKKU Carbon-Neutral Research Center, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jae-Hyun Lee
- Department of Materials Science and Engineering & Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Hak Ki Yu
- Department of Materials Science and Engineering & Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Jae-Young Choi
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
- KIST-SKKU Carbon-Neutral Research Center, Sungkyunkwan University, Suwon 16419, Republic of Korea
| |
Collapse
|
8
|
Smyth CM, Cain JM, Boehm A, Ohlhausen JA, Lam MN, Yan X, Liu SE, Zeng TT, Sangwan VK, Hersam MC, Chou SS, Ohta T, Lu TM. Direct Characterization of Buried Interfaces in 2D/3D Heterostructures Enabled by GeO 2 Release Layer. ACS APPLIED MATERIALS & INTERFACES 2024; 16:2847-2860. [PMID: 38170963 DOI: 10.1021/acsami.3c12849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Inconsistent interface control in devices based on two-dimensional materials (2DMs) has limited technological maturation. Astounding variability of 2D/three-dimensional (2D/3D) interface properties has been reported, which has been exacerbated by the lack of direct investigations of buried interfaces commonly found in devices. Herein, we demonstrate a new process that enables the assembly and isolation of device-relevant heterostructures for buried interface characterization. This is achieved by implementing a water-soluble substrate (GeO2), which enables deposition of many materials onto the 2DM and subsequent heterostructure release by dissolving the GeO2 substrate. Here, we utilize this novel approach to compare how the chemistry, doping, and strain in monolayer MoS2 heterostructures fabricated by direct deposition vary from those fabricated by transfer techniques to show how interface properties differ with the heterostructure fabrication method. Direct deposition of thick Ni and Ti films is found to react with the monolayer MoS2. These interface reactions convert 50% of MoS2 into intermetallic species, which greatly exceeds the 10% conversion reported previously and 0% observed in transfer-fabricated heterostructures. We also measure notable differences in MoS2 carrier concentration depending on the heterostructure fabrication method. Direct deposition of thick Au, Ni, and Al2O3 films onto MoS2 increases the hole concentration by >1012 cm-2 compared to heterostructures fabricated by transferring MoS2 onto these materials. Thus, we demonstrate a universal method to fabricate 2D/3D heterostructures and expose buried interfaces for direct characterization.
Collapse
Affiliation(s)
| | - John M Cain
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Alex Boehm
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - James A Ohlhausen
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Mila Nhu Lam
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Xiaodong Yan
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Stephanie E Liu
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Thomas T Zeng
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Vinod K Sangwan
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Stanley S Chou
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Taisuke Ohta
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Tzu-Ming Lu
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
- Center for Integrated Nanotechnologies (CINT), Sandia National Laboratories, Albuquerque, New Mexico 87123, United States
| |
Collapse
|
9
|
Lin WH, Li CS, Wu CI, Rossman GR, Atwater HA, Yeh NC. Dramatically Enhanced Valley-Polarized Emission by Alloying and Electrical Tuning of Monolayer WTe 2 x S 2(1- x ) Alloys at Room Temperature with 1T'-WTe 2 -Contact. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2304890. [PMID: 37974381 PMCID: PMC10787083 DOI: 10.1002/advs.202304890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 09/25/2023] [Indexed: 11/19/2023]
Abstract
Monolayer ternary tellurides based on alloying different transition metal dichalcogenides (TMDs) can result in new two-dimensional (2D) materials ranging from semiconductors to metals and superconductors with tunable optical and electrical properties. Semiconducting WTe2 x S2(1- x ) monolayer possesses two inequivalent valleys in the Brillouin zone, each valley coupling selectively with circularly polarized light (CPL). The degree of valley polarization (DVP) under the excitation of CPL represents the purity of valley polarized photoluminescence (PL), a critical parameter for opto-valleytronic applications. Here, new strategies to efficiently tailor the valley-polarized PL from semiconducting monolayer WTe2 x S2(1- x ) at room temperature (RT) through alloying and back-gating are presented. The DVP at RT is found to increase drastically from < 5% in WS2 to 40% in WTe0.12 S1.88 by Te-alloying to enhance the spin-orbit coupling. Further enhancement and control of the DVP from 40% up to 75% is demonstrated by electrostatically doping the monolayer WTe0.12 S1.88 via metallic 1T'-WTe2 electrodes, where the use of 1T'-WTe2 substantially lowers the Schottky barrier height (SBH) and weakens the Fermi-level pinning of the electrical contacts. The demonstration of drastically enhanced DVP and electrical tunability in the valley-polarized emission from 1T'-WTe2 /WTe0.12 S1.88 heterostructures paves new pathways towards harnessing valley excitons in ultrathin valleytronic devices for RT applications.
Collapse
Affiliation(s)
- Wei-Hsiang Lin
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Chia-Shuo Li
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 106, P. R. China
| | - Chih-I Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 106, P. R. China
| | - George R Rossman
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Harry A Atwater
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Nai-Chang Yeh
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
- Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA, 91125, USA
| |
Collapse
|
10
|
Shanmugam A, Thekke Purayil MA, Dhurjati SA, Thalakulam M. Physical vapor deposition-free scalable high-efficiency electrical contacts to MoS 2. NANOTECHNOLOGY 2023; 35:115201. [PMID: 38055966 DOI: 10.1088/1361-6528/ad12e4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 12/05/2023] [Indexed: 12/08/2023]
Abstract
Fermi-level pinning caused by the kinetic damage during metallization has been recognized as one of the major reasons for the non-ideal behavior of electrical contacts, forbidding reaching the Schottky-Mott limit. In this manuscript, we present a scalable technique wherein Indium, a low-work-function metal, is diffused to contact a few-layered MoS2flake. The technique exploits a smooth outflow of Indium over gold electrodes to make edge contacts to pre-transferred MoS2flakes. We compare the performance of three pairs of contacts made onto the same MoS2flake, the bottom-gold, top-gold, and Indium contacts, and find that the Indium contacts are superior to other contacts. The Indium contacts maintain linearI-Vcharacteristics down to cryogenic temperatures with an extracted Schottky barrier height of ∼2.1 meV. First-principle calculations show the induced in-gap states close to the Fermi level, and the damage-free contact interface could be the reason for the nearly Ohmic behavior of the Indium/MoS2interface.
Collapse
Affiliation(s)
- Anusha Shanmugam
- Indian Institute of Science Education & Research Thiruvananthapuram, Kerala 695551, India
| | | | | | - Madhu Thalakulam
- Indian Institute of Science Education & Research Thiruvananthapuram, Kerala 695551, India
| |
Collapse
|
11
|
Cai J, Sun Z, Wu P, Tripathi R, Lan HY, Kong J, Chen Z, Appenzeller J. High-Performance Complementary Circuits from Two-Dimensional MoTe 2. NANO LETTERS 2023. [PMID: 37976291 DOI: 10.1021/acs.nanolett.3c03184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Two-dimensional (2D) materials hold great promise for future complementary metal-oxide semiconductor (CMOS) technology. However, the lack of effective methods to tune the Schottky barrier poses a challenge in constructing high-performance complementary circuits from the same material. Here, we reveal that the polarity of pristine MoTe2 field-effect transistors (FETs) with minimized air exposure is n-type, irrespective of the metal contact type. The fabricated n-FETs with palladium contact can reach electron currents up to 275 μA/μm at VDS = 2 V. For p-FETs, we introduce a novel nitric oxide doping strategy, allowing a controlled transition of MoTe2 FETs from n-type to unipolar p-type. By doping only in the contact region, we demonstrate hole currents up to 170 μA/μm at VDS= -2 V with preserved Ion/Ioff ratios of 105. Finally, we present a complementary inverter circuit comprising the high-performance n- and p-type FETs based on MoTe2, promoting the application of 2D materials in future electronic systems.
Collapse
Affiliation(s)
- Jun Cai
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Zheng Sun
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Peng Wu
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Rahul Tripathi
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Hao-Yu Lan
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jing Kong
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Zhihong Chen
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Joerg Appenzeller
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| |
Collapse
|
12
|
Nisar S, Basha B, Dastgeer G, Shahzad ZM, Kim H, Rabani I, Rasheed A, Al‐Buriahi MS, Irfan A, Eom J, Kim D. A Novel Biosensing Approach: Improving SnS 2 FET Sensitivity with a Tailored Supporter Molecule and Custom Substrate. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303654. [PMID: 37863822 PMCID: PMC10667857 DOI: 10.1002/advs.202303654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/28/2023] [Indexed: 10/22/2023]
Abstract
The exclusive features of two-dimensional (2D) semiconductors, such as high surface-to-volume ratios, tunable electronic properties, and biocompatibility, provide promising opportunities for developing highly sensitive biosensors. However, developing practical biosensors that can promptly detect low concentrations of target analytes remains a challenging task. Here, a field-effect-transistor comprising n-type transition metal dichalcogenide tin disulfide (SnS2 ) is developed over the hexagonal boron nitride (h-BN) for the detection of streptavidin protein (Strep.) as a target analyte. A self-designed receptor based on the pyrene-lysine conjugated with biotin (PLCB) is utilized to maintain the sensitivity of the SnS2 /h-BN FET because of the π-π stacking. The detection capabilities of SnS2 /h-BN FET are investigated using both Raman spectroscopy and electrical characterizations. The real-time electrical measurements exhibit that the SnS2 /h-BN FET is capable of detecting streptavidin at a remarkably low concentration of 0.5 pm, within 13.2 s. Additionally, the selectivity of the device is investigated by measuring its response against a Cow-like serum egg white protein (BSA), having a comparative molecular weight to that of the streptavidin. These results indicate a high sensitivity and rapid response of SnS2 /h-BN biosensor against the selective proteins, which can have significant implications in several fields including point-of-care diagnostics, drug discovery, and environmental monitoring.
Collapse
Affiliation(s)
- Sobia Nisar
- Department of Electrical EngineeringSejong UniversitySeoul05006Republic of Korea
- Department of Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Republic of Korea
| | - Beriham Basha
- Department of PhysicsCollege of SciencesPrincess Nourah bint Abdulrahman UniversityP. O Box 84428Riyadh11671Saudi Arabia
| | - Ghulam Dastgeer
- Department of Physics and AstronomySejong UniversitySeoul05006Republic of Korea
| | - Zafar M. Shahzad
- SKKU Advanced Institute of Nanotechnology (SAINT) and Department of Chemical and Polymer EngineeringSungkyunkwan UniversitySuwon16419Republic of Korea
- Department of Chemical and Polymer EngineeringUniversity of Engineering & TechnologyFaisalabad CampusLahore38000Pakistan
| | - Honggyun Kim
- Department of Semiconductor Systems EngineeringSejong UniversitySeoul05006Republic of Korea
| | - Iqra Rabani
- Department of Nanotechnology and Advanced Materials EngineeringSejong UniversitySeoul05006Republic of Korea
| | - Aamir Rasheed
- School of Materials Science and EngineeringAnhui UniversityHefeiAnhui230601People's Republic of China
| | | | - Ahmad Irfan
- Department of ChemistryCollege of ScienceKing Khalid UniversityP.O. Box 9004Abha61413Saudi Arabia
| | - Jonghwa Eom
- Department of Physics and AstronomySejong UniversitySeoul05006Republic of Korea
| | - Deok‐kee Kim
- Department of Electrical EngineeringSejong UniversitySeoul05006Republic of Korea
- Department of Semiconductor Systems EngineeringSejong UniversitySeoul05006Republic of Korea
| |
Collapse
|
13
|
Sayers C, Genco A, Trovatello C, Conte SD, Khaustov VO, Cervantes-Villanueva J, Sangalli D, Molina-Sanchez A, Coletti C, Gadermaier C, Cerullo G. Strong Coupling of Coherent Phonons to Excitons in Semiconducting Monolayer MoTe 2. NANO LETTERS 2023; 23:9235-9242. [PMID: 37751559 PMCID: PMC10603802 DOI: 10.1021/acs.nanolett.3c01936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 09/19/2023] [Indexed: 09/28/2023]
Abstract
The coupling of the electron system to lattice vibrations and their time-dependent control and detection provide unique insight into the nonequilibrium physics of semiconductors. Here, we investigate the ultrafast transient response of semiconducting monolayer 2H-MoTe2 encapsulated with hBN using broadband optical pump-probe microscopy. The sub-40 fs pump pulse triggers extremely intense and long-lived coherent oscillations in the spectral region of the A' and B' exciton resonances, up to ∼20% of the maximum transient signal, due to the displacive excitation of the out-of-plane A1g phonon. Ab initio calculations reveal a dramatic rearrangement of the optical absorption of monolayer MoTe2 induced by an out-of-plane stretching and compression of the crystal lattice, consistent with an A1g -type oscillation. Our results highlight the extreme sensitivity of the optical properties of monolayer TMDs to small structural modifications and their manipulation with light.
Collapse
Affiliation(s)
| | - Armando Genco
- Dipartimento
di Fisica, Politecnico di Milano, 20133 Milano, Italy
| | - Chiara Trovatello
- Dipartimento
di Fisica, Politecnico di Milano, 20133 Milano, Italy
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | | | - Vladislav O. Khaustov
- Center
for Nanotechnology Innovation @ NEST, Istituto
Italiano di Tecnologia, 56127 Pisa, Italy
- Scuola
Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Jorge Cervantes-Villanueva
- Institute
of Materials Science (ICMUV), University
of Valencia, Catedrático Beltrán 2, E-46980 Valencia, Spain
| | - Davide Sangalli
- Division
of Ultrafast Processes in Materials (FLASHit), Istituto di Struttura della Materia-CNR (ISM-CNR), Area della Ricerca di Roma 1, 00016 Monterotondo, Scalo, Italy
| | - Alejandro Molina-Sanchez
- Institute
of Materials Science (ICMUV), University
of Valencia, Catedrático Beltrán 2, E-46980 Valencia, Spain
| | - Camilla Coletti
- Center
for Nanotechnology Innovation @ NEST, Istituto
Italiano di Tecnologia, 56127 Pisa, Italy
- Graphene
Labs, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | | | - Giulio Cerullo
- Dipartimento
di Fisica, Politecnico di Milano, 20133 Milano, Italy
| |
Collapse
|
14
|
Wafer-scale and universal van der Waals metal semiconductor contact. Nat Commun 2023; 14:1014. [PMID: 36823424 PMCID: PMC9950472 DOI: 10.1038/s41467-023-36715-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 02/13/2023] [Indexed: 02/25/2023] Open
Abstract
Van der Waals (vdW) metallic contacts have been demonstrated as a promising approach to reduce the contact resistance and minimize the Fermi level pinning at the interface of two-dimensional (2D) semiconductors. However, only a limited number of metals can be mechanically peeled and laminated to fabricate vdW contacts, and the required manual transfer process is not scalable. Here, we report a wafer-scale and universal vdW metal integration strategy readily applicable to a wide range of metals and semiconductors. By utilizing a thermally decomposable polymer as the buffer layer, different metals were directly deposited without damaging the underlying 2D semiconductor channels. The polymer buffer could be dry-removed through thermal annealing. With this technique, various metals could be vdW integrated as the contact of 2D transistors, including Ag, Al, Ti, Cr, Ni, Cu, Co, Au, Pd. Finally, we demonstrate that this vdW integration strategy can be extended to bulk semiconductors with reduced Fermi level pinning effect.
Collapse
|
15
|
Miao J, Zhang X, Tian Y, Zhao Y. Recent Progress in Contact Engineering of Field-Effect Transistor Based on Two-Dimensional Materials. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3845. [PMID: 36364620 PMCID: PMC9658022 DOI: 10.3390/nano12213845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/23/2022] [Accepted: 10/26/2022] [Indexed: 06/16/2023]
Abstract
Two-dimensional (2D) semiconductors have been considered as promising candidates to fabricate ultimately scaled field-effect transistors (FETs), due to the atomically thin thickness and high carrier mobility. However, the performance of FETs based on 2D semiconductors has been limited by extrinsic factors, including high contact resistance, strong interfacial scattering, and unintentional doping. Among these challenges, contact resistance is a dominant issue, and important progress has been made in recent years. In this review, the Schottky-Mott model is introduced to show the ideal Schottky barrier, and we further discuss the contribution of the Fermi-level pinning effect to the high contact resistance in 2D semiconductor devices. In 2D FETs, Fermi-level pinning is attributed to the high-energy metal deposition process, which would damage the lattice of atomically thin 2D semiconductors and induce the pinning of the metal Fermi level. Then, two contact structures and the strategies to fabricate low-contact-resistance short-channel 2D FETs are introduced. Finally, our review provides practical guidelines for the realization of high-performance 2D-semiconductors-based FETs with low contact resistance and discusses the outlook of this field.
Collapse
Affiliation(s)
- Jialei Miao
- Department of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211, China
- School of Micro-Nano Electronics, Hangzhou Global Scientific and Technological Innovation Centre, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China
| | - Xiaowei Zhang
- Department of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211, China
| | - Ye Tian
- Department of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211, China
| | - Yuda Zhao
- School of Micro-Nano Electronics, Hangzhou Global Scientific and Technological Innovation Centre, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China
- Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Jianghan University, Wuhan 430056, China
| |
Collapse
|
16
|
Khan MA, Khan MF, Rehman S, Patil H, Dastgeer G, Ko BM, Eom J. The non-volatile electrostatic doping effect in MoTe 2 field-effect transistors controlled by hexagonal boron nitride and a metal gate. Sci Rep 2022; 12:12085. [PMID: 35840642 PMCID: PMC9287407 DOI: 10.1038/s41598-022-16298-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/07/2022] [Indexed: 11/09/2022] Open
Abstract
The electrical and optical properties of transition metal dichalcogenides (TMDs) can be effectively modulated by tuning their Fermi levels. To develop a carrier-selectable optoelectronic device, we investigated intrinsically p-type MoTe2, which can be changed to n-type by charging a hexagonal boron nitride (h-BN) substrate through the application of a writing voltage using a metal gate under deep ultraviolet light. The n-type part of MoTe2 can be obtained locally using the metal gate pattern, whereas the other parts remain p-type. Furthermore, we can control the transition rate to n-type by applying a different writing voltage (i.e., − 2 to − 10 V), where the n-type characteristics become saturated beyond a certain writing voltage. Thus, MoTe2 was electrostatically doped by a charged h-BN substrate, and it was found that a thicker h-BN substrate was more efficiently photocharged than a thinner one. We also fabricated a p–n diode using a 0.8 nm-thick MoTe2 flake on a 167 nm-thick h-BN substrate, which showed a high rectification ratio of ~ 10−4. Our observations pave the way for expanding the application of TMD-based FETs to diode rectification devices, along with optoelectronic applications.
Collapse
Affiliation(s)
- Muhammad Asghar Khan
- Department of Physics and Astronomy, and Graphene Research Institute-Texas Photonics Center International Research Center (GRI-TPC IRC), Sejong University, Seoul, 05006, Korea
| | | | - Shania Rehman
- Department of Electrical Engineering, Sejong University, Seoul, 05006, Korea.,Department of Convergence Engineering for Intelligent Drone, Sejong University, Seoul, 05006, Korea
| | - Harshada Patil
- Department of Electrical Engineering, Sejong University, Seoul, 05006, Korea.,Department of Convergence Engineering for Intelligent Drone, Sejong University, Seoul, 05006, Korea
| | - Ghulam Dastgeer
- Department of Physics and Astronomy, and Graphene Research Institute-Texas Photonics Center International Research Center (GRI-TPC IRC), Sejong University, Seoul, 05006, Korea
| | - Byung Min Ko
- Department of Physics and Astronomy, and Graphene Research Institute-Texas Photonics Center International Research Center (GRI-TPC IRC), Sejong University, Seoul, 05006, Korea
| | - Jonghwa Eom
- Department of Physics and Astronomy, and Graphene Research Institute-Texas Photonics Center International Research Center (GRI-TPC IRC), Sejong University, Seoul, 05006, Korea.
| |
Collapse
|
17
|
Liu X, Choi MS, Hwang E, Yoo WJ, Sun J. Fermi Level Pinning Dependent 2D Semiconductor Devices: Challenges and Prospects. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108425. [PMID: 34913205 DOI: 10.1002/adma.202108425] [Citation(s) in RCA: 49] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/29/2021] [Indexed: 06/14/2023]
Abstract
Motivated by the high expectation for efficient electrostatic modulation of charge transport at very low voltages, atomically thin 2D materials with a range of bandgaps are investigated extensively for use in future semiconductor devices. However, researchers face formidable challenges in 2D device processing mainly originated from the out-of-plane van der Waals (vdW) structure of ultrathin 2D materials. As major challenges, untunable Schottky barrier height and the corresponding strong Fermi level pinning (FLP) at metal interfaces are observed unexpectedly with 2D vdW materials, giving rise to unmodulated semiconductor polarity, high contact resistance, and lowered device mobility. Here, FLP observed from recently developed 2D semiconductor devices is addressed differently from those observed from conventional semiconductor devices. It is understood that the observed FLP is attributed to inefficient doping into 2D materials, vdW gap present at the metal interface, and hybridized compounds formed under contacting metals. To provide readers with practical guidelines for the design of 2D devices, the impact of FLP occurring in 2D semiconductor devices is further reviewed by exploring various origins responsible for the FLP, effects of FLP on 2D device performances, and methods for improving metallic contact to 2D materials.
Collapse
Affiliation(s)
- Xiaochi Liu
- School of Physics and Electronics, Central South University, Changsha, 410083, China
| | - Min Sup Choi
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Euyheon Hwang
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Won Jong Yoo
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jian Sun
- School of Physics and Electronics, Central South University, Changsha, 410083, China
| |
Collapse
|
18
|
Borchert JW, Weitz RT, Ludwigs S, Klauk H. A Critical Outlook for the Pursuit of Lower Contact Resistance in Organic Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2104075. [PMID: 34623710 DOI: 10.1002/adma.202104075] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 08/20/2021] [Indexed: 06/13/2023]
Abstract
To take full advantage of recent and anticipated improvements in the performance of organic semiconductors employed in organic transistors, the high contact resistance arising at the interfaces between the organic semiconductor and the source and drain contacts must be reduced significantly. To date, only a small portion of the accumulated research on organic thin-film transistors (TFTs) has reported channel-width-normalized contact resistances below 100 Ωcm, well above what is regularly demonstrated in transistors based on inorganic semiconductors. A closer look at these cases and the relevant literature strongly suggests that the most significant factor leading to the lowest contact resistances in organic TFTs so far has been the control of the thin-film morphology of the organic semiconductor. By contrast, approaches aimed at increasing the charge-carrier density and/or reducing the intrinsic Schottky barrier height have so far played a relatively minor role in achieving the lowest contact resistances. Herein, the possible explanations for these observations are explored, including the prevalence of Fermi-level pinning and the difficulties in forming optimized interfaces with organic semiconductors. An overview of the research on these topics is provided, and potential device-engineering solutions are discussed based on recent advancements in the theoretical and experimental work on both organic and inorganic semiconductors.
Collapse
Affiliation(s)
- James W Borchert
- 1st Institute of Physics, Georg August University of Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - R Thomas Weitz
- 1st Institute of Physics, Georg August University of Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Sabine Ludwigs
- IPOC - Functional Polymers, Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Hagen Klauk
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569, Stuttgart, Germany
| |
Collapse
|
19
|
High-specific-power flexible transition metal dichalcogenide solar cells. Nat Commun 2021; 12:7034. [PMID: 34887383 PMCID: PMC8660876 DOI: 10.1038/s41467-021-27195-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/01/2021] [Indexed: 11/17/2022] Open
Abstract
Semiconducting transition metal dichalcogenides (TMDs) are promising for flexible high-specific-power photovoltaics due to their ultrahigh optical absorption coefficients, desirable band gaps and self-passivated surfaces. However, challenges such as Fermi-level pinning at the metal contact–TMD interface and the inapplicability of traditional doping schemes have prevented most TMD solar cells from exceeding 2% power conversion efficiency (PCE). In addition, fabrication on flexible substrates tends to contaminate or damage TMD interfaces, further reducing performance. Here, we address these fundamental issues by employing: (1) transparent graphene contacts to mitigate Fermi-level pinning, (2) MoOx capping for doping, passivation and anti-reflection, and (3) a clean, non-damaging direct transfer method to realize devices on lightweight flexible polyimide substrates. These lead to record PCE of 5.1% and record specific power of 4.4 W g−1 for flexible TMD (WSe2) solar cells, the latter on par with prevailing thin-film solar technologies cadmium telluride, copper indium gallium selenide, amorphous silicon and III-Vs. We further project that TMD solar cells could achieve specific power up to 46 W g−1, creating unprecedented opportunities in a broad range of industries from aerospace to wearable and implantable electronics. Ultrathin transition metal dichalcogenides (TMDs) hold promise for next-generation lightweight photovoltaics. Here, the authors demonstrate the first flexible high power-per-weight TMD solar cells with notably improved power conversion efficiency.
Collapse
|
20
|
Pan Y, Liu X, Yang J, Yoo WJ, Sun J. Controlling Carrier Transport in Vertical MoTe 2/MoS 2 van der Waals Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2021; 13:54294-54300. [PMID: 34739218 DOI: 10.1021/acsami.1c16594] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional (2D) transition-metal dichalcogenide (TMDC)-based semiconducting van der Waals (vdW) heterostructures are considered as potential candidates for next-generation nanoelectronics due to their unique and tunable properties. Controlling the carrier type and band alignment in 2D TMDCs and their vdW heterostructures is critical for realizing heterojunctions with the desired performances and functionalities. In this report, controlling the carrier type and band alignment in a vertical MoTe2/MoS2 heterojunction is presented via thickness engineering and surface charge transfer doping. A highly rectifying p-n diode and a nonrectifying n-n junction are obtained with different MoTe2 thicknesses due to their different doping conditions. A vertical tunnel diode is subsequently achieved with a controlled oxygen plasma treatment, which selectively induces degenerate p-type doping to MoTe2, whereas the intrinsic n-type characteristic of MoS2 is maintained during the treatment. These techniques to realize multifunctional diodes are universal and applicable to emerging nanoelectronics based on 2D materials.
Collapse
Affiliation(s)
- Yuchuan Pan
- School of Physics and Electronics, Central South University, Changsha 410083, China
| | - Xiaochi Liu
- School of Physics and Electronics, Central South University, Changsha 410083, China
| | - Junqiang Yang
- School of Physics and Electronics, Central South University, Changsha 410083, China
| | - Won Jong Yoo
- SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jian Sun
- School of Physics and Electronics, Central South University, Changsha 410083, China
| |
Collapse
|
21
|
Deng Y, Zhao X, Zhu C, Li P, Duan R, Liu G, Liu Z. MoTe 2: Semiconductor or Semimetal? ACS NANO 2021; 15:12465-12474. [PMID: 34379388 DOI: 10.1021/acsnano.1c01816] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Transition metal tellurides (TMTs) have attracted intense interest due to their intriguing physical properties arising from their diverse phase topologies. To date, a wide range of physical properties have been discovered for TMTs, including that they can act as topological insulators, semiconductors, Weyl semimetals, and superconductors. Among the TMT families, MoTe2 is a representative material because of its Janus nature and rich phases. In this Perspective, we first introduce phase structures in monolayer and bulk MoTe2 and then summarize MoTe2 synthesis strategies. We highlight recent advances of Janus MoTe2 in terms of material structures and emerging quantum states. We also provide insight into the opportunities and challenges faced by MoTe2-associated device design and applications.
Collapse
Affiliation(s)
- Ya Deng
- School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
| | - Xiaoxu Zhao
- School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
| | - Chao Zhu
- School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
| | - Peiling Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ruihuan Duan
- School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
| | - Guangtong Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
- School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore
- CINTRA CNRS/NTU/THALES, UMI 3288, 637553 Singapore
| |
Collapse
|
22
|
Wang CH, Chen V, McClellan CJ, Tang A, Vaziri S, Li L, Chen ME, Pop E, Wong HSP. Ultrathin Three-Monolayer Tunneling Memory Selectors. ACS NANO 2021; 15:8484-8491. [PMID: 33944559 DOI: 10.1021/acsnano.1c00002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
High-density memory arrays require selector devices, which enable selection of a specific memory cell within a memory array by suppressing leakage current through unselected cells. Such selector devices must have highly nonlinear current-voltage characteristics and excellent endurance; thus selectors based on a tunneling mechanism present advantages over those based on the physical motion of atoms or ions. Here, we use two-dimensional (2D) materials to build an ultrathin (three-monolayer-thick) tunneling-based memory selector. Using a sandwich of h-BN, MoS2, and h-BN monolayers leads to an "H-shaped" energy barrier in the middle of the heterojunction, which nonlinearly modulates the tunneling current when the external voltage is varied. We experimentally demonstrate that tuning the MoS2 Fermi level can improve the device nonlinearity from 10 to 25. These results provide a fundamental understanding of the tunneling process through atomically thin 2D heterojunctions and lay the foundation for developing high endurance selectors with 2D heterojunctions, potentially enabling high-density non-volatile memory systems.
Collapse
Affiliation(s)
- Ching-Hua Wang
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Victoria Chen
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Connor J McClellan
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Alvin Tang
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Sam Vaziri
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Linsen Li
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Michelle E Chen
- Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Eric Pop
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
- Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Precourt Institute for Energy, Stanford University, Stanford, California 94305, United States
| | - H-S Philip Wong
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| |
Collapse
|
23
|
Sasaki T, Ueno K, Taniguchi T, Watanabe K, Nishimura T, Nagashio K. Material and Device Structure Designs for 2D Memory Devices Based on the Floating Gate Voltage Trajectory. ACS NANO 2021; 15:6658-6668. [PMID: 33765381 DOI: 10.1021/acsnano.0c10005] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Two-dimensional heterostructures have been extensively investigated as next-generation nonvolatile memory (NVM) devices. In the past decade, drastic performance improvements and further advanced functionalities have been demonstrated. However, this progress is not sufficiently supported by the understanding of their operations, obscuring the material and device structure design policy. Here, detailed operation mechanisms are elucidated by exploiting the floating gate (FG) voltage measurements. Systematic comparisons of MoTe2, WSe2, and MoS2 channel devices revealed that the tunneling behavior between the channel and FG is controlled by three kinds of current-limiting paths, i.e., tunneling barrier, 2D/metal contact, and p-n junction in the channel. Furthermore, the control experiment indicated that the access region in the device structure is required to achieve 2D channel/FG tunneling by preventing electrode/FG tunneling. The present understanding suggests that the ambipolar 2D-based FG-type NVM device with the access region is suitable for further realizing potentially high electrical reliability.
Collapse
Affiliation(s)
- Taro Sasaki
- Department of Materials Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Keiji Ueno
- Department of Chemistry, Saitama University, Saitama 338-8570, Japan
| | | | | | - Tomonori Nishimura
- Department of Materials Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Kosuke Nagashio
- Department of Materials Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| |
Collapse
|
24
|
Lv L, Yu J, Hu M, Yin S, Zhuge F, Ma Y, Zhai T. Design and tailoring of two-dimensional Schottky, PN and tunnelling junctions for electronics and optoelectronics. NANOSCALE 2021; 13:6713-6751. [PMID: 33885475 DOI: 10.1039/d1nr00318f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Owing to their superior carrier mobility, strong light-matter interactions, and flexibility at the atomically thin thickness, two-dimensional (2D) materials are attracting wide interest for application in electronic and optoelectronic devices, including rectifying diodes, transistors, memory, photodetectors, and light-emitting diodes. At the heart of these devices, Schottky, PN, and tunneling junctions are playing an essential role in defining device function. Intriguingly, the ultrathin thickness and unique van der Waals (vdW) interlayer coupling in 2D materials has rendered enormous opportunities for the design and tailoring of various 2D junctions, e.g. using Lego-like hetero-stacking, surface decoration, and field-effect modulation methods. Such flexibility has led to marvelous breakthroughs during the exploration of 2D electronics and optoelectronic devices. To advance further, it is imperative to provide an overview of existing strategies for the engineering of various 2D junctions for their integration in the future. Thus, in this review, we provide a comprehensive survey of previous efforts toward 2D Schottky, PN, and tunneling junctions, and the functional devices built from them. Though these junctions exhibit similar configurations, distinct strategies have been developed for their optimal figures of merit based on their working principles and functional purposes.
Collapse
Affiliation(s)
- Liang Lv
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China.
| | | | | | | | | | | | | |
Collapse
|
25
|
Pace S, Martini L, Convertino D, Keum DH, Forti S, Pezzini S, Fabbri F, Mišeikis V, Coletti C. Synthesis of Large-Scale Monolayer 1T'-MoTe 2 and Its Stabilization via Scalable hBN Encapsulation. ACS NANO 2021; 15:4213-4225. [PMID: 33605730 PMCID: PMC8023802 DOI: 10.1021/acsnano.0c05936] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 02/02/2021] [Indexed: 06/02/2023]
Abstract
Out of the different structural phases of molybdenum ditelluride (MoTe2), the distorted octahedral 1T' possesses great interest for fundamental physics and is a promising candidate for the implementation of innovative devices such as topological transistors. Indeed, 1T'-MoTe2 is a semimetal with superconductivity, which has been predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. Large instability of monolayer 1T'-MoTe2 in environmental conditions, however, has made its investigation extremely challenging so far. In this work, we demonstrate homogeneous growth of large single-crystal (up to 500 μm) monolayer 1T'-MoTe2 via chemical vapor deposition (CVD) and its stabilization in air with a scalable encapsulation approach. The encapsulant is obtained by electrochemically delaminating CVD hexagonal boron nitride (hBN) from copper foil, and it is applied on the freshly grown 1T'-MoTe2 via a top-down dry lamination step. The structural and electrical properties of encapsulated 1T'-MoTe2 have been monitored over several months to assess the degree of degradation of the material. We find that when encapsulated with hBN, the lifetime of monolayer 1T'-MoTe2 successfully increases from a few minutes to more than a month. Furthermore, the encapsulated monolayer can be subjected to transfer, device processing, and heating and cooling cycles without degradation of its properties. The potential of this scalable heterostack is confirmed by the observation of signatures of low-temperature phase transition in monolayer 1T'-MoTe2 by both Raman spectroscopy and electrical measurements. The growth and encapsulation methods reported in this work can be employed for further fundamental studies of this enticing material as well as facilitate the technological development of monolayer 1T'-MoTe2.
Collapse
Affiliation(s)
- Simona Pace
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Leonardo Martini
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Domenica Convertino
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Dong Hoon Keum
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Stiven Forti
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Sergio Pezzini
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Filippo Fabbri
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Vaidotas Mišeikis
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Camilla Coletti
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| |
Collapse
|
26
|
Han B, Yang C, Xu X, Li Y, Shi R, Liu K, Wang H, Ye Y, Lu J, Yu D, Gao P. Correlating the electronic structures of metallic/semiconducting MoTe 2 interface to its atomic structures. Natl Sci Rev 2021; 8:nwaa087. [PMID: 34691565 PMCID: PMC8288393 DOI: 10.1093/nsr/nwaa087] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/03/2020] [Accepted: 04/15/2020] [Indexed: 11/13/2022] Open
Abstract
Contact interface properties are important in determining the performances of devices that are based on atomically thin two-dimensional (2D) materials, especially for those with short channels. Understanding the contact interface is therefore important to design better devices. Herein, we use scanning transmission electron microscopy, electron energy loss spectroscopy, and first-principles calculations to reveal the electronic structures within the metallic (1T')-semiconducting (2H) MoTe2 coplanar phase boundary across a wide spectral range and correlate its properties to atomic structures. We find that the 2H-MoTe2 excitonic peaks cross the phase boundary into the 1T' phase within a range of approximately 150 nm. The 1T'-MoTe2 crystal field can penetrate the boundary and extend into the 2H phase by approximately two unit-cells. The plasmonic oscillations exhibit strong angle dependence, that is a red-shift of π+σ (approximately 0.3-1.2 eV) occurs within 4 nm at 1T'/2H-MoTe2 boundaries with large tilt angles, but there is no shift at zero-tilted boundaries. These atomic-scale measurements reveal the structure-property relationships of the 1T'/2H-MoTe2 boundary, providing useful information for phase boundary engineering and device development based on 2D materials.
Collapse
Affiliation(s)
- Bo Han
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Department of Material Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Chen Yang
- State Key Laboratory for Artificial Microstructure & Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Xiaolong Xu
- State Key Laboratory for Artificial Microstructure & Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Yuehui Li
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ruochen Shi
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Kaihui Liu
- State Key Laboratory for Artificial Microstructure & Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Haicheng Wang
- State Key Laboratory of Advanced Materials for Smart Sensing, GRINM Group Co. Ltd., Beijing, and GRIMAT Engineering Institute Co. Ltd., Beijing 101402, China
| | - Yu Ye
- State Key Laboratory for Artificial Microstructure & Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Jing Lu
- State Key Laboratory for Artificial Microstructure & Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Dapeng Yu
- Shenzhen Key Laboratory of Quantum Science and Engineering, Shenzhen 518055, China
| | - Peng Gao
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| |
Collapse
|
27
|
Hynek DJ, Singhania RM, Hart JL, Davis B, Wang M, Strandwitz NC, Cha JJ. Effects of growth substrate on the nucleation of monolayer MoTe 2. CrystEngComm 2021. [DOI: 10.1039/d1ce00275a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Choice of growth substrate is shown to have a significant effect on the conversion of ALD grown molybdenum oxide to monolayer 2H molybdenum ditelluride.
Collapse
Affiliation(s)
- David J. Hynek
- Energy Sciences Institute, Department of Mechanical Engineering and Materials Science, Yale University, West Haven, CT 06516, USA
| | - Raivat M. Singhania
- Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - James L. Hart
- Energy Sciences Institute, Department of Mechanical Engineering and Materials Science, Yale University, West Haven, CT 06516, USA
| | - Benjamin Davis
- Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Mengjing Wang
- Energy Sciences Institute, Department of Mechanical Engineering and Materials Science, Yale University, West Haven, CT 06516, USA
| | - Nicholas C. Strandwitz
- Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Judy J. Cha
- Energy Sciences Institute, Department of Mechanical Engineering and Materials Science, Yale University, West Haven, CT 06516, USA
| |
Collapse
|
28
|
Schauble K, Zakhidov D, Yalon E, Deshmukh S, Grady RW, Cooley KA, McClellan CJ, Vaziri S, Passarello D, Mohney SE, Toney MF, Sood AK, Salleo A, Pop E. Uncovering the Effects of Metal Contacts on Monolayer MoS 2. ACS NANO 2020; 14:14798-14808. [PMID: 32905703 DOI: 10.1021/acsnano.0c03515] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here, we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to 5.2 eV) and monolayer MoS2 grown by chemical vapor deposition. We evaporate thin metal films onto MoS2 and study the interfaces by Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and electrical characterization. We uncover that (1) ultrathin oxidized Al dopes MoS2 n-type (>2 × 1012 cm-2) without degrading its mobility, (2) Ag, Au, and Ni deposition causes varying levels of damage to MoS2 (e.g. broadening Raman E' peak from <3 to >6 cm-1), and (3) Ti, Sc, and Y react with MoS2. Reactive metals must be avoided in contacts to monolayer MoS2, but control studies reveal the reaction is mostly limited to the top layer of multilayer films. Finally, we find that (4) thin metals do not significantly strain MoS2, as confirmed by X-ray diffraction. These are important findings for metal contacts to MoS2 and broadly applicable to many other 2D semiconductors.
Collapse
Affiliation(s)
- Kirstin Schauble
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Dante Zakhidov
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Eilam Yalon
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Sanchit Deshmukh
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Ryan W Grady
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Kayla A Cooley
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Connor J McClellan
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Sam Vaziri
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Donata Passarello
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Suzanne E Mohney
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Michael F Toney
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - A K Sood
- Department of Physics, India Institute of Science, Bangalore 560012, India
| | - Alberto Salleo
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Eric Pop
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Precourt Institute for Energy, Stanford University, Stanford, California 94305, United States
| |
Collapse
|
29
|
Jiang W, Zheng T, Wu B, Jiao H, Wang X, Chen Y, Zhang X, Peng M, Wang H, Lin T, Shen H, Ge J, Hu W, Xu X, Meng X, Chu J, Wang J. A versatile photodetector assisted by photovoltaic and bolometric effects. LIGHT, SCIENCE & APPLICATIONS 2020; 9:160. [PMID: 32963772 PMCID: PMC7484767 DOI: 10.1038/s41377-020-00396-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/31/2020] [Accepted: 08/24/2020] [Indexed: 05/13/2023]
Abstract
The advent of low-dimensional materials with peculiar structure and superb band properties provides a new canonical form for the development of photodetectors. However, the limited exploitation of basic properties makes it difficult for devices to stand out. Here, we demonstrate a hybrid heterostructure with ultrathin vanadium dioxide film and molybdenum ditelluride nanoflake. Vanadium dioxide is a classical semiconductor with a narrow bandgap, a high temperature coefficient of resistance, and phase transformation. Molybdenum ditelluride, a typical two-dimensional material, is often used to construct optoelectronic devices. The heterostructure can realize three different functional modes: (i) the p-n junction exhibits ultrasensitive detection (450 nm-2 μm) with a dark current down to 0.2 pA and a response time of 17 μs, (ii) the Schottky junction works stably under extreme conditions such as a high temperature of 400 K, and (iii) the bolometer shows ultrabroad spectrum detection exceeding 10 μm. The flexible switching between the three modes makes the heterostructure a potential candidate for next-generation photodetectors from visible to longwave infrared radiation (LWIR). This type of photodetector combines versatile detection modes, shedding light on the hybrid application of novel and traditional materials, and is a prototype of advanced optoelectronic devices.
Collapse
Affiliation(s)
- Wei Jiang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Tan Zheng
- Department of Applied Physics, Donghua University, No. 2999, North Renmin Road, Songjiang District, Shanghai, 201620 China
| | - Binmin Wu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Hanxue Jiao
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Xudong Wang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Yan Chen
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Xiaoyu Zhang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Meng Peng
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Hailu Wang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Tie Lin
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Hong Shen
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Jun Ge
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Weida Hu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Xiaofeng Xu
- Department of Applied Physics, Donghua University, No. 2999, North Renmin Road, Songjiang District, Shanghai, 201620 China
| | - Xiangjian Meng
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Junhao Chu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| | - Jianlu Wang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083 China
| |
Collapse
|
30
|
Ogorzałek Z, Seredyński B, Kret S, Kwiatkowski A, Korona KP, Grzeszczyk M, Mierzejewski J, Wasik D, Pacuski W, Sadowski J, Gryglas-Borysiewicz M. Charge transport in MBE-grown 2H-MoTe 2 bilayers with enhanced stability provided by an AlO x capping layer. NANOSCALE 2020; 12:16535-16542. [PMID: 32790820 DOI: 10.1039/d0nr03148h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Thin layers of transition metal dichalcogenides have been intensively studied over the last few years due to their novel physical phenomena and potential applications. One of the biggest problems in laboratory handling and moving on to application-ready devices lies in the high sensitivity of their physicochemical properties to ambient conditions. We demonstrate that novel, in situ capping with an ultra-thin, aluminum film efficiently protects thin MoTe2 layers stabilizing their electronic transport properties after exposure to ambient conditions. The experiments have been performed on bilayers of 2H-MoTe2 grown by molecular beam epitaxy on large area GaAs(111)B substrates. The crystal structure, surface morphology and thickness of the deposited MoTe2 layers have been precisely controlled in situ with a reflection high energy electron diffraction system. As evidenced by high resolution transmission electron microscopy, MoTe2 films exhibit perfect arrangement in the 2H phase and the epitaxial relation to the GaAs(111)B substrates. After the growth, the samples were in situ capped with a thin (3 nm) film of aluminum, which oxidizes after exposure to ambient conditions. This oxide serves as a protective layer to the underlying MoTe2. Resistivity measurements of the MoTe2 layers with and without the cap, exposed to low vacuum, nitrogen and air, revealed a huge difference in their stability. The significant rise of resistance is observed for the unprotected sample while the resistance of the protected one is constant. Wide range temperature resistivity studies showed that charge transport in MoTe2 is realized by hopping with an anomalous hopping exponent of x ≃ 0.66, reported also previously for ultra-thin, metallic layers.
Collapse
Affiliation(s)
- Zuzanna Ogorzałek
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | | | - Sławomir Kret
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668, Warsaw, Poland
| | - Adam Kwiatkowski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | - Krzysztof P Korona
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | | | - Janusz Mierzejewski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | - Dariusz Wasik
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | - Wojciech Pacuski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland.
| | - Janusz Sadowski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland. and Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668, Warsaw, Poland and Department of Physics and Electrical Engineering, Linnaeus University, SE-391 82, Kalmar, Sweden
| | | |
Collapse
|
31
|
Datye IM, Rojo MM, Yalon E, Deshmukh S, Mleczko MJ, Pop E. Localized Heating and Switching in MoTe 2-Based Resistive Memory Devices. NANO LETTERS 2020; 20:1461-1467. [PMID: 31951419 DOI: 10.1021/acs.nanolett.9b05272] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Two-dimensional (2D) materials have recently been incorporated into resistive memory devices because of their atomically thin nature, but their switching mechanism is not yet well understood. Here we study bipolar switching in MoTe2-based resistive memory of varying thickness and electrode area. Using scanning thermal microscopy (SThM), we map the surface temperature of the devices under bias, revealing clear evidence of localized heating at conductive "plugs" formed during switching. The SThM measurements are correlated to electro-thermal simulations, yielding a range of plug diameters (250 to 350 nm) and temperatures at constant bias and during switching. Transmission electron microscopy images reveal these plugs result from atomic migration between electrodes, which is a thermally-activated process. However, the initial forming may be caused by defect generation or Te migration within the MoTe2. This study provides the first thermal and localized switching insights into the operation of such resistive memory and demonstrates a thermal microscopy technique that can be applied to a wide variety of traditional and emerging memory devices.
Collapse
Affiliation(s)
- Isha M Datye
- Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Miguel Muñoz Rojo
- Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Eilam Yalon
- Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Sanchit Deshmukh
- Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Michal J Mleczko
- Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States
| | - Eric Pop
- Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States
- Department of Materials Science & Engineering , Stanford University , Stanford , California 94305 , United States
- Precourt Institute for Energy , Stanford University , Stanford , California 94305 , United States
| |
Collapse
|