1
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Nibhanupudi SST, Roy A, Chowdhury S, Schalip R, Coupin MJ, Matthews KC, Alam MH, Satpati B, Movva HCP, Luth CJ, Wu S, Warner JH, Banerjee SK. Low-Temperature Synthesis of WSe 2 by the Selenization Process under Ultrahigh Vacuum for BEOL Compatible Reconfigurable Neurons. ACS APPLIED MATERIALS & INTERFACES 2024; 16:22326-22333. [PMID: 38635965 DOI: 10.1021/acsami.3c18446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Low-temperature large-area growth of two-dimensional (2D) transition-metal dichalcogenides (TMDs) is critical for their integration with silicon chips. Especially, if the growth temperatures can be lowered below the back-end-of-line (BEOL) processing temperatures, the Si transistors can interface with 2D devices (in the back end) to enable high-density heterogeneous circuits. Such configurations are particularly useful for neuromorphic computing applications where a dense network of neurons interacts to compute the output. In this work, we present low-temperature synthesis (400 °C) of 2D tungsten diselenide (WSe2) via the selenization of the W film under ultrahigh vacuum (UHV) conditions. This simple yet effective process yields large-area, homogeneous films of 2D TMDs, as confirmed by several characterization techniques, including reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, and different spectroscopy methods. Memristors fabricated using the grown WSe2 film are leveraged to realize a novel compact neuron circuit that can be reconfigured to enable homeostasis.
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Affiliation(s)
- S S Teja Nibhanupudi
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Anupam Roy
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
- Department of Physics, Birla Institute of Technology Mesra, Ranchi, Jharkhand 835215, India
| | - Sayema Chowdhury
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Ryan Schalip
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Matthew J Coupin
- Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Kevin C Matthews
- Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Md Hasibul Alam
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Biswarup Satpati
- Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064, India
| | - Hema C P Movva
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Christopher J Luth
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Siyu Wu
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Jamie H Warner
- Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sanjay K Banerjee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, United States
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2
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Sovizi S, Angizi S, Ahmad Alem SA, Goodarzi R, Taji Boyuk MRR, Ghanbari H, Szoszkiewicz R, Simchi A, Kruse P. Plasma Processing and Treatment of 2D Transition Metal Dichalcogenides: Tuning Properties and Defect Engineering. Chem Rev 2023; 123:13869-13951. [PMID: 38048483 PMCID: PMC10756211 DOI: 10.1021/acs.chemrev.3c00147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 08/31/2023] [Accepted: 11/09/2023] [Indexed: 12/06/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) offer fascinating opportunities for fundamental nanoscale science and various technological applications. They are a promising platform for next generation optoelectronics and energy harvesting devices due to their exceptional characteristics at the nanoscale, such as tunable bandgap and strong light-matter interactions. The performance of TMD-based devices is mainly governed by the structure, composition, size, defects, and the state of their interfaces. Many properties of TMDs are influenced by the method of synthesis so numerous studies have focused on processing high-quality TMDs with controlled physicochemical properties. Plasma-based methods are cost-effective, well controllable, and scalable techniques that have recently attracted researchers' interest in the synthesis and modification of 2D TMDs. TMDs' reactivity toward plasma offers numerous opportunities to modify the surface of TMDs, including functionalization, defect engineering, doping, oxidation, phase engineering, etching, healing, morphological changes, and altering the surface energy. Here we comprehensively review all roles of plasma in the realm of TMDs. The fundamental science behind plasma processing and modification of TMDs and their applications in different fields are presented and discussed. Future perspectives and challenges are highlighted to demonstrate the prominence of TMDs and the importance of surface engineering in next-generation optoelectronic applications.
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Affiliation(s)
- Saeed Sovizi
- Faculty of
Chemistry, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Shayan Angizi
- Department
of Chemistry and Chemical Biology, McMaster
University, Hamilton, Ontario L8S 4M1, Canada
| | - Sayed Ali Ahmad Alem
- Chair in
Chemistry of Polymeric Materials, Montanuniversität
Leoben, Leoben 8700, Austria
| | - Reyhaneh Goodarzi
- School of
Metallurgy and Materials Engineering, Iran
University of Science and Technology (IUST), Narmak, 16846-13114, Tehran, Iran
| | | | - Hajar Ghanbari
- School of
Metallurgy and Materials Engineering, Iran
University of Science and Technology (IUST), Narmak, 16846-13114, Tehran, Iran
| | - Robert Szoszkiewicz
- Faculty of
Chemistry, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Abdolreza Simchi
- Department
of Materials Science and Engineering and Institute for Nanoscience
and Nanotechnology, Sharif University of
Technology, 14588-89694 Tehran, Iran
- Center for
Nanoscience and Nanotechnology, Institute for Convergence Science
& Technology, Sharif University of Technology, 14588-89694 Tehran, Iran
| | - Peter Kruse
- Department
of Chemistry and Chemical Biology, McMaster
University, Hamilton, Ontario L8S 4M1, Canada
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3
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Yang S, Liu K, Xu Y, Liu L, Li H, Zhai T. Gate Dielectrics Integration for 2D Electronics: Challenges, Advances, and Outlook. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2207901. [PMID: 36226584 DOI: 10.1002/adma.202207901] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/28/2022] [Indexed: 05/05/2023]
Abstract
2D semiconductors have emerged both as an ideal platform for fundamental studies and as promising channel materials in beyond-silicon field-effect-transistors due to their outstanding electrical properties and exceptional tunability via external field. However, the lack of proper dielectrics for 2D semiconductors has become a major roadblock for their further development toward practical applications. The prominent issues between conventional 3D dielectrics and 2D semiconductors arise from the integration and interface quality, where defect states and imperfections lead to dramatic deterioration of device performance. In this review article, the root causes of such issues are briefly analyzed and recent advances on some possible solutions, including various approaches of adapting conventional dielectrics to 2D semiconductors, and the development of novel dielectrics with van der Waals surface toward high-performance 2D electronics are summarized. Then, in the perspective, the requirements of ideal dielectrics for state-of-the-art 2D devices are outlined and an outlook for their future development is provided.
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Affiliation(s)
- Sijie Yang
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Kailang Liu
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Yongshan Xu
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Lixin Liu
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Huiqiao Li
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
| | - Tianyou Zhai
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China
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4
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Zhang D, Yang M. Surface Chemistry of MoS 2 in Remote Oxygen Plasma. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12112-12117. [PMID: 34613732 DOI: 10.1021/acs.langmuir.1c01954] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Miniaturization of electronic devices down to the nanoscale needs corresponding processing technologies with precision at the atomic layer level. The plasma atomic layer etching (ALE) technique is playing an active role in this demand. However, theoretical research on the ALE mechanism is a great challenge. We propose a method of spontaneously searching adsorption sites (SSASs) to understand what surface chemistry occurs in the ALE processing of MoS2 treated by the remote oxygen plasma. The SSAS results are in good agreement with experimental observations. Chemical adsorption of O atoms occurs only in the topmost layer of the MoS2 surface. The MoS2 surface has four different adsorption sites with different probabilities of binding an O atom, denoted by 0Sbb, 0Sbbc, 2Sbb, and 3Sbb configurations, which have zero, zero, two, and three S-Mo bonds broken by the introduced O atom, respectively. Four adsorption sites of the MoS2 surface play different roles in the surface oxidation in the remote oxygen plasma.
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Affiliation(s)
- Daoyu Zhang
- School of Physics, Southeast University, Nanjing 211189, China
| | - Minnan Yang
- Department of Physics, China Pharmaceutical University, Nanjing 211198, China
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Lee K, Kim Y, Kim D, Lee J, Lee H, Joo MK, Cho YH, Shin J, Ji H, Kim GT. Metal-Contact Improvement in a Multilayer WSe 2 Transistor through Strong Hot Carrier Injection. ACS APPLIED MATERIALS & INTERFACES 2021; 13:2829-2835. [PMID: 33410320 DOI: 10.1021/acsami.0c18319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Hot carrier injection (HCI), occurring when the horizontal electric field is strongly applied, usually affects the degradation of nanoelectronic devices. In addition, metal contacts play a significant role in nanoelectronic devices. In this study, Schottky contacts in multilayer tungsten diselenide (WSe2) field-effect transistors (FETs) by hot carrier injection (HCI), occurring when a high drain voltage is applied, is investigated. A small number of hot carriers with high energy reduces the Schottky barrier height and improves the performance of FETs effectively rather than damaging the channel. Thermal annealing at the end of the fabrication process increases device performance by causing interfacial reactions of the source/drain electrodes. HCI causes a significant enhancement in the local asymmetry, especially in the subthreshold region. The subthreshold swing (SS) of the thermally annealed FETs is significantly improved from 9.66 to 0.562 V dec-1 through the energy of HCI generated by a strong horizontal electric field. In addition, the contact resistances (RSD), also called series resistances, extracted by a four-probe measurement and a Y-function method were also improved by decreasing to a 10th through the energy of HCI. To understand the asymmetrical characteristics of the channel after the stress, we performed electrical analysis, electrostatic force microscopy (EFM), and Raman spectroscopy.
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Affiliation(s)
- Kookjin Lee
- IMEC, 3001 Leuven, Belgium
- Department of Materials Science, KU Leuven, 3001 Leuven, Belgium
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Yeonsu Kim
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Doyoon Kim
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Jaewoo Lee
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Hyebin Lee
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
- Samsung Electronics Co. Ltd., 1 Samsung-ro, Yongin-si, Gyeonggi-do 17113, Republic of Korea
| | - Min-Kyu Joo
- Department of Applied Physics, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Young-Hoon Cho
- Samsung Electronics Co. Ltd., 1 Samsung-ro, Yongin-si, Gyeonggi-do 17113, Republic of Korea
| | - Jinwoo Shin
- Agency of Defense Development, Daejeon 305-600, Republic of Korea
| | - Hyunjin Ji
- School of Electrical Engineering, University of Ulsan, Ulsan 680-749, Republic of Korea
| | - Gyu-Tae Kim
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
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6
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Kropp JA, Sharma A, Zhu W, Ataca C, Gougousi T. Surface Defect Engineering of MoS 2 for Atomic Layer Deposition of TiO 2 Films. ACS APPLIED MATERIALS & INTERFACES 2020; 12:48150-48160. [PMID: 32970942 DOI: 10.1021/acsami.0c13095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this manuscript, we combine experimental and computational approaches to study the atomic layer deposition (ALD) of dielectrics on MoS2 surfaces for a very common class of ALD precursors, the alkylamines. More specifically, we study the thermal ALD of TiO2 from TDMAT and H2O. Depositions on as-produced chemical vapor deposition MoS2 flakes result in discontinuous films. Surface treatment with mercaptoethanol (ME) does not improve the surface coverage, and DFT calculations show that ME reacts very weakly with the MoS2 surface. However, creation of sulfur vacancies on the MoS2 surface using Ar ion beam irradiation results in much improved surface coverage for films with a nominal thickness of 6 nm, and the calculations show that TDMAT reacts moderately with either single or extended sulfur vacancies. ME also reacts with the vacancies, and defect-rich surfaces treated with ME provide an equally good surface for the nucleation of ALD TiO2 films. The computational studies however reveal that the creation of surface vacancies results in the introduction of gap states that may deteriorate the electronic properties of the stack. Treatment with ME results in the complete removal of the gap states originating from the most commonly found single vacancies and reduces substantially the density of states for double and line vacancies. As a result, we provide a pathway for the deposition of high-quality ALD dielectrics on the MoS2 surfaces, which is required for the successful integration of these 2D materials in functional devices.
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Affiliation(s)
- Jaron A Kropp
- Department of Physics, UMBC, Baltimore, Maryland 21250, United States
| | - Ankit Sharma
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Wenjuan Zhu
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Can Ataca
- Department of Physics, UMBC, Baltimore, Maryland 21250, United States
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7
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Iacovella F, Koroleva A, Rybkin AG, Fouskaki M, Chaniotakis N, Savvidis P, Deligeorgis G. Impact of thermal annealing in forming gas on the optical and electrical properties of MoS 2monolayer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:035001. [PMID: 33078711 DOI: 10.1088/1361-648x/abbe76] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
Technological applications involving 2D MoS2require transfer of chemical vapor deposition (CVD) grown material from its original substrate and subsequent lithographic processes. Inevitably, those steps contaminate the surface of the 2D material with polymeric residues affecting the electronic and optical properties of the MoS2. Annealing in forming gas is considered an efficient treatment to partially remove such residues. However, hydrogen also interacts with MoS2creating or saturating sulfur vacancies. Sulfur vacancies are known to be at the origin of n-doping evident in the majority of as-grown MoS2samples. In this context, investigating the impact of thermal annealing in forming gas on the electronic and optical properties of MoS2monolayer is technologically important. In order to address this topic, we have systematically studied the evolution of CVD grown MoS2monolayer using Raman spectroscopy, photoluminescence, x-ray photoelectron spectroscopy and transport measurements through a series of thermal annealing in forming gas at temperatures up to 500 °C. Efficient removal of the polymeric residues is demonstrated at temperatures as low as 200 °C. Above this value, carrier density modulation is identified by photoluminescence, x-ray photoelectron spectroscopy and electrical characterization and is correlated to the creation of sulfur vacancies. Finally, the degradation of the MoS2single layer is verified with annealing at or above 350 °C through Raman and photocurrent measurements.
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Affiliation(s)
- Fabrice Iacovella
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71110, Greece
- Department of Physics, University of Crete, Heraklion 71003, Greece
| | - Aleksandra Koroleva
- St. Petersburg State University, 7/9 Universitetskaya Nab., St. Petersburg 199034, Russia
| | - Artem G Rybkin
- St. Petersburg State University, 7/9 Universitetskaya Nab., St. Petersburg 199034, Russia
| | - Maria Fouskaki
- Department of Chemistry, University of Crete, Heraklion 71003, Greece
| | | | - Pavlos Savvidis
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71110, Greece
- Department of Materials Science and Technology, University of Crete, Heraklion 71003, Greece
- Department of Nanophotonics and Metamaterials, ITMO University, St. Petersburg 197101, Russia
- Westlake University, 18 Shilongshan Rd, Hangzhou 310024, Zhejiang, People's Republic of China
- Westlake Institute for Advanced Study, 18 Shilongshan Rd, Hangzhou 310024, Zhejiang, People's Republic of China
| | - George Deligeorgis
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71110, Greece
- Department of Physics, University of Crete, Heraklion 71003, Greece
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8
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Ke JA, Garaj S, Gradečak S. Nanopores in 2D MoS 2: Defect-Mediated Formation and Density Modulation. ACS APPLIED MATERIALS & INTERFACES 2019; 11:26228-26234. [PMID: 31305058 DOI: 10.1021/acsami.9b03531] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Oxidation is a scalable process for introducing nanopores in two-dimensional transitional metal dichalcogenides (TMDs) for membrane applications. The nanopore density is determined by the areal density of their nucleation sites; understanding the nature of the defects and their control would enable tailoring of TMD membranes for targeted applications. In this work, we show that the nanopore distribution is dramatically different in strained and unstrained MoS2 crystals. We correlate this spatial distribution to the underlying arrangement of dislocations in MoS2 crystals, in contrast to previously suggested sulfur vacancies. To control the nucleation density of MoS2 nanopores, we demonstrate that the pore density can be modulated by electron beam exposure prior to the nanopore formation. Raman analysis of electron beam-exposed samples indicates that hydrocarbon adsorption activates defect species other than dislocations, which significantly enhances the nanopore density in MoS2.
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Affiliation(s)
- Jian-An Ke
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Slaven Garaj
- Department of Physics , National University of Singapore , Singapore 117551 , Singapore
- Centre of Advanced 2D Materials , National University of Singapore , Singapore 117546 , Singapore
| | - Silvija Gradečak
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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9
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Poly(amidoxime) functionalized MoS2 for efficient adsorption of uranium(VI) in aqueous solutions. J Radioanal Nucl Chem 2018. [DOI: 10.1007/s10967-018-6338-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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10
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Progress in Contact, Doping and Mobility Engineering of MoS2: An Atomically Thin 2D Semiconductor. CRYSTALS 2018. [DOI: 10.3390/cryst8080316] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Atomically thin molybdenum disulfide (MoS2), a member of the transition metal dichalcogenide (TMDC) family, has emerged as the prototypical two-dimensional (2D) semiconductor with a multitude of interesting properties and promising device applications spanning all realms of electronics and optoelectronics. While possessing inherent advantages over conventional bulk semiconducting materials (such as Si, Ge and III-Vs) in terms of enabling ultra-short channel and, thus, energy efficient field-effect transistors (FETs), the mechanically flexible and transparent nature of MoS2 makes it even more attractive for use in ubiquitous flexible and transparent electronic systems. However, before the fascinating properties of MoS2 can be effectively harnessed and put to good use in practical and commercial applications, several important technological roadblocks pertaining to its contact, doping and mobility (µ) engineering must be overcome. This paper reviews the important technologically relevant properties of semiconducting 2D TMDCs followed by a discussion of the performance projections of, and the major engineering challenges that confront, 2D MoS2-based devices. Finally, this review provides a comprehensive overview of the various engineering solutions employed, thus far, to address the all-important issues of contact resistance (RC), controllable and area-selective doping, and charge carrier mobility enhancement in these devices. Several key experimental and theoretical results are cited to supplement the discussions and provide further insight.
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11
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Zhang Z, Qian Q, Li B, Chen KJ. Interface Engineering of Monolayer MoS 2/GaN Hybrid Heterostructure: Modified Band Alignment for Photocatalytic Water Splitting Application by Nitridation Treatment. ACS APPLIED MATERIALS & INTERFACES 2018; 10:17419-17426. [PMID: 29706066 DOI: 10.1021/acsami.8b01286] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Interface engineering is a key strategy to deal with the two-dimensional (2D)/three-dimensional (3D) hybrid heterostructure, since the properties of this atomic-layer-thick 2D material can easily be impacted by the substrate environment. In this work, the structural, electronic, and optical properties of the 2D/3D heterostructure of monolayer MoS2 on wurtzite GaN surface without and with nitridation interfacial layer are systematically investigated by first-principles calculation and experimental analysis. The nitridation interfacial layer can be introduced into the 2D/3D heterostructure by remote N2 plasma treatment to GaN sample surface prior to stacking monolayer MoS2 on top. The calculation results reveal that the 2D/3D integrated heterostructure is energetically favorable with a negative formation energy. Both interfaces demonstrate indirect band gap, which is a benefit for longer lifetime of the photoexcited carriers. Meanwhile, the conduction band edge and valence band edge of the MoS2 side increases after nitridation treatment. The modification to band alignment is then verified by X-ray photoelectron spectroscopy measurement on MoS2/GaN heterostructures constructed by a modified wet-transfer technique, which indicates that the MoS2/GaN heterostructure without nitridation shows a type-II alignment with a conduction band offset (CBO) of only 0.07 eV. However, by the deployment of interface nitridation, the band edges of MoS2 move upward for ∼0.5 eV as a result of the nitridized substrate property. The significantly increased CBO could lead to better electron accumulation capability at the GaN side. The nitridized 2D/3D heterostructure with effective interface treatment exhibits a clean band gap and substantial optical absorption ability and could be potentially used as practical photocatalyst for hydrogen generation by water splitting using solar energy.
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Affiliation(s)
- Zhaofu Zhang
- Department of Electronic and Computer Engineering , The Hong Kong University of Science and Technology , Clear Water Bay , Kowloon , Hong Kong
| | - Qingkai Qian
- Department of Electronic and Computer Engineering , The Hong Kong University of Science and Technology , Clear Water Bay , Kowloon , Hong Kong
| | - Baikui Li
- College of Optoelectronic and Computer Engineering , Shenzhen University , Shenzhen 518060 , China
| | - Kevin J Chen
- Department of Electronic and Computer Engineering , The Hong Kong University of Science and Technology , Clear Water Bay , Kowloon , Hong Kong
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12
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Qian Q, Zhang Z, Chen KJ. In Situ Resonant Raman Spectroscopy to Monitor the Surface Functionalization of MoS 2 and WSe 2 for High-k Integration: A First-Principles Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2882-2889. [PMID: 29400978 DOI: 10.1021/acs.langmuir.7b03840] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Surface functionalization of the dangling-bond-free MoS2, WSe2, and other TMDs (transition metal dichalcogenides) is of large practical importance, for example, in providing nucleation sites for the subsequent high-k dielectric integration. Of the surface functionalization methods, the reversible O or N atom adsorption on top of the chalcogen atoms is most promising. However, hazards such as severe oxidation or nitridation persist when the adsorption coverage is high. An in situ characterization technique, which can be integrated with the surface functionalization and dielectric deposition chamber, becomes valuable to enable the real-time monitoring of surface adsorption conditions. Raman spectroscopy, as a nondestructive characterization method without vacuum requirement, is a strong candidate. By utilizing first-principles calculations, Raman spectra of single-layer MoS2 and WSe2 with various O/N adsorption coverages are studied. The calculations suggest that the low-coverage O/N adsorbates will act as perturbations to the periodic lattice and activate the acoustic-phonon Raman scatterings. While high-coverage adsorptions will further activate and intensify the optical-phonon Raman scatterings of previously silent A2u and E1g modes, due to the breaking of reflection symmetry in the z direction, new phonon modes associated with the adatom oscillations are also introduced. All these pieces of evidence, together with the peak shifts of previously active A1g and E2g1 modes, suggest that in situ resonant Raman spectroscopy is capable of providing important information to quantify the O/N adsorption coverage and can be used as a valuable real-time characterization technique to monitor and control the surface functionalization conditions of MoS2 and WSe2.
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Affiliation(s)
- Qingkai Qian
- Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong SAR, China
| | - Zhaofu Zhang
- Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong SAR, China
| | - Kevin J Chen
- Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong SAR, China
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