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Li L, Xiang H, Zheng H, Chien YC, Duong NT, Gao J, Ang KW. Physical reservoirs based on MoS 2-HZO integrated ferroelectric field-effect transistors for reservoir computing systems. Nanoscale Horiz 2024; 9:752-763. [PMID: 38465422 DOI: 10.1039/d3nh00524k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Reservoir computing (RC), a variant of recurrent neural networks (RNNs), is well-known for its reduced energy consumption through exclusive focus on training the output weight and its superior performance in handling spatiotemporal information. Implementing these networks in hardware requires devices with superior fading memory behavior. Unlike filament-based two-terminal devices, those relying on ferroelectric switching demonstrate improved voltage reliability, while three-terminal transistors provide additional active control. HfO2-based ferroelectric materials such as Hf0.5Zr0.5O2 (HZO), have garnered attention for their scalability and seamless integration with CMOS technology. This study implements a RC hardware based on MoS2-HZO integrated device structure with enhanced spontaneous polarization field. By adjusting the oxygen vacancy concentration, the devices exhibit consistent responses to both identical and nonidentical voltages, making them suitable for diverse RC applications. The high accuracy of MNIST handwritten digits recognition highlights the rich reservoir states of the traditional RC architecture. Additionally, the impact of masks on RC implementation is assessed, showcasing the device's capability for spatiotemporal signal analysis. This development paves the way for implementing energy-efficient and high-performance computing solutions.
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Affiliation(s)
- Lingqi Li
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
| | - Heng Xiang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
| | - Haofei Zheng
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
| | - Yu-Chieh Chien
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
| | - Ngoc Thanh Duong
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
| | - Jing Gao
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
| | - Kah-Wee Ang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583.
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Duong NT, Shi Y, Li S, Chien YC, Xiang H, Zheng H, Li P, Li L, Wu Y, Ang KW. Coupled Ferroelectric-Photonic Memory in a Retinomorphic Hardware for In-Sensor Computing. Adv Sci (Weinh) 2024; 11:e2303447. [PMID: 38234245 DOI: 10.1002/advs.202303447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 09/14/2023] [Indexed: 01/19/2024]
Abstract
The development of all-in-one devices for artificial visual systems offers an attractive solution in terms of energy efficiency and real-time processing speed. In recent years, the proliferation of smart sensors in the growth of Internet-of-Things (IoT) has led to the increasing importance of in-sensor computing technology, which places computational power at the edge of the data-flow architecture. In this study, a prototype visual sensor inspired by the human retina is proposed, which integrates ferroelectricity and photosensitivity in two-dimensional (2D) α-In2Se3 material. This device mimics the functions of photoreceptors and amacrine cells in the retina, performing optical reception and memory computation functions through the use of electrical switching polarization in the channel. The gate-tunable linearity of excitatory and inhibitory functions in photon-induced short-term plasticity enables to encode and classify 12 000 images in the Mixed National Institute of Standards and Technology (MNIST) dataset with remarkable accuracy, achieving ≈94%. Additionally, in-sensor convolution image processing through a network of phototransistors, with five convolutional kernels electrically pre-programmed into the transistors is demonstrated. The convoluted photocurrent matrices undergo straightforward arithmetic calculations to produce edge and feature-enhanced scenarios. The findings demonstrate the potential of ferroelectric α-In2Se3 for highly compact and efficient retinomorphic hardware implementation, regardless of ambipolar transport in the channel.
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Affiliation(s)
- Ngoc Thanh Duong
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Yufei Shi
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Sifan Li
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Yu-Chieh Chien
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Heng Xiang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Haofei Zheng
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Peiyang Li
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Lingqi Li
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Yangwu Wu
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Kah-Wee Ang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
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Chien YC, Xiang H, Shi Y, Duong NT, Li S, Ang KW. A MoS 2 Hafnium Oxide Based Ferroelectric Encoder for Temporal-Efficient Spiking Neural Network. Adv Mater 2023; 35:e2204949. [PMID: 36366910 DOI: 10.1002/adma.202204949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/26/2022] [Indexed: 06/16/2023]
Abstract
Spiking neural network (SNN), where the information is evaluated recurrently through spikes, has manifested significant promises to minimize the energy expenditure in data-intensive machine learning and artificial intelligence. Among these applications, the artificial neural encoders are essential to convert the external stimuli to a spiking format that can be subsequently fed to the neural network. Here, a molybdenum disulfide (MoS2 ) hafnium oxide-based ferroelectric encoder is demonstrated for temporal-efficient information processing in SNN. The fast domain switching attribute associated with the polycrystalline nature of hafnium oxide-based ferroelectric material is exploited for spike encoding, rendering it suitable for realizing biomimetic encoders. Accordingly, a high-performance ferroelectric encoder is achieved, featuring a superior switching efficiency, negligible charge trapping effect, and robust ferroelectric response, which successfully enable a broad dynamic range. Furthermore, an SNN is simulated to verify the precision of the encoded information, in which an average inference accuracy of 95.14% can be achieved, using the Modified National Insitute of Standards and Technology (MNIST) dataset for digit classification. Moreover, this ferroelectric encoder manifests prominent resilience against noise injection with an overall prediction accuracy of 94.73% under various Gaussian noise levels, showing practical promises to reduce the computational load for the neural network.
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Affiliation(s)
- Yu-Chieh Chien
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Heng Xiang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Yufei Shi
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Ngoc Thanh Duong
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Sifan Li
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Kah-Wee Ang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
- Institute of Materials Research and Engineering, A*STAR, 2 Fusionopolis Way, Singapore, 138634, Singapore
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Lee J, Bang S, Park HJ, Park DY, Park C, Duong NT, Won YS, Jang J, Oh HM, Choi SH, Kim KK, Jeong MS. Interface Trap Suppression and Electron Doping in Van der Waals Materials Using Cross-Linked Poly(vinylpyrrolidone). ACS Appl Mater Interfaces 2021; 13:55489-55497. [PMID: 34761893 DOI: 10.1021/acsami.1c12968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The instability of van der Waals (vdW) materials leads to spontaneous morphological and chemical transformations in the air. Although the passivation of vdW materials with other resistive materials is often used to solve stability issues, this passivation layer can block carrier injection and thus interfere with charge transfer doping. In this study, a facile method is proposed for n-doping and mediation of Se vacancies in tungsten diselenide (WSe2) by poly(vinylpyrrolidone) (PVP) coating. The major carrier type of the PVP-coated WSe2-based field-effect transistor (FET) was converted from hole (p-type) to electron (n-type). Furthermore, the vacancy-induced interface trap density was reduced by approximately 500 times. This study provides a practical doping and passivation method for the van der Waals materials, as well as a comprehensive understanding of the chemical reaction and electronic transport in these materials.
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Affiliation(s)
- Juchan Lee
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Seungho Bang
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Hyeon Jung Park
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
| | - Dae Young Park
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
| | - Chulho Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Ngoc Thanh Duong
- Department of Materials Science and Engineering, Phenikaa University, Hanoi 12116, Viet Nam
| | - Yo Seob Won
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Jiseong Jang
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Hye Min Oh
- Department of Physics, Kunsan National University, Kunsan 54150, Republic of Korea
| | - Soo Ho Choi
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Suwon 16419, Republic of Korea
| | - Ki Kang Kim
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Suwon 16419, Republic of Korea
| | - Mun Seok Jeong
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
- Department of Energy Engineering, Hanyang University (HYU), Seoul 04763, Republic of Korea
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Nguyen DA, Park DY, Duong NT, Lee KN, Im H, Yang H, Jeong MS. Large-Area MoS 2 via Colloidal Nanosheet Ink for Integrated Memtransistor. Small Methods 2021; 5:e2100558. [PMID: 34927977 DOI: 10.1002/smtd.202100558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 08/24/2021] [Indexed: 06/14/2023]
Abstract
2D transition metal dichalcogenides (TMDs) exhibit intriguing properties for applications in optoelectronics and electronics, among which memtransistors received extensive attention as multifunctional devices. For practical applications of 2D TMDs, large-area fabrication of the materials via reliable processes, which is in trade-off with their quality, has been a long-standing issue. Here, a simple and effective way is proposed to fabricate large-area and high-quality molybdenum disulfide thin films using MoS2 colloidal ink through a spray coating, followed by a postsulfurization process. High-quality MoS2 thin films exhibit excellent optical and electrical properties that can be utilized in field-effect transistors (FETs) and memtransistor arrays. The MoS2 FETs show an average on/off ratio of 5 × 106 and a high electron mobility of 10.34 cm2 V-1 s-1 , which can be understood by the healing of sulfur vacancies, recrystallization, and the removal of the carbon contamination of the MoS2 . These MoS2 -based memtransistors present stable operations with a high switching ratio tuned by back gate and light illumination, which is promising for multiple-levels memory and complex neuromorphic computing. This study demonstrates a new strategy to fabricate 2D TMDs with large-area and high quality for integrated optoelectronic and memory device applications.
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Affiliation(s)
- Duc Anh Nguyen
- Division of Physics and Semiconductor Science, Dongguk University, Seoul, 04620, Republic of Korea
| | - Dae Young Park
- Department of Physics, Department of Energy Engineering, Hanyang University, Seoul, 04763, Republic of Korea
| | - Ngoc Thanh Duong
- Faculty of Materials Science and Engineering, Phenikaa University, Hanoi, 12116, Viet Nam
| | - Kang-Nyeoung Lee
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Hyunsik Im
- Division of Physics and Semiconductor Science, Dongguk University, Seoul, 04620, Republic of Korea
| | - Heejun Yang
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Mun Seok Jeong
- Department of Physics, Department of Energy Engineering, Hanyang University, Seoul, 04763, Republic of Korea
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Lee J, Duong NT, Bang S, Park C, Nguyen DA, Jeon H, Jang J, Oh HM, Jeong MS. Modulation of Junction Modes in SnSe 2/MoTe 2 Broken-Gap van der Waals Heterostructure for Multifunctional Devices. Nano Lett 2020; 20:2370-2377. [PMID: 32031411 DOI: 10.1021/acs.nanolett.9b04926] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We study the electronic and optoelectronic properties of a broken-gap heterojunction composed of SnSe2 and MoTe2 with gate-controlled junction modes. Owing to the interband tunneling current, our device can act as an Esaki diode and a backward diode with a peak-to-valley current ratio approaching 5.7 at room temperature. Furthermore, under an 811 nm laser irradiation the heterostructure exhibits a photodetectivity of up to 7.5 × 1012 Jones. In addition, to harness the electrostatic gate bias, Voc can be tuned from negative to positive by switching from the accumulation mode to the depletion mode of the heterojunction. Additionally, a photovoltaic effect with a fill factor exceeding 41% was observed, which highlights the significant potential for optoelectronic applications. This study not only demonstrates high-performance multifunctional optoelectronics based on the SnSe2/MoTe2 heterostructure but also provides a comprehensive understanding of broken-band alignment and its applications.
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Affiliation(s)
- Juchan Lee
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ngoc Thanh Duong
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Seungho Bang
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Chulho Park
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Duc Anh Nguyen
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hobeom Jeon
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jiseong Jang
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hye Min Oh
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Mun Seok Jeong
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
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Lee KN, Bang S, Duong NT, Yun SJ, Park DY, Lee J, Choi YC, Jeong MS. Encapsulation of a Monolayer WSe 2 Phototransistor with Hydrothermally Grown ZnO Nanorods. ACS Appl Mater Interfaces 2019; 11:20257-20264. [PMID: 31074258 DOI: 10.1021/acsami.9b03508] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Transition metal dichalcogenides (TMDCs) are promising two-dimensional (2D) materials for realizing next-generation electronics and optoelectronics with attractive physical properties. However, monolayer TMDCs (1LTMDCs) have various serious issues, such as instability under ambient conditions and low optical quantum yield from their extremely thin thickness of ∼0.7 nm. To overcome these issues, we constructed a hybrid structure (HS) by growing zinc oxide nanorods (ZnO NRs) on a monolayer tungsten diselenide (1LWSe2) using the hydrothermal method. Consequently, we confirmed not only enhanced photoluminescence of 1LWSe2 but also improved optoelectronic properties by fabricating the HS phototransistor. Through various investigations, we found that these phenomena were due to the antenna and p-type doping effects attributed to the ZnO NRs. In addition, we verified that the optoelectronic properties of 1LTMDCs are maintained for 2 weeks in ambient condition through the sustainable encapsulation effect induced by our HS. This encapsulation method with inorganic materials is expected to be applied to improve the stability and performance of various emerging 2D material-based devices.
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Affiliation(s)
- Kang-Nyeoung Lee
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Korea Institute of Carbon Convergence Technology , Jeonju 54853 , Republic of Korea
| | - Seungho Bang
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science , Suwon 16419 , Republic of Korea
| | - Ngoc Thanh Duong
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Seok Joon Yun
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science , Suwon 16419 , Republic of Korea
| | - Dae Young Park
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science , Suwon 16419 , Republic of Korea
| | - Juchan Lee
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Young Chul Choi
- Korea Institute of Carbon Convergence Technology , Jeonju 54853 , Republic of Korea
| | - Mun Seok Jeong
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science , Suwon 16419 , Republic of Korea
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Duong NT, Lee J, Bang S, Park C, Lim SC, Jeong MS. Modulating the Functions of MoS 2/MoTe 2 van der Waals Heterostructure via Thickness Variation. ACS Nano 2019; 13:4478-4485. [PMID: 30938981 DOI: 10.1021/acsnano.9b00014] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Various functional devices including p-n forward, backward, and Zener diodes are realized with a van der Waals heterostructure that are composed of molybdenum disulfide (MoS2) and molybdenum ditelluride (MoTe2) by changing the thickness of the MoTe2 layer and common gate bias. In addition, the available negative differential transconductance of the heterostructure is utilized to fabricate a many-valued logic device that exhibits three different logic states ( i.e., a ternary inverter). Furthermore, the multivalued logic device can be transformed into a binary inverter using laser irradiation. This work provides a comprehensive understanding of the device fabrication and electronic-device design utilizing thickness control.
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Affiliation(s)
- Ngoc Thanh Duong
- Department of Energy Science , Sungkyunkwan University (SKKU) , Suwon 16419 , Republic of Korea
| | - Juchan Lee
- Department of Energy Science , Sungkyunkwan University (SKKU) , Suwon 16419 , Republic of Korea
| | - Seungho Bang
- Department of Energy Science , Sungkyunkwan University (SKKU) , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
| | - Chulho Park
- Department of Energy Science , Sungkyunkwan University (SKKU) , Suwon 16419 , Republic of Korea
| | - Seong Chu Lim
- Department of Energy Science , Sungkyunkwan University (SKKU) , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
| | - Mun Seok Jeong
- Department of Energy Science , Sungkyunkwan University (SKKU) , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
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Park C, Duong NT, Bang S, Nguyen DA, Oh HM, Jeong MS. Photovoltaic effect in a few-layer ReS 2/WSe 2 heterostructure. Nanoscale 2018; 10:20306-20312. [PMID: 30375621 DOI: 10.1039/c8nr07219a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two-dimensional transition-metal dichalcogenides (TMDCs) are notable materials owing to their flexibility, transparency, and appropriate bandgaps. Because of their unique advantages, TMDC p-n diodes have been studied for next-generation electronics and optoelectronics. However, their efficiency must be increased for commercialization. In this study, we demonstrated a heterostructure composed of few-layer ReS2 and WSe2. This few-layer ReS2/WSe2 heterostructure exhibits a p-n junction and an n-n junction in different gate-bias regimes. In the p-n junction regime, the heterostructure shows outstanding rectification behavior. Additionally, we identify three carrier-transfer mechanisms - direct tunneling, Fowler-Nordheim tunneling, and the space charge region - depending on the drain bias. Furthermore, the photovoltaic effect is observed in this few-layer ReS2/WSe2 heterostructure. As a result, a high fill factor (≈ 0.56), power conversion (≈ 1.5%), and external quantum efficiency (≈ 15.3%) were obtained. This study provides new guidelines for flexible optoelectronic devices.
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Affiliation(s)
- Chulho Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Korea.
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Duong NT, Bang S, Lee SM, Dang DX, Kuem DH, Lee J, Jeong MS, Lim SC. Parameter control for enhanced peak-to-valley current ratio in a MoS 2/MoTe 2 van der Waals heterostructure. Nanoscale 2018; 10:12322-12329. [PMID: 29946582 DOI: 10.1039/c8nr01711e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The Ids-Vds properties of a van der Waals cross-junction of few layered MoS2/MoTe2 were investigated, and the physical device parameters were altered in order to transform the conduction mechanism from thermionic emission to interband tunneling. The pristine heterostructure demonstrated rectification behavior of typical p-n junction diodes, because of the p-type and n-type nature of MoTe2 and MoS2, respectively. Lowering the contact resistance between the metal and channel materials, by changing the electrode metals from Au to Pd and Ti, alone did not give rise to carrier conduction through the hetero-interband tunneling between MoTe2 and MoS2. In addition to the reduction in contact resistance, the chemical doping of MoS2 using Benzyl Viologen (BV) achieves hetero-interband tunneling between MoTe2 and MoS2, which probably narrows the depletion layer by degenerating MoS2. The peak-to-valley ratio of the tunneling current of the BV-doped heterostructure of MoS2/MoTe2 is about 4.8, which is comparable to that of the commercially available Si tunneling diode.
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Affiliation(s)
- Ngoc Thanh Duong
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea.
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Bang S, Duong NT, Lee J, Cho YH, Oh HM, Kim H, Yun SJ, Park C, Kwon MK, Kim JY, Kim J, Jeong MS. Augmented Quantum Yield of a 2D Monolayer Photodetector by Surface Plasmon Coupling. Nano Lett 2018; 18:2316-2323. [PMID: 29561626 DOI: 10.1021/acs.nanolett.7b05060] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Monolayer (1L) transition metal dichalcogenides (TMDCs) are promising materials for nanoscale optoelectronic devices because of their direct band gap and wide absorption range (ultraviolet to infrared). However, 1L-TMDCs cannot be easily utilized for practical optoelectronic device applications (e.g., photodetectors, solar cells, and light-emitting diodes) because of their extremely low optical quantum yields (QYs). In this investigation, a high-gain 1L-MoS2 photodetector was successfully realized, based on the surface plasmon (SP) of the Ag nanowire (NW) network. Through systematic optical characterization of the hybrid structure consisting of a 1L-MoS2 and the Ag NW network, it was determined that a strong SP and strain relaxation effect influenced a greatly enhanced optical QY. The photoluminescence (PL) emission was drastically increased by a factor of 560, and the main peak was shifted to the neutral exciton of 1L-MoS2. Consequently, the overall photocurrent of the hybrid 1L-MoS2 photodetector was observed to be 250 times better than that of the pristine 1L-MoS2 photodetector. In addition, the photoresponsivity and photodetectivity of the hybrid photodetector were effectively improved by a factor of ∼1000. This study provides a new approach for realizing highly efficient optoelectronic devices based on TMDCs.
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Affiliation(s)
- Seungho Bang
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Ngoc Thanh Duong
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Jubok Lee
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Yoo Hyun Cho
- Department of Photonic Engineering , Chosun University , Gwangju 61452 , Republic of Korea
- Bio-Health Research Center , Korea Photonics Technology Institute (KOPTI) , Gwangju 61007 , Republic of Korea
| | - Hye Min Oh
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Hyun Kim
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Seok Joon Yun
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Chulho Park
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Min-Ki Kwon
- Department of Photonic Engineering , Chosun University , Gwangju 61452 , Republic of Korea
| | - Ja-Yeon Kim
- Bio-Health Research Center , Korea Photonics Technology Institute (KOPTI) , Gwangju 61007 , Republic of Korea
| | - Jeongyong Kim
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Mun Seok Jeong
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
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Nguyen DA, Oh HM, Duong NT, Bang S, Yoon SJ, Jeong MS. Highly Enhanced Photoresponsivity of a Monolayer WSe 2 Photodetector with Nitrogen-Doped Graphene Quantum Dots. ACS Appl Mater Interfaces 2018; 10:10322-10329. [PMID: 29508611 DOI: 10.1021/acsami.7b18419] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Hybrid structures of two-dimensional (2D) materials and quantum dots (QDs) are particularly interesting in the field of nanoscale optoelectronic devices because QDs are efficient light absorbers and can inject photocarriers into thin layers of 2D transition-metal dichalcogenides, which have high carrier mobility. In this study, we present a heterostructure that consists of a monolayer of tungsten diselenide (ML WSe2) covered by nitrogen-doped graphene QDs (N-GQDs). The improved photoluminescence of ML WSe2 is attributed to the dominant neutral exciton emission caused by the n-doping effect. Owing to strong light absorption and charge transfer from N-GQDs to ML WSe2, N-GQD-covered ML WSe2 showed up to 480% higher photoresponsivity than that of a pristine ML WSe2 photodetector. The hybrid photodetector exhibits good environmental stability, with 46% performance retention after 30 days under ambient conditions. The photogating effect also plays a key role in the improvement of hybrid photodetector performance. On applying the back-gate voltage modulation, the hybrid photodetector shows a responsivity of 2578 A W-1, which is much higher than that of the ML WSe2-based device.
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Mancy A, Antignac M, Minoletti C, Dijols S, Mouries V, Duong NT, Battioni P, Dansette PM, Mansuy D. Diclofenac and its derivatives as tools for studying human cytochromes P450 active sites: particular efficiency and regioselectivity of P450 2Cs. Biochemistry 1999; 38:14264-70. [PMID: 10572000 DOI: 10.1021/bi991195u] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A comparison of the oxidations of diclofenac with microsomes of yeasts expressing various human liver cytochromes P450 showed that P450 2C9 regioselectively led to 4'-hydroxy diclofenac (4'-OHD) whereas P450 3A4 only led to 5-hydroxy diclofenac (5-OHD). P450 2C19, 2C18, and 2C8 led to the simultaneous formation of 4'-OHD and 5-OHD (respective molar ratios of 1.3, 0.37, and 0.17), and P450 1A1, 1A2, 2D6, and 2E1 failed to give any detectable hydroxylated metabolite under identical conditions. P450 2C9 was found to be much more efficient for diclofenac hydroxylation than all the other P450s tested (k(cat)/K(M) of 1.6 min(-1) microM(-1) instead of 0.025 for the second more active P450), mainly because of markedly lower K(M) values (15 +/- 8 instead of values between 170 and 630 microM). Oxidation of diclofenac with chemical model systems of cytochrome P450 based on iron porphyrin catalysts exclusively led to the quinone imine derived from two-electron oxidation of 5-OHD, in an almost quantitative yield. Two derivatives of diclofenac lacking its COO(-) function were then synthesized; their oxidation by recombinant human P450 2Cs always led to a major product coming from their 5-hydroxylation. Substrate 2, which derives from reduction of the COO(-) function of diclofenac to the CH(2)OH function, was studied in more detail. All the P450s tested (1A1, 1A2, 2C8, 2C9, 2C18, 2C19, 2D6, and 3A4) almost exclusively led to its 5-hydroxylation. P450s of the 2C subfamily were found to be the most efficient catalysts for this reaction, with k(cat)/K(M) values between 0.2 and 1.6 min(-1) microM(-1). Oxidation of 2 with an iron porphyrin-based chemical model of cytochrome P450 also led to a product derived from the oxidation of 2 at position 5. These results show that oxidation of diclofenac and its derivative 2, either with chemical model systems of cytochrome P450 or with recombinant human P450s, generally occurs at position 5. This position, para to the NH group on the more electron-rich aromatic ring of diclofenac derivatives, is thus, as expected, the privileged site of reaction of electrophilic, oxidant species. The most spectacular exception to this chemoselective 5-oxidation of diclofenac derivatives was found for oxidation of diclofenac itself with P450 2C9 (and P450 2C19 and 2C18 to a lesser extent), which only led to 4'-OHD. A likely explanation for this result is a strict positioning of diclofenac in the P450 2C9 active site, via its COO(-) function, to completely orientate its hydroxylation toward position 4', which is not chemically preferred. P450 2C19, 2C18, and 2C8 would not lead to such a strict positioning as they give mixtures of 4'-OHD and 5-OHD. The above results show that diclofenac derivatives are interesting tools to compare the active site topologies of human P450 2Cs.
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Affiliation(s)
- A Mancy
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris V, Paris, France
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