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Shi M, Lv Y, Wu G, Cho J, Abid M, Hung KM, Coileáin CÓ, Chang CR, Wu HC. Band Alignment Transition and Enhanced Performance in Vertical SnS 2/MoS 2 van der Waals Photodetectors. ACS Appl Mater Interfaces 2024; 16:22622-22631. [PMID: 38625091 DOI: 10.1021/acsami.4c00781] [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: 04/17/2024]
Abstract
The strong light-matter interaction and naturally passivated surfaces of van der Waals materials make heterojunctions of such materials ideal candidates for high-performance photodetectors. In this study, we fabricated SnS2/MoS2 van der Waals heterojunctions and investigated their photoelectric properties. Using an applied gate voltage, we can effectively alter the band arrangement and achieve a transition in type II and type I junctions. It is found that the SnS2/MoS2 van der Waals heterostructures are type II heterojunctions when the gate voltage is above -25 V. Below this gate voltage, the heterojunctions become type I. Photoelectric measurements under various wavelengths of incident light reveal enhanced sensitivity in the ultraviolet region and a broadband sensing range from 400 to 800 nm. Moreover, due to the transition from type II to type I band alignment, the measured photocurrent saturates at a specific gate voltage, and this value depends crucially on the bias voltage and light wavelength, providing a potential avenue for designing compact spectrometers.
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Affiliation(s)
- Mingyu Shi
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yanhui Lv
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Jiung Cho
- Western Seoul Center, Korea Basic Science Institute, Seoul 03579, Republic of Korea
- Department of Materials Science and Engineering, Hongik University, Sejong 30016, Republic of Korea
| | - Mohamed Abid
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan, ROC
| | - Cormac Ó Coileáin
- Institute of Physics, EIT 2, Faculty of Electrical Engineering and Information Technology, University of the Bundeswehr Munich, Neubiberg 85577, Germany
| | - Ching-Ray Chang
- Quantum Information Center, Chung Yuan Christian University, Taoyuan 32023, Taiwan, ROC
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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2
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Cao Z, Zhao Y, Wu G, Cho J, Abid M, Choi M, Ó Coileáin C, Hung KM, Chang CR, Wu HC. Enhanced NO 2 Sensitivity of Vertically Stacked van der Waals Heterostructure Gas Sensor and Its Remarkable Electric and Mechanical Tunability. ACS Appl Mater Interfaces 2024; 16:9495-9505. [PMID: 38334441 DOI: 10.1021/acsami.3c17194] [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: 02/10/2024]
Abstract
Nanodevices based on van der Waals heterostructures have been predicted, and shown, to have unprecedented operational principles and functionalities that hold promise for highly sensitive and selective gas sensors with rapid response times and minimal power consumption. In this study, we fabricated gas sensors based on vertical MoS2/WS2 van der Waals heterostructures and investigated their gas sensing capabilities. Compared with individual MoS2 or WS2 gas sensors, the MoS2/WS2 van der Waals heterostructure gas sensors are shown to have enhanced sensitivity, faster response times, rapid recovery, and a notable selectivity, especially toward NO2. In combination with a theoretical model, we show that it is important to take into account created trapped states (flat bands) induced by the adsorption of gas molecules, which capture charges and alter the inherent built-in potential of van der Waals heterostructure gas sensors. Additionally, we note that the performance of these MoS2/WS2 heterostructure gas sensors could be further enhanced using electrical gating and mechanical strain. Our findings highlight the importance of understanding the effects of altered built-in potentials arising from gas molecule adsorption induced flat bands, thus offering a way to enhance the gas sensing performance of van der Waals heterostructure gas sensors.
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Affiliation(s)
- Ze Cao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yue Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Jiung Cho
- Western Seoul Center, Korea Basic Science Institute, Seoul 03579, Republic of Korea
- Department of Advanced Materials Engineering, Chung-Ang University, 4726, Seodong-daero, Daedeok-myeon, Anseong-si, Gyeonggi-do 17546, Republic of Korea
| | - Mohamed Abid
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Miri Choi
- Chuncheon Center, Korea Basic Science Institute, Chuncheon 24341, Republic of Korea
| | - Cormac Ó Coileáin
- Institute of Physics, Faculty of Electrical Engineering and Information Technology, University of the Bundeswehr Munich, Neubiberg 85577, Germany
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan, ROC
| | - Ching-Ray Chang
- Quantum information center, Chung Yuan Christian University, Taoyuan 32023, Taiwan, ROC
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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3
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Wu G, Abid M, Zerara M, Cho J, Choi M, Ó Coileáin C, Hung KM, Chang CR, Shvets IV, Wu HC. Miniaturized spectrometer with intrinsic long-term image memory. Nat Commun 2024; 15:676. [PMID: 38263315 PMCID: PMC10805890 DOI: 10.1038/s41467-024-44884-1] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 01/09/2024] [Indexed: 01/25/2024] Open
Abstract
Miniaturized spectrometers have great potential for use in portable optoelectronics and wearable sensors. However, current strategies for miniaturization rely on von Neumann architectures, which separate the spectral sensing, storage, and processing modules spatially, resulting in high energy consumption and limited processing speeds due to the storage-wall problem. Here, we present a miniaturized spectrometer that utilizes a single SnS2/ReSe2 van der Waals heterostructure, providing photodetection, spectrum reconstruction, spectral imaging, long-term image memory, and signal processing capabilities. Interface trap states are found to induce a gate-tunable and wavelength-dependent photogating effect and a non-volatile optoelectronic memory effect. Our approach achieves a footprint of 19 μm, a bandwidth from 400 to 800 nm, a spectral resolution of 5 nm, and a > 104 s long-term image memory. Our single-detector computational spectrometer represents a path beyond von Neumann architectures.
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Affiliation(s)
- Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing, 100081, P. R. China
| | - Mohamed Abid
- School of Physics, Beijing Institute of Technology, Beijing, 100081, P. R. China
| | | | - Jiung Cho
- Western Seoul Cente, Korea Basic Science Institute, Seoul, 03579, Republic of Korea
- Department of Advanced Materials Engineering, Chung-Ang University, 4726, Seodong-daero, Daedeok-myeon, Anseong-si, Gyeonggi-do, 17546, Republic of Korea
| | - Miri Choi
- Chuncheon Center, Korea Basic Science Institute, Chuncheon, 24341, Republic of Korea
| | - Cormac Ó Coileáin
- Institute of Physics, Faculty of Electrical Engineering and Information Technology, University of the Bundeswehr Munich, Neubiberg, 85577, Germany
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 807, Taiwan, ROC
| | - Ching-Ray Chang
- Quantum Information Center, Chung Yuan Christian University, Taoyuan, 32023, Taiwan, ROC
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan, ROC
| | - Igor V Shvets
- School of Physics, Trinity College Dublin, Dublin, Dublin 2, Ireland
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing, 100081, P. R. China.
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4
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Zhao Y, Wu G, Hung KM, Cho J, Choi M, Ó Coileáin C, Duesberg GS, Ren XK, Chang CR, Wu HC. Field Effect Transistor Gas Sensors Based on Mechanically Exfoliated Van der Waals Materials. ACS Appl Mater Interfaces 2023; 15:17335-17343. [PMID: 36972407 DOI: 10.1021/acsami.2c23086] [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: 06/18/2023]
Abstract
The high surface-to-volume ratio and flatness of mechanically exfoliated van der Waals (vdW) layered materials make them an ideal platform to investigate the Langmuir absorption model. In this work, we fabricated field effect transistor gas sensors, based on a variety of mechanically exfoliated vdW materials, and investigated their electrical field-dependent gas sensing properties. The good agreement between the experimentally extracted intrinsic parameters, such as equilibrium constant and adsorption energy, and theoretically predicted values suggests validity of the Langmuir absorption model for vdW materials. Moreover, we show that the device sensing behavior depends crucially on the availability of carriers, and giant sensitivities and strong selectivity can be achieved at the sensitivity singularity. Finally, we demonstrate that such features provide a fingerprint for different gases to quickly detect and differentiate between low concentrations of mixed hazardous gases using sensor arrays.
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Affiliation(s)
- Yue Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan 807, ROC
| | - Jiung Cho
- Western Seoul Center, Korea Basic Science Institute, Seoul 03579, Republic of Korea
| | - Miri Choi
- Chuncheon Center, Korea Basic Science Institute, Chuncheon 24341, Republic of Korea
| | - Cormac Ó Coileáin
- Institute of Physics, Faculty of Electrical Engineering and Information Technology (EIT 2) and Center for Integrated Sensor Systems, University of the Bundeswehr Munich, Neubiberg 85577, Germany
| | - Georg S Duesberg
- Institute of Physics, Faculty of Electrical Engineering and Information Technology (EIT 2) and Center for Integrated Sensor Systems, University of the Bundeswehr Munich, Neubiberg 85577, Germany
| | - Xiang-Kui Ren
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Ching-Ray Chang
- Quantum Information Center, Chung Yuan Christian University, Taoyuan, Taiwan 32023, ROC
- Department of Physics, National Taiwan University, Taipei, Taiwan 106, ROC
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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5
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Zhao Y, Cho J, Choi M, Ó Coileáin C, Arora S, Hung KM, Chang CR, Abid M, Wu HC. Light-Tunable Polarity and Erasable Physisorption-Induced Memory Effect in Vertically Stacked InSe/SnS 2 Self-Powered Photodetector. ACS Nano 2022; 16:17347-17355. [PMID: 36153977 DOI: 10.1021/acsnano.2c08177] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
van der Waals heterojunctions with tunable polarity are being actively explored for more Moore and more-than-Moore device applications, as they can greatly simplify circuit design. However, inadequate control over the multifunctional operational states is still a challenge in their development. Here, we show that a vertically stacked InSe/SnS2 van der Waals heterojunction exhibits type-II band alignment, and its polarity can be tuned by an external electric field and by the wavelength and intensity of an illuminated light source. Moreover, such SnS2/InSe diodes are self-powered broadband photodetectors with good performance. The self-powered performance can be further enhanced significantly with gas adsorption, and the device can be quickly restored to the state before gas injection using a gate voltage pulse. Our results suggest a way to achieve and design multiple functions in a single device with multifield coupling of light, electrical field, gas, or other external stimulants.
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Affiliation(s)
- Yue Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P.R. China
| | - Jiung Cho
- Western Seoul Center, Korea Basic Science Institute, Seoul 03579, Republic of Korea
| | - Miri Choi
- Chuncheon Center, Korea Basic Science Institute, Chuncheon 24341, Republic of Korea
| | - Cormac Ó Coileáin
- Institute of Physics, EIT 2, Faculty of Electrical Engineering and Information Technology, University of the Bundeswehr Munich, Neubiberg 85577, Germany
| | - Sunil Arora
- Centre for Nanoscience and Nanotechnology, Panjab University, Chandigarh 160014, India
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan, ROC
| | - Ching-Ray Chang
- Quantum information center, Chung Yuan Christian University, Taoyuan 32023, Taiwan, ROC
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Mohamed Abid
- School of Physics, Beijing Institute of Technology, Beijing 100081, P.R. China
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P.R. China
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6
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Wu G, Chung HS, Bae TS, Cho J, Lee KC, Cheng HH, Coileáin CÓ, Hung KM, Chang CR, Wu HC. Efficient Suppression of Charge Recombination in Self-Powered Photodetectors with Band-Aligned Transferred van der Waals Metal Electrodes. ACS Appl Mater Interfaces 2021; 13:61799-61808. [PMID: 34927430 DOI: 10.1021/acsami.1c20499] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Recombination of photogenerated electron-hole pairs dominates the photocarrier lifetime and then influences the performance of photodetectors and solar cells. In this work, we report the design and fabrication of band-aligned van der Waals-contacted photodetectors with atomically sharp and flat metal-semiconductor interfaces through transferred metal integration. A unity factor α is achieved, which is essentially independent of the wavelength of the light, from ultraviolet to near-infrared, indicating effective suppression of charge recombination by the device. The short-circuit current (0.16 μA) and open-circuit voltage (0.72 V) of the band-aligned van der Waals-contacted devices are at least 1 order of magnitude greater than those of band-aligned deposited devices and 2 orders of magnitude greater than those of non-band-aligned deposited devices. High responsivity, detectivity, and polarization sensitivity ratio of 283 mA/W, 6.89 × 1012 cm Hz1/2 W-1, and 3.05, respectively, are also obtained for the device at zero bias. Moreover, the efficient suppression of charge recombination in our air-stable self-powered photodetectors also results in a fast response speed and leads to polarization-sensitive performance.
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Affiliation(s)
- Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Hee-Suk Chung
- Jeonju Center, Korea Basic Science Institute, Jeonju 54896, Republic of Korea
| | - Tae-Sung Bae
- Jeonju Center, Korea Basic Science Institute, Jeonju 54896, Republic of Korea
| | - Jiung Cho
- Western Seoul Center, Korea Basic Science Institute, Seoul 03579, Republic of Korea
| | - Kuo-Chih Lee
- Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Hung Hsiang Cheng
- Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Cormac Ó Coileáin
- Institute of Physics, EIT 2, Faculty of Electrical Engineering and Information Technology, Universität der Bundeswehr München, Neubiberg 85579, Germany
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan, ROC
| | - Ching-Ray Chang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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7
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Zhao Y, Tsai TY, Wu G, Ó Coileáin C, Zhao YF, Zhang D, Hung KM, Chang CR, Wu YR, Wu HC. Graphene/SnS 2 van der Waals Photodetector with High Photoresponsivity and High Photodetectivity for Broadband 365-2240 nm Detection. ACS Appl Mater Interfaces 2021; 13:47198-47207. [PMID: 34546715 DOI: 10.1021/acsami.1c11534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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 fabrication of graphene/SnS2 van der Waals photodetectors and their photoelectrical properties are systematically investigated. It was found that a dry transferred graphene/SnS2 van der Waals heterostructure had a broadband sensing range from ultraviolet (365 nm) to near-infrared (2.24 μm) and respective improved responsivities and photodetectivities of 7.7 × 103 A/W and 8.9 × 1013 jones at 470 nm and 2 A/W and 1.8 × 1010 jones at 1064 nm. Moreover, positive and negative photoconductance effects were observed when the photodetectors were illuminated by photon sources with energies greater and smaller than the bandgap of SnS2, respectively. The photoresponsivity (R) versus incident power density (P) follows the empirical law R ∝ Pinβ, with β > -1 for positive photoconductance effects and β < -1 for negative photoconductance effects. On the basis of the Fowler-Nordheim tunneling model and a Poisson and drift-diffusion simulation, we show quantitatively that the barrier height and barrier width of the heterostructure photodetector could be controlled by a laser and an external electrical field through a photogating effect generated by carriers trapped at the interface, which could be used to tune the separation and transport of photogenerated carriers. Our results may be useful for the design of high performance van der Waals heterojunction photodetectors.
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Affiliation(s)
- Yue Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Tsung-Yin Tsai
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Cormac Ó Coileáin
- Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bioengineering Research (AMBER), School Chemistry, Trinity College, Dublin, Ireland
| | - Yan-Feng Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Duan Zhang
- Elementary Educational College, Beijing key Laboratory for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing 100048, P. R. China
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan
| | - Ching-Ray Chang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Yuh-Renn Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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8
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Yan W, Fuh HR, Lv Y, Chen KQ, Tsai TY, Wu YR, Shieh TH, Hung KM, Li J, Zhang D, Ó Coileáin C, Arora SK, Wang Z, Jiang Z, Chang CR, Wu HC. Giant gauge factor of Van der Waals material based strain sensors. Nat Commun 2021; 12:2018. [PMID: 33795697 PMCID: PMC8016834 DOI: 10.1038/s41467-021-22316-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 03/10/2021] [Indexed: 02/07/2023] Open
Abstract
There is an emergent demand for high-flexibility, high-sensitivity and low-power strain gauges capable of sensing small deformations and vibrations in extreme conditions. Enhancing the gauge factor remains one of the greatest challenges for strain sensors. This is typically limited to below 300 and set when the sensor is fabricated. We report a strategy to tune and enhance the gauge factor of strain sensors based on Van der Waals materials by tuning the carrier mobility and concentration through an interplay of piezoelectric and photoelectric effects. For a SnS2 sensor we report a gauge factor up to 3933, and the ability to tune it over a large range, from 23 to 3933. Results from SnS2, GaSe, GeSe, monolayer WSe2, and monolayer MoSe2 sensors suggest that this is a universal phenomenon for Van der Waals semiconductors. We also provide proof of concept demonstrations by detecting vibrations caused by sound and capturing body movements.
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Affiliation(s)
- Wenjie Yan
- School of Physics, Beijing Institute of Technology, Beijing, P. R. China
| | - Huei-Ru Fuh
- Department of Physics, National Taiwan University, Taipei, Taiwan
- Department of Chemical Engineering & Materials Science, Yuan Ze University, Taoyuan City, Taiwan
| | - Yanhui Lv
- School of Physics, Beijing Institute of Technology, Beijing, P. R. China
| | - Ke-Qiu Chen
- Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha, P. R. China
| | - Tsung-Yin Tsai
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan
| | - Yuh-Renn Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan
| | - Tung-Ho Shieh
- Department of Intelligent Robotics Engineering, Kun-Shan University, Tainan, Taiwan
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan.
| | - Juncheng Li
- School of Physics, Beijing Institute of Technology, Beijing, P. R. China
| | - Duan Zhang
- Elementary Educational College, Beijing key Laboratory for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing, P. R. China
| | - Cormac Ó Coileáin
- Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bioengineering Research (AMBER), School Chemistry, Trinity College Dublin, Dublin, Ireland
| | - Sunil K Arora
- Centre for Nanoscience and Nanotechnology, Panjab University, Chandigarh, India
| | - Zhi Wang
- School of Physics, Beijing Institute of Technology, Beijing, P. R. China
| | - Zhaotan Jiang
- School of Physics, Beijing Institute of Technology, Beijing, P. R. China
| | - Ching-Ray Chang
- Department of Physics, National Taiwan University, Taipei, Taiwan
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing, P. R. China.
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9
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Yan W, Lv C, Zhang D, Chen Y, Zhang L, Ó Coileáin C, Wang Z, Jiang Z, Hung KM, Chang CR, Wu HC. Enhanced NO 2 Sensitivity in Schottky-Contacted n-Type SnS 2 Gas Sensors. ACS Appl Mater Interfaces 2020; 12:26746-26754. [PMID: 32426961 DOI: 10.1021/acsami.0c07193] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Layered materials are highly attractive in gas sensor research due to their extraordinary electronic and physicochemical properties. The development of cheaper and faster room-temperature detectors with high sensitivities especially in the parts per billion level is the main challenge in this rapidly developing field. Here, we show that sensitivity to NO2 (S) can be greatly improved by at least two orders of magnitude using an n-type electrode metal. Unconventionally for such devices, the ln(S) follows the classic Langmuir isotherm model rather than S as is for a p-type electrode metal. Excellent device sensitivities, as high as 13,000% for 9 ppm and 97% for 1 ppb NO2, are achieved with Mn electrodes at room temperature, which can be further tuned and enhanced with the application of a bias. Long-term stability, fast recovery, and strong selectivity toward NO2 are also demonstrated. Such impressive features provide a real solution for designing a practical high-performance layered material-based gas sensor.
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Affiliation(s)
- Wenjie Yan
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Chengzhai Lv
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Duan Zhang
- Elementary Educational College, Beijing key Laboratory for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing 100048, P. R. China
| | - Yanhui Chen
- Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing, 100124, China
| | - Lei Zhang
- Foshan (Southern China) Institute for New Materials, Guangdong 528000, China
| | - Cormac Ó Coileáin
- CRANN and AMBER, School of Chemistry, Trinity College, Dublin Dublin 2, Ireland
| | - Zhi Wang
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Zhaotan Jiang
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan, ROC
| | - Ching-Ray Chang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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10
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Lv C, Yan W, Shieh TH, Zhao Y, Wu G, Zhao Y, Lv Y, Zhang D, Chen Y, Arora SK, Ó Coileáin C, Chang CR, Cheng HH, Hung KM, Wu HC. Electrical Contact Barriers between a Three-Dimensional Metal and Layered SnS 2. ACS Appl Mater Interfaces 2020; 12:15830-15836. [PMID: 32134622 DOI: 10.1021/acsami.9b21996] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Field-effect transistors derived from traditional 3D semiconductors are rapidly approaching their fundamental limits. Layered semiconducting materials have emerged as promising candidates to replace restrictive 3D semiconductor materials. However, contacts between metals and layered materials deviate from Schottky-Mott behavior when determined by transport methods, while X-ray photoelectron spectroscopy measurements suggest that the contacts should be at the Schottky limit. Here, we present a systematic investigation on the influence of metal selection when electrically contacting SnS2, a layered metal dichalcogenide semiconductor with the potential to replace silicon. It is found that the electrically measured barrier height depends also weakly on the work function of the metal contacts with slopes of 0.09 and -0.34 for n-type and p-type Schottky contacts, respectively. Based on the Kirchhoff voltage law and considering a current path induced by metallic defects, we found that the Schottky barrier still follows the Schottky-Mott limits and the electrically measured barrier height mainly originates from the van der Waals gap between the metal and SnS2, and the slope depends on the magnitude of the van der Waals capacitance.
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Affiliation(s)
- Chengzhai Lv
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Wenjie Yan
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Tung-Ho Shieh
- Department of Computer and Communication, Kun Shan University, Tainan 710, Taiwan, ROC
| | - Yue Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Gang Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yanfeng Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yanhui Lv
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Duan Zhang
- Elementary Educational College, Beijing key Laboratory for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing 100048, P. R. China
| | - Yanhui Chen
- Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China
| | - Sunil K Arora
- Centre for Nano Science and Nano Technology, Panjab University, Chandigarh 160014, India
| | - Cormac Ó Coileáin
- AMBER and CRANN, School of Chemistry, Trinity College Dublin, Dublin 2, Ireland
| | - Ching-Ray Chang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Hung Hsiang Cheng
- Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Kuan-Ming Hung
- Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan, ROC
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
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Hung KM. Alteration of imaging properties of an optical pickup's objective lens by a nonrotationally symmetric coating. Appl Opt 2000; 39:4013-4020. [PMID: 18349983 DOI: 10.1364/ao.39.004013] [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: 05/26/2023]
Abstract
One can control the aberrations of an optical readout system by varying the width of a strip of antireflection coatings deposited upon plastic objective lenses. It is found that one can control the magnitude of the third-order astigmatism of the system by changing the coating width. This process has the advantage that it does not significantly cause other kinds of aberration such as coma and spherical aberrations to deteriorate. When these nonrotational symmetrically (NRS) coated lenses are used for off-axis operations such as tracking movements in optical drives, the change in the magnitude of the astigmatism (DAS) that is generated can be made smaller than those of symmetrically coated or noncoated lenses. As much as a 73% decrease in DAS was observed experimentally with a NRS-coated lens. Including the birefringence of the plastic material in the analysis yields a low and constant level of astigmatism generated by shifting of the objective lens.
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Affiliation(s)
- K M Hung
- Components R&D Division, Sony Precision Engineering Center(S) PteLtd, 52 Tuas Avenue 9, Singapore.
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Hung KM. Effects of an asymmetrically molded plastic objective lens on the push-pull tracking-error signal in an optical disk drive. Appl Opt 2000; 39:1309-1314. [PMID: 18338015 DOI: 10.1364/ao.39.001309] [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: 05/26/2023]
Abstract
The effects of a plastic objective lens's astigmatism on the push-pull tracking-error signal (TES) of an optical disk data storage system were investigated theoretically and experimentally. Astigmatism of plastic objective lenses arises commonly from the asymmetric deviation from their designed shape during the molding process. By carefully studying the aberration characteristics of the objective lens and including the astigmatism of the laser diode in the analysis, we can calculate the combined effects of astigmatism of these two components on the push-pull TES. It is found, from both the simulations and the experiments, that, by rotation of the objective lens about the optical axis, the peak-to-peak value of the push-pull TES varies with the lens's rotation angle, and a change as great as 340% in its value was observed in a given optical pickup.
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Affiliation(s)
- K M Hung
- Components Research and Development Division, Sony Precision Engineering Center S Pte Ltd, 52 Tuas Avenue 9, 639193, Singapore.
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Wong MH, Hung KM, Chiu ST. Sludge-Grown Algae for Culturing Aquatic Organisms: Part II. Sludge-Grown Algae as Feeds for Aquatic Organisms. Environ Manage 1996; 20:375-384. [PMID: 8661608 DOI: 10.1007/bf01203845] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This project investigated the feasibility of using sewage sludge to culture microalgae (Chlorella-HKBU) and their subsequent usage as feeds for rearing different organisms. Part II of the project evaluated the results of applying the sludge-grown algae to feed Oreochromis mossambicus (fish), Macrobrachium hainenese (shrimp), and Moina macrocopa (cladocera). In general, the yields of the cultivated organisms were unsatisfactory when they were fed the sludge-grown algae directly. The body weights of O. mossambicus and M. macrocopa dropped 21% and 37%, respectively, although there was a slight increase (4.4%) in M. hainenese. However, when feeding the algal-fed cladocerans to fish and shrimp, the body weights of the fish and shrimp were increased 7% and 11% accordingly. Protein contents of the cultivated organisms were comparable to the control diet, although they contained a rather high amount of heavy metals. When comparing absolute heavy metal contents in the cultivated organisms, the following order was observed: alga > cladocera > shrimp, fish > sludge extracts. Bioelimination of heavy metals may account for the decreasing heavy metal concentrations in higher trophic organisms.
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Affiliation(s)
- MH Wong
- Department of Biology & Centre for Waste Recycling and Environmental Biotechnology, Hong Kong Baptist University, Kowloon Tong, Hong Kong
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Hung KM, Chiu ST, Wong MH. Sludge-Grown Algae for Culturing Aquatic Organisms: Part I. Algal Growth in Sludge Extracts. Environ Manage 1996; 20:361-374. [PMID: 8661607 DOI: 10.1007/bf01203844] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This project is aimed at studying the feasibility of using sewage sludge to prepare culture media for microalgae (Chlorella-HKBU) and the use of the sludge-grown algae as a feed for some aquatic organisms. Part I of the project included results on preparing sludge extracts and their use on algal culture. By comparing two culturing techniques, "aeration" and "shaking," it was noted that both lag and log phases were shortened in the aeration system. A subsequent experiment noted that algal growth subject to aeration rates of 1.0 and 1.5 liters/min had similar lag and log phases. In addition, both aeration rates had a significantly higher (P<0.05) final cell density than that of 0.5 liters/min. A detailed study on the variation of growth conditions on the algal growth was done. The results indicated that pH values of all the cultures declined below 5 at day 12. The removal rates of ammonia N ranged from 62% to 70%. The sludge-grown algae contained a rather substantial amount of heavy metals (&mgr;g/g): Zn 289-581, Cu 443-682, Ni 310-963, Mn 96-126, Cr 25-118, and Fe 438-653. This implied that the rather high levels of heavy metals may impose adverse effects on higher trophic organisms.
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Affiliation(s)
- KM Hung
- Department of Biology & Centre for Waste Recycling and Environmental Biotechnology, Hong Kong Baptist University, Kowloon Tong, Hong Kong
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Abstract
Histamine and serotonin levels in gastric secretion and the effects of pharmacological antagonists were studied in rats in which stomach ulceration was induced by electrical vagal stimulation. Electrical vagal stimulation (2 and 5 V) produced a graded increase in haemorrhagic glandular mucosal ulcers. NaHCO3 perfusion completely neutralised the increased acid output but failed to prevent ulceration. Atropine inhibited gastric mast cell degranulation as well as histamine and serotonin release. Diphenhydramine, atropine and sub-diaphragmatic vagotomy antagonised the increase in intragastric pressure. Diphenhydramine, cimetidine, atropine or vagotomy but not methysergide reduced ulcer severity. It is concluded that gastric acid and serotonin do not play an important role in glandular ulceration induced by electrical vagal stimulation. The lesions probably result from increased intragastric pressure and release of gastric histamine which stimulates H1 and H2 receptors in the stomach. The similarities between the aetiologies of glandular ulcers due to electrical vagal stimulation and to stress are also discussed.
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