Bo Lei
Position: Grad Students
Research Type: Experiment
Email: a0129479@u.nus.edu
Contact: tel:(65) 8671 1738
Group: Prof Chen Wei
CA2DM Publications:
2019 |
Guo, Rui; Li, Qiang; Zheng, Yue; Lei, Bo; Sun, Haicheng; Hu, Zehua; Zhang, Jialin; Wang, Li; Longhi, Elena; Barlow, Stephen; Marder, Seth R; Wang, Jinlan; Chen, Wei Degenerate electron-doping in two-dimensional tungsten diselenide with a dimeric organometallic reductant Journal Article MATERIALS TODAY, 30 , pp. 26-33, 2019, ISSN: 1369-7021. @article{ISI:000496248100014, title = {Degenerate electron-doping in two-dimensional tungsten diselenide with a dimeric organometallic reductant}, author = {Rui Guo and Qiang Li and Yue Zheng and Bo Lei and Haicheng Sun and Zehua Hu and Jialin Zhang and Li Wang and Elena Longhi and Stephen Barlow and Seth R Marder and Jinlan Wang and Wei Chen}, doi = {10.1016/j.mattod.2019.04.017}, times_cited = {0}, issn = {1369-7021}, year = {2019}, date = {2019-11-01}, journal = {MATERIALS TODAY}, volume = {30}, pages = {26-33}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {The large Schottky barriers formed at metal-semiconductor junctions severely limit the development of transition metal dichalcogenide (TMDC)-based ultrathin electronics and optoelectronics. Various approaches to create Ohmic contacts at TMDC and metal interface have been developed, including contact phase engineering, contact doping, buffer layer engineering, and contact integration engineering. Here, we report degenerate electron doping of mono- and bi-layer tungsten diselenide (WSe2) by a molecular organometallic donor, [RuCp*(mes)](2). In-situ evaporation of [RuCp*(mes)](2) molecules onto WSe2 field-effect transistors in vacuum leads to a remarkably diminished gate dependence of the transport property and a large enhancement of electrical conductance by five orders of magnitude, implying the great potential of this doping approach in tuning the Schottky barrier for TMDC devices. The interfacial electronic structure at the WSe2-dopant interface was revealed through the combination of in-situ photoelectron spectroscopy investigations and theoretical calculations. Moreover, the doped device is found to be robust in oxygen and nitrogen atmosphere and also moderately stable in humid air, which is favorable in device applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The large Schottky barriers formed at metal-semiconductor junctions severely limit the development of transition metal dichalcogenide (TMDC)-based ultrathin electronics and optoelectronics. Various approaches to create Ohmic contacts at TMDC and metal interface have been developed, including contact phase engineering, contact doping, buffer layer engineering, and contact integration engineering. Here, we report degenerate electron doping of mono- and bi-layer tungsten diselenide (WSe2) by a molecular organometallic donor, [RuCp*(mes)](2). In-situ evaporation of [RuCp*(mes)](2) molecules onto WSe2 field-effect transistors in vacuum leads to a remarkably diminished gate dependence of the transport property and a large enhancement of electrical conductance by five orders of magnitude, implying the great potential of this doping approach in tuning the Schottky barrier for TMDC devices. The interfacial electronic structure at the WSe2-dopant interface was revealed through the combination of in-situ photoelectron spectroscopy investigations and theoretical calculations. Moreover, the doped device is found to be robust in oxygen and nitrogen atmosphere and also moderately stable in humid air, which is favorable in device applications. |
Lei, Bo; Zheng, Yue; Hu, Zehua; Guo, Rui; Xiang, Du; Liu, Tao; Wang, Yanan; Lai, Min; Hes, Jun; Chen, Wei Nondestructive hole doping enabled photocurrent enhancement of layered tungsten diselenide Journal Article 2D MATERIALS, 6 (2), 2019, ISSN: 2053-1583. @article{ISI:000460066300001, title = {Nondestructive hole doping enabled photocurrent enhancement of layered tungsten diselenide}, author = {Bo Lei and Yue Zheng and Zehua Hu and Rui Guo and Du Xiang and Tao Liu and Yanan Wang and Min Lai and Jun Hes and Wei Chen}, doi = {10.1088/2053-1583/ab0708}, times_cited = {0}, issn = {2053-1583}, year = {2019}, date = {2019-04-01}, journal = {2D MATERIALS}, volume = {6}, number = {2}, publisher = {IOP PUBLISHING LTD}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {Atomically thin tungsten diselenide (WSe2) has emerged as a promising material for the next generation electronic and optoelectronic devices. Here, we report an enhancement of WSe2 photodetector performance via surface functionalization with molybdenum trioxide (MoO3). Strong hole doping from MoO3 to WSe2 was revealed by in situ field-effect transistor device evaluation, x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements. Moreover, the responsivity and external quantum efficiency of WSe2 photodetector increased around eight folders after the surface functionalization with MoO3. We attribute the enhanced performance to the narrowed Schottky barrier and the modulation of the trap states by surface functionalization.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Atomically thin tungsten diselenide (WSe2) has emerged as a promising material for the next generation electronic and optoelectronic devices. Here, we report an enhancement of WSe2 photodetector performance via surface functionalization with molybdenum trioxide (MoO3). Strong hole doping from MoO3 to WSe2 was revealed by in situ field-effect transistor device evaluation, x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements. Moreover, the responsivity and external quantum efficiency of WSe2 photodetector increased around eight folders after the surface functionalization with MoO3. We attribute the enhanced performance to the narrowed Schottky barrier and the modulation of the trap states by surface functionalization. |
2018 |
Hu, Zehua; Li, Qiang; Lei, Bo; Wu, Jing; Zhou, Qionghua; Gu, Chengding; Wen, Xinglin; Wang, Junyong; Liu, Yanpeng; Li, Shisheng; Zheng, Yue; Lu, Junpeng; He, Jun; Wang, Li; Xiong, Qihua; Wang, Jinlan; Chen, Wei Abnormal Near-Infrared Absorption in 2D Black Phosphorus Induced by Ag Nanoclusters Surface Functionalization Journal Article ADVANCED MATERIALS, 30 (43), 2018, ISSN: 0935-9648. @article{ISI:000448786000009, title = {Abnormal Near-Infrared Absorption in 2D Black Phosphorus Induced by Ag Nanoclusters Surface Functionalization}, author = {Zehua Hu and Qiang Li and Bo Lei and Jing Wu and Qionghua Zhou and Chengding Gu and Xinglin Wen and Junyong Wang and Yanpeng Liu and Shisheng Li and Yue Zheng and Junpeng Lu and Jun He and Li Wang and Qihua Xiong and Jinlan Wang and Wei Chen}, doi = {10.1002/adma.201801931}, times_cited = {0}, issn = {0935-9648}, year = {2018}, date = {2018-10-25}, journal = {ADVANCED MATERIALS}, volume = {30}, number = {43}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {Black phosphorus (BP), as a fast emerging 2D material, shows promising potential in near-infrared (NIR) photodetection owing to its relatively small direct thickness-dependent bandgaps. However, the poor NIR absorption due to the atomically thin nature strongly hinders the practical application. In this study, it is demonstrated that surface functionalization of Ag nanoclusters on 2D BP can induce an abnormal NIR absorption at approximate to 746 nm, leading to approximate to 35 (138) times enhancement in 808 (730) nm NIR photoresponse for BP-based field-effect transistors. First-principles calculations reveal that localized bands are introduced into the bandgap of BP, serving as the midgap states, which create new transitions to the conduction band of BP and eventually lead to the abnormal absorption. This work provides a simple yet effective method to dramatically increase the NIR absorption of BP, which is crucial for developing high-performance NIR optoelectronic devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Black phosphorus (BP), as a fast emerging 2D material, shows promising potential in near-infrared (NIR) photodetection owing to its relatively small direct thickness-dependent bandgaps. However, the poor NIR absorption due to the atomically thin nature strongly hinders the practical application. In this study, it is demonstrated that surface functionalization of Ag nanoclusters on 2D BP can induce an abnormal NIR absorption at approximate to 746 nm, leading to approximate to 35 (138) times enhancement in 808 (730) nm NIR photoresponse for BP-based field-effect transistors. First-principles calculations reveal that localized bands are introduced into the bandgap of BP, serving as the midgap states, which create new transitions to the conduction band of BP and eventually lead to the abnormal absorption. This work provides a simple yet effective method to dramatically increase the NIR absorption of BP, which is crucial for developing high-performance NIR optoelectronic devices. |
Gong, Lili; Zhang, Qi; Wang, Liangjun; Wu, Jianfeng; Han, Cheng; Lei, Bo; Chen, Wei; Eda, Goki; Goh, Kuan Eng Johnson; Sow, Chorng Haur Emergence of photoluminescence on bulk MoS2 by laser thinning and gold particle decoration Journal Article NANO RESEARCH, 11 (9), pp. 4574-4586, 2018, ISSN: 1998-0124. @article{ISI:000441237100010, title = {Emergence of photoluminescence on bulk MoS_{2} by laser thinning and gold particle decoration}, author = {Lili Gong and Qi Zhang and Liangjun Wang and Jianfeng Wu and Cheng Han and Bo Lei and Wei Chen and Goki Eda and Kuan Eng Johnson Goh and Chorng Haur Sow}, doi = {10.1007/s12274-018-2037-5}, times_cited = {0}, issn = {1998-0124}, year = {2018}, date = {2018-09-01}, journal = {NANO RESEARCH}, volume = {11}, number = {9}, pages = {4574-4586}, publisher = {TSINGHUA UNIV PRESS}, address = {B605D, XUE YAN BUILDING, BEIJING, 100084, PEOPLES R CHINA}, abstract = {We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoS2, photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl3 solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS2 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl3 treatment enables the functionalization of bulk MoS2 for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS2 flakes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoS2, photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl3 solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS2 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl3 treatment enables the functionalization of bulk MoS2 for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS2 flakes. |
Xiang, Du; Liu, Tao; Xu, Jilian; Tan, Jun Y; Hu, Zehua; Lei, Bo; Zheng, Yue; Wu, Jing; Neto, Castro A H; Liu, Lei; Chen, Wei Two-dimensional multibit optoelectronic memory with broadband spectrum distinction Journal Article 11 NATURE COMMUNICATIONS, 9 , 2018, ISSN: 2041-1723. @article{ISI:000439971400007, title = {Two-dimensional multibit optoelectronic memory with broadband spectrum distinction}, author = {Du Xiang and Tao Liu and Jilian Xu and Jun Y Tan and Zehua Hu and Bo Lei and Yue Zheng and Jing Wu and Castro A H Neto and Lei Liu and Wei Chen}, doi = {10.1038/s41467-018-05397-w}, times_cited = {11}, issn = {2041-1723}, year = {2018}, date = {2018-07-27}, journal = {NATURE COMMUNICATIONS}, volume = {9}, publisher = {NATURE PUBLISHING GROUP}, address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND}, abstract = {Optoelectronic memory plays a vital role in modern semiconductor industry. The fast emerging requirements for device miniaturization and structural flexibility have diverted research interest to two-dimensional thin layered materials. Here, we report a multibit nonvolatile optoelectronic memory based on a heterostructure of monolayer tungsten diselenide and few-layer hexagonal boron nitride. The tungsten diselenide/boron nitride memory exhibits a memory switching ratio approximately 1.1 x 10(6), which ensures over 128 (7 bit) distinct storage states. The memory demonstrates robustness with retention time over 4.5 x 10(4) s. Moreover, the ability of broadband spectrum distinction enables its application in filter-free color image sensor. This concept is further validated through the realization of integrated tungsten diselenide/boron nitride pixel matrix which captured a specific image recording the three primary colors (red, green, and blue). The heterostructure architecture is also applicable to other two-dimensional materials, which is confirmed by the realization of black phosphorus/boron nitride optoelectronic memory.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Optoelectronic memory plays a vital role in modern semiconductor industry. The fast emerging requirements for device miniaturization and structural flexibility have diverted research interest to two-dimensional thin layered materials. Here, we report a multibit nonvolatile optoelectronic memory based on a heterostructure of monolayer tungsten diselenide and few-layer hexagonal boron nitride. The tungsten diselenide/boron nitride memory exhibits a memory switching ratio approximately 1.1 x 10(6), which ensures over 128 (7 bit) distinct storage states. The memory demonstrates robustness with retention time over 4.5 x 10(4) s. Moreover, the ability of broadband spectrum distinction enables its application in filter-free color image sensor. This concept is further validated through the realization of integrated tungsten diselenide/boron nitride pixel matrix which captured a specific image recording the three primary colors (red, green, and blue). The heterostructure architecture is also applicable to other two-dimensional materials, which is confirmed by the realization of black phosphorus/boron nitride optoelectronic memory. |
Lei, Bo; Pan, Yuanyuan; Hu, Zehua; Zhang, Jialin; Xiang, Du; Zheng, Yue; Guo, Rui; Han, Cheng; Wang, Lianhui; Lu, Jing; Yang, Li; Chen, Wei Direct Observation of Semiconductor-Metal Phase Transition in Bilayer Tungsten Diselenide Induced by Potassium Surface Functionalization Journal Article ACS NANO, 12 (2), pp. 2070-+, 2018, ISSN: 1936-0851. @article{ISI:000426615600121, title = {Direct Observation of Semiconductor-Metal Phase Transition in Bilayer Tungsten Diselenide Induced by Potassium Surface Functionalization}, author = {Bo Lei and Yuanyuan Pan and Zehua Hu and Jialin Zhang and Du Xiang and Yue Zheng and Rui Guo and Cheng Han and Lianhui Wang and Jing Lu and Li Yang and Wei Chen}, doi = {10.1021/acsnano.8b00398}, times_cited = {0}, issn = {1936-0851}, year = {2018}, date = {2018-02-01}, journal = {ACS NANO}, volume = {12}, number = {2}, pages = {2070-+}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Structures determine properties of materials, and controllable phase transitions are, therefore, highly desirable for exploring exotic physics and fabricating devices. We report a direct observation of a controllable semiconductor-metal phase transition in bilayer tungsten diselenide (WSe2) with potassium (K) surface functionalization. Through the integration of in situ field-effect transistors, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy measurements, and first-principles calculations, we identify that the electron doping from K adatoms drives bilayer WSe2 from a 2H phase semiconductor to a IT' phase metal. The phase transition mechanism is satisfactorily explained by the electronic structures and energy alignment of the 2H and IT' phases. This explanation can be generally applied to understand doping-induced phase transitions in two-dimensional (2D) structures. Finally, the associated dramatic changes of electronic structures and electrical conductance make this controllable semiconductor-metal phase transition of interest for 2D semiconductor based electronic and optoelectronic devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Structures determine properties of materials, and controllable phase transitions are, therefore, highly desirable for exploring exotic physics and fabricating devices. We report a direct observation of a controllable semiconductor-metal phase transition in bilayer tungsten diselenide (WSe2) with potassium (K) surface functionalization. Through the integration of in situ field-effect transistors, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy measurements, and first-principles calculations, we identify that the electron doping from K adatoms drives bilayer WSe2 from a 2H phase semiconductor to a IT' phase metal. The phase transition mechanism is satisfactorily explained by the electronic structures and energy alignment of the 2H and IT' phases. This explanation can be generally applied to understand doping-induced phase transitions in two-dimensional (2D) structures. Finally, the associated dramatic changes of electronic structures and electrical conductance make this controllable semiconductor-metal phase transition of interest for 2D semiconductor based electronic and optoelectronic devices. |
2017 |
Song, Zhibo; Schultz, Thorsten; Ding, Zijing; Lei, Bo; Han, Cheng; Amsalem, Patrick; Lin, Tingting; Chi, Dongzhi; Wong, Swee Liang; Zheng, Yu Jie; Li, Ming-Yang; Li, Lain Jong; Chen, Wei; Koch, Norbert; Huang, Yu Li; Wee, Andrew Thye Shen Electronic Properties of a 1D Intrinsic/p-Doped Heterojunction in a 2D Transition Metal Dichalcogenide Semiconductor Journal Article ACS NANO, 11 (9), pp. 9128-9135, 2017, ISSN: 1936-0851. @article{ISI:000411918200061, title = {Electronic Properties of a 1D Intrinsic/p-Doped Heterojunction in a 2D Transition Metal Dichalcogenide Semiconductor}, author = {Zhibo Song and Thorsten Schultz and Zijing Ding and Bo Lei and Cheng Han and Patrick Amsalem and Tingting Lin and Dongzhi Chi and Swee Liang Wong and Yu Jie Zheng and Ming-Yang Li and Lain Jong Li and Wei Chen and Norbert Koch and Yu Li Huang and Andrew Thye Shen Wee}, doi = {10.1021/acsnano.7b03953}, times_cited = {5}, issn = {1936-0851}, year = {2017}, date = {2017-09-01}, journal = {ACS NANO}, volume = {11}, number = {9}, pages = {9128-9135}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Two-dimensional (2D) semiconductors offer a convenient platform to study 2D physics, for example, to understand doping in an atomically thin semiconductor. Here, we demonstrate the fabrication and unravel the electronic properties of a lateral doped/intrinsic heterojunction in a single-layer (SL) tungsten diselenide (WSe2), a prototype semiconducting transition metal dichalcogenide (TMD), partially covered with a molecular acceptor layer, on a graphite substrate. With combined experiments and theoretical modeling, we reveal the fundamental acceptor-induced p doping mechanism for SL-WSe2. At the 1D border between the doped and undoped SL-WSe2 regions, we observe band bending and explain it by Thomas Fermi screening. Using atomically resolved scanning tunneling microscopy and spectroscopy, the screening length is determined to be in the few manometer range, and we assess the carrier density of intrinsic SL-WSe2. These findings are of fundamental and technological importance for understanding and employing surface doping, for example, in designing lateral organic TMD heterostructures for future devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional (2D) semiconductors offer a convenient platform to study 2D physics, for example, to understand doping in an atomically thin semiconductor. Here, we demonstrate the fabrication and unravel the electronic properties of a lateral doped/intrinsic heterojunction in a single-layer (SL) tungsten diselenide (WSe2), a prototype semiconducting transition metal dichalcogenide (TMD), partially covered with a molecular acceptor layer, on a graphite substrate. With combined experiments and theoretical modeling, we reveal the fundamental acceptor-induced p doping mechanism for SL-WSe2. At the 1D border between the doped and undoped SL-WSe2 regions, we observe band bending and explain it by Thomas Fermi screening. Using atomically resolved scanning tunneling microscopy and spectroscopy, the screening length is determined to be in the few manometer range, and we assess the carrier density of intrinsic SL-WSe2. These findings are of fundamental and technological importance for understanding and employing surface doping, for example, in designing lateral organic TMD heterostructures for future devices. |
Hu, Zehua; Li, Qiang; Lei, Bo; Zhou, Qionghua; Xiang, Du; Lyu, Zhiyang; Hu, Fang; Wang, Junyong; Ren, Yinjuan; Guo, Rui; Goki, Eda; Wang, Li; Han, Cheng; Wang, Jinlan; Chen, Wei Water-Catalyzed Oxidation of Few-Layer Black Phosphorous in a Dark Environment Journal Article ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 56 (31), pp. 9131-9135, 2017, ISSN: 1433-7851. @article{ISI:000424260200035, title = {Water-Catalyzed Oxidation of Few-Layer Black Phosphorous in a Dark Environment}, author = {Zehua Hu and Qiang Li and Bo Lei and Qionghua Zhou and Du Xiang and Zhiyang Lyu and Fang Hu and Junyong Wang and Yinjuan Ren and Rui Guo and Eda Goki and Li Wang and Cheng Han and Jinlan Wang and Wei Chen}, doi = {10.1002/anie.201705012}, times_cited = {0}, issn = {1433-7851}, year = {2017}, date = {2017-07-24}, journal = {ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, volume = {56}, number = {31}, pages = {9131-9135}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semi-conducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semi-conducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices. |
Han, Cheng; Hu, Zehua; Gomes, Lidia C; Bao, Yang; Carvalho, Alexandra; Tan, Sherman J R; Lei, Bo; Xiang, Du; Wu, Jing; Qi, Dianyu; Wang, Li; Huo, Fengwei; Huang, Wei; Loh, Kian Ping; Chen, Wei Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices Journal Article NANO LETTERS, 17 (7), pp. 4122-4129, 2017, ISSN: 1530-6984. @article{ISI:000405643300018, title = {Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices}, author = {Cheng Han and Zehua Hu and Lidia C Gomes and Yang Bao and Alexandra Carvalho and Sherman J R Tan and Bo Lei and Du Xiang and Jing Wu and Dianyu Qi and Li Wang and Fengwei Huo and Wei Huang and Kian Ping Loh and Wei Chen}, doi = {10.1021/acs.nanolett.7b00903}, times_cited = {0}, issn = {1530-6984}, year = {2017}, date = {2017-07-01}, journal = {NANO LETTERS}, volume = {17}, number = {7}, pages = {4122-4129}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view toward high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations. The electron mobility of black phosphorus is significantly enhanced to 262 (377) cm(2) V-1 s(-1) by over 1 order of magnitude after potassium modification for two-terminal (four-terminal) measurements. Using lithography technique, a spatially controlled potassium doping technique is developed to establish high-performance complementary devices on a single black phosphorus nanosheet, for example, the p-n homojunction-based diode achieves a near-unity ideality factor of 1.007 with an on/off ratio of similar to 10(4). Our findings coupled with the tunable nature of in situ modification scheme enable black phosphorus as a promising candidate for further complementary electronics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view toward high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations. The electron mobility of black phosphorus is significantly enhanced to 262 (377) cm(2) V-1 s(-1) by over 1 order of magnitude after potassium modification for two-terminal (four-terminal) measurements. Using lithography technique, a spatially controlled potassium doping technique is developed to establish high-performance complementary devices on a single black phosphorus nanosheet, for example, the p-n homojunction-based diode achieves a near-unity ideality factor of 1.007 with an on/off ratio of similar to 10(4). Our findings coupled with the tunable nature of in situ modification scheme enable black phosphorus as a promising candidate for further complementary electronics. |
Han, Cheng; Hu, Zehua; Carvalho, Alexandra; Guo, Na; Zhang, Jialin; Hu, Fang; Xiang, Du; Wu, Jing; Lei, Bo; Wang, Li; Zhang, Chun; Neto, Castro A H; Chen, Wei Oxygen induced strong mobility modulation in few-layer black phosphorus Journal Article 2D MATERIALS, 4 (2), 2017, ISSN: 2053-1583. @article{ISI:000416729200001, title = {Oxygen induced strong mobility modulation in few-layer black phosphorus}, author = {Cheng Han and Zehua Hu and Alexandra Carvalho and Na Guo and Jialin Zhang and Fang Hu and Du Xiang and Jing Wu and Bo Lei and Li Wang and Chun Zhang and Castro A H Neto and Wei Chen}, doi = {10.1088/2053-1583/aa59ce}, times_cited = {0}, issn = {2053-1583}, year = {2017}, date = {2017-06-01}, journal = {2D MATERIALS}, volume = {4}, number = {2}, publisher = {IOP PUBLISHING LTD}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {2D black phosphorus configured field-effect transistors generally show a hole-transport-dominated ambipolar characteristic, owing to the severely restricted electron mobility by air ambient. Here, we demonstrate the strongly modulated mobility of few-layer black phosphorus in contact with oxygen. Pure oxygen exposure can dramatically decrease the electron mobility of black phosphorus by over three orders of magnitudes without degrading the hole transport. In situ x-ray photoelectron spectroscopy characterization reveals the physisorption nature of oxygen on black phosphorus. Density functional theory calculations identify the unoccupied states of molecular oxygen physisorbed on few-layer black phosphorus, that serves as electron trap but not as hole trap, consistent with the aforementioned mobility modulation. In contrast, oxygen exposure upon light illumination exhibits a significant attenuation for both electron and hole transport, originating from the photoactivated oxidation of black phosphorus, as corroborated by in situ x-ray photoelectron spectroscopy measurements. Our findings clarify the predominant role of oxygen in modulating transport properties of black phosphorus, thereby providing deeper insight to the design of black phosphorus based complementary electronics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 2D black phosphorus configured field-effect transistors generally show a hole-transport-dominated ambipolar characteristic, owing to the severely restricted electron mobility by air ambient. Here, we demonstrate the strongly modulated mobility of few-layer black phosphorus in contact with oxygen. Pure oxygen exposure can dramatically decrease the electron mobility of black phosphorus by over three orders of magnitudes without degrading the hole transport. In situ x-ray photoelectron spectroscopy characterization reveals the physisorption nature of oxygen on black phosphorus. Density functional theory calculations identify the unoccupied states of molecular oxygen physisorbed on few-layer black phosphorus, that serves as electron trap but not as hole trap, consistent with the aforementioned mobility modulation. In contrast, oxygen exposure upon light illumination exhibits a significant attenuation for both electron and hole transport, originating from the photoactivated oxidation of black phosphorus, as corroborated by in situ x-ray photoelectron spectroscopy measurements. Our findings clarify the predominant role of oxygen in modulating transport properties of black phosphorus, thereby providing deeper insight to the design of black phosphorus based complementary electronics. |
Lei, Bo; Hu, Zehua; Xiang, Du; Wang, Junyong; Eda, Goki; Han, Cheng; Chen, Wei Significantly enhanced optoelectronic performance of tungsten diselenide phototransistor via surface functionalization Journal Article NANO RESEARCH, 10 (4), pp. 1282-1291, 2017, ISSN: 1998-0124. @article{ISI:000398382300015, title = {Significantly enhanced optoelectronic performance of tungsten diselenide phototransistor via surface functionalization}, author = {Bo Lei and Zehua Hu and Du Xiang and Junyong Wang and Goki Eda and Cheng Han and Wei Chen}, doi = {10.1007/s12274-016-1386-1}, times_cited = {0}, issn = {1998-0124}, year = {2017}, date = {2017-04-01}, journal = {NANO RESEARCH}, volume = {10}, number = {4}, pages = {1282-1291}, publisher = {TSINGHUA UNIV PRESS}, address = {B605D, XUE YAN BUILDING, BEIJING, 100084, PEOPLES R CHINA}, abstract = {Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide (WSe2) exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate (Cs2CO3). WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2CO3/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materials-based optoelectronic devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide (WSe2) exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate (Cs2CO3). WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2CO3/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materials-based optoelectronic devices. |
2015 |
Xiang, Du; Han, Cheng; Hu, Zehua; Lei, Bo; Liu, Yiyang; Wang, Li; Hu, Wen Ping; Chen, Wei Surface Transfer Doping-Induced, High-Performance Graphene/Silicon Schottky Junction-Based, Self-Powered Photodetector Journal Article SMALL, 11 (37), pp. 4829-4836, 2015, ISSN: 1613-6810. @article{ISI:000362819400003, title = {Surface Transfer Doping-Induced, High-Performance Graphene/Silicon Schottky Junction-Based, Self-Powered Photodetector}, author = {Du Xiang and Cheng Han and Zehua Hu and Bo Lei and Yiyang Liu and Li Wang and Wen Ping Hu and Wei Chen}, doi = {10.1002/smll.201501298}, times_cited = {4}, issn = {1613-6810}, year = {2015}, date = {2015-10-07}, journal = {SMALL}, volume = {11}, number = {37}, pages = {4829-4836}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, keywords = {}, pubstate = {published}, tppubtype = {article} } |