Lei Zhang
Position: Grad Students
Research Type: Experiment
Office: S11-01-07
Email: e0001007@u.nus.edu
Contact: tel:(65) 9811 0259
CA2DM Publications:
2023 |
Subagyo, Riki; Maulida, Pramitha Y D; Kowal, Dominik; Hartati, Sri; Muslimawati, Rossyaila M; Zetra, Yulfi; Diguna, Lina J; Akhlus, Syafsir; Mahyuddin, Muhammad H; Zhang, Lei; Tang, Chi S; Diao, Caozheng; Wee, Andrew T S; Birowosuto, Muhammad D; Arramel, Andrivo; Rusydi, Andrivo; Kusumawati, Yuly Spectroscopic Evidence of Localized Small Polarons in Low-Dimensional Ionic Liquid Lead-Free Hybrid Perovskites Journal Article ACS APPLIED MATERIALS & INTERFACES, 15 (47), pp. 54677-54691, 2023, ISSN: 1944-8244. @article{ISI:001111123400001, title = {Spectroscopic Evidence of Localized Small Polarons in Low-Dimensional Ionic Liquid Lead-Free Hybrid Perovskites}, author = {Riki Subagyo and Pramitha Y D Maulida and Dominik Kowal and Sri Hartati and Rossyaila M Muslimawati and Yulfi Zetra and Lina J Diguna and Syafsir Akhlus and Muhammad H Mahyuddin and Lei Zhang and Chi S Tang and Caozheng Diao and Andrew T S Wee and Muhammad D Birowosuto and Andrivo Arramel and Andrivo Rusydi and Yuly Kusumawati}, doi = {10.1021/acsami.3c12889}, times_cited = {0}, issn = {1944-8244}, year = {2023}, date = {2023-11-15}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {15}, number = {47}, pages = {54677-54691}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Rational design is an important approach to consider in the development of low-dimensional hybrid organic-inorganic perovskites (HOIPs). In this study, 1-butyl-1-methyl pyrrolidinium (BMP), 1-(3-aminopropyl)imidazole (API), and 1-butyl-3-methyl imidazolium (BMI) serve as prototypical ionic liquid components in bismuth-based HOIPs. Element-sensitive X-ray absorption spectroscopy measurements of BMPBiBr4 and APIBiBr(5) reveal distinct resonant excitation profiles across the N K-edges, where contrasting peak shifts are observed. These 1D-HOIPs exhibit a large Stokes shift due to the small polaron contribution, as probed by photoluminescence spectroscopy at room temperature. Interestingly, the incorporation of a small fraction of tin (Sn) into the APIBiBr(5) (Sn/Bi mole ratio of 1:3) structure demonstrates a strong spectral weight transfer accompanied by a fast decay lifetime (2.6 ns). These phenomena are the direct result of Sn-substitution in APIBiBr(5), decreasing the small polaron effect. By changing the active ionic liquid, the electronic interactions and optical responses can be moderately tuned by alteration of their intermolecular interaction between the semiconducting inorganic layers and organic moieties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Rational design is an important approach to consider in the development of low-dimensional hybrid organic-inorganic perovskites (HOIPs). In this study, 1-butyl-1-methyl pyrrolidinium (BMP), 1-(3-aminopropyl)imidazole (API), and 1-butyl-3-methyl imidazolium (BMI) serve as prototypical ionic liquid components in bismuth-based HOIPs. Element-sensitive X-ray absorption spectroscopy measurements of BMPBiBr4 and APIBiBr(5) reveal distinct resonant excitation profiles across the N K-edges, where contrasting peak shifts are observed. These 1D-HOIPs exhibit a large Stokes shift due to the small polaron contribution, as probed by photoluminescence spectroscopy at room temperature. Interestingly, the incorporation of a small fraction of tin (Sn) into the APIBiBr(5) (Sn/Bi mole ratio of 1:3) structure demonstrates a strong spectral weight transfer accompanied by a fast decay lifetime (2.6 ns). These phenomena are the direct result of Sn-substitution in APIBiBr(5), decreasing the small polaron effect. By changing the active ionic liquid, the electronic interactions and optical responses can be moderately tuned by alteration of their intermolecular interaction between the semiconducting inorganic layers and organic moieties. |
Noviyanto, Alfian; Amalia, Ratih; Maulida, Pramitha Yuniar Diah; Dioktyanto, Mudzakkir; Arrosyid, Bagas Haqi; Aryanto, Didik; Zhang, Lei; Wee, Andrew T S; Arramel, Anomalous Temperature-Induced Particle Size Reduction in Manganese Oxide Nanoparticles Journal Article ACS OMEGA, 8 (47), pp. 45152-45162, 2023, ISSN: 2470-1343. @article{ISI:001110569800001, title = {Anomalous Temperature-Induced Particle Size Reduction in Manganese Oxide Nanoparticles}, author = {Alfian Noviyanto and Ratih Amalia and Pramitha Yuniar Diah Maulida and Mudzakkir Dioktyanto and Bagas Haqi Arrosyid and Didik Aryanto and Lei Zhang and Andrew T S Wee and Arramel}, doi = {10.1021/acsomega.3c08012}, times_cited = {0}, issn = {2470-1343}, year = {2023}, date = {2023-11-13}, journal = {ACS OMEGA}, volume = {8}, number = {47}, pages = {45152-45162}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {The intricate role of temperature in the structure-property relationship of manganese oxide nanoparticles (Mn3O4 NPs) remains an open question. In this study, we successfully synthesized Mn3O4 NPs using the hydrothermal method with two differing temperatures, namely, 90 and 150 degrees C. Interestingly, a smaller average particle size is found when Mn3O4 NPs are synthesized at 150 degrees C compared to 90 degrees C, corresponding to 46.54 and 63.37 nm, respectively. This was confirmed by the time variation of temperature setting of 150 degrees C where the size evolution was insignificant, indicating a competing effect of nucleation and growth particles. Under varying NaOH concentrations (2-6 M) at 150 degrees C, a reduction in the particle size is found at the highest NaOH concentration (6 M). The particle grows slightly, indicating that the growth state is dominant compared to the nucleation state at low concentrations of NaOH. This finding implies that the high nucleation rate originates from the excessive monomer supply in the high-temperature reaction. In terms of crystallinity order, the structural arrangement of Mn3O4 NPs (150 degrees C) is largely decreased; this is likely due to a facile redox shift to the higher oxidation state of manganese. In addition, the higher ratio of adsorbed oxygen and lattice oxygen in Mn3O4 NPs at 150 degrees C is indirectly due to the higher oxygen vacancy occupancies, which supported the crystallinity decrease. Our findings provide a new perspective on manganese oxide formation in hydrothermal systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The intricate role of temperature in the structure-property relationship of manganese oxide nanoparticles (Mn3O4 NPs) remains an open question. In this study, we successfully synthesized Mn3O4 NPs using the hydrothermal method with two differing temperatures, namely, 90 and 150 degrees C. Interestingly, a smaller average particle size is found when Mn3O4 NPs are synthesized at 150 degrees C compared to 90 degrees C, corresponding to 46.54 and 63.37 nm, respectively. This was confirmed by the time variation of temperature setting of 150 degrees C where the size evolution was insignificant, indicating a competing effect of nucleation and growth particles. Under varying NaOH concentrations (2-6 M) at 150 degrees C, a reduction in the particle size is found at the highest NaOH concentration (6 M). The particle grows slightly, indicating that the growth state is dominant compared to the nucleation state at low concentrations of NaOH. This finding implies that the high nucleation rate originates from the excessive monomer supply in the high-temperature reaction. In terms of crystallinity order, the structural arrangement of Mn3O4 NPs (150 degrees C) is largely decreased; this is likely due to a facile redox shift to the higher oxidation state of manganese. In addition, the higher ratio of adsorbed oxygen and lattice oxygen in Mn3O4 NPs at 150 degrees C is indirectly due to the higher oxygen vacancy occupancies, which supported the crystallinity decrease. Our findings provide a new perspective on manganese oxide formation in hydrothermal systems. |
2022 |
Jiang, Yucheng; He, Anpeng; Luo, Kai; Zhang, Jinlei; Liu, Guozhen; Zhao, Run; Zhang, Qing; Wang, Zhuo; Zhao, Chen; Wang, Lin; Qi, Yaping; Gao, Ju; Loh, Kian Ping; Wee, Andrew T S; Qiu, Cheng-Wei Giant bipolar unidirectional photomagnetoresistance Journal Article PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 119 (27), 2022, ISSN: 0027-8424. @article{ISI:000838706400010, title = {Giant bipolar unidirectional photomagnetoresistance}, author = {Yucheng Jiang and Anpeng He and Kai Luo and Jinlei Zhang and Guozhen Liu and Run Zhao and Qing Zhang and Zhuo Wang and Chen Zhao and Lin Wang and Yaping Qi and Ju Gao and Kian Ping Loh and Andrew T S Wee and Cheng-Wei Qiu}, doi = {10.1073/pnas.2115939119}, times_cited = {0}, issn = {0027-8424}, year = {2022}, date = {2022-07-05}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {119}, number = {27}, publisher = {NATL ACAD SCIENCES}, address = {2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA}, abstract = {Positive magnetoresistance (PMR) and negative magnetoresistance (NMR) describe two opposite responses of resistance induced by a magnetic field. Materials with giant PMR are usually distinct from those with giant NMR due to different physical natures. Here, we report the unusual photomagnetoresistance in the van der Waals heterojunctions of WSe2/quasi-two-dimensional electron gas, showing the coexistence of giant PMR and giant NMR. The PMR and NMR reach 1,007.5% at -9 T and -93.5% at 2.2 T in a single device, respectively. The magnetoresistance spans over two orders of magnitude on inversion of field direction, implying a giant unidirectional magnetoresistance (UMR). By adjusting the thickness of the WSe2 layer, we achieve the maxima of PMR and NMR, which are 4,900,000% and -99.8%, respectively. The unique magnetooptical transport shows the unity of giant UMR, PMR, and NMR, referred to as giant bipolar unidirectional photomagnetoresistance. These features originate from strong out-of-plane spin splitting, magnetic field-enhanced recombination of photocarriers, and the Zeeman effect through our experimental and theoretical investigations. This work offers directions for high-performance light-tunable spintronic devices.NMR)}, keywords = {}, pubstate = {published}, tppubtype = {article} } Positive magnetoresistance (PMR) and negative magnetoresistance (NMR) describe two opposite responses of resistance induced by a magnetic field. Materials with giant PMR are usually distinct from those with giant NMR due to different physical natures. Here, we report the unusual photomagnetoresistance in the van der Waals heterojunctions of WSe2/quasi-two-dimensional electron gas, showing the coexistence of giant PMR and giant NMR. The PMR and NMR reach 1,007.5% at -9 T and -93.5% at 2.2 T in a single device, respectively. The magnetoresistance spans over two orders of magnitude on inversion of field direction, implying a giant unidirectional magnetoresistance (UMR). By adjusting the thickness of the WSe2 layer, we achieve the maxima of PMR and NMR, which are 4,900,000% and -99.8%, respectively. The unique magnetooptical transport shows the unity of giant UMR, PMR, and NMR, referred to as giant bipolar unidirectional photomagnetoresistance. These features originate from strong out-of-plane spin splitting, magnetic field-enhanced recombination of photocarriers, and the Zeeman effect through our experimental and theoretical investigations. This work offers directions for high-performance light-tunable spintronic devices.NMR) |
Zhang, Lei; Yang, Tong; Arramel, ; Feng, Yuan Ping; Wee, Andrew T S; Wang, Zhuo MBE-grown ultrathin PtTe2 films and their layer-dependent electronic structures Journal Article NANOSCALE, 14 (20), pp. 7650-7658, 2022, ISSN: 2040-3364. @article{ISI:000793896300001, title = {MBE-grown ultrathin PtTe_{2} films and their layer-dependent electronic structures}, author = {Lei Zhang and Tong Yang and Arramel and Yuan Ping Feng and Andrew T S Wee and Zhuo Wang}, doi = {10.1039/d2nr00944g}, times_cited = {0}, issn = {2040-3364}, year = {2022}, date = {2022-04-19}, journal = {NANOSCALE}, volume = {14}, number = {20}, pages = {7650-7658}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {2D platinum ditelluride (PtTe2) has received significant attention for 2D photodetector applications due to its novel physical properties. One of the critical factors that affect device performance is the film quality. Here, using molecular beam epitaxy, we investigate the role of growth temperature in determining the film quality of PtTe2 on highly oriented pyrolytic graphite, and unveil its layer-dependent electronic properties by X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning tunneling microscopy/spectroscopy (STM/STS), as well as density functional theory (DFT) calculations. At low growth temperature (<= 250 degrees C), the PtTe2 film prefers a stack of the monolayer and bilayer, while at approximate to 300 degrees C large-area continuous bilayer films are formed. In contrast, high growth temperature (>300 degrees C) leads to the formation of thick films with high Te deficiency and poor crystallinity. Theoretical calculations confirm the higher thermal stability of bilayer PtTe2 over other layer numbers above a critical crystal size of approximate to 100 nm(2). STS shows that PtTe2 is a semiconductor in the monolayer with a bandgap of 0.80 +/- 0.05 eV, and changes to a semimetal from the bilayer. DFT calculations support our experimental results and suggest an indirect bandgap structure of the monolayer. This work provides a systematic study of the layer-dependent electronic structure of 2D PtTe2, and demonstrates that with appropriate substrate and growth temperature choices, high-quality ultrathin PtTe2 films can be obtained, important for device applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 2D platinum ditelluride (PtTe2) has received significant attention for 2D photodetector applications due to its novel physical properties. One of the critical factors that affect device performance is the film quality. Here, using molecular beam epitaxy, we investigate the role of growth temperature in determining the film quality of PtTe2 on highly oriented pyrolytic graphite, and unveil its layer-dependent electronic properties by X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning tunneling microscopy/spectroscopy (STM/STS), as well as density functional theory (DFT) calculations. At low growth temperature (<= 250 degrees C), the PtTe2 film prefers a stack of the monolayer and bilayer, while at approximate to 300 degrees C large-area continuous bilayer films are formed. In contrast, high growth temperature (>300 degrees C) leads to the formation of thick films with high Te deficiency and poor crystallinity. Theoretical calculations confirm the higher thermal stability of bilayer PtTe2 over other layer numbers above a critical crystal size of approximate to 100 nm(2). STS shows that PtTe2 is a semiconductor in the monolayer with a bandgap of 0.80 +/- 0.05 eV, and changes to a semimetal from the bilayer. DFT calculations support our experimental results and suggest an indirect bandgap structure of the monolayer. This work provides a systematic study of the layer-dependent electronic structure of 2D PtTe2, and demonstrates that with appropriate substrate and growth temperature choices, high-quality ultrathin PtTe2 films can be obtained, important for device applications. |
2021 |
Zhong, Linxin; Jiang, Chengyu; Zheng, Mengting; Peng, Xinwen; Liu, Tongchao; Xi, Shibo; Chi, Xiao; Zhang, Qinghua; Gu, Lin; Zhang, Shanqing; Shi, Ge; Zhang, Lei; Wu, Kunze; Chen, Zehong; Li, Tingzhen; Dahbi, Mouad; Alami, Jones; Amine, Khalil; Lu, Jun Wood Carbon Based Single-Atom Catalyst for Rechargeable Zn-Air Batteries Journal Article ACS ENERGY LETTERS, 6 (10), pp. 3624-3633, 2021, ISSN: 2380-8195. @article{ISI:000707987500030, title = {Wood Carbon Based Single-Atom Catalyst for Rechargeable Zn-Air Batteries}, author = {Linxin Zhong and Chengyu Jiang and Mengting Zheng and Xinwen Peng and Tongchao Liu and Shibo Xi and Xiao Chi and Qinghua Zhang and Lin Gu and Shanqing Zhang and Ge Shi and Lei Zhang and Kunze Wu and Zehong Chen and Tingzhen Li and Mouad Dahbi and Jones Alami and Khalil Amine and Jun Lu}, doi = {10.1021/acsenergylett.1c01678}, times_cited = {0}, issn = {2380-8195}, year = {2021}, date = {2021-09-21}, journal = {ACS ENERGY LETTERS}, volume = {6}, number = {10}, pages = {3624-3633}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Low-cost and efficient oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional electrocatalysts are vital for the applications of rechargeable Zn-air batteries (ZABs). Given the high catalytic activity of single-atom catalysts (SACs), preparing SACs on a large scale for ZABs is desirable but remains challenging. Herein, in situ formation of single-atom Fe-N-C catalysts on plate wood-based porous carbon is achieved via a facile Lewis acid pretreatment and carbonization process. Lewis acid FeCl3 pretreatment on the cell wall of wood not only produces abundant microchannels but also successfully introduces atomically dispersed Fe-N active species into the hierarchical structure. Such uniformly dispersive SACs on the hierarchical structure enhance the ORR/OER performance and durability. A ZAB using the catalyst in the cathode shows a high power density (70.2 mW cm(-2), at quasi solid state) and long-term stability. This work provides a new path for the large-scale preparation of high-performance SACs.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Low-cost and efficient oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional electrocatalysts are vital for the applications of rechargeable Zn-air batteries (ZABs). Given the high catalytic activity of single-atom catalysts (SACs), preparing SACs on a large scale for ZABs is desirable but remains challenging. Herein, in situ formation of single-atom Fe-N-C catalysts on plate wood-based porous carbon is achieved via a facile Lewis acid pretreatment and carbonization process. Lewis acid FeCl3 pretreatment on the cell wall of wood not only produces abundant microchannels but also successfully introduces atomically dispersed Fe-N active species into the hierarchical structure. Such uniformly dispersive SACs on the hierarchical structure enhance the ORR/OER performance and durability. A ZAB using the catalyst in the cathode shows a high power density (70.2 mW cm(-2), at quasi solid state) and long-term stability. This work provides a new path for the large-scale preparation of high-performance SACs. |
Zhang, Lei; Yang, Tong; Sahdan, Muhammad Fauzi; Arramel, ; Xu, Wenshuo; Xing, Kaijian; Feng, Yuan Ping; Zhang, Wenjing; Wang, Zhuo; Wee, Andrew T S Precise Layer-Dependent Electronic Structure of MBE-Grown PtSe2 Journal Article ADVANCED ELECTRONIC MATERIALS, 7 (11), 2021, ISSN: 2199-160X. @article{ISI:000691730400001, title = {Precise Layer-Dependent Electronic Structure of MBE-Grown PtSe_{2}}, author = {Lei Zhang and Tong Yang and Muhammad Fauzi Sahdan and Arramel and Wenshuo Xu and Kaijian Xing and Yuan Ping Feng and Wenjing Zhang and Zhuo Wang and Andrew T S Wee}, doi = {10.1002/aelm.202100559}, times_cited = {1}, issn = {2199-160X}, year = {2021}, date = {2021-09-01}, journal = {ADVANCED ELECTRONIC MATERIALS}, volume = {7}, number = {11}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {2D platinum diselenide (PtSe2) has received significant attention for 2D transistor applications due to its high carrier mobility. Here, using molecular beam epitaxy, the growth of 2D PtSe2 is investigated on highly oriented pyrolytic graphite (HOPG) and their electronic properties are unveiled via X-ray photoelectron spectroscopy, Raman spectra, and scanning tunnelling microscopy/spectroscopy as well as density functional theory (DFT) calculations. PtSe2 adopts a layer-by-layer growth mode on HOPG and shows a decreasing bandgap with increasing layer number. For the layer numbers from one to four, PtSe2 has bandgaps of 2.0 +/- 0.1, 1.1 +/- 0.1, 0.6 +/- 0.1, and 0.20 +/- 0.1 eV, respectively, and becomes semimetal from the fifth layer. DFT calculations reproduce the layer-dependent evolution of both the bandgap and band edges, suggest an indirect bandgap structure, and elucidate the underlying physics at the atomic level.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 2D platinum diselenide (PtSe2) has received significant attention for 2D transistor applications due to its high carrier mobility. Here, using molecular beam epitaxy, the growth of 2D PtSe2 is investigated on highly oriented pyrolytic graphite (HOPG) and their electronic properties are unveiled via X-ray photoelectron spectroscopy, Raman spectra, and scanning tunnelling microscopy/spectroscopy as well as density functional theory (DFT) calculations. PtSe2 adopts a layer-by-layer growth mode on HOPG and shows a decreasing bandgap with increasing layer number. For the layer numbers from one to four, PtSe2 has bandgaps of 2.0 +/- 0.1, 1.1 +/- 0.1, 0.6 +/- 0.1, and 0.20 +/- 0.1 eV, respectively, and becomes semimetal from the fifth layer. DFT calculations reproduce the layer-dependent evolution of both the bandgap and band edges, suggest an indirect bandgap structure, and elucidate the underlying physics at the atomic level. |
2020 |
Wang, Qixing; Zhang, Qi; Luo, Xin; Wang, Junyong; Zhu, Rui; Liang, Qijie; Zhang, Lei; Yong, Justin Zhou; Wong, Calvin Pei Yu; Eda, Goki; Smet, Jurgen H; Wee, Andrew T S Optoelectronic Properties of a van der Waals WS2 Monolayer/2D Perovskite Vertical Heterostructure Journal Article ACS APPLIED MATERIALS & INTERFACES, 12 (40), pp. 45235-45242, 2020, ISSN: 1944-8244. @article{ISI:000579956100085, title = {Optoelectronic Properties of a van der Waals WS_{2} Monolayer/2D Perovskite Vertical Heterostructure}, author = {Qixing Wang and Qi Zhang and Xin Luo and Junyong Wang and Rui Zhu and Qijie Liang and Lei Zhang and Justin Zhou Yong and Calvin Pei Yu Wong and Goki Eda and Jurgen H Smet and Andrew T S Wee}, doi = {10.1021/acsami.0c14398}, times_cited = {0}, issn = {1944-8244}, year = {2020}, date = {2020-10-07}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {12}, number = {40}, pages = {45235-45242}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Two-dimensional (2D) Ruddlesden-Popper perovskites have been demonstrated to possess great potential for optical and optoelectronic devices. Because they exhibit better ambient stability than three-dimensional (3D) perovskites, they have been considered as potential substitutes for 3D perovskites as light absorbing layers to improve the photoresponsivity of monolayer transition metal dichalcogenide (TMDC)-based photodetectors. Investigation of the optoelectronic properties of TMDC monolayer/2D perovskite vertical heterostructures is however at an early stage. Here, we address the photovoltaic effect and the photodetection performance in tungsten disulfide (WS2) monolayer/2D perovskite (C6H5C2H4NH3)(2)PbI4 (PEPI) vertical heterostructures. A vertical device geometry with separate graphene contacts to both heterointerface constituents acted as a photovoltaic device and self-driven photodetector. The photovoltaic device exhibited an open circuit voltage of-0.57 V and a short circuit current of 41.6 nA. A photoresponsivity of 0.13 mA/W at the WS2/PEPI heterointerface was achieved, which was signified by a factor of 5 compared to that from the individual WS2 region. The current on/off ratio of the self-driven photodetector was approximately 1500. The photoresponsivity and external quantum efficiency of the self-driven photodetector were estimated to be 24.2 mu A/W and 5.7 x 10(5), respectively. This work corroborates that 2D perovskites are promising light absorbing layers in optoelectronic devices with a TMDC-based heterointerface.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional (2D) Ruddlesden-Popper perovskites have been demonstrated to possess great potential for optical and optoelectronic devices. Because they exhibit better ambient stability than three-dimensional (3D) perovskites, they have been considered as potential substitutes for 3D perovskites as light absorbing layers to improve the photoresponsivity of monolayer transition metal dichalcogenide (TMDC)-based photodetectors. Investigation of the optoelectronic properties of TMDC monolayer/2D perovskite vertical heterostructures is however at an early stage. Here, we address the photovoltaic effect and the photodetection performance in tungsten disulfide (WS2) monolayer/2D perovskite (C6H5C2H4NH3)(2)PbI4 (PEPI) vertical heterostructures. A vertical device geometry with separate graphene contacts to both heterointerface constituents acted as a photovoltaic device and self-driven photodetector. The photovoltaic device exhibited an open circuit voltage of-0.57 V and a short circuit current of 41.6 nA. A photoresponsivity of 0.13 mA/W at the WS2/PEPI heterointerface was achieved, which was signified by a factor of 5 compared to that from the individual WS2 region. The current on/off ratio of the self-driven photodetector was approximately 1500. The photoresponsivity and external quantum efficiency of the self-driven photodetector were estimated to be 24.2 mu A/W and 5.7 x 10(5), respectively. This work corroborates that 2D perovskites are promising light absorbing layers in optoelectronic devices with a TMDC-based heterointerface. |
Zhang, Lei; Yang, Tong; He, Xiaoyue; Zhang, Wen; Vinai, Giovanni; Tang, Chi Sin; Yin, Xinmao; Torelli, Piero; Feng, Yuan Ping; Wong, Ping Kwan Johnny; Wee, Andrew T S Molecular Beam Epitaxy of Two-Dimensional Vanadium-Molybdenum Diselenide Alloys Journal Article ACS NANO, 14 (9), pp. 11140-11149, 2020, ISSN: 1936-0851. @article{ISI:000576958900006, title = {Molecular Beam Epitaxy of Two-Dimensional Vanadium-Molybdenum Diselenide Alloys}, author = {Lei Zhang and Tong Yang and Xiaoyue He and Wen Zhang and Giovanni Vinai and Chi Sin Tang and Xinmao Yin and Piero Torelli and Yuan Ping Feng and Ping Kwan Johnny Wong and Andrew T S Wee}, doi = {10.1021/acsnano.0c02124}, times_cited = {0}, issn = {1936-0851}, year = {2020}, date = {2020-09-22}, journal = {ACS NANO}, volume = {14}, number = {9}, pages = {11140-11149}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Two-dimensional (2D) alloys represent a versatile platform that extends the properties of atomically thin transition-metal dichalcogenides. Here, using molecular beam epitaxy, we investigate the growth of 2D vanadium-molybdenum diselenide alloys, VxMo1-xSe2, on highly oriented pyrolytic graphite and unveil their structural, chemical, and electronic integrities via measurements by scanning tunneling microscopy/spectroscopy, synchrotron X-ray photoemission, and X-ray absorption spectroscopy (XAS). Essentially, we found a critical value of x = similar to 0.44, below which phase separation occurs and above which a homogeneous metallic phase is favored. Another observation is an effective increase in the density of mirror twin boundaries of constituting MoSe2 in the low V concentration regime (x <= 0.05). Density functional theory calculations support our experimental results on the thermal stability of 2D VxMo1-xSe2 alloys and suggest an H phase of the homogeneous alloys with alternating parallel V and Mo strips randomly in-plane stacked. Element-specific XAS of the 2D alloys, which clearly indicates quenched atomic multiplets similar to the case of 2H-VSe2, provides strong evidence for the H phase of the 2D alloys. This work provides a comprehensive understanding of the thermal stability, chemical state, and electronic structure of 2D VxMo1-xSe2 alloys, useful for the future design of 2D electronic devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional (2D) alloys represent a versatile platform that extends the properties of atomically thin transition-metal dichalcogenides. Here, using molecular beam epitaxy, we investigate the growth of 2D vanadium-molybdenum diselenide alloys, VxMo1-xSe2, on highly oriented pyrolytic graphite and unveil their structural, chemical, and electronic integrities via measurements by scanning tunneling microscopy/spectroscopy, synchrotron X-ray photoemission, and X-ray absorption spectroscopy (XAS). Essentially, we found a critical value of x = similar to 0.44, below which phase separation occurs and above which a homogeneous metallic phase is favored. Another observation is an effective increase in the density of mirror twin boundaries of constituting MoSe2 in the low V concentration regime (x <= 0.05). Density functional theory calculations support our experimental results on the thermal stability of 2D VxMo1-xSe2 alloys and suggest an H phase of the homogeneous alloys with alternating parallel V and Mo strips randomly in-plane stacked. Element-specific XAS of the 2D alloys, which clearly indicates quenched atomic multiplets similar to the case of 2H-VSe2, provides strong evidence for the H phase of the 2D alloys. This work provides a comprehensive understanding of the thermal stability, chemical state, and electronic structure of 2D VxMo1-xSe2 alloys, useful for the future design of 2D electronic devices. |
Wu, Kunze; Zhang, Lei; Yuan, Yifei; Zhong, Linxin; Chen, Zhongxin; Chi, Xiao; Lu, Hao; Chen, Zehong; Zou, Ren; Li, Tingzhen; Jiang, Chengyu; Chen, Yongkang; Peng, Xinwen; Lu, Jun An Iron-Decorated Carbon Aerogel for Rechargeable Flow and Flexible Zn-Air Batteries Journal Article ADVANCED MATERIALS, 32 (32), 2020, ISSN: 0935-9648. @article{ISI:000544595300001, title = {An Iron-Decorated Carbon Aerogel for Rechargeable Flow and Flexible Zn-Air Batteries}, author = {Kunze Wu and Lei Zhang and Yifei Yuan and Linxin Zhong and Zhongxin Chen and Xiao Chi and Hao Lu and Zehong Chen and Ren Zou and Tingzhen Li and Chengyu Jiang and Yongkang Chen and Xinwen Peng and Jun Lu}, doi = {10.1002/adma.202002292}, times_cited = {0}, issn = {0935-9648}, year = {2020}, date = {2020-07-01}, journal = {ADVANCED MATERIALS}, volume = {32}, number = {32}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {Mechanically stable and foldable air cathodes with exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are key components of wearable metal-air batteries. Herein, a directional freeze-casting and annealing approach is reported for the construction of a 3D honeycomb nanostructured, N,P-doped carbon aerogel incorporating in situ grown FeP/Fe(2)O(3)nanoparticles as the cathode in a flexible Zn-air battery (ZAB). The aqueous rechargeable Zn-air batteries assembled with this carbon aerogel exhibit a remarkable specific capacity of 648 mAh g(-1)at a current density of 20 mA cm(-2)with a good long-term durability, outperforming those assembled with commercial Pt/C+RuO(2)catalyst. Furthermore, such a foldable carbon aerogel with directional channels can serve as a freestanding air cathode for flexible solid-state Zn-air batteries without the use of carbon paper/cloth and additives, giving a specific capacity of 676 mAh g(-1)and an energy density of 517 Wh kg(-1)at 5 mA cm(-2)together with good cycling stability. This work offers a new strategy to design and synthesize highly effective bifunctional air cathodes to be applied in electrochemical energy devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mechanically stable and foldable air cathodes with exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are key components of wearable metal-air batteries. Herein, a directional freeze-casting and annealing approach is reported for the construction of a 3D honeycomb nanostructured, N,P-doped carbon aerogel incorporating in situ grown FeP/Fe(2)O(3)nanoparticles as the cathode in a flexible Zn-air battery (ZAB). The aqueous rechargeable Zn-air batteries assembled with this carbon aerogel exhibit a remarkable specific capacity of 648 mAh g(-1)at a current density of 20 mA cm(-2)with a good long-term durability, outperforming those assembled with commercial Pt/C+RuO(2)catalyst. Furthermore, such a foldable carbon aerogel with directional channels can serve as a freestanding air cathode for flexible solid-state Zn-air batteries without the use of carbon paper/cloth and additives, giving a specific capacity of 676 mAh g(-1)and an energy density of 517 Wh kg(-1)at 5 mA cm(-2)together with good cycling stability. This work offers a new strategy to design and synthesize highly effective bifunctional air cathodes to be applied in electrochemical energy devices. |
Zhang, Lei; Yang, Tong; Zhang, Wen; Qi, Dongchen; He, Xiaoyue; Xing, Kaijian; Wong, Ping Kwan Johnny; Feng, Yuan Ping; Wee, Andrew Thye Shen Bi-stable electronic states of cobalt phthalocyanine molecules on two-dimensional vanadium diselenide Journal Article APPLIED MATERIALS TODAY, 18 , 2020, ISSN: 2352-9407. @article{ISI:000530651100006, title = {Bi-stable electronic states of cobalt phthalocyanine molecules on two-dimensional vanadium diselenide}, author = {Lei Zhang and Tong Yang and Wen Zhang and Dongchen Qi and Xiaoyue He and Kaijian Xing and Ping Kwan Johnny Wong and Yuan Ping Feng and Andrew Thye Shen Wee}, doi = {10.1016/j.apmt.2019.100535}, times_cited = {0}, issn = {2352-9407}, year = {2020}, date = {2020-03-01}, journal = {APPLIED MATERIALS TODAY}, volume = {18}, publisher = {ELSEVIER}, address = {RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS}, abstract = {Hybrid organic/2D interfaces combine the wide spectrum of 2D material properties with the major advantages of organic materials, such as low cost, mechanical flexibility, and chemical tunability. Here, we report the electronic properties of cobalt phthalocyanine (CoPc) molecules adsorbed on molecular beam epitaxy-grown monolayer vanadium diselenide (VSe2). Using scanning tunneling microscopy/spectroscopy, we provide evidence of highly ordered molecular assembly on monolayer VSe2, with two distinctive bright and regular molecular contrasts, which are not observed on graphite. These contrasts also lead to a distinct difference in the electronic state of the molecule's central Co atom, for which density functional theory calculations indicate the regular state as the ground state. A correlation between these two molecular states and the charged states of individual molecules is postulated, as demonstrated by the possibility of switching the bright state to the regular state using a negative tip voltage pulse. (C) 2019 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hybrid organic/2D interfaces combine the wide spectrum of 2D material properties with the major advantages of organic materials, such as low cost, mechanical flexibility, and chemical tunability. Here, we report the electronic properties of cobalt phthalocyanine (CoPc) molecules adsorbed on molecular beam epitaxy-grown monolayer vanadium diselenide (VSe2). Using scanning tunneling microscopy/spectroscopy, we provide evidence of highly ordered molecular assembly on monolayer VSe2, with two distinctive bright and regular molecular contrasts, which are not observed on graphite. These contrasts also lead to a distinct difference in the electronic state of the molecule's central Co atom, for which density functional theory calculations indicate the regular state as the ground state. A correlation between these two molecular states and the charged states of individual molecules is postulated, as demonstrated by the possibility of switching the bright state to the regular state using a negative tip voltage pulse. (C) 2019 Elsevier Ltd. All rights reserved. |
2019 |
Zhang, Lei; He, Xiaoyue; Xing, Kaijian; Zhang, Wen; Tadich, Anton; Wong, Ping Kwan Johnny; Qi, Dong-Chen; Wee, Andrew T S Is Charge-Transfer Doping Possible at the Interfaces of Monolayer VSe2 with MoO3 and K? Journal Article ACS APPLIED MATERIALS & INTERFACES, 11 (46), pp. 43789-43795, 2019, ISSN: 1944-8244. @article{ISI:000499740300098, title = {Is Charge-Transfer Doping Possible at the Interfaces of Monolayer VSe_{2} with MoO_{3} and K?}, author = {Lei Zhang and Xiaoyue He and Kaijian Xing and Wen Zhang and Anton Tadich and Ping Kwan Johnny Wong and Dong-Chen Qi and Andrew T S Wee}, doi = {10.1021/acsami.9b16822}, times_cited = {0}, issn = {1944-8244}, year = {2019}, date = {2019-11-20}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {11}, number = {46}, pages = {43789-43795}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Being a metallic transition-metal dichalcogenide, monolayer vanadium diselenide (VSe2) exhibits many novel properties, such as charge density waves and magnetism. Its interfaces with other materials can potentially be used in device applications as well as for manipulating its intrinsic properties. Here, we present a scanning tunneling microscopy and synchrotron-based X-ray photoemission spectroscopy study of the surface charge-transfer doping using efficient electron-withdrawing and electron-donating materials, that is, molybdenum trioxide (MoO3) and potassium (K), on the molecular beam epitaxy-grown monolayer VSe2 on highly oriented pyrolytic graphite (HOPG). We demonstrate that monolayer VSe2 is immune to MoO3- and K-doping effects. However, at the monolayer edges where the local chemical reactivity is higher because of Se deficiency, MoO3 is seen to react with VSe2 to form molybdenum dioxide (MoO2) and vanadium dioxide (VO2). Compared to the obvious charge-transfer doping effects of MoO3 and K on HOPG, the electronic structure of monolayer VSe2 is barely perturbed. This is attributed to the large density of states at the Fermi level of monolayer VSe2 carrying the metallic character. This work provides new insights into the chemical and electronic properties of monolayer VSe2, important for future VSe2-based electronic device design.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Being a metallic transition-metal dichalcogenide, monolayer vanadium diselenide (VSe2) exhibits many novel properties, such as charge density waves and magnetism. Its interfaces with other materials can potentially be used in device applications as well as for manipulating its intrinsic properties. Here, we present a scanning tunneling microscopy and synchrotron-based X-ray photoemission spectroscopy study of the surface charge-transfer doping using efficient electron-withdrawing and electron-donating materials, that is, molybdenum trioxide (MoO3) and potassium (K), on the molecular beam epitaxy-grown monolayer VSe2 on highly oriented pyrolytic graphite (HOPG). We demonstrate that monolayer VSe2 is immune to MoO3- and K-doping effects. However, at the monolayer edges where the local chemical reactivity is higher because of Se deficiency, MoO3 is seen to react with VSe2 to form molybdenum dioxide (MoO2) and vanadium dioxide (VO2). Compared to the obvious charge-transfer doping effects of MoO3 and K on HOPG, the electronic structure of monolayer VSe2 is barely perturbed. This is attributed to the large density of states at the Fermi level of monolayer VSe2 carrying the metallic character. This work provides new insights into the chemical and electronic properties of monolayer VSe2, important for future VSe2-based electronic device design. |
Wong, Ping Kwan Johnny; Zhang, Wen; Zhou, Jun; Bussolotti, Fabio; Yin, Xinmao; Zhang, Lei; N'Diaye, Alpha T; Morton, Simon A; Chen, Wei; Goh, Johnson; de Jong, Michel P; Feng, Yuan Ping; Wee, Andrew T S Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular Beam Epitaxy Grown Monolayer Vanadium Ditelluride Journal Article ACS NANO, 13 (11), pp. 12894-12900, 2019, ISSN: 1936-0851. @article{ISI:000500650000062, title = {Metallic 1T Phase, 3d^{1} Electronic Configuration and Charge Density Wave Order in Molecular Beam Epitaxy Grown Monolayer Vanadium Ditelluride}, author = {Ping Kwan Johnny Wong and Wen Zhang and Jun Zhou and Fabio Bussolotti and Xinmao Yin and Lei Zhang and Alpha T N'Diaye and Simon A Morton and Wei Chen and Johnson Goh and Michel P de Jong and Yuan Ping Feng and Andrew T S Wee}, doi = {10.1021/acsnano.9b05349}, times_cited = {0}, issn = {1936-0851}, year = {2019}, date = {2019-11-01}, journal = {ACS NANO}, volume = {13}, number = {11}, pages = {12894-12900}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {We present a combined experimental and theoretical study of monolayer vanadium ditelluride, VTe2, grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using various in situ microscopic and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, together with theoretical analysis by density functional theory calculations, we demonstrate direct evidence of the metallic IT phase and 3d(1) electronic configuration in monolayer VTe2 that also features a (4 x 4) charge density wave order at low temperatures. In contrast to previous theoretical predictions, our element-specific characterization by X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to the monolayer. Our findings provide essential knowledge necessary for understanding this interesting yet less explored metallic monolayer in the emerging family of van der Waals magnets.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a combined experimental and theoretical study of monolayer vanadium ditelluride, VTe2, grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using various in situ microscopic and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, together with theoretical analysis by density functional theory calculations, we demonstrate direct evidence of the metallic IT phase and 3d(1) electronic configuration in monolayer VTe2 that also features a (4 x 4) charge density wave order at low temperatures. In contrast to previous theoretical predictions, our element-specific characterization by X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to the monolayer. Our findings provide essential knowledge necessary for understanding this interesting yet less explored metallic monolayer in the emerging family of van der Waals magnets. |
Zhang, Wen; Zhang, Lei; Wong, Ping Kwan Johnny; Yuan, Jiaren; Vinai, Giovanni; Torelli, Piero; van der Laan, Gerrit; Feng, Yuan Ping; Wee, Andrew T S Magnetic Transition in Monolayer VSe2 via Interface Hybridization Journal Article ACS NANO, 13 (8), pp. 8997-9004, 2019, ISSN: 1936-0851. @article{ISI:000484077800049, title = {Magnetic Transition in Monolayer VSe_{2} \textit{via} Interface Hybridization}, author = {Wen Zhang and Lei Zhang and Ping Kwan Johnny Wong and Jiaren Yuan and Giovanni Vinai and Piero Torelli and Gerrit van der Laan and Yuan Ping Feng and Andrew T S Wee}, doi = {10.1021/acsnano.9b02996}, times_cited = {0}, issn = {1936-0851}, year = {2019}, date = {2019-08-01}, journal = {ACS NANO}, volume = {13}, number = {8}, pages = {8997-9004}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Magnetism in monolayer (ML) VSe2 has attracted broad interest in spintronics, while existing reports have not reached consensus. Using element-specific X-ray magnetic circular dichroism, a magnetic transition in ML VSe2 has been demonstrated at the contamination-free interface between Co and VSe2. Through interfacial hybridization with a Co atomic overlayer, a magnetic moment of about 0.4 NB per V atom in ML VSe2 is revealed, approaching values predicted by previous theoretical calculations. Promotion of the ferromagnetism in ML VSe2 is accompanied by its antiferromagnetic coupling to Co and a reduction in the spin moment of Co. In comparison to the absence of this interface-induced ferromagnetism at the Fe/ML MoSe2 interface, these findings at the Co/ML VSe2 interface provide clear proof that the ML VSe2, initially with magnetic disorder, is on the verge of magnetic transition.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Magnetism in monolayer (ML) VSe2 has attracted broad interest in spintronics, while existing reports have not reached consensus. Using element-specific X-ray magnetic circular dichroism, a magnetic transition in ML VSe2 has been demonstrated at the contamination-free interface between Co and VSe2. Through interfacial hybridization with a Co atomic overlayer, a magnetic moment of about 0.4 NB per V atom in ML VSe2 is revealed, approaching values predicted by previous theoretical calculations. Promotion of the ferromagnetism in ML VSe2 is accompanied by its antiferromagnetic coupling to Co and a reduction in the spin moment of Co. In comparison to the absence of this interface-induced ferromagnetism at the Fe/ML MoSe2 interface, these findings at the Co/ML VSe2 interface provide clear proof that the ML VSe2, initially with magnetic disorder, is on the verge of magnetic transition. |
Wang, Qixing; Zhang, Qj; Zhao, Xiaoxu; Zheng, Yu Jie; Wang, Junyong; Luo, Xin; Dan, Jiadong; Zhu, Rui; Liang, Qijie; Zhang, Lei; Wong, Johnny P K; He, Xiaoyue; Huang, Yu Li; Wang, Xinyun; Pennycook, Stephen J; Eda, Goki; Wee, Andrew T S High-Energy Gain Upconversion in Monolayer Tungsten Disulfide Photodetectors Journal Article NANO LETTERS, 19 (8), pp. 5595-5603, 2019, ISSN: 1530-6984. @article{ISI:000481563800100, title = {High-Energy Gain Upconversion in Monolayer Tungsten Disulfide Photodetectors}, author = {Qixing Wang and Qj Zhang and Xiaoxu Zhao and Yu Jie Zheng and Junyong Wang and Xin Luo and Jiadong Dan and Rui Zhu and Qijie Liang and Lei Zhang and Johnny P K Wong and Xiaoyue He and Yu Li Huang and Xinyun Wang and Stephen J Pennycook and Goki Eda and Andrew T S Wee}, doi = {10.1021/acs.nanolett.9b02136}, times_cited = {0}, issn = {1530-6984}, year = {2019}, date = {2019-08-01}, journal = {NANO LETTERS}, volume = {19}, number = {8}, pages = {5595-5603}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Photodetectors usually operate in the wavelength range with photon energy above the bandgap of channel semiconductors so that incident photons can excite electrons from valence band to conduction band to generate photo current. Here, however, we show that monolayer WS2 photodetectors can detect photons with energy even lying 219 meV below the bandgap of WS2 at room temperature. With the increase of excitation wavelength from 620 to 680 nm, photoresponsivity varies from 551 to 59 mA/W. This anomalous phenomenon is ascribed to energy upconversion, which is a combination effect of one-photon excitation and multiphonon absorption through an intermediate state created most likely by sulfur divacancy with oxygen adsorption. These findings will arouse research interests on other upconversion optoelectronic devices, photovoltaic devices, for example, of monolayer transition metal dichalcogenides (TMDCs).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Photodetectors usually operate in the wavelength range with photon energy above the bandgap of channel semiconductors so that incident photons can excite electrons from valence band to conduction band to generate photo current. Here, however, we show that monolayer WS2 photodetectors can detect photons with energy even lying 219 meV below the bandgap of WS2 at room temperature. With the increase of excitation wavelength from 620 to 680 nm, photoresponsivity varies from 551 to 59 mA/W. This anomalous phenomenon is ascribed to energy upconversion, which is a combination effect of one-photon excitation and multiphonon absorption through an intermediate state created most likely by sulfur divacancy with oxygen adsorption. These findings will arouse research interests on other upconversion optoelectronic devices, photovoltaic devices, for example, of monolayer transition metal dichalcogenides (TMDCs). |
He, Xiaoyue; Zhang, Lei; Chua, Rebekah; Wong, Ping Kwan Johnny; Arramel, Arramel; Feng, Yuan Ping; Wang, Shi Jie; Chi, Dongzhi; Yang, Ming; Huang, Yu Li; Wee, Andrew Thye Shen Selective self-assembly of 2,3-diaminophenazine molecules on MoSe2 mirror twin boundaries Journal Article NATURE COMMUNICATIONS, 10 , 2019, ISSN: 2041-1723. @article{ISI:000473132200011, title = {Selective self-assembly of 2,3-diaminophenazine molecules on MoSe_{2} mirror twin boundaries}, author = {Xiaoyue He and Lei Zhang and Rebekah Chua and Ping Kwan Johnny Wong and Arramel Arramel and Yuan Ping Feng and Shi Jie Wang and Dongzhi Chi and Ming Yang and Yu Li Huang and Andrew Thye Shen Wee}, doi = {10.1038/s41467-019-10801-0}, times_cited = {1}, issn = {2041-1723}, year = {2019}, date = {2019-06-28}, journal = {NATURE COMMUNICATIONS}, volume = {10}, publisher = {NATURE PUBLISHING GROUP}, address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND}, abstract = {The control of the density and type of line defects on two-dimensional (2D) materials enable the development of new methods to tailor their physical and chemical properties. In particular, mirror twin boundaries (MTBs) on transition metal dichacogenides have attracted much interest due to their metallic state with charge density wave transition and spin-charge separation property. In this work, we demonstrate the self-assembly of 2,3-diaminophenazine (DAP) molecule porous structure with alternate L-type and T-type aggregated configurations on the MoSe2 hexagonal wagon-wheel pattern surface. This site-specific molecular self-assembly is attributed to the more chemically reactive metallic MTBs compared to the pristine semiconducting MoSe2 domains. First-principles calculations reveal that the active MTBs couple with amino groups in the DAP molecules facilitating the DAP assembly. Our results demonstrate the site-dependent electronic and chemical properties of MoSe2 monolayers, which can be exploited as a natural template to create ordered nanostructures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The control of the density and type of line defects on two-dimensional (2D) materials enable the development of new methods to tailor their physical and chemical properties. In particular, mirror twin boundaries (MTBs) on transition metal dichacogenides have attracted much interest due to their metallic state with charge density wave transition and spin-charge separation property. In this work, we demonstrate the self-assembly of 2,3-diaminophenazine (DAP) molecule porous structure with alternate L-type and T-type aggregated configurations on the MoSe2 hexagonal wagon-wheel pattern surface. This site-specific molecular self-assembly is attributed to the more chemically reactive metallic MTBs compared to the pristine semiconducting MoSe2 domains. First-principles calculations reveal that the active MTBs couple with amino groups in the DAP molecules facilitating the DAP assembly. Our results demonstrate the site-dependent electronic and chemical properties of MoSe2 monolayers, which can be exploited as a natural template to create ordered nanostructures. |