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Electronic and optical properties of single-layer mos2

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Frontiers of physics 2018年第4期13卷 123-128页

作者： Hai-Ming Dong San-Dong Guo Yi-Feng Duan Fei Huang Wen Xu Jin Zhang School of Physical Science and Technology China University of Mining and Technology Xuzhou 221116 China Low Carbon Energy Institute China University of Mining and Technology Xuzhou 221116 China Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China Department of Physics Yunnan University Kunming 650091 China

The electronic structures of a mos2 monolayer are investigated with the all-electron first principle calculations based on the density functional theory （DFT） and the spin-orbital couplings （SOCs）. Ore＂ results show that the monolayer mos2 is a direct band gap semiconductor with a band gap of 1.8 eV. The SOCs and d-electrons in Mo play a very significant role in deciding its electronic and optical properties. Moreover, electronic elementary excitations are studied theoretically within the diagram- matic self-consistent field theory. Under random phase approximation, it shows that two branches of plasmon modes can be achieved via the conduction-band transitions due to the SOCs, which are different from the plasmons in a two-dimensional electron gas and graphene owing to the quasi-linear energy dispersion in single-layer mos2. Moreover, the strong optical absorption up to 105 cm-1 and two optical absorption edges I and II can be observed. This study is relevant to the applications of monolayer mos2 as an advanced photoelectronic device.

关键词： mos2 electronic and optical properties

Preparation of Novel Ultrathin Co doped mos2 Nanosheets Piezocatalyst for Fast Simultaneous Decomposition of Cr(Ⅵ) and MB in Dark

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Chemical Research in Chinese Universities 2019年第5期35卷 892-900页

作者： WIN Thi Yein WANG Qun JIAN Jiahuang LI Yang WU Xiaohong MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical Engineerings Harbin Institute of Technology Harbin 150001P.R.China

Ultrathin Co doped mos2 nanosheets(NSs) with thickness of 3.2 nm was used to simultaneously decompose Cr(Ⅵ) and MB in dark through ultrasonic vibration-assisted piezocatalytic effect. The significantly enhanced piezocatalytic performance of Co doped mos2 NSs was found in comparison to the pristine mos2 NSs. The high piezocatalytic activity of Co doped mos2 NSs may originate from the large amount of charge carriers due to Co doping. The efficient separation of electron-hole pairs under spontaneous polarization were also investigated ill detail, which is responsible for reduction of Cr(Ⅵ) and oxidation of methylene blue(MB). The active species trapping experiments demonstrate that e and ·O2^- are main active substances for Cr(Ⅵ) reduction, while h+,·OH, and ·O2^- participate in MB degradation.

关键词： Co doped mos2 Piezocatalytic Organic dyes Cr(Ⅵ)

Solution processed mos2-PVA composite for subbandgap mode-locking of a wideband tunable ultrafast Er：fiber laser

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Nano Research 2015年第5期8卷 1522-1534页

作者： Meng Zhang Richard C. T. Howe Robert I. Woodward Edmund J. R. Kelleher Felice Torrisi Guohua Hu Sergei V. Popov J. Roy Taylor Tawfique Hasan Femtosecond Optics Group Blackett Laboratory Prince Consort Road Imperial College London London SW7 2AZ UK Cambridge Graphene Centre University of Cambridge Cambridge CB3 OFA UK

我们制作自立的很少层铝二硫化物(瞬间由化学上太古的 mos2 晶体和使用的液体阶段脱落合成的 2 )-polymer 这表明一条宽带悦耳， ultrafast 锁模式的纤维激光。稳定，微微秒脉搏，从 1,535 nm 悦耳到 1,565 nm，被产生，相应于在瞬间... 详细信息

我们制作自立的很少层铝二硫化物(瞬间由化学上太古的 mos2 晶体和使用的液体阶段脱落合成的 2 )-polymer 这表明一条宽带悦耳， ultrafast 锁模式的纤维激光。稳定，微微秒脉搏，从 1,535 nm 悦耳到 1,565 nm，被产生，相应于在瞬间下面的光子精力 2 材料 bandgap。这些结果贡献学习转变金属 dichalcogenides 的非线性的光性质的工作的成长身体为 ultrafast photonic 应用的现在的新机会。

关键词：聚合物复合材料锁模光纤激光器宽带可调谐二硫化钼非线性光学性质加工 mos2 皮秒脉冲

Selective and localized laser annealing effect for high- performance flexible multilayer mos2 thin-film transistors

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Nano Research 2014年第8期7卷 1137-1145页

作者： Hyukjun Kwon Woong Choi Daeho Lee Yunsung Lee Junyeon Kwon Byungwook Yoo Costas P. Grigoropoulos Sunkook Kim Department of Mechanical Engineering University of California Berkeley CA 94720-1740 USA School of Advanced Materials Engineering Kookmin University Seoul 136-702 South Korea Department of Mechanical Engineering 6achon University Seongnam-si Gyeonggi 461-701 South Korea Department of Electronics and Radio Engineering Kyung Hee University Gyeonggi 446-70 I South Korea Flexible Display Research Center Korea Electronics Technology Institute Seongnam Gyeonggi 463-816 South Korea

We report the use of ultra-short, pulsed-laser annealed Ti/Au contacts to enhance the performance of multilayer mos2 field effect transistors (FETs) on flexible plastic substrates without thermal damage. An analysis of the temperature distribution, based on finite difference methods, enabled understanding of the compatibility of our picosecond laser annealing for flexible poly(ethylene naphthalate) (PEN) substrates with low thermal budget (200 °C). The reduced contact resistance after laser annealing provided a significant improvement in transistor performance including higher peak field-effect mobility (from 24.84 to 44.84 cm2·V−1·s−1), increased output resistance (0.42 MΩ at V gs − V th = 20 V, a three-fold increase), a six-fold increase in the self-gain, and decreased sub-threshold swing. Transmission electron microscopy analysis and current-voltage measurements suggested that the reduced contact resistance resulted from the decrease of Schottky barrier width at the mos2-metal junction. These results demonstrate that selective contact laser annealing is an attractive technology for fabricating low-resistivity metal-semiconductor junctions, providing important implications for the application of high-performance two-dimensional semiconductor FETs in flexible electronics.

关键词：激光退火薄膜晶体管 mos2 柔性性能退火效应透射电子显微镜分析场效应晶体管

Sulfur-resistant methanation over MoO_3/CeO_2–ZrO_2 catalyst: Influence of Ce-addition methods

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Journal of Energy Chemistry 2019年第1期28卷 31-38页

作者： Zhaopeng Liu Yan Xu Zhenhua Li Baowei Wang Weihan Wang Xinbin Ma Renjie Liu Key Laboratory for Green Chemical Technology of Ministry of Education School of Chemical Engineering and Technology Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University

In this paper, Ce_(0.2)Zr_(0.8)O_2 composite supports were prepared by different Ce-addition methods including impregnation of cerium(CeZr-imp), impregnation of citric acid and cerium(CeZr-CA) simultaneously and deposition precipitation method(CeZr-DP), respectively. The as-prepared supports were applied to prepare 10 wt% MoO_3/Ce_(0.2)Zr_(0.8)O_2 catalysts for sulfur-resistant methanation. The N_2 adsorption/desorption,X-ray diffraction(XRD), Raman spectroscopy(RS), X-ray photoelectron(XPS), temperature-programmed reduction by hydrogen(H_2-TPR) were undertaken to get textural properties, morphological information and structures of the catalysts. The results showed that Mo O_3 was highly dispersed on the surface of these three supports and Ce was mostly of coexisted in Ce^(4+)/Ce^(3+) redox pairs. Compared with Mo/CeZrimp, the CO conversion increased by 10% and 15% for Mo/CeZr-CA and Mo/CeZr-DP, respectively. This was mainly attributed to the larger specific surface area, Ce^(3+) concentration and content of active mos_2 on the surface of catalysts.

关键词： Sulfur-resistant methanation Ce introducing methods Reducible Ce^3+ Synthetic natural gas Active mos2

Raman spectroscopy characterization of two-dimensional materials

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Chinese Physics B 2018年第3期27卷 80-93页

作者：梁芳徐何军吴幸王超伦骆晨张健 Shanghai Key Laboratory of Multidimensional Information Processing Department of Electronic EngineeringEast China Normal University

Two-dimensional （2D） materials have become a hot study topic in recent years due to their outstanding electronic, optical, and thermal properties. The unique band structures of strong in-plane chemical bonds and weak out-of-plane van der Waals （vdW） interactions make 2D materials promising for nanodevices and various other applications. Raman spectroscopy is a powerful and non-destructive characterization tool to study the properties of 2D materials. In this work, we review the research on the characterization of 2D materials with Raman spectroscopy. In addition, we discuss the application of the Raman spectroscopy technique to semiconductors, superconductivity, photoelectricity, and thermoelectricity.

关键词： Raman mos2 graphene 2D materials non-destructive characterization

Enhanced NO_2 gas sensing of a single-layer mos_2 by photogating and piezo-phototronic effects

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Science Bulletin 2019年第2期64卷 128-135页

作者： Junmeng Guo Rongmei Wen Junyi Zhai Zhong Lin Wang CAS Center for Excellence in Nanoscience Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences School of Nanoscience and Technology University of Chinese Academy of Sciences Center on Nanoenergy Research School of Physical Science and Technology Guangxi University School of Materials Science and Engineering Georgia Institute of Technology

NO_2 sensors with ultrahigh sensitivity are demanded for future electronic sensing systems. However,traditional sensors are considerably limited by the relative low sensitivity, high cost and complicated process. Here, we report a simply and reliable flexible NO_2 sensor based on single-layer mos_2. The flexible sensor exhibits high sensitivity to NO_2 gas due to ultra-large specific surface area and the nature of two-dimensional(2 D) semiconductor. When the NO_2 is 400 ppb(parts per billion), compared with the dark and strain-free conditions, the sensitivity of the single-layer sensor is enhanced to 671% with a625 nm red light-emitting diode(LED) illumination of 4 mW/cm^2 power under 0.67% tensile strain.More important, the response time is dramatically reduced to $16 s and it only needs $65 s to complete90% recovery. A theoretical model is proposed to discuss the microscopic mechanisms. We find that the remarkable sensing characteristics are the result of coupling among piezoelectricity, photoelectricity and adsorption-desorption induced charges transfer in the single-layer mos_2 Schottky junction based device.Our work opens up the way to further enhancements in the sensitivity of gas sensor based on single-layer mos_2 by introducing photogating and piezo-phototronic effects in mesoscopic systems.

关键词： Ultrahigh sensitivity Flexible NO2 sensor Single-layer mos2 Photogating effect Piezo-phototronic effect

2D hierarchical yolk-shell heterostructures as advanced host-interlayer integrated electrode for enhanced Li-S batteries

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Journal of Energy Chemistry 2019年第9期28卷 64-73页

作者： Yanfeng Dong Pengfei Lu Haodong Shi Jieqiong Qin Jian Chen Wencai Ren Hui-Ming Cheng Zhong-Shuai Wu Department of Chemistry College of Sciences Northeastern UniversityShenyang 110819 Liaoning China Dalian National Laboratory for Clean Energy Dalian Institute of Chemical Physics Chinese Academy of SciencesDalian 116023 Liaoning China University of Chinese Academy of Sciences Beijing 100049 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 Liaoning China Tsinghua-Berkeley Shenzhen Institute Shenzhen 518055 Guangdong China

Lithium sulfur(Li-S)batteries hold great promising for high-energy-density batteries,but appear rapid capacity fading due to the lack of overall and elaborated design of both sulfur host and interlayer.Herein,we developed a novel two-dimensional(2D)hierarchical yolk-shell heterostructure,constructed by a graphene yolk,2D void and outer shell of vertically aligned carbon-mediated mos2 nanosheets(G@void@mos2/C),as advanced host-interlayer integrated electrode for Li-S batteries.Notably,the 2D void,with a typical thickness of^80 nm,provided suitable space for loading and confining nano sulfur,and vertically aligned ultrathin mos2 nanosheets guaranteed enriched catalytically active sites to effectively promote the transition of soluble polysulfides.The conductive graphene yolk and carbon mediated shell sufficiently accelerated electron transport.Therefore,the integrated electrode of G@void@mos2/C not only exceptionally confined the sulfur/polysulfides in 2D yolk-shell heterostructures,but also achieved catalytic transition of the residual polysulfides dissolved in electrolyte to solid Li2S2/Li2S,both of which synergistically achieved an extremely low capacity fading rate of 0.05%per cycle over 1000 times at 2C,outperforming most reported Mo based cathodes and interlayers for Li-S batteries.2D hierarchical yolkshell heterostructures developed here may shed new insight on elaborated design of integrated electrodes for Li-S batteries.

关键词： mos2 Graphene Yolk shell 2D heterostructure Lithium sulfur batteries

Manipulation of Coherent Optical Propagation Based on Monolayer mos2 Resonator

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Photonic Sensors 2019年第4期9卷 317-326页

作者： Huajun CHEN School of Mechanics and Photoelectric Physics Anhui University of Science and TechnologyHuainan 232001China

Atomically thin two-dimensional semiconductor nanomaterials have attained considerable attention currently.We here theoretically investigate the phenomena of slow and superluminal light based on the mos2 resonator system driven by two-tone fields.Superluminal and ultraslow probe light without absorption can be obtained via manipulating the pump laser on-and off-resonant with the exciton frequency under different parameters regimes,respectively,of which the magnitude is larger than that in a carbon nanotube resonator.The bandwidth of the probe spectrum determined by the quality factor Q of mos2 resonator is also presented.Furthermore,we also demonstrate the phenomenon of phonon induced transparency and show an optical transistor in the system.The all-optical device based on mos2 resonator may indicate potential chip-scale applications in quantum information with the currently popular pump-probe technology.

关键词： mos2 nanomechanical resonator fast and slow light optical transistor