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Facile synthesis of two-dimensional MoS_(2)/WS_(2) lateral heterostructures with controllable core/shell size ratio by a one-step chemical vapor deposition method

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Science China(Physics,Mechanics & Astronomy) 2021年第10期64卷 88-94页

作者： Baofan Sun Jiajun Chen Xinyi Zhou Min Liu Yaping Wu Yuanzheng Xia Xu Li Zhiming Wu Junyong Kang Department of Physics Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient DevicesFujian Provincial Key Laboratory of Semiconductor Materials and ApplicationsXiamen UniversityXiamen 361005China National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China

Heterostructures based on two-dimensional(2D) transition-metal dichalcogenides(TMDCs) possess unique electronic and optical properties, which open up unprecedented opportunities in nanoscale optoelectronic devices. Synthesizing high-quality 2D TMDC heterostructures with different core/shell size ratios is of great significance for practical applications. Here, we report a simple one-step chemical vapor deposition(CVD) method for fabricating MoS2/WS2 lateral heterostructures with controllable core/shell size ratio. An ultrathin MoO3/WO3 film prepared by thermal evaporation was used as the precursor, and a step-like heating process was adopted to separately grow MoS2 and WS2 monolayers by taking advantage of the different melting points of MoO3 and WO3 sources. High-quality MoS2/WS2 lateral heterostructures with sharp interfaces were fabricated by optimizing the key growth parameters. Furthermore, the core/shell size ratio of heterostructures could be easily controlled by changing the thickness ratio of MoO3/WO3 film, and an approximately linear dependence between them is revealed. Compared with MoS2 or WS2 monolayers, the MoS2/WS2 heterostructure exhibited a shortened exciton lifetime owing to the type-Ⅱ energy band alignment, which is conducive to the application of high-performance devices. This work provides a facile strategy for the synthesis of 2D lateral heterostructures with controllable size ratio.

关键词： lateral heterostructures controllable size ratio chemical vapor deposition thermal evaporation one-step growth

Controllable optical emission wavelength in all-inorganic halide perovskite alloy microplates grown by two-step chemical vapor deposition

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Nano Research 2020年第11期13卷 2939-2949页

作者： Mohammad K.Hossain Pengfei Guo Wayesh Qarony Yuen H.Tsang Chaoping Liu Sai W.Tsang Johnny C.Ho Kin M.Yu Department of Physics City University of Hong KongKowloonHong Kong SARChina Department of Physics Comilla UniversityKotbariCumilla3506Bangladesh Department of Materials Science and Engineering City University of Hong KongKowloonHong Kong SARChina Department of Applied Physics The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARChina College of Physics and Optoelectronics Taiyuan University of TechnologyTaiyuan030024China Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou515063China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou UniversityShantou515063China

All-inorganic halide perovskites(IHP),CsPbX_(3)(X=Cl,Br,I)exhibiting efficient optical emissions within the spectral range of 410 to 730 nm are potential candidates for many optoelectronic *** alloying of these IHPs is expected to achieve tunable emission wavelength covering the entire visible ***,we developed a two-step chemical vapor deposition(CVD)process for growing quaternary IHP CsPbX_(3)(X=Cl/Br and Br/I)*** exploiting the fast diffusion of halide anions in IHPs,the alloy composition can be precisely controlled by the growth time of the respective layers once the growth of the individual ternary IHP is *** complexities in the multi-parameter optimization in the conventional CVD growth of quaternary alloys can be *** this process,we synthesized single crystalline,homogeneous and thermally stable CsPbCl3_((1−X))Br_(3x)and CsPbBr3_((1−X))I_(3x)perovskites alloy microplates and demonstrated continuously tunable emission covering the spectrum from 428 to 715 nm by varying the halide compositions in the *** alloy microplates also exhibit room temperature amplified spontaneous emissions(ASE)along with strong photonic discharges from the microplate’s edges and hence are potentially useful as a gain medium as well as optical cavities for emissions with wavelengths covering the visible spectrum.

关键词： chemical vapor deposition inorganic perovskites quaternary alloys emission spectrum amplified spontaneous emissions(ASE)

Direct growth of graphene on gallium nitride by using chemical vapor deposition without extra catalyst

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Chinese Physics B 2014年第9期23卷 358-363页

作者：赵云王钢杨怀超安铁雷陈闽江余芳陶立羊建坤魏同波段瑞飞孙连峰 Semiconductor Lighting Technology Research and Development Center Institute of SemiconductorsChinese Academy of Sciences National Center for Nanoscience and Technology University of Chinese Academy of Sciences

Graphene on gallium nitride （GaN） will be quite useful when the graphene is used as transparent electrodes to improve the performance of gallium nitride devices. In this work, we report the direct synthesis of graphene on GaN without an extra catalyst by chemical vapor deposition. Raman spectra indicate that the graphene films are uniform and about 5-6 layers in thickness. Meanwhile, the effects of growth temperatures on the growth of graphene films are systematically studied, of which 950 ℃ is found to be the optimum growth temperature. The sheet resistance of the grown graphene is 41.1 Ω/square, which is close to the lowest sheet resistance of transferred graphene reported. The mechanism of graphene growth on GaN is proposed and discussed in detail. XRD spectra and photoluminescence spectra indicate that the quality of GaN epi-layers will not be affected after the growth of graphene.

关键词： graphene photoluminescence gallium nitride chemical vapor deposition Raman spectroscopy

Numerical modeling of SiC by low-pressure chemical vapor deposition from methyltrichlorosilane

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Chinese Journal of chemical Engineering 2020年第6期28卷 1733-1743页

作者： Kang Guan Yong Gao Qingfeng Zeng Xingang Luan Yi Zhang Laifei Cheng Jianqing Wu Zhenya Lu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640China Science and Technology on Thermostructural Composite Materials Laboratory School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China MSEA International Institute for Materials Genome Gu'an 065500China

The development of functional relationships between the observed deposition rate and the experimental conditions is an important step toward understanding and optimizing low-pressure chemical vapor deposition(LPCVD)or low-pressure chemical vapor infiltration(LPCVI).In the field of ceramic matrix composites(CMCs),methyltrichlorosilane(CH3 SiCl3,MTS)is the most widely used source gas system for SiC,because stoichiometric SiC deposit can be facilitated at 900°C–1300°***,the reliability and accuracy of existing numerical models for these processing conditions are rarely *** this study,a comprehensive transport model was coupled with gas-phase and surface *** resulting gas-phase kinetics was confirmed via the measured concentration of gaseous *** relationship between deposition rate and 24 gaseous species has been effectively evaluated by combining the special superiority of the novel extreme machine learning method and the conventional sticking coefficient *** kinetics were then proposed and shown to reproduce the experimental *** proposed simulation strategy can be used for different material systems.

关键词： chemical vapor deposition MTS/H2 Gas-phase and surface kinetics Extreme learning machine method Numerical model

Mg-doped ZnO radial spherical structures via chemical vapor deposition

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Rare Metals 2011年第3期30卷 292-297页

作者： PENG Jiangqiang GUO Jian DING Shulong XU Qiao LI Hang TAN Xuwei ZHAO Xian Faculty of Materials Optoelectronics and Physics Xiangtan University Xiangtan 411105 China

Mg-doped ZnO radial spherical structures with nanorods grown on both sides of the spherical shell were successfully prepared via chemical vapor deposition （CVD） of Zn and Mg powders in the absence of a catalyst. The structures associated with different growth temperatures （700, 800, and 850°C） were monitored by scanning electron microscopy （SEM）, and the result shows that the length of the nanorods increase progressively with the growth temperature increasing. X-ray diffraction （XRD） shows that the as-obtained samples can be indexed to high crystallinity with wurtzite structure. The growth of the nanostructures mainly depends on the formation of sphere-like Mg-doped Zn droplets before adding oxygen. Photoluminescence （PL） spectra that show a 39 meV blue shift indicates that the band gap becomes large, because Mg substitutes Zn in the lattice.

关键词： zinc oxide magnesium doping nanorods chemical vapor deposition photoluminescence spectroscopy

Versatile and scalable chemical vapor deposition of vertically aligned MoTe2 on reusable Mo foils

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Nano Research 2020年第9期13卷 2371-2377页

作者： Jinjun Lin Hong Wang Roland Yingjie Tay Hongling Li Maziar Shakerzadeh Siu Hon Tsang Zheng Liu Edwin Hang Tong Teo School of Electrical and Electronic Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore Temasek Laboratories@NTU 50 Nanyang AvenueSingapore 639798Singapore School of Materials Science and Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

Layered MoTe2 has shown great promises for optoelectronics and energy-storage applications due to its exceptional optical and electrochemical *** date,considerable efforts have been devoted to fabricating layered MoTe2 with lateral orientation by means of mechanical/chemical exfoliation and chemical vapor deposition(CVD)*** compared to its horizontal counterparts,vertically aligned MoTe2 with higher density of active edge sites is expected to possess unique optoelectronic and electrochemical properties,while which has not been reported *** this work,we report a versatile and scalable CVD growth of vertically aligned MoTe2 with length of up to〜7.5 fjm on Mo ***,the dominant phase of the vertically aligned MoTe2 can be tuned from 2H to 1T’by increasing the growth temperature from 630 to *** to the weak interaction between the as-grown MoTe2 and Mo foil,the as-grown MoTe2 can be easily detached from the Mo *** in turn enabled economic reuse of the Mo foil for multiple ***,the vertical growth of the MoTe2 is proposed to be caused by the internal strain generated during tellurization of Mo ***,the as-grown MoTe2 can also be directly dispersed in solvent to produce high-quality MoTe2 *** versatility of this growth strategy was further demonstrated by fabricating other vertically aligned transition metal chalcogenides(TMDs)such as TaTe2 and ***,this work paves the path towards achieving unique TMDs structures to enable high-performance optoelectronic and electrochemical devices.

关键词： molybdenum dltelluride chemical vapor deposition vertical growth reusable substrate

Self-organization of various“phase-separated”nanostructures in a single chemical vapor deposition

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Nano Research 2020年第6期13卷 1723-1732页

作者： Jinmei Wang Dongyue Xie Zhen Li Xiaohang Zhang Xing Sun Amanda L.Coughlin Thomas Ruch Qiang Chen Yaroslav Losovyj Seunghun Lee Heshan Yu Haidong Zhou Haiyan Wang Jian Wang Shixiong Zhang Department of Physics Indiana UniversityBloomingtonIndiana47405USA Department of Mechanical&Materials Engineering University of Nebraska-LincolnLincolnNE68588USA Department of Materials Science and Engineering University of MarylandCollege ParkMaryland20742USA School of Materials Engineering Purdue UniversityWest LafayetteIndiana47907USA Department of Physics and Astronomy University of TennesseeKnoxvilleTennessee37996USA Department of Chemistry Indiana UniversityBloomingtonIndiana47408USA College of Optoelectronic Engineering Chongqing University of Posts and TelecommunicationsChongqing400065China Department of Materials Science and NanoEngineering Rice UniversityHoustonTexas77005USA

chemical vapor deposition(CVD)is one of the most versatile techniques for the controlled synthesis of functional *** multiple precursors are induced,the CVD process often gives rise to the growth of doped or alloy *** this work,we demonstrate the self-assembly of a variety of‘phase-separated’functional nanostructures from a single CVD in the presence of various *** specific,with silicon substrate and powder of Mn and SnTe as precursors,we achieved self-organized nanostructures including Si/SiOx core-shell nanowire heterostructures both with and without embedded manganese silicide particles,Mn11Si19 nanowires,and SnTe *** Si/SiOx core-shell nanowires embedded with manganese silicide particles were grown along thedirection of the crystalline Si via an Au-catalyzed vapor-liquid-solid process,in which the Si and Mn vapors were supplied from the heated silicon substrates and Mn powder,*** contrast,direct vapor-solid deposition led to particle-free-oriented Si/SiOx core-shell nanowires and-oriented Mn11Si19 nanowires,a promising thermoelectric *** Sn or Te impurities were detected in these nanostructures down to the experimental *** crystalline insulator SnTe nanoplates with dominant{100}and{111}facets were found to be free of Mn(and Si)impurities,although nanoparticles and nanowires containing Mn were found in the vicinity of the *** multiple-channel transport was observed in the SnTe nanoplates,it may not be related to the topological surface states due to surface ***,we carried out thermodynamic analysis and density functional theory calculations to understand the‘phase-separation’phenomenon and further discuss general approaches to grow phase-pure samples when the precursors contain residual impurities.

关键词： nanomaterials synthesis silicon nanowires topological crystalline insulators phase separation chemical vapor deposition

Micro-and Nano-structure Characterization of Isotropic Pyrocarbon Obtained via chemical vapor deposition in Hot Wall Reactor

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Journal of Materials Science & Technology 2010年第12期26卷 1133-1138页

作者： Kezhi Li,Dongsheng Zhang,Lingjun Guo and Hejun Li State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi an 710072,China State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China

The hot wall reactor was used to deposit isotropic pyrocarbon. The density of the product was measured by Archimedes method. The fracture morphology and texture of the product were investigated by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Raman spectroscopy was also applied to characterizing the structure of the product. The results show that the density of the product is about 1.31 g/cm^3. The pyrocarbon consists of granular particles with the size of about 1.5 μm under SEM images. Under TEM images, the pyrocarbon is composed of irregular grains and onion-like particles are also detected. The orientation angle （180 deg.） of pyrocarbon reveals its isotropic character. The ID/IG ratio in Raman spectrum is about 1.2, indicating the isotropic feature of the product qualitatively.

关键词： Isotropic pyrocarbon chemical vapor deposition Structure characterization Onion-like pyrocarbon

Gold-vapor-assisted chemical vapor deposition of aligned monolayer WSe2 with large domain size and fast growth rate

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Nano Research 2020年第10期13卷 2625-2631页

作者： Mingrui Chen Anyi Zhang Yihang Liu Dingzhou Cui Zhen Li Yu-Han Chung Sai Praneetha Mutyala Matthew Mecklenburg Xiao Nie Chi Xu Fanqi Wu Qingzhou Liu Chongwu Zhou Mork Family Department of chemical Engineering and Materials Science Ming Hsieh Department of Electrical EngineeringCore Center of Excellence in Nano Imaging and Department of Physics and AstronomyUniversity of Southern CaliforniaLos AngelesCA 90089USA

Orientation-controlled growth of two-dimensional(2D)transition metal dichalcogenides(TMDCs)may enable many new electronic and optical ***,previous studies reporting aligned growth of WSe2 usually yielded very small domain ***,we introduced gold vapor into the chemical vapor deposition(CVD)process as a catalyst to assist the growth of WSe2 and successfully achieved highly aligned monolayer WSe2 triangular flakes grown on c-plane sapphire with large domain sizes(130μm)and fast growth rate(4.3μm·s^−1).When the aligned WSe2 domains merged together,a continuous monolayer WSe2 was formed with good *** transferring to Si/SiO2 substrates,field effect transistors were fabricated on the continuous monolayer WSe2,and an average mobility of 12 cm^2·V^−1·s−1 was achieved,demonstrating the good quality of the *** report paves the way to study the effect of catalytic metal vapor in the CVD process of TMDCs and contributes a novel approach to realize the growth of aligned TMDC flakes.

关键词： two-dimensional materials transition metal dichalcogenides tungsten diselenide(WSe2) chemical vapor deposition aligned growth