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Mechanisms of the epitaxial growth of two-dimensional polycrystals

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npj Computational Materials 2022年第1期8卷 1016-1026页

作者： Jichen Dong Yunqi Liu Feng Ding Centre for Multidimensional Carbon Materials Institute for Basic ScienceUlsan44919Korea Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic SolidsInstitute of ChemistryChinese Academy of SciencesBeijing100190P.R.China University of Chinese Academy of Sciences Beijing100049P.R.China School of Materials Science and Engineering Ulsan National Institute of Science and TechnologyUlsan44919Korea

In the epitaxial growth of two-dimensional(2D)materials on substrates,2D polycrystals with various shapes have been broadly observed,but their formation mechanisms are still highly elusive.Here we present a complete study on the formation mechanisms of various 2D polycrystals.The structures of the 2D polycrystals are dependent on the symmetries of both the 2D material and the substrate.We build four complete libraries of 2D polycrystals for(i)threefold symmetric 2D materials on two-or six-fold symmetric substrates(i.e.,family-Ⅲ/Ⅱor-Ⅲ/Ⅵ),(ii)threefold symmetric 2D materials on fourfold symmetric substrates(i.***.family-Ⅲ/Ⅳ),(iii)fourfold symmetric 2D materials on three-or six-fold symmetric substrates(i.e.,family-Ⅳ/Ⅲor-Ⅳ/Ⅵ),and(iv)sixfold symmetric 2D materials on fourfold symmetric substrates(i.e.,family-Ⅵ/Ⅳ),respectively.The four libraries of 2D polycrystals are consistent with many existing experimental observations and can be used to guide the experimental synthesis of various 2D polycrystals.

关键词： symmetric polycrystals epitaxial

epitaxially aligned single-crystal gold nanoplates formed in large-area arrays at high yield

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Nano Research 2022年第1期15卷 296-303页

作者： Trevor B.Demille Robert D.Neal Arin S.Preston Zijuan Liang Allen G.Oliver Robert A.Hughes Svetlana Neretina College of Engineering University of Notre DameNotre DameIndiana 46556USA Department of Chemistry and Biochemistry University of Notre DameNotre DameIndiana 46556USA

Well-tailored nanomaterials with a single-crystal character provide ideal building blocks for on-chip plasmonic devices.Although colloidal methods have demonstrated mastery over the synthesis of such structures,it has proven quite difficult to deploy these same nanomaterials on substrate surfaces in a highly deterministic manner where precise control over position and orientation is ensured.Herein,we demonstrate a room-temperature two-reagent liquid-phase seed-mediated synthesis of gold nanoplates directly on substrate surfaces in arrays over a square-centimeter area.The synthesis is reliant on benchtop lithographic and directed-assembly processes that give rise to single-crystal seeds of gold that express both an epitaxial relationship with the underlying substrate and the internal defect structure required to promote a two-dimensional growth mode.The resulting structures are highly faceted and,because seed-substrate epitaxy is imposed upon the growing nanoplates,are identically aligned on the substrate surface.Nanoplate yields are increased to values as high as 95%using a post-processing sonication procedure that selectively removes a small population of irregularly shaped nanostructures from the substrate surface,and in doing so,gives rise to an uncompromised plasmonic response.The work,therefore,advances the techniques needed to integrate single-crystal nanomaterials with wafer-based technologies and provides leading-edge capabilities in terms of defining large-area arrays of plasmonic structures with the nanoplate geometry.

关键词： nanoplates epitaxial array plasmon Brij-700 block copolymer substrate

epitaxial growth and electrical transport properties of La_(0.5)Sr_(0.5)CoO_3 thin films prepared by pulsed laser deposition

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Science China Mathematics 1999年第8期42卷 865-872页

作者：李美亚熊光成王忠烈范守善赵清太林揆训 Science Center Shantou University Shantou 515063 China Department of Physics Peking University Beijing 100871 China Microelectronic Institute Peking University Beijing 100871 China Department of Physics Tsinghua University Beijing 100084 China

epitaxial growth of the La0.5Sr0.5CoO3（LSCO） thin films has been realized on LaAlO3, SrTiO3 and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of these films were studied systematically. The temperature dependencies of the resistivity of the film have been determined. Studies indicate that close dependencies exist between the crystal structures and the electrical transport properties of the epitaxial LSCO films, and that the epitaxial thin films are of low resistivity and metallic conductive features. The epitaxial films deposited on the LaAlO3 substrates at about 700℃ possess the optimal properties compared with the others. Discussions of the dependencies and the mechanisms of the epitaxial structures on the electrical transport properties of the LSCO films have been made.

关键词： epitaxial growth pulsed laser deposition La0.5Sr0.5CoO3 thin film electrical transport properties.

Interfacial Structure Between epitaxial Diamond Films and Silicon Substrates

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Chinese Physics Letters 1997年第2期14卷 145-147页

作者：高巧君尤力平潘晓辉张帆彭晓芙林增栋 Department of Physics Peking UniversityBeijing 100871 Laboratory of Electron Microscopy Peking UniversityBeijing 100871 Beijing Institute of Powder Metallurgy Beijing 100078

epitaxial diamond films on non-mirror polished silicon substrate was achieved using hot filament chemical vapor deposition method with one flat horizontal filament.The orientation relationship of epitaxial diamond films on silicon substrate has been investigated by cross-sectional high-resolution transmission electron microscopy We found one excellent epitaxial configuration and according to the experimental result we suggest a corresponding model.The lattice misfit is only 0.1-2.8% related to our model and the analysis of 60° type interface dislocation also supports this model.

关键词： sectional mirror epitaxial

Dynamic and nonlinear properties of epitaxial quantum dot lasers on silicon for isolator-free integration

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Photonics Research 2019年第11期7卷 1222-1228页

作者： Jianan Duan Heming Huang Bozhang Dong Justin C.Norman Zeyu Zhang John E.Bowers Frederic Grillot LTCI Telecom ParisInstitut Polytechnique de Paris46 rue Barrault75013 ParisFrance Materials Department University of CaliforniaSanta BarbaraCalifornia 93106USA Department of Electrical and Computer Engineering University of CaliforniaSanta BarbaraCalifornia 93106USA Institute for Energy Efficiency University of CaliforniaSanta BarbaraCalifornia 93106USA Center for High Technology Materials University of New MexicoAlbuquerqueNew Mexico 87106USA

This work investigates the dynamic and nonlinear properties of quantum dot(QD) lasers directly grown on silicon with a view to isolator-free applications. Among them, the chirp parameter, also named the αHfactor,is featured through a thermally insensitive method analyzing the residual side-mode dynamics under optical injection locking. The αHat threshold is found as low as 0.32. Then, the nonlinear gain is investigated from the gain compression factor viewpoint. The latter is found higher for epitaxial QD lasers on silicon than that in heterogeneously integrated quantum well(QW) devices on silicon. Despite that, the power dependence of the αHdoes not lead to a large increase of the chirp coefficient above the laser’s threshold at higher bias. This effect is confirmed from an analytical model and attributed to the strong lasing emission of the ground-state transition, which transforms into a critical feedback level as high as-6.5 d B, which is ~19 d B higher than a comparable QW laser.Finally, the intensity noise analysis confirms that QD lasers are overdamped oscillators with damping frequencies as large as 33 GHz. Altogether, these features contribute to fundamentally enhancing the reflection insensitivity of the epitaxial QD lasers. This last feature is unveiled by the 10 Gbit/s error-free high-speed transmission experiments. Overall, we believe that this work is of paramount importance for future isolator-free photonics technologies and cost-efficient high-speed transmission systems.

关键词： quantum nonlinear epitaxial

Characterization of Obtuse Triangular Defects on 4H-SiC 4° off-Axis epitaxial Wafers

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Chinese Physics Letters 2013年第9期30卷 109-111页

作者：董林孙国胜俞军郑柳刘兴昉张峰闫果果李锡光王占国杨霏 Key Laboratory of Semiconductor Materials Science Institute of SemiconductorsChinese Academy of SciencesBeijing 100083 Dongguan Tianyu Semiconductor Inc.Dongguan 523000 State Grid Smart Grid Research Institute Beijing 100192

We investigate the triangular defects with different structural features on 4H-SiC epilayers by a Nomarski micro-scope,a Candela optical surface analyzer and ultraviolet photoluminescence(UV-PL)imaging.Both the foreign particles and the substrate scratches can cause the formation of the obtuse triangular defects.The central area of some obtuse triangular defects can have the spatially confined core,in which the in-grown stacking faults can be observed under the UV-PL imaging.In contrast,the obtuse triangular defects induced by the scratches appear in the form of band-like defects,of which the width depends on the scratch direction and reaches the maximum when the scratch direction is parallel to the step flow direction.The formation mechanisms of these obtuse triangular defects are discussed.

关键词： triangular epitaxial ultraviolet

Fast Liquid Phase epitaxial Growth for Perovskite Single Crystals

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Chinese Physics Letters 2020年第1期37卷 97-100页

作者：李雨巍王昕李冠文吴瑶潘禹竹徐玉冰陈静雷威 Joint International Research Laboratory of Information Display and Visualization School of Electronic Science and EngineeringSoutheast UniversityNanjing 210096

Semiconductors grown by the solution-processed method have shown low-cost,facile fabrication process and comparable performance.However,there are many reasons why it is difficult to achieve high quality films.For example,lattice constant mismatch is one of the problems when photovoltaic devices made of organ metallic perovskites.In this work,MAPbBr^(MA=CH3NH3^+)perovskites single crystals grown on the surface of MAPbBr2.5 CI0.5 perovskites single crystals via liquid epitaxial growth method is demonstrated.It is found that when the lattice constants of the two perovskite single crystals are matched,another crystal can be grown on the surface of one crystal by epitaxial growth.The whole epitaxy growth process does not require high heating temperature and long heating time.X-ray diffraction method is used to prove the lattice plane of the substrate and the epitaxial grown layer.A scanning electron microscope is used to measure the thickness of the epitaxial layer.Compared with perovskite-based photodetectors without epitaxial growth layer,perovskite-based photodetectors with epitaxial growth layer have lower dark current density and higher optical responsibility.

关键词： Crystal perovskite epitaxial

A General Synthetic Approach of Organic Lateral Heterostructures for Optical Signal Converters in All-Color Wavelength

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CCS Chemistry 2023年第2期5卷 423-433页

作者： Qiang Lv Xue-Dong Wang Wan-Ying Yang Kai-Li Wang Chao-Fei Xu Min Zheng Liang-Sheng Liao National Engineering Laboratory for Modern Silk College of Textile and Clothing EngineeringResearch Center of Cooperative Innovation for Functional Organic/Polymer Material Micro/NanofabricationSoochow UniversitySuzhouJiangsu 215123 Institute of Functional Nano&Soft Materials(FUNSOM) Soochow UniversitySuzhouJiangsu 215123 Jiangsu General Science&Technology Co. Ltd.Suzhou Industrial ParkSuzhouJiangsu 215123 Macao Institute of Materials Science and Engineering Macao University of Science and TechnologyTaipa 999078Macao SAR

Organic heterostructures with precisely defined compositions,architectures,and interfaces are considered promising building blocks for integrated optoelectronic devices.However,it remains a great challenge to rationally design and synthesize a heterostructure with tunable performance for promising applications such as optoelectronic devices.Herein,we report a universal strategy for the synthesis of organic lateral heterostructures(OLHs)with tunable function and optical properties.We fabricated cocrystals based on the tunable intermolecular distance(dπ–πfrom 3.33 to 3.48Å)ofBenzo[ghi]perylene(BGP)-based driven by arene-perfluoroarene interaction or charge transfer interaction;these different components were selectively constructed into organic solid solution microwires or OLHs.Importantly,the solid solution microwires obtained could be epitaxially grown on the BGP-tetrabromophthalicanhydride trunk microwire to construct a series of OLHs microwires,which led to the successful demonstration of both photonic signal conversion and optical logic gate in all-color wavelength.This work gives a new insight into the fine synthesis of heterostructures with tunable structures/performances,providing predictable synthetic pathways to multifunctional organic heterostructures for the future realization of integrated optoelectronics.

关键词： organic heterostructure low-dimensional structure crystal epitaxial growth integrated photonics

Field dependence of magnetoresistance in epitaxial single-crystal La_(2/3)Ca_(1/3)MnO_(3-δ) thin film

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Science China Mathematics 1999年第1期42卷 99-105页

作者：李可斌程荣胜王守国陈志祥方军王智河曹效文许小军朱警生张裕恒 Institute of Solid State Physics Chinese Academy of Sciences Hefei China High Magnetic Field Laboratory Institute of Plasma Physics Chinese Academy of Sciences Hefei China Structural Research Laboratory University of Science and Technology of China Hefei China

epitaxial La2/3Ca1/3MnO3 thin films were prepared on NdGaO3 （110） substrates by d.c. magnetron sputtering method. The measurements of magnetoresistance ρ（H） upon magnetic field at different temperatures were carried out in the field range of 0—8 T. It is found that ρ（H） obeys the following relations: when the temperature （T） is higher than the Curie temperature TC, ρ（H）=1/（α（T）+β（T）H2）; below TC, ρ（H）=ρ0（T）+1/(A（T）+B（T）exp（H/c（T））, and ρ（H）=（1/（σ（T）+γ（T）H）） when T is far below TC. It is suggested that the negative magnetoresistive effect is mainly due to enhancement of the magnetoconductanee.

关键词： epitaxial La2/3Ca1/3Mno3 thin films colossal magnetoresistive effect field dependence of magnetore-sistance.