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Coupling Stacking Orders with Interlayer Magnetism in Bilayer H-VSe2

Chinese Physics Letters 2020年第10期37卷 61-67页

作者： Aolin Li Wenzhe Zhou Jiangling Pan Qinglin Xia Mengqiu Long Fangping Ouyang State Key Laboratory of Powder Metallurgy and Powder Metallurgy Research InstituteCentral South UniversityChangsha 410083China School of Physics and Electronics and Hunan Key Laboratory for Super-Microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China School of Physics and Technology Xinjiang UniversityUrumqi 830046China

Stacking-dependent magnetism in van der Waals materials has caught intense *** on the first principle calculations,we investigate the coupling between stacking orders and interlayer magnetic orders in bilayer H-VSe *** is found that there are two stable stacking orders in bilayer H-VSe 2,named AB-stacking and A′*** standard DFT framework,the A′B-stacking prefers the interlayer AFM order and is semiconductive,whereas the AB-stacking prefers the FM order and is ***,under the DFT+U framework both the stacking orders prefer the interlayer AFM order and are *** detailedly analyzing this difference,we find that the interlayer magnetism originates from the competition between antiferromagnetic interlayer super-superexchange and ferromagnetic interlayer double exchange,in which both the interlayer Se-4 p z orbitals play a crucial *** the DFT+U calculations,the double exchange is suppressed due to the opened bandgap,such that the interlayer magnetic orders are decoupled with the stacking *** on this competition mechanism,we propose that a moderate hole doping can significantly enhance the interlayer double exchange,and can be used to switch the interlayer magnetic orders in bilayer VSe *** method is also applicable to a wide range of semiconductive van der Waals magnets.

关键词： stacking interlayer orders

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Janus monolayer TaNF:A new ferrovalley material with large valley splitting and tunable magnetic properties

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Frontiers of physics 2023年第5期18卷 173-181页

作者：郑贵博蘧水仙周文哲欧阳方平 School of Physics and Electronics and Hunan Key Laboratory for Super-Microstructure and Ultrafast Processand Hunan Key Laboratory of Nanophotonics and DevicesCentral South UniversityChangsha 410083China School of Physics and Technology Xinjiang UniversityUrumqi 830046China State Key Laboratory of Powder Metallurgy and Powder Metallurgy Research InstituteCentral South UniversityChangsha 410083China

Materials with large intrinsic valley splitting and high Curie temperature are a huge advantage for studying valleytronics and practical *** this work,using first-principles calculations,a new Janus TaNF monolayer is predicted to exhibit excellent piezoelectric properties and intrinsic valley splitting,resulting from the spontaneous spin polarization,the spatial inversion symmetry breaking and strong spin-orbit coupling(SOC).TaNF is also a potential two-dimensional(2D)magnetic material due to its high Curie temperature and large magnetic anisotropy *** effective control of the band gap of TaNF can be achieved by biaxial strain,which can transform TaNF monolayer from semiconductor to *** magnitude of valley splitting at the CBM can be effectively tuned by biaxial strain due to the changes of orbital composition at the *** magnetic anisotropy energy(MAE)can be manipulated by changing the energy and occupation(unoccupation)states of d orbital compositions through biaxial *** addition,Curie temperature reaches 373 K under only−3%biaxial strain,indicating that Janus TaNF monolayer can be used at high temperatures for spintronic and valleytronic devices.

关键词： Janus valley splitting Curie temperature magnetic anisotropy energy first-principles calculations

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Tuning the alignment of pentacene on copper substrate by annealing-assistant surface functionalization

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Chinese Physics B 2020年第7期29卷 421-427页

作者： Qiao-Jun Cao Shuang Wen Hai-Peng Xie Bi-Yun Shi Qun Wang Cong-Rong Lu Yongli Gao Wei-Dong Dou Laboratory of Low-dimensional Carbon Materials and Department of Physics Shaoxing UniversityShaoxing 312000China Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Department of Physics and Astronomy University of RochesterRochesterNY 14627USA

Controlling the alignment and packing structure of organic molecules on solid substrate surfaces at molecule level is essential to develop high-performance organic thin film(OTF)***,which is a typical p-type semiconductor material usually adopts lying-down geometry on metal substrates owning toπ-d coupling between pentacene and metal ***,in this study,we found that pentacene molecules can be adsorbed on an anneal-treated Cu(111)surface with their long axis perpendicular to substrate *** ordered single-layer pentacene film with stand-up molecular geometry was achieved on this *** was found that the functionalization of Cu surface with C=O groups due to annealing treatment should be accounted for standing-up geometry of pentacene on Cu *** observation shed light on the tuning of the alignment and packing structure of organic molecules.

关键词： ultra-thin film molecular alignment metal substrate interfacial tuning

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Four-terminal perovskite tandem solar cells

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iEnergy 2024年第4期3卷 216-241页

作者： Muhammad Rafiq Hengyue Li Junliang Yang Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China Hunan Key Laboratory of Nanophotonics and Devices School of PhysicsCentral South UniversityChangsha 410083China State Key Labo-ratory of Powder Metallurgy Central South UniversityChangsha 410083China

One of the primary barriers to the advancement of high-efficiency energy conversion technologies is the Shockley–Queisser limit,which imposes a fundamental efficiency constraint on single-junction solar *** advent of multi-junction solar cells provides a formidable alternative to this *** these,organic-inorganic perovskite solar cells(PSCs)have captured substantial interest due to their outstanding optoelectronic properties,including tunable bandgaps and high-power conversion efficiencies,positioning them as prime candidates for multi-junction photovoltaic *** give a review of the latest advancements in four-terminal(4T)perovskite tandem solar cells(TSCs),emphasizing four pertinent configurations:perovskite-silicon(PVK/Si),per-ovskite-perovskite(PVK/PVK),perovskite-Cu(In,Ga)Se_(2)(PVK/CIGS),and perovskite-organic(PVK/organic),as well as other emerging 4T perovskite ***,it also emphasizes the advancement of semitransparent wide-bandgap PSCs for TSC applications,tackling important issues and outlining potential future directions for optimizing 4T tandem design performance.

关键词： Four-terminal tandem solar cells perovskite solar cells transparent electrode.

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van der Waals epitaxial growth of ultrathin metallic NiSe nanosheets on WSe2 as high performance contacts for WSe2 transistors

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Nano Research 2019年第7期12卷 1683-1689页

作者： Bei Zhao Weiqi Dang Xiangdong Yang Jia Li Haihong Bao Kai Wang Jun Luo Zhengwei Zhang Bo Li Haipeng Xie Yuan Liu Xidong Duan Hunan Key Laboratory of Two-Dimensional Materials State Key Laboratory for Chemo/Biosensing and ChemometricsCollege of Chemistry and Chemical EngineeringHunan UniversityChangsha 410082China School of Physics and Electronics Hunan UniversityChangsha 410082China Center for Electron Microscopy Institute for New Energy Materials and Low-Carbon Technologies School of Materials Tianjin University of TechnologyTianjin 300384China Hunan Key Laboratory of Super-microstructure and Ultrafast Process College of Physics and ElectronicsCentral South UniversityChangsha 410083China

A prerequisite for widespread applications of atomically thin transition metal dichalcogenides in future electronics is to achieve reliable electrical contacts,which is of considerable challenge due to the difficulties in selectively doping and inevitable physical damages of these atomically thin materials during typical metal integration ***,we report the in situ growth of ultrathin metallic NiSe single crystals on WSe2 in which the metallic NiSe nanosheets function as the contact electrodes to WSe2,creating an interface that is essentially free from chemical *** NiSe/WSe2 heterostructures also exhibit well-aligned lattice orientation between the two layers,forming a periodic Moire *** transport studies demonstrate that the NiSe nanosheets exhibit an excellent metallic feature,as evidenced by the extra-high electrical conductivity of up to 1.6×10^6 *** WSe2 transistors with the NiSe contact show field-effect mobilities (/vFe) more than double that with Cr/Au *** study demonstrates an effective pathway to achieve reliable electrical contacts to the atomically thin 2D materials,and maybe readily extended for fabricating 2D/2D low-resistance contacts for a variety of transition metal dichalcogenides.

关键词： in situ growth nonlayered NiSe nanosheets Schottky barrier metal-semiconductor junctions chemical vapor deposition

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Ordered porous TiO2 films obtained by freezing and the application in dye sensitized solar cells

Ordered porous TiO2 films obtained by freezing and the appli...

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Optoelectronic Devices and Integration, OEDI 2015

作者： Zhou, Conghua Wang, Xingxing Liu, Gang Yang, Bingchu Zhang, Dou Li, Zhiyou Zhou, Kechao Institute of Super-Microstructure and Ultrafast Process in Advanced Materials School of Physics and Electronics Central South University Changsha410083 China State Key Laboratory for Powder Metallurgy Research Institute of Powder Metallurgy Central South University Changsha410083 China Hunan Key Laboratory for Super-microstructure and Ultrafast Process Changsha410083 China

TiO2 films with ordered porous structure were prepared by freezing and used to fabricate dye sensitized solar cells. Due to the enhanced light scattering by the ordered porous structure, Increase of 13% in photo-curre... 详细信息

ISBN: (纸本)9781943580019

关键词： Dye-sensitized solar cells

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Vertical phase separation and morphology optimization of layer-by-layer non-fullerene organic solar cells

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Journal of Central South University 2024年第12期31卷 4338-4365页

作者： NING Bo-cheng MA Yu-meng ZHANG Jun ZOU Ying-ping YANG Jun-liang YUAN Yong-bo ZHANG Lin Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of PhysicsCollege of Chemistry and Chemical EngineeringCentral South UniversityChangsha 410083China

The development of high-performance non-fullerene acceptors with extended exciton diffusion lengths has positioned the sequential layer-by-layer(LBL)solution processing technique as a promising approach for fabricating high-performance and large-area organic solar cells(OSCs).This method allows for the independent dissolution and deposition of donor and acceptor materials,enabling precise morphology *** this review,we provide a comprehensive overview of the LBL processing technique,focusing on the morphology of the active *** swelling intercalation phase-separation(SIPS)model is introduced as the mainstream theory of morphology evolution,with a detailed discussion on vertical phase *** summarize recent strategies for morphology ***,we review the progress in LBL-based large-area device and module fabrication,as well as green processing ***,we highlight current challenges and future prospects,paving the way for the commercialization of LBL-processed OSCs.

关键词： organic solar cells layer-by-layer(LBL)solution processing technique vertical phase separation morphology optimization non-fullerene acceptors

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Large-scale roll-to-roll printed,flexible and stable organic bulk heterojunction photodetector

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npj Flexible Electronics 2018年第1期2卷 42-49页

作者： Sichao Tong Jun Yuan Chujun Zhang Chunhua Wang Baoxing Liu Jianqiang Shen Huayan Xia Yingping Zou Haipeng Xie Jia Sun Si Xiao Jun He Yongli Gao Junliang Yang Hunan Key Laboratory for Super-Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083 HunanChina College of Chemistry and Chemical Engineering Central South UniversityChangsha 410083 HunanChina Department of Physics and Astronomy University of RochesterRochesterNY 14627USA

A flexible and stable photodetector shows great potential applications in intelligent wearable devices,health monitoring,and biological *** high-output fabrication of flexible and stable photodetector via the large-scale printing process would accelerate its ***,a high performance,flexible organic bulk heterojunction(BHJ)photodetector with good stability is designed and fabricated via a large-scale roll-to-roll(R2R)micro-gravure printing technique on polyethylene terephthalate(PET)or paper substrate,in which the organic BHJ active layer is structured with[6,6]-phenyl C_(61)butyric acid methyl ester(PCBM)and a donor-acceptor copolymer,i.e.,employing 4,8-bis(2-ethylhexylthiophene)benzo[1,2-b;3,4-b′]dithiophene(BDTT)as the donor unit and 5,8-bis(5-thiophen-2-yl)-6,7-difluoro-2,3-bis(4-ethylhexyloxy-1-mata-luorophenyl)quinoxaline(ffQx)as the acceptor unit(PBDTT-ffQx).The PBDTT-ffQx/PCBM BHJ photodetector shows a broad photoresponse in ultraviolet and visible light,a high detectivity(D^(*))value up to 6.19×10^(11)Jones,and an excellent Iphoto/Idark as high as 5.6×10^(2).It exhibits excellent flexibility and *** performance parameters could maintain over 80%of original values after bending 10,000 cycles or exposing in ambient condition(humidity~50%,temperature~30℃)for 50 days without any *** importantly,the R2R micro-gravure printed PBDTT-ffQx/PCBM BHJ active layer is great homogeneous,and the responsivity(R)values of photodetector arrays show a very narrow *** research results show that a high-performance PBDTT-ffQx/PCBM BHJ photodetector with well reliability and reproducibility can be fabricated via the R2R micro-gravure printing technique,which provides an available strategy for fabricating large-area and flexible electronic and optoelectronic devices.

关键词： printing heterojunction donor

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Multiorder rotational Raman transitions in molecular alignment and orientation

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Physical Review A 2024年第2期110卷 023116页

作者： Shuwu Xu Zhenzhong Lian Qian-Qian Hong Lingxiao Wang Huajie Chen Yunxia Huang Chuan-Cun Shu School of Physics and Technology Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics

Nonresonant two-photon Raman transitions with ΔJ=±2 selection rules induce molecular alignment by altering the rotational quantum number J, whereas three-photon Raman transitions with ΔJ=±1 cause molecular orientation. Here, we perform a combined numerical and theoretical investigation to explore how these Raman transitions depend on laser intensity and to discern multiorder Raman transitions in laser-induced alignment and orientation going beyond two- and three-photon processes. Our results demonstrate the presence of higher-order transitions in molecular alignment and shed light on how alignment affects subsequent three-photon rotational Raman transitions as revealed by the alignment and orientation spectra and the Dyson series expansion of the unitary operator. As the laser pulse strength increases, multiorder transitions become directly observable, which can be utilized to enhance the alignment and orientation of molecules through the excitation of multiple rotational states.

关键词： Atomic & molecular processes in external fields Light-matter interaction Molecular evolution Rotational states

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Structural and magnetic properties of micropolycrystalline cobalt thin films fabricated by direct current magnetron sputtering

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International Journal of Minerals,Metallurgy and Materials 2024年第2期31卷 384-394页

作者： Kerui Song Zhou Li Mei Fang Zhu Xiao Qian Lei School of Materials Science and Engineering Central South UniversityChangsha 410083China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics and electronicsCentral South UniversityChangsha 410083China Key Laboratory of Non-Ferrous Metal Materials Science and Engineering Ministry of EducationChangsha 410083China

Pure cobalt(Co)thin films were fabricated by direct current magnetron sputtering,and the effects of sputtering power and pres-sure on the microstructure and electromagnetic properties of the films were *** the sputtering power increases from 15 to 60 W,the Co thin films transition from an amorphous to a polycrystalline state,accompanied by an increase in the intercrystal pore ***,the resistivity decreases from 276 to 99μΩ·cm,coercivity increases from 162 to 293 Oe,and in-plane magnetic aniso-tropy *** the sputtering pressure decreases from 1.6 to 0.2 Pa,grain size significantly increases,resistivity significantly de-creases,and the coercivity significantly increases(from 67 to 280 Oe),which can be attributed to the increase in defect ***-pondingly,a quantitative model for the coercivity of Co thin films was *** polycrystalline films sputtered under pressures of 0.2 and 0.4 Pa exhibit significant in-plane magnetic anisotropy,which is primarily attributable to increased microstress.

关键词： cobalt thin film magnetron sputtering microstructure electromagnetic properties

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