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Low-Programmable-Voltage Nonvolatile Memory Devices Based on Omega-shaped Gate Organic Ferroelectric P(VDF-TrFE) Field Effect Transistors Using p-type Silicon Nanowire Channels

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Nano-Micro Letters 2015年第1期7卷 35-41页

作者： Ngoc Huynh Van Jae-Hyun Lee Dongmok Whang dae joon kang Department of Physics Institute of Basic SciencesSungkyunkwan University School of Advanced Materials Science and Engineering SKKU Advanced Institute of Nanotechnology Sungkyunkwan University

A facile approach was demonstrated for fabricating high-performance nonvolatile memory devices based on ferroelectric-gate field effect transistors using a p-type Si nanowire coated with omega-shaped gate organic ferroelectric poly(vinylidene fluoride-trifluoroethylene)(P(VDF-Tr FE)). We overcame the interfacial layer problem by incorporating P(VDF-Tr FE) as a ferroelectric gate using a low-temperature fabrication process. Our memory devices exhibited excellent memory characteristics with a low programming voltage of ±5 V, a large modulation in channel conductance between ON and OFF states exceeding 105, a long retention time greater than 3 9 104 s, and a high endurance of over 105 programming cycles while maintaining an ION/IOFFratio higher than 102.

关键词： Si nanowires Field effect transistor Ferroelectric memory

Durable hierarchical phosphorus‐doped biphase MoS_(2)electrocatalysts with enhanced H^(*)adsorption

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Carbon Energy 2024年第4期6卷 104-114页

作者： Yongteng Qian Jianmin Yu Zhiyi Lyu Qianwen Zhang Tae Hyeong Lee Huan Pang dae joon kang College of Pharmacy Jinhua PolytechnicJinhuaZhejiangChina Department of Physics Sungkyunkwan UniversitySuwonGyeonggi‐doRepublic of Korea International Collaborative Laboratory of 2D Materials for Optoelectronic Science and Technology of Ministry of Education Institute of Microscale OptoelectronicsShenzhen UniversityShenzhenGuangdongChina School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhouJiangsuChina

Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic ***,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine ***,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER *** optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),*** mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization *** study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.

关键词： 1T/2H MoS_(2) density functional theory electrocatalysts phase engineering phosphorous doping

Lead halide perovskite sensitized WSe_(2) photodiodes with ultrahigh open circuit voltages

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eLight 2023年第1期3卷 188-197页

作者： Sung-joon Lee Hung-Chieh Cheng Yiliu Wang Boxuan Zhou Dehui Li Gongming Wang Yuan Liu Jian Guo Hao Wu dae joon kang Yu Huang Xiangfeng Duan Department of Materials Science and Engineering University of CaliforniaLos AngelesCAUSA Department of Physics Sungkyunkwan UniversitySuwonRepublic of Korea Department of Chemistry and Biochemistry University of CaliforniaLos AngelesCAUSA Present Address:Materials Science and Technology Division U.S.Naval Research LaboratoryWashingtonDCUSA

Two-dimensional semiconductors(2DSCs)have attracted considerable interests for optoelectronic devices,but are often plagued by the difficulties in tailoring the charge doping type and poor optical absorption due to their atomically thin ***,we report a methylammonium lead iodide perovskite(CH_(3)NH_(3)PbI_(3))/2DSC heterojunction device,in which the electric-field controllable ion migration in the perovskite layer is exploited to induce reversible electron-and hole-doping effects in the underlying monolayer tungsten diselenide(WSe_(2))to form a programmable p-n *** the same time,the CH_(3)NH_(3)PbI_(3) layer functions as a highly efficient sensitization layer to greatly boost the optical absorption and external quantum efficiency(EQE)of the resulting *** asymmetrically poling the perovskite layer,gold-contacted CH_(3)NH_(3)PbI_(3)/WSe_(2) devices show a switchable open circuit voltage up to 0.78 V,along with a high EQE of 84.3%.The integration of tunable graphene-contacts further improves the photodiode performance to achieve a highest open circuit voltage of 1.08 V and a maximum EQE of 91.3%,greatly exceeding those achieved previously in 2DSC lateral *** studies establish a non-invasive approach to switch optoelectronic functions and open up a new avenue toward high-performance reconfigurable optoelectronic devices from 2DSCs.

关键词： Electrostatic doping Programmable optoelectronic devices Lead halide perovskite Two-dimensional

Olfactory Response of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) to Volatiles Emitted by Mungbean Plants

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Agricultural Sciences in China 2011年第4期10卷 560-565页

作者： BAI Shu-xiong WANG Zhen-ying HE kang-lai Im dae-joon State Key Laboratory of Plant Diseases and Insect Pests Institute of Plant Protection Chinese Academy of Agricultural Sciences Beijing 100193 P.R.China National Crop Experiment Station Rural Development Administration Suwon 441-100 Republic of Korea

Intercropping maize with the prostrate variety of mungbean, Vigna radiata （L.） Wilczek which grows flat along the ground can increase parasitism of the eggs of the Asian corn borer, Ostrinia furnacalis （Guenée）, a crucial insect pest of maize in China, by Trichogramma ostriniae Pang Chen. This study investigated the behavioural responses of T. ostriniae to plant volatiles emitted from whole plants, leaves, and flowers of prostrate and erect varieties of mungbean in a 4-armed olfactometer. Female parasitiods were significantly attracted to the odours from some varieties of prostrate mungbean when the visit duration and the number of visits were considered, but were not attracted to the odours from any erect varieties. The attractive odours were shown to emanate from the leaves, rather than from the flowers of prostrate mungbean plants. These results have implications for the augmentation of Trichogramma parasitoids in bio-control of O. furnacalis and other crop pests.

关键词： Trichogramma ostriniae olfactory response Vigna radiata plant volatile

Feasibility of wear reduction for soft nanostructured thin film through enhanced elastic recoverability and contact stress relief

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Friction 2023年第7期11卷 1292-1306页

作者： Kuk-Jin SEO Hyun-joon KIM dae-Eun KIM Department of Mechanical Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Precision Mechanical Engineering Kyungpook National UniversitySangju 37224Republic of Korea Department of Advanced Science and Technology Convergence Kyungpook National UniversitySangju 37224Republic of Korea

This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stress relief originating from its mesh *** investigate the wear characteristics of the mesh structure compared to those of the homogeneous thin film,multi-walled CNTs(MWCNTs)and diamond-like carbon(DLC)thin films were prepared to conduct nanoscale tribological experiments using the atomic force microscopy(AFM).The MWCNT thin film showed unmeasurably low wear compared with the DLC thin film under a certain range of normal *** demonstrate the wear reduction mechanism of the MWCNT thin film,its indentation and frictional behaviors were *** indentation behavior of the MWCNT thin film revealed repetitive elastic deformation with a wide strain range and a significantly lower elastic modulus than that of the DLC thin *** permanent deformation of the MWCNT thin film was observed through frictional experiments under relatively high normal load *** results are expected to provide insights into the design of highly wear-resistant surfaces using nanostructures.

关键词： carbon nanotube(CNT) thin film wear friction elastic recovery

Identifying the relationships between subsurface absorber defects and the characteristics of kesterite solar cells

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Carbon Energy 2023年第8期5卷 42-54页

作者： dae-Ho Son Dong-Hwan Jeon dae-Hwan Kim Jin-Kyu kang Shi-joon Sung Jaebaek Lee Taeseon Lee Enkhjargal Enkhbayar JunHo Kim Kee-Jeong Yang Division of Energy Technology DGISTDaeguRepublic of Korea Research Center for Thin Film Solar Cells DGISTDaeguRepublic of Korea Department of Physics Incheon National UniversityIncheonRepublic of Korea

Understanding the defect characteristics that occur near the space-charge regions(SCRs)of kesterite(CZTSSe)solar cells is important because the recombination loss at the CZTSSe/CdS interface is considered the main cause of their low *** surfaces with different elemental compositions were formed without polishing(C00)and with polishing for 20 s(C20)and 60 s(C60).For C60,a specific region near the SCR was excessively Cu-rich and Zn-poor compared to C00 and *** charged defects formed where the elemental variation was *** the main deep acceptor defect energy level(E_(a2))near the SCR increased,the efficiency,open-circuit voltage deficit,and current density degraded,and this phenomenon was especially rapid for large E_(a2) *** the E_(a2) near the SCR became deep,the carrier diffusion length decreased more for the CZTSSe solar cells with a low carrier mobility than for the CuInGaSe_(2)(CIGSe)solar *** large amplitude of the electrostatic potential fluctuation in the CZTSSe solar cells induced a high carrier recombination and a short carrier ***,the properties of the CZTSSe solar cells were more strongly degraded by defects with deep energy levels near the SCR than those of the CIGSe solar cells.

关键词： defect density defect energy level elemental variation kesterite space charge region

Rational design and synthesis of hierarchically structured SnO2 microspheres assembled from hollow porous nanoplates as superior anode materials for lithium-ion batteries

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Nano Research 2018年第3期11卷 1301-1312页

作者： Gi dae Park Yun Chan kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seoul 136-713 Republic of Korea

Herein, hierarchically structured SnO2 microspheres are designed and synthesized as an efficient anode material for lithium-ion batteries using hollow SnO2 nanoplates. Three-dimensionally ordered macroporous （3-DOM） SnOx-C microspheres synthesized by spray pyrolysis are transformed into hierarchically structured SnO2 microspheres by a two-step post-treatment process. Sulfidation produces hierarchically structured SnS-SnS2-C microspheres comprising tin sulfide nanoplate and carbon building blocks. A subsequent oxidation process produces SnO2 microspheres from hollow SnO2 nanoplate building blocks, which are formed by Kirkendall diffusion. The discharge capacity of the hierarchically structured SnO2 microspheres at a current density of 5 Ag^-1 for the 600th cycle is 404 mA·h·g^-1. The hierarchically structured SnO2 microspheres have reversible discharge capacities of 609 and 158 mA·h·g^-1 at current densities of 0.5 and 30 Ag^-1, respectively. The ultrafine nanosheets contain empty voids that allow excellent lithium-ion storage performance, even at high current densities.

关键词： Kirkendall diffusion nanoplate tin oxide lithium-ion batter spray pyrolysis

Effects of deforestation on microbial diversity in a Siberian larch(Larix sibirica) stand in Mongolia

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Journal of Forestry Research 2019年第5期30卷 1885-1893页

作者： Jun Won kang Yeong dae Park Division of Forest Tree Improvement National Institute of Forest ScienceSuwonGyeonggi 16631Republic of Korea Department of Forest Resources Daegu UniversityGyeongbuk 38453Republic of Korea

For evaluating microbial community changes in a Siberian larch stand disturbed by forest fire or clearcutting,357 clones were randomly selected and sequenced using a culture-independent approach and 16S rRNA sequencing to characterize the bacterial composition and diversity from the different disturbed Siberian larch ***,the burned larch stand had an increase in the relative amounts of b-proteobacteria and Firmicutes and a decrease in Acidobacteria,while Gemmatimonadetes increased Verrucomicrobia decreased in the harvested larch *** diversity and richness were higher in the undisturbed larch stand than the disturbed(burned or clear-cut)larch stands,and the influence of clear-cutting was more negative than that of the forest *** study indicates that evaluating the microbial diversity of undisturbed,burned,and clear-cutting Siberian larch stands provides information about the impact of forest disturbances on soil microbial communities,which may be helpful for understanding and evaluating soil health and devising reafforestation strategies for larch.

关键词： Forest fire Forest health Harvest Microbial diversity Reafforestation Siberian Larch(Larix sibirica) Soil microbiome

Exploration of cobalt selenite-carbon composite porous nanofibers as anode for sodium-ion batteries and unveiling their conversion reaction mechanism

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Journal of Materials Science & Technology 2021年第30期89卷 24-35页

作者： Jin-Sung Park Gi dae Park Yun Chan kang Department of Materials Science and Engineering Korea UniversityAnam-DongSeongbuk-GuSeoul136-713Republic of Korea

Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition metal cation coupled with two anions is *** cobalt selenite(CoSeO_(3))-carbon composite nanofibers containing numerous pores are synthesized via electrospinning *** heat treatment of the electrospun nanofibers containing selenium,CoSe_(2)nanoclusters are *** the subsequent oxidation,CoSe_(2)transformed into amorphous CoSeO_(3)and some part of carbon was oxidized into CO_(2),leaving the pores inside the *** unveil the electrochemical reaction mechanism,analytical methods including cyclic voltammetry,ex-situ X-ray photoelectron spectroscopy,ex-situ transmission electron microscopy,and in-situ electrochemical impedance spectroscopy techniques were *** on the analyses,the following conversion reaction from the second cycle onward is suggested:CoO+xSeO_(2)+(1-x)Se+4(x+1)Na^(+)+4(x+1)e~-?Co+(2x+1)Na_(2)O+Na_(2)***,the electrochemical properties of porous CoSeO_(3)-carbon composite nanofibers are analyzed in *** anode material exhibited stable cycle stability up to 200 cycles at 0.5 A g^(-1)and high rate performance up to 5 A g^(-1).

关键词： Anode materials Sodium-ion batteries Conversion reaction Metal selenite Electrospinning