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Optoelectronic properties of bottom gate-defined in-plane monolayer WSe_2 p–n junction

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Chinese Physics B 2018年第8期27卷 476-481页

作者： Di Liu xiao-Zhuo Qi Takashi Taniguchi xi-feng ren Guo-Ping Guo Key Laboratory of Quantum Information University of Science and Technology of ChinaChinese Academy of SciencesHefei 230026China Synergetic Innovation Center of Quantum Information&Quantum Physics University of Science and Technology of ChinaHefei 230026China National Institute for Materials Science Namiki 1-1Ibaraki 305-0044Japan

Monolayer transition-metal dichalcogenides （TMDs） are considered to be fantastic building blocks for a wide variety of optical and optoelectronic devices such as sensors, photodetectors, and quantum emitters, owing to their direct band gap, transparency, and mechanical flexibility. The core element of many conventional electronic and optoelectronic devices is the p-n junction, in which the p- and n-types of the semiconductor are formed by chemical doping in different regions. Here, we report a series of optoelectronic studies on a monolayer WSe2 in-plane p-n photodetector, demonstrating a low- power dissipation by showing an ambipolar behavior with a reduced threshold voltage by a factor of two compared with the previous results on a lateral electrostatically doped WSe2 p-n junction. The fabrication of the device is based on a polycarbonates （PC） transfer technique and hence no electron-beam exposure induced damage to the monolayer WSe2 is expected. Upon optical excitation, the photodetector demonstrates a photoresponsivity of 0.12 mA.W-1 and a maximum external quantum efficiency of 0.03%. Our study provides an alternative platform for a flexible and transparent two- dimensional photodetector, from which we expect to further promote the development of next-generation optoelectronic devices.

关键词： WSe2, photodetector transfer technique p-n junction

Spectrally multiplexed and bright entangled photon pairs in a lithium niobate microresonator

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Science China(Physics,Mechanics & Astronomy) 2022年第9期65卷 3-9页

作者： Bo-Yu Xu Li-Kun Chen Jin-Tian Lin Lan-Tian feng Rui Niu Zhi-Yuan Zhou ren-Hong Gao Chun-Hua Dong Guang-Can Guo Qi-Huang Gong Ya Cheng Yun-feng xiao xi-feng ren CAS Key Laboratory of Quantum Information University of Science and Technology of ChinaHefei 230026China State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics School of PhysicsPeking UniversityBeijing 100871China State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science Shanghai Institute of Optics and Fine Mechanics(SIOM)Chinese Academy of Sciences(CAS)Shanghai 201800China CAS Synergetic Innovation Center of Quantum Information&Quantum Physics University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

On-chip bright quantum sources with multiplexing ability are extremely high in demand for integrated quantum networks with unprecedented scalability and ***,we demonstrate a bright and broadband biphoton quantum source with spectral multiplexing generated in a lithium niobate microresonator *** introducing the conventional domain poling,the on-chip microdisk produces photon pairs covering a broad bandwidth promised by natural phase matching in spontaneous parametric down ***,the multiplexed photon pairs are characterized by 30 nm bandwidth limited by the filtering system,providing over 40 multiplexing channels with a 0.8 nm channel ***,the generation rate reaches 5.13 MHz/μW with a coincidence-to-accidental ratio up to 804,and the quantum source manifests a high purity with a heralded single photon correlation g^((2))_(H)(0)=0.0098±***,the energy-time entanglement is demonstrated with an excellent interference visibility of 96.5%±2%.Such a quantum source at the telecommunication band paves the way for high-dimensional entanglement and future integrated quantum information systems.

关键词： quantum entangled source spectral multiplexing lithium niobate on insulator microresonator

Gap plasmon-enhanced photoluminescence of monolayer MoS_2 in hybrid nanostructure

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Chinese Physics B 2018年第4期27卷 408-412页

作者： Le Yu Di Liu xiao-Zhuo Qi xiao xiong Lan-Tian feng Ming Li Guo-Ping Guo Guang-Can Guo xi-feng ren Key Laboratory of Quantum Information Chinese Academy of Sciences University of Science and Technology of China Hefei 230026 China Synergetic Innovation Center of Quantum Information ＆ Quantum Physics University of Science and Technology of China Hefei 230026 China

Monolayer transition-metal dichalcogenides（TMDs） have attracted a lot of attention for their applications in optics and *** disulfide（MoS2）,as one of those important materials,has been widely investigated due to its direct band gap and photoluminescence（PL） in visible *** to the fact that the monolayer MoS2 suffers low light absorption and emission,surface plasmon polaritons（SPPs） are used to enhance both the excitation and emission ***,we demonstrate that the PL of MoS2 sandwiched between 200-nm-diameter gold nanoparticle（Au NP） and 150-nm-thick gold film is improved by more than 4 times compared with bare MoS2 *** study shows that gap plasmons can possess more optical and optoelectronic applications incorporating with many other emerging two-dimensional materials.

关键词： MoS2 surface plasmon polaritons gap plasmons

Parameter Estimation of Sub-/Super-synchronous Oscillation Based on Interpolated All-phase Fast Fourier Transform with Optimized Window Function

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Journal of Modern Power Systems and Clean Energy 2024年第4期12卷 1031-1041页

作者： Bo Sun xi Wu xi Chen Zixiao Zou Qiang Li Bixing ren School of Electrical Engineering Southeast UniversityNanjingChina State Grid Jiangsu Electric Power Company Limited Research Institute NanjingChina

In recent years,with increasing amounts of renew-able energy sources connecting to power grids,sub-/super-syn-chronous oscillations(SSOs)occurred more *** to the time-variant nature of SsO magnitudes and frequencies,as well as the mutual interferences among SsO modes with close frequencies,the accurate parameter estimation of SsO has be-come a particularly challenging *** solve this issue,this paper proposes an improved spectrum analysis method by im-proving the window function and a spectrum correction method to achieve higher ***,by aiming at the sidelobe characteristics of the window function as evaluation criteria,a combined cosine function is optimized using a genetic algorithm(GA).Furthermore,the obtained window function is self-con-volved to extend its excellent characteristics,which have better performance in reducing mutual interference from other SSO ***,a new form of interpolated all-phase fast Fourier transform(IpApFFT)using the optimized window func-tion is proposed to estimate the parameters of *** meth-od allows for phase-unbiased estimation while maintaining algo-rithmic simplicity and *** performance of the pro-posed method is demonstrated under various conditions,com-pared with other estimation *** results vali-date the effectiveness and superiority of the proposed method.

关键词： Sub-/Super-synchronous oscillation(SSO) window function parameter estimation interpolated all-phase fast Fourier transform(ApFFT)

Parameter-Free Shifted Laplacian Reconstruction for Multiple Kernel Clustering

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 1072-1074页

作者： xi Wu Zhenwen ren F.Richard Yu the School of National Defence Science and Technology Southwest University of Science and TechnologyMianyang 621010China the School of National Defence Science and Technology Southwest University of Science and TechnologyMianyang 621010 the Guangxi Key Laboratory of Machine Vision and Intelligent Control Wuzhou UniversityWuzhou 543002 the Guangdong Laboratory of Artificial Intelligence and Digital Economy(SZ) Shenzhen 518060China

Dear Editor,This letter proposes a parameter-free multiple kernel clustering(MKC)method by using shifted Laplacian *** MKC can effectively cluster nonlinear data,but it faces two main challenges:1)As an unsupervised method,it is up against parameter problems which makes the parameters intractable to tune and is unfeasible in real-life applications;2)Only considers the clustering information,but ignores the interference of noise within Laplacian.

关键词： parameter letter Parameter

An effective bimetallic oxide catalyst of RuO_(2)-Co_(3)O_(4) for alkaline overall water splitting

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Nano Research 2024年第5期17卷 3785-3793页

作者： Fangfang ren Jiayu Xu Ligang feng College of Chemical and Environmental Engineering Yancheng Teachers UniversityYancheng 224007China School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225002China

The rational design of effective bifunctional electrocatalysts is of paramount importance for overall water-splitting technology in sustainable energy ***,bimetallic oxide catalysts(RuO_(2)-Co_(3)O_(4))derived from Ru combined MOF-derivatives(MOF=metal-organic framework)were demonstrated effective for overall water splitting in an alkaline solution,owing to the combined merits such as the two-dimensional interconnected network structure,the synergetic coupling effects and increased chemical *** as-prepared RuO_(2)-Co_(3)O_(4) only requires an overpotential of 260 mV for oxygen evolution and 75 mV for hydrogen evolution at 10 mA/cm^(2) in 1 M KOH solution;a low cell voltage of 1.54 V was required to reach the kinetic current density of 10 mA/cm^(2) for the water electrolysis when supporting on glass carbon electrode,and very good stability for 40 h was *** and theoretical results demonstrated the electronic structure optimization of bimetallic RuO_(2)-Co_(3)O_(4) compared to the individual metal oxide,which promoted interface charges redistribution and the d-band center downshift,resulting in increased activity and stability for water-splitting *** work provides a feasible approach for developing bimetallic oxides for application in energy-relevant electrocatalysis reactions.

关键词： ruthenium dioxide cobalt oxide metal-organic frameworks heterostructures overall water splitting

Energy and exergy analyses and optimizations for two-stage TEC driven by two-stage TEG with Thomson effect

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Science China(Technological Sciences) 2024年第4期67卷 1077-1093页

作者： CHEN LinGen GE YanLin feng HuiJun ren TingTing Institute of Thermal Science and Power Engineering Wuhan Institute of TechnologyWuhan 430205China Hubei Provincial Engineering Technology Research Center of Green Chemical Equipment Wuhan 430205China School of Mechanical&Electrical Engineering Wuhan Institute of TechnologyWuhan 430205China

Based on the non-equilibrium thermodynamics and energy and exergy analyses,a thermodynamic model of two-stage thermoelectric(TE)cooler(TTEC)driven by two-stage TE generator(TTEG)(TTEG-TTEC)combined TE device is established with involving Thomson effect by fitting method of variable physical parameters of TE *** total number of TE elements as constraint,influences of number distributions of TE elements on three device performance indictors,that is,cooling load,maximum COP and maximum exergetic efficiency,are *** number distributions of TE elements are optimized with three maximum performance indictors as the objectives,*** of hot-junction temperature of TTEG and coldjunction temperature of TTEC on optimization results are analyzed,and difference between optimization results corresponding to three performance indicators are *** performance intervals and optimal variable intervals are *** of Thomson effect on three general performance indicators,three optimal performance indicators and optimal variables are comparatively *** effect reduces three general performance indicators and three optimal performance indicators of *** hot-and cold-junction temperatures of TTEG and TTEC are 450,305,325 and 295 K,respectively,Thomson effect reduced maximum cooling load,maximum COP and maximum exergetic efficiency from 9.528 W,9.043×10^(-2)and2.552%to 6.651 W,6.286×10^(-2)and 1.752%,respectively.

关键词： non-equilibrium thermodynamics cooling load COP exergetic efficiency combined thermoelectric device performance optimization

Primitive functional groups directed distinct photocatalytic performance of imine-linked donor-acceptor covalent organic frameworks

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Nano Research 2024年第6期17卷 4994-5001页

作者： xitong ren Jiajie Sun Yusen Li feng Bai Key Laboratory for Special Functional Materials of Ministry of Education National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting TechnologySchool of Materials Science and Engineeringand Collaborative Innovation Center of Nano Functional Materials and ApplicationsHenan UniversityKaifeng 475004China School of Physics and Electronics Henan UniversityKaifeng 475004China

The combination of donor-acceptor(D-A)structures presents a viable strategy for fabricating covalent organic frameworks(COFs)with exceptional photocatalytic ***,the selection of functional groups on donor or acceptor building blocks and their effect on the macroscopic properties of COFs are *** this study,we tactfully synthesized a pair of Py-DBT-COFs from the same pyrene(Py)donor and 4,7-diphenylbenzo[c][1,2,5]thiadiazole(DBT)acceptor cores with distinct primitive functional *** primitive functional groups of building units determine the photocatalytic properties of corresponding ***,Py-C-DBT-COF synthesized from Py-4CHO and DBT-2NH_(2)showcases a splendid H_(2)evolution rate as high as 21,377.7μmol/(g·h)(with 5 wt.%Pt)originating from better charge transfer capacity,which is significantly superior to that of Py-N-DBT-COF constructed from Py-4NH_(2)and *** distinct photocatalytic performances of the two COFs are demonstrated to originate from the different charge separation and transfer *** work supplies a new avenue for optimizing the photocatalytic performance of D-A COFs from the perspective of primitive functional group selections.

关键词： covalent organic frameworks functional group donor-acceptor photocatalysis

Path signature-based XAI-enabled network time series classification

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Science China(Information Sciences) 2024年第7期67卷 91-106页

作者： Le SUN Yueyuan WANG Yongjun ren feng xiA Department of Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology(CICAEET) Nanjing University of Information Science and Technology School of Computing Technologies Royal Melbourne Institute of Technology

Classifying network time series(NTS) is crucial for automating network administration and ensuring cyberspace security. It enables the detection of anomalies, the identification of network attacks,and the monitoring of performance issues, thereby providing valuable support for network protection and optimization. However, modern communication networks pose challenges for NTS classification *** include handling large-scale and complex NTS data, extracting features from intricate datasets, and addressing explainability requirements. These challenges are particularly pronounced for complex 5G networks. Notably, explainability has become crucial for the widespread deployment of network automation for 5G networks and beyond. To tackle these challenges, we propose a path-signature-based NTS classification model called recurrent signature(Recur Sig). This innovative model is designed to overcome the time-consuming feature selection problem by utilizing deep-learning(DL) techniques. Additionally, it provides a solution for addressing the black-box issue associated with DL models in network automation systems(NAS) by incorporating an explainable classification approach. Extensive experimentation on various public datasets demonstrates that Recur Sig outperforms existing models in accuracy and explainability. The results indicate its potential for application in cyberspace security and automated network management, offering an explainable solution for network protection and optimization.

关键词： network time series classification explainable artificial intelligence path signature automated network management recurrent neural network