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Density-functional theory study of the effect of pressure on the elastic properties of CaB_6

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Chinese physics B 2013年第7期22卷 420-425页

作者：韩晗 surface physics {2. (National key {2.) Key Laboratory of Computational Physical Sciencesand Department of PhysicsFudan University

Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties of CaB6 are obtained. The calculated bulk, shear, and Young’s moduli of the recently synthesized high pressure phase tI56-CaB6 are larger than those of the low pressure phase. Moreover, the high pressure phase of CaB6 has ductile behaviors, and its ductility increases with the increase of pressure. On the contrary, the calculated results indicate that the low pressure phase of CaB6 is brittle. The calculated Debye temperature indicates that the thermal conductivity of CaB6 is not very good. Furthermore, based on the Christoffel equation, the slowness surface of the acoustic waves is obtained.

关键词： density-functional theory elastic properties pressure effects acoustic properties

TURNING-OVER OF THE ELECTRIC DIPOLE IN A POLYMER

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Chinese Journal of Polymer Science 2001年第6期19卷 573-578页

作者： Guang-qi Li Xin Sun and Sheng Li state key {2. of surface physics and Research Center for Theoretical physics, fudan university shanghai 200433, china National {2. of Infrared physics, shanghai Institute of Technical physics,shanghai 2.0083, china Stt. key Lab. of surface {2. Res. Center for Theoretical Physics Fudan University Shanghai 200433 China Natl. laboratory of Infrared physics Shanghai Inst. of Technical Physics Shanghai 200083 China

The transition from the biexciton to the exciton can turn over the direction of the electric dipole of a polymericmolecule. This turning-over action combined with the photoinduced polarization reversion can be used as a switch. Theswitching speed is governed by the relaxation time of the turning-over process, which can be determined by a dynamicalsimulation.

关键词： exciton biexciton electric dipole switch relaxation

Interfacial processes in small molecule organic solar cells

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Science china(physics,Mechanics & Astronomy) 2010年第2期53卷 288-300页

作者： LI WenBin,SONG QunLiang,SUN XiaoYu,WANG MeiLiang,WU HuanRong,DING XunMin & HOU XiaoYuan surface physics {2. (National key {2.),fudan university,shanghai 200433,china surface physics {2. (National key {2.) Fudan University Shanghai China

This paper presents an overview of the recent progress of small molecule organic solar cells mainly based on the previous worksof our group. We will mainly focus on the interfacial processes in the cells. The dissociation of excitons at electrode/organic andorganic/organic interfaces can be directly observed by transient photovoltage measurements. A simple model including dissociationof excitons at the interface and drift of free carriers in the built-in field is proposed to explain the observed signals of transientphotovoltage. Besides exciton-blocking and preventing damage due to cathode evaporation,blocking permeation of oxygen and/orwater molecules and modulating the built-in field are proposed as functions of the buffer layer between C60 and Al. By the use ofthe inverted structure,a shelf lifetime of over 1500 h is achieved for unencapsulated small-molecule organic solar cells.

关键词： organic solar cell interface organic semiconductor

Studies on the microstructure,optical and electrical properties of organic microcavity devices based on a porous silicon reflector

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Science china(Technological Sciences) 2005年第2期48卷 191-201页

作者： XIONG Zuhong1, FAN Yongliang2. ZHAN Yiqiang2. ZHANG Songtao2. DING Xunmin2.& HOU Xiaoyuan2.1. School of physics, Southwest china-Normal {2., Chongqing 400715, china 2. surface physics laboratory (National key laboratory), fudan university, shanghai 200433, china School of physics Southwest China-Normal University Chongqing China surface physics {2. (National key {2.) Fudan University Shanghai China

A novel type of microcavity organic light-emitting diode based on a porous silicon distributed Bragg reflector (PS-DBR) has first been achieved and its microstructure, optical, and electrical properties have also been investigated in detail. The microcavity is made up of the central active organic multilayer sandwiched between a top silver film and a bottom PS-DBR, formed by electrochemical etching of p++-Si substrate. The field- emission scanning electron microscopy cross-section images show the nanometer-scale layered structure and flat interfaces inside the microcavity. The reflectivity (relative to an Al mirror) of the PS-DBR is up to 99%, and the stopband is about 160 nm wide. Resonant cavity mode appears as a tip in the reflectivity spectrum of the Si-based organic multilayer films, which is a symbol that the Si-based organic multilayer structure is indeed a microcavity. The peak widths of the electroluminescence (EL) spectra from the cavities emitting green and red light are greatly reduced from 85 nm and 70 nm to 8 nm and 12.nm, respectively, as compared with those measured from non-cavity structures. Note that the EL emission from the cavity devices is single-mode, and the off-resonant optical modes are highly suppressed. Moreover, increases of a factor of about 6 and 4 of the resonant peak intensity from the cavities emitting green and red light are also observed, respectively. In addition, the current-brightness-voltage characteristics and effect parameters on the lifetime of the cavity devices are also discussed. The present technique for obtaining enhanced EL emission from Si-based organic microcavity may also be another novel effective method for realizing Si-based optoelectronics device integration.

关键词： electrochemical etching, Si-based microcavity, electroluminescence, organic light-emitting diodes.

Study on Stabilization of a Synchronously Pumped Dye Laser

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Chinese Journal of Lasers 1995年第3期B4卷 223-228页

作者： ZHU Heyuan SUN Diechi HU Yimei LI Fuming(state key Joint {2. for Material Modification by Laser,Ion and Electron beams, fudan BranchDept. of physics, fudan university, shanghai 200433, china) fudan Univ Shanghai China

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关键词： coherent photon seeding time-bandwidth product frequency hopping

Analysis of microwave brightness temperature of lunar surface and inversion of regolith layer thickness:Primary results of Chang-E 1 multi-channel radiometer observation

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Science china(Information Sciences) 2010年第1期53卷 168-181页

作者： FA WenZhe & JIN YaQiu key laboratory of Wave Scattering and Remote Sensing Information (MoE),{2., shanghai 200433, china key laboratory of Wave Scattering and Remote Sensing Information (MoE) Fudan University Shanghai China

In china’s first lunar exploration project, Chang-E 1 (CE-1), a multi-channel microwave radiometer was aboard the satellite, with the purpose of measuring microwave brightness temperature from lunar surface and surveying the global distribution of lunar regolith layer thickness. In this paper, the primary 62. tracks of swath data measured by Chang-E 1 microwave radiometer from November 2.07 to February 2.08 are collected and analyzed. Using nearest neighbor interpolation based on the sun incidence angle in observations, global distributions of microwave brightness temperature from lunar surface at lunar daytime and nighttime are constructed. Using the three-layer model (the top dust-soil, regolith and underlying rock media) for microwave thermal emission of lunar surface, the measurements of brightness temperature and dependence upon latitude, frequency and FeO+TiO2.content, etc. are discussed. On the basis of the ground measurements at Apollo landing sites, the observed brightness temperature at these locations are validated and calibrated by numerical three-layer modeling. Using the empirical dependence of physical temperature upon the latitude verified by the measurements at Apollo landing sites, the global distribution of regolith layer thickness is then inverted from the brightness temperature data of CE-1 at 3 GHz channel. Those inversions at Apollo landing sites are com- pared with the Apollo in situ measurements. Finally, the statistical property of regolith thickness distribution is analyzed and discussed.

关键词： Chang-E 1 multi-channel brightness temperature Apollo landing site physical temperature inversion of regolith layer thickness

Ab-initio molecular dynamics simulation on nano-system under external pressure

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Science china Mathematics 2004年第Z1期47卷 92-100页

作者： Jl Min, SUN Deyan & GONG Xingaosurface physics {2. and Department of physics, fudan university, shanghai 200433, china Institute of Solid state physics, Chinese Academy of Sciences, Hefei 2.0031, china Interdisciplary Center for Theoretical studies, Chinese Academy of Sciences, Beijing 100080, china surface physics {2. and Department of physics Fudan University Shanghai China Institute of Solid state physics Chinese Academy of Sciences Hefei China Interdisciplary Center for Theoretical studies Chinese Academy of Sciences Beijing China

A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube (SWCNT) under external pressure is found, which is in agreement with the experiments.

关键词： phase transition, simulation, nano-particles

PREPARATION AND TRANSPORT PROPERTIES OF SUPERCONDUCTING BPSCCO THIN FILMS

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低温物理学报 1993年第5期 350-352页

作者： Yang Yu surface physics {2., fudan university, shanghai, 200433.Li Guozhen, Cao yan, Zeng GuangliKunming Institute of physics, Kunming, 6502.3

The perparation of BPSCCO thin films by DC magnetron sputtering is reported. We prepared high mass density target of Bi2.b0.6Sr2.a2.u3O10. By varying the substrate temperature, ratio of Ar and O2.pressure as well as the distance between target and substrate, we were able to optimize the process for c -axis oriented thin films of Bi-Compounds. As deposited films show Tcon at about 95K. These films were examined using the electron-probe microanalysic (EMPA) and X-ray diffraction (XRD). The results of electrical resistivity and Hall effect have been discussed. Hall voltage in the mixed state is strongly nonlinear, showing certain features that suggests that vortex depinning mechanism plays an important role in the Hall effect behaviour.

关键词： Hall PREPARATION AND TRANSPORT PROPERTIES OF SUPERCONDUCTING BPSCCO THIN FILMS Pb Figure

Formation of substitutional metallofullerenes by laser ablation of externally doped fullerenes C_(60)M_x(M=Sm,Pt,Ni and Rh)

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Chinese Science Bulletin 2002年第4期47卷 284-291页

作者： KONG Qingyu, SHEN Yifeng, ZHUANG Jun, ZHAO Li, QIAN Shixiong, LI Yufen, LI Xu, LIN Yanghui & CAI RuifangDepartment of physics, fudan university,{2., china state key Joint laboratory for Materials Modification by Laser, Ion and Electro Department of physics Fudan University Shanghai China state key Joint {2. for Materials Modification by Laser Ion and Electron Beams Fudan University Shanghai China Department of Chemistry Fudan University Shanghai China

Photofragmentation study of metal fullerides C60Mx (M=Sm, Pt, Ni and Rh) by excimer laser ablation-TOF mass spectrometry shows that metallofullerenes C2.M and C2.+1M formed in both the positive and negative ionic modes. The isotopic distributions of the metallofullerenes C2.M and C2.+1M are consistent with the calculated spectra based on the natural abundance of isotopes of C and M, confirming the formation of metallofullerenes. The metal atom is sup-posed to be incorporated into the network of the fullerene cage to replace one carbon atom of the cage forming substi-tutional metallofullerene. Odd-numbered high carbon clusters are observed in our laser ablation study of all the metal fullerides in the negative ion channel. Evolution of mass spectrum with irradiation laser shots shows that the formation of the substitutionally doped fullerenes is closely related to the production of metal carbide (MC). The structures, as well as formation mechanism, of metallofullerenes C2.+1M and C2.M with even and odd

关键词： TOF-MS laser ablation substitutional metallofullerenes odd-numbered high carbon clusters.