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Pattern phenomena in an rf discharge dusty plasma system

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Science china(physics,Mechanics & Astronomy) 2006年第5期49卷 588-596页

作者： HUANG Feng1,2. YE Maofu2.& WANG Long2.1. College of Science, china Agricultural University, beijing 100083, china 2. institute of physics, chinese academy of sciences, beijing 100080, china College of Science China Agricultural University Beijing China institute of physics Chinese Academy of Sciences Beijing China

Various dust patterns are observed in an rf discharge dusty plasma system. According to the dust growth process from small to large in size, the formation of different dust patterns can be divided into two stages: the small-particle stage (or dust cloud stage), and the large-particle stage (or dust crystal stage). The evolution relations between different dust patterns with gas pressure changing are investigated. Dust voids, dust acoustic waves and strong turbulence modes are presented at the small-particle stage. The self-organized dust lattices and dust clusters are investigated at the large-particle stage. The static structure of a dust lattice is characterized by means of the pair correlation function. Dust clusters formed by particles with different numbers and the regular evolution of the clusters with gas pressure are also investigated. The packing sequences of dust clusters are verified through two-dimensional confined molecular dynamics simulations.

关键词： dusty plasma dust patterns

Experimental study of electron capture excitation in collisions between Li-like N^(4+) ions and Na atoms

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chinese Science Bulletin 1997年第5期42卷 368-371页

作者： LIU Zhanwen, ZHOU Sixin, ZHANG Wen, ZHANG Xuezhen GUOXiaohong, WANG Youde, MA Xinwen, YANGZhihu, LIU Huiping, ZHAO Mengchun, YANG Feng, PAN Guangyan and LI Dawan1. institute of Modern physics,{{2., Lanzhou 730000, china {2. institute of physics,{{2., beijing 100080, china institute of Modern physics Chinese Academy of Sciences Lamhou China institute of Physia Chinese Academy of Sciences Beijing China

WITH the rapid development of the technique of ionized atoms, the charge states of atoms that can be obtained now are so high that the H-like U91+ ions and naked U92. ions

关键词： single electron capture double electron capture emission cross section excited states.

Large-scale boron nanowire nanojunctions and their highly-oriented arrays

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Science china(physics,Mechanics & Astronomy) 2004年第5期47卷 621-632页

作者： CAO Limin1,2. ZHANG Ze2.& WANG Wenkui1,2.1. Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, china 2. institute of physics,{2., beijing 100080, china Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao China institute of physics Chinese Academy of Sciences Beijing China

Highly oriented multiple boron nanowire nanojunctions with unilateral feather- like morphology were first successfully prepared using a radio-frequency magnetron sputtering method. The branched boron nano-feathers always nucleate and grow on the same sidewall of the stems, and align in parallel to form multiple T- and/or Y-type nanojunctions. The diameters of the branches and the stems are in the range of 2.—40 and 60—80 nm, respectively. The thinner branches and thicker stems of the boron nanowires self-assembled into large-scale, highly ordered arrays on various substrates. During the formation and self-assembly of the arrays, no template or catalyst was needed. We believe that the approach presented here can be used to fabricate heterostructures with bottom-up assembly of a wide variety of one-dimensional nanostructures via the rational design of targets and the proper control of the experimental conditions.

关键词： boron nanowires, nanojunctions, self-assembly, magnetron sputtering.

Conductance and dielectric properties of pure C_(60) single crystal

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chinese Science Bulletin 1997年第1期42卷 40-43页

作者： YANG Guoquan, WANG Gang, WEN Weijia, ZHOU Weiya, LU Kunquan and XIE Sisheng1. Central University for Nationalities, beijing 100081, china {2.{{2., chinese academy of sciences, beijing 100080, china Central University for Nationalities Beijing China institute of physics Chinese Academy of Sciences Beijing China

THE C60 is the third stable allotrope of carbon. Much attention has been focused on C60 since it has unique properties. Much work has been carried out on it, such as the preparation of large quantities of C60, the structure studies of C60, the superconducting alkali-metal-C60 compounds, the growth of pure C60 single crystal. There is still a lot of work to do in detail, but because the size of the single ctystal is not large enough, there is some difficulty in research, for example, the electric and optical properties of the C60 single crystal.

关键词： C60 single crystal vapor phase growth conductance dielectric properties.

Magnetron sputtering synthesis of large area well-ordered boron nanowire arrays

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Science china(physics,Mechanics & Astronomy) 2004年第4期47卷 403-415页

作者： CAO Limin1,2. ZHANG Ze2.& WANG Wenkui1,2.1. Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, china 2. institute of physics,{2., beijing 100080, china Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering Yanshan University Qinhuangdao China institute of physics Chinese Academy of Sciences Beijing China

One-dimensionally nanostructured materials, such as nanowires and nanotubes, are the smallest dimensional structures for efficient transport of electrons and excitons, and are therefore critical building blocks for nanoscale electronic and mechanical devices. In this paper, boron nanowires with uniform diameters from 2. to 80 nm were synthesized by radio-frequency magnetron sputtering of pure boron powder and B2.3 powder mixtures in argon atmosphere. The boron nanowires produced stand vertically on the substrate surface to form well-ordered arrays over large areas with self- organized arrangements without involvement of any template and patterned catalyst. The high-density boron nanowires are parallel to each other and well distributed, forming highly ordered and uniform arrays. A more interesting and unique feature of the boron nanowires is that most of their tips are flat rather than hemispherical in morphologies. Detailed studies on its structure and composition indicate that boron nanowires are amorphous. Boron nanowire appears as a new member in the family of one-dimensional nanostructures. Considering the unique properties of boron-rich solids and other nanostructures, it is reasonable to expect that the boron nanowires will display some exceptional and interesting properties. A vapor-cluster-solid (VCS) mechanism was proposed to explain the growth of boron nanowires based on our experimental observations.

关键词： boron nanowires, magnetron sputtering, arrays, self-assembly.

Grain evolution of nano-crystals ZnO under HP and HT

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Science china(physics,Mechanics & Astronomy) 2006年第3期49卷 281-290页

作者： SHAO Guangjie1, QIN Xiujuan1, LIU Riping1, WANG Wenkui1,2.& YAO Yushu2.1. Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004,{2. 2. institute of physics,{2., beijing 100080,{2. Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao China institute of physics Chinese Academy of Sciences Beijing China

Grain evolution of nano-crystals ZnO under high temperature and pressure is studied using a cubic high pressure apparatus. The structure, grain sizes and morphology of the samples are characterized by X-ray diffraction and field emission scanning electron microscopy. The results show that the grain sizes of ZnO grow rapidly at temperature 2.0℃ under pressure. At temperature lower than 300 ℃ (including 300 ℃), the grain sizes of the samples first increase with the pressure increasing from 1 to 3 GPa and later de- crease from 4 to 6 GPa. The activation volume from 1 to 3 GPa and from 4 to 6 GPa is calculated respectively using the phenomenological kinetic grain growth equation at temperature 300 ℃. At temperature higher than 400℃ (including 400 ℃), the grain sizes of the samples increase with the pressure increasing from 1 to 6 GPa. ZnO nano-bulks with good quality can be obtained under the specific conditions.

关键词： nano-crystals ZnO,high temperature and pressure,grain evolution

Morphologies of Fe-66.7 at.%Si alloy solidified in a drop tube

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Science china(physics,Mechanics & Astronomy) 2005年第6期48卷 658-666页

作者： WANG Haiyan1,2. LIU Riping1, MA Mingzhen1, JING Qin1, LI Gong1, SUN Liling2.& WANG Wenkui1,2.1. Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, china 2. institute of physics,{2., beijing 100080, china Key Laboratory of Metastable Materials Science & Technology Yanshan University Qinhuangdao China institute of physics Chinese Academy of Sciences Beijing China

Solidification of 0.1―1.0 mm diameter droplets of Fe-66.7 at.%Si alloy was achieved in a 3 m drop tube. The XRD, EDS, and SEM measurements reveal that all the droplets are composed of the primary phase α and the α+ε eutectic. With decreasing droplet diameter, the growth mode of the primary phase α changes from faceted to nonfaceted growth and the eutectic changes from needle-like to anomalous eutectic. In addition, the width of the primary phase α decreases with decreasing droplet size. The different cooling rates and undercooling levels corresponding to the samples with different sizes are responsible for the morphology changes. The cooling rates of the samples with different diameters during free fall were calculated and their effects on the microstructure formation were discussed. This kind of transition is also found inside the same sample, which is due to the larger cooling rate on the surface than at the center.

关键词： Fe-Si alloy, solidification, drop tube, undercooling.

High Power VCSEL Device with Periodic Gain Active Region

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光机电信息 2007年第12期24卷 26-30,35页

作者： NING Yong-qiang1, QIN Li1, SUN Yan-fang1, LI Te1, CUI Jin-jiang1, PENG Biao1, LIU Guang-yu1, ZHANG Yan1, LIU Yun1, WANG Li-jun1, GUI Da-fu2. XU Zu-yan2.(1. Key Laboratory of Excited State Processes, Changchun {2. of Optics, Fine Mechanics and physics,{2., Changchun, 130033, china 2. institute of physics,{2., beijing, 100080, china) Key Laboratory of Excited State Processes Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of Sciences Changchun 130033 China institute of physics Chinese Academy of Sciences Beijing 100080 China

High power vertical cavity surface emitting lasers(VCSEKLs) with large aperture have been fabricated through improving passivation, lateral oxidation and heat dissipation techniques. Different from conventional three quantum well structures, a periodic gain active region with nine quantum wells was incorporated into the VCSEL structure, with which high efficiency and high power operation were expected. The nine quantum wells were divided into three groups with each of them located at the antinodes of the cavity to enhance the coupling between the optical field and the gain region. Large aperture and bottom-emitting configuration were used to improve the beam quality and the heat dissipation. A maximum output power of 1.4 W was demonstrated at CW operation for a 400 μm-diameter device. The lasing wavelength shifted to 995.5 nm with a FWHM of 2.nm at a current of 4.8 A due to the internal heating and the absence of active water cooling. A ring-shape far field pattern was induced by the non-homogeneous lateral current distribution in large diameter device. The light intensity at the center of the ring increased with increasing current. A symmetric round light spot at the center and single transverse mode operation with a divergence angle of 16° were observed with current beyond 4.8 A.

关键词： VCSEL large aperture high power periodic gain Al2.3

Recent beijing Spectroscopy (BES) results

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Science china(physics,Mechanics & Astronomy) 2008年第6期51卷 567-576页

作者： LI WeiGuo institute of High Energy physics,{{2., beijing 100049, china institute of High Energy physics Chinese Academy of Sciences Beijing China

Recent experimental results from beijing Spectroscopy (BES) are reviewed, including the hadron spectroscopy from J/ψ decays, and a number of new states are found or confirmed, including σ, κ, X(1835), ωφ threshold enhancement in J/ψ→γωφ, a broad resonance in J/ψ→K + K ? π 0, decay studies of ψ(2.) and χ CJ , as well as the results of ψ(3770) non-D $ \bar D $ decays. The current status of BEPCII/BESIII, the major upgrade of BEPC/BESII, is also reported.

关键词： beijing Spectroscopy hadron spectroscopy charm physics BEPCII