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Experimental Prospects of the B_c Studies of the LHCb Experiment
GAO Yuan-Ning, , HE Ji-Bo, , Patrick Robbe, Marie-HéléneSchune, YANG Zhen-Wei,
Chin. Phys. Lett. 2010, 27 (6):
061302
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DOI: 10.1088/0256-307X/27/6/061302
The experimental prospects of the Bc studies of the LHCb experiment are discussed. Production rates of Bc mesons at different center-of-mass energies are estimated with the dedicated generator BCVEGPY. Theoretical estimates and experimental measurements of the inclusive production cross section at =1.96 TeV are compared. The possibilities of studying Bc production, Bc spectroscopy, Bc decays and CP violation in Bc decays in the LHCb experiment are evaluated.
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Properties of the β-Delayed Proton Decay of 147Er
MA Fei, ZHOU Xiao-Hong, ZHENG Yong, XU Shu-Wei, XIE Yuan-Xiang, CHEN Liang, ZHANG Yu-Hu, LI Zhan-Kui, QIANG Yun-Hua, LEI Xiang-Guo, GUO Ying-Xiang, GUO Song, DING Bing, WANG Hai-Xia, LI Guang-Shun, ZHOU Hou-Bing,
Chin. Phys. Lett. 2010, 27 (6):
062104
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DOI: 10.1088/0256-307X/27/6/062104
The β-delayed proton decay of 147Er is studied experimentally using the 58Ni+92Mo reaction at a beam energy of 383 MeV. Based on a He-jet apparatus coupled with a tape transport system, theβ-delayed proton radioactivities both from the νs1/2 ground state and the νh11/2 isomer in 147Er are identified by proton-γ coincidence measurements. By analyzing the time distribution of the 4+→ 2+γ transition in the grand-daughter nucleus 146Dy, a half-life of 1.6±0.2 s is determined for the νh11/2 isomer in 147Er. The half-life for the ground state of 147Er is estimated to be 3.2±1.2 s.
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Collective Band Structures and Identification of One-Phonon and Two-Phonon γ-Vibrational Bands in 109Tc
GU Long, ZHU Sheng-Jiang, J. H. Hamilton, A. V. Ramayya, J. K. Hwang, S. H. Liu, WANG Jian-Guo, Y. X. Luo, J. O. Rasmussen, I. Y. Lee, XU Qiang, E. Y. Yeoh, W. C. Ma
Chin. Phys. Lett. 2010, 27 (6):
062501
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DOI: 10.1088/0256-307X/27/6/062501
The high spin states of the neutron-rich 109Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. The previously known yrast band based on the 7/2+ state is updated. A side band built on the 11/2+ state is expanded and a new band based on the 15/2+ state is identified. Band crossing in the yrast band occurs around ≈0.36 MeV. This band crossing is associated with the alignment of two h11/2 neutrons according to the cranked shell model calculations. The band based on the 11/2+ state is proposed as a candidate for the one-phonon γ-vibrational band, and the band built on the 15/2+ state is proposed as a candidate for the two-phonon γ-vibrational band. Other characteristics for the observed bands are discussed.
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Transmission Properties of One-Dimensional Photonic Crystals Containing Anisotropic Metamaterials
ZHANG Li-Wei, YAN Ling-Ling, ZHAO Yu-Huan, LIU Li
Chin. Phys. Lett. 2010, 27 (6):
064101
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DOI: 10.1088/0256-307X/27/6/064101
The transmission properties of one-dimensional photonic crystals (1DPCs) containing anisotropic metamaterials are theoretically studied. It is shown that the 1DPCs can possess a similar zero average index (zero-n)gaps, the edges of zero-n gap are weakly dependent on the incident angles, scale length and the polarization of the electromagnetic wave. When an impurity is introduced, a defect mode appears inside the zero-n gap with a very weak dependence on incident angles and scaling. It is found that in such photonic crystals, a transmitted Gaussian pulse with its carrier frequency lying in the lower gap edge, in the defect mode and in the bandgap, can experience a positive or negative group delay and hence a subluminal, ultraslow or superluminal propagation with small distortions. These properties of the photonic crystals have potential applications in the transfer of information.
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Turbulence Modulations in the Boundary Layer of a Horizontal Particle-Laden Channel Flow
LI Jing, LIU Zhao-Hui, WANG Han-Feng, CHEN Sheng, LIU Ya-Ming, HAN Hai-Feng, ZHENG Chu-Guang
Chin. Phys. Lett. 2010, 27 (6):
064701
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DOI: 10.1088/0256-307X/27/6/064701
Turbulence modulations are experimentally investigated using particle image velocimetry (PIV) in the lower boundary layer of a fully developed horizontal channel flow. A simultaneous two-phase PIV measurement technique is adopted to acquire the turbulent statistics quantities and to examine the coherent structures in the near-wall region. Polythene beads with diameters of 60μm are used as dispersed phases, and the PIV measurements have been performed at three mass loadings varying from 2.5×10-4 to 5× 10-3. All the experiments are performed at a wall shear Reynolds number of ReΤ=430. The results show that the presence of the particles suppresses the coherent structures, with shorter streamwise extent of the quasistreamwise structures, and then, the wall-normal velocity fluctuations and shear Reynolds stresses are both decreased in the near-core region. In addition, as a result of the particle wake, the turbulence intensity and shear Reynolds stress both increase in the vicinity of the wall. Due to the drag effects of the particles on the gas, the streamwise velocity gradients decrease in the outer region and increase in the viscous sublayer, meanwhile the thickness of the viscous sublayer also decreases. These results cause the peak values of the streamwise velocity fluctuations adjacent to the wall to increase, and the peak positions shift to the wall. This is the reason for decreasing the near-wall region and increasing the near-core region of the streamwise velocity fluctuations in appearance.
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Fabrication of Anodic Aluminum Oxide Templates with Small Interpore Distances
WANG Na, ZHANG Wen-Di, XU Ji-Peng, MA Bin, ZHANG Zong-Zhi, JIN Qing-Yuan, E. Bunte, J. Hüpkes, H. P. Bochem
Chin. Phys. Lett. 2010, 27 (6):
066801
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DOI: 10.1088/0256-307X/27/6/066801
The influence of the electropolishing and anodization voltage on surface morphology has been carefully studied for fabrication of ordered anodic aluminum oxide (AAO) templates. In accordance with that in the anodization experiment, the size of small patterns on the foil surface formed from the electropolishing treatment increases with voltage. Using a combined method of small-voltage electropolishing and anodization, we have fabricated well-ordered templates with much smaller interpore distances compared with that under normal-voltage fabrication conditions. The Ni nanowire arrays with two small diameters are electrodeposited through the above templates, exhibiting different magnetic properties. This also helps us to clarify the inner structure of this kind of templates.
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Edge Effects on Growth of Ordered Stress Relief Patterns in Free Sustained Aluminum Films
YU Sen-Jiang, ZHANG Yong-Ju, CHEN Miao-Gen,
Chin. Phys. Lett. 2010, 27 (6):
066803
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DOI: 10.1088/0256-307X/27/6/066803
An unusual form of ordered stress relief patterns is observed in a nearly free sustained aluminum film system deposited on liquid substrates by the thermal evaporation method. The edge effects on the growth of the ordered patterns are systematically studied. It is found that the patterns initiate from the film edges, preexisting ordered patterns, or other imperfections of the film. When the patterns extend in the film regions, they decay gradually and finally disappear. If they develop along the boundaries, however, the sizes are almost unchanged over several millimeters. The stress relief patterns look like rectangular waves in appearance, which are proven to evolve from sinusoidal to triangular waves gradually. The morphological evolution can be well explained by the general theory of buckling of plates.
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Modifying Quantum Well States of Pb Thin Films via Interface Engineering
FU Ying-Shuang, JI Shuai-Hua, ZHANG Tong, CHEN Xi, JIA Jin-Feng, XUE Qi-Kun, MA Xu-Cun
Chin. Phys. Lett. 2010, 27 (6):
066804
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DOI: 10.1088/0256-307X/27/6/066804
We demonstrate the importance of interface modification on improving electron confinement by preparing Pb quantum islands on Si(111) substrates with two different surface reconstructions, i.e., Si(111)-7× 7 and Si(111)-Root3×Root3-Pb (hereafter, 7× 7 and R3). Characterization with scanning tunneling microscopy/spectroscopy shows that growing Pb films directly on a 7×7 surface will generate many interface defects, which makes the lifetime of quantum well states (QWSs) strongly dependent on surface locations. On the other hand, QWSs in Pb films on an R3 surface are well defined with small variations in linewidth on different surface locations and are much sharper than those on the 7×7 surface. We show that the enhancement in quantum confinement is primarily due to the reduced electron-defect scattering at the interface.
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Improved Programming Efficiency through Additional Boron Implantation at the Active Area Edge in 90nm Localized Charge-Trapping Non-volatile Memory
XU Yue, YAN Feng, CHEN Dun-Jun, SHI Yi, WANG Yong-Gang, LI Zhi-Guo, YANG Fan, WANG Jos-Hua, LIN Peter, CHANG Jian-Guang
Chin. Phys. Lett. 2010, 27 (6):
067201
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DOI: 10.1088/0256-307X/27/6/067201
As the scaling-down of non-volatile memory (NVM) cells continues, the impact of shallow trench isolation (STI) on NVM cells becomes more severe. It has been observed in the 90 nm localized charge-trapping non-volatile memory (NROMTM) that the programming efficiency of edge cells adjacent to STI is remarkably lower than that of other cells when channel hot electron injection is applied. Boron segregation is found to be mainly responsible for the low programming efficiency of edge cells. Meanwhile, an additional boron implantation of 10\circ tilt at the active area edge as a new solution to solve this problem is developed.
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Van der Pauw Hall Measurement on Intended Doped ZnO Films for p-Type Conductivity
GUO Yang, LIU Yao-Ping, LI Jun-Qiang, ZHANG Sheng-Li, MEI Zeng-Xia, DU Xiao-Long
Chin. Phys. Lett. 2010, 27 (6):
067203
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DOI: 10.1088/0256-307X/27/6/067203
A Van der Pauw Hall measurement is performed on the intended doped ZnO films (Na doped ZnO) grown by using the molecular beam epitaxial method. All as-grown samples show n-type conductivity, whereas the annealed samples (annealing temperature 900°C) show ambiguous carrier conductivity type (n- and p-type) in the automatic Van der Pauw Hall measurement. A similar result has been observed in Li doped ZnO and in as-doped ZnO films by other groups before. However, by tracing the Hall voltage in the Van der Pauw Hall measurement, it is found that this alternative appearance of both n- and p-type conductivity is not intrinsic behavior of the intended doped ZnO films, but is due to the persistent photoconductivity effect in ZnO. The persistent photoconductivity effect would strongly affect the accurate determination of the carrier conductivity type of a highly resistive intended doped ZnO sample.
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Capacitance of Organic Schottky Diodes Based on Copper Phthalocyanine (CuPc)
LI Zhong-Liang, WU Zhao-Xin, JIAO Bo, MAO Gui-Lin, HOU Xun
Chin. Phys. Lett. 2010, 27 (6):
067204
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DOI: 10.1088/0256-307X/27/6/067204
The capacitance of an organic Schottky diode based on copper phthalocyanine (CuPc) is investigated. Based on the organic small-signal equivalent model established, we calculate the reverse capacitance CMetal of the organic Schottky diode with different kinds of metal cathodes (Mg, Al, Au). It is found that the reverse capacitance of the organic Schottky diode shows behavior as C Mg >C Al >C Au at the same frequency, and according to our analysis, the reverse Schottky junction capacitance Cj is expected to have little effect on the reverse capacitance of the organic Schottky diode, and the space-charge limited current capacitance CS is considered to dominate the reverse capacitance, which limits the improvement of frequency characteristics of organic Schottky diodes.
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Measurement of GaN/Ge(001) Heterojunction Valence Band Offset by X-Ray Photoelectron Spectroscopy
GUO Yan, LIU Xiang-Lin, SONG Hua-Ping, YANG An-Li, ZHENG Gao-Lin, WEI Hong-Yuan, YANG Shao-Yan, ZHU Qin-Sheng, WANG Zhan-Guo
Chin. Phys. Lett. 2010, 27 (6):
067302
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DOI: 10.1088/0256-307X/27/6/067302
X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) at the GaN/Ge heterostructure interface. The VBO is directly determined to be 1.13±0.19 eV, according to the relationship between the conduction band offset ΔEC and the valence band offset ΔEV: Δ EC=EgGaN-EgGe-Δ EV, and taking the room-temperature band-gaps as 3.4 and 0.67 eV for GaN and Ge, respectively. The conduction band offset is deduced to be 1.6\pm 0.19 eV, which indicates a type-I band alignment for GaN/Ge. Accurate determination of the valence and conduction band offsets is important for the use of GaN/Ge based devices.
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Self-Consistent Study of Conjugated Aromatic Molecular Transistors
WANG Jing, LIANG Yun-Ye, CHEN Hao, WANG Peng, R. Note, H. Mizuseki, Y. Kawazoe
Chin. Phys. Lett. 2010, 27 (6):
067303
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DOI: 10.1088/0256-307X/27/6/067303
We study the current through conjugated aromatic molecular transistors modulated by a transverse field. The self-consistent calculation is realized with density function theory through the standard quantum chemistry software Gaussian03 and the non-equilibrium Green's function formalism. The calculated I-V curves controlled by the transverse field present the characteristics of different organic molecular transistors, the transverse field effect of which is improved by the substitutions of nitrogen atoms or fluorine atoms. On the other hand, the asymmetry of molecular configurations to the axis connecting two sulfur atoms is in favor of realizing the transverse field modulation. Suitably designed conjugated aromatic molecular transistors possess different I-V characteristics, some of them are similar to those of metal-oxide-semiconductor field-effect transistors (MOSFET). Some of the calculated molecular devices may work as elements in graphene electronics. Our results present the richness and flexibility of molecular transistors, which describe the colorful prospect of next generation devices.
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Shot Noise in Aharonov-Casher Rings
LIN Liang-Zhong, ZHU Rui, DENG Wen-Ji
Chin. Phys. Lett. 2010, 27 (6):
067306
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DOI: 10.1088/0256-307X/27/6/067306
We investigate the shot noise of electron transport through an Aharonov-Casher ring subject to the Rashba spin-orbit coupling (SOC). Analytic expressions for the coefficients of reflection and transmission are derived by using the Griffith boundary conditions. For this kind of SOC, the ballistic transport of electrons can be analyzed as two independent spin channels, and both of them have the same transmission and reflection coefficients. The dependences of shot noise and Landauer-Büttiker conductance on controllable factors, including the strength of Rashba SOC, the asymmetrical angle of lead-connection positions, the radius of the rings, and the wave vector (or energy) of the incident Fermi electrons, are explicitly described by some new combined parameters. The ways that the shot noise and conductance vary with Rashba SOC and with asymmetrical angle are demonstrated by numerical simulations, respectively. It is revealed that the shot noise reaches its maximum for the particular situation of half transmission and half reflection and zero shot noise occurs at conductance maxima.
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Synthesis and Characteristics of Electrodeposited CoxZn1-x Nanorods
LIU Li-Hu, GU Jian-Jun, , LI Hai-Tao, , CAI Ning, SUN Hui-Yuan,
Chin. Phys. Lett. 2010, 27 (6):
067501
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DOI: 10.1088/0256-307X/27/6/067501
CoxZn1-x nanorod arrays were fabricated by electrodeposition in porous anodic aluminum oxide templates at different electric potentials. X-ray diffraction and transmission electron microscopy indicate that highly-ordered and uniform nanorods have been fabricated. The amounts of Co and Zn contents are investigated using energy dispersive spectroscopy, which demonstrates that the atom ratio of the alloy nanorods changes with the deposition potential. In addition, magnetic measurements show that the magnetic isotropy Co-rich CoZn nanorods will change to magnetic anisotropy nanorods with the easy axis parallel to the rod long axis with decreasing Co content.
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Soft Magnetism and High Frequency Properties of Fe65Co35-MgF2 Granular Thin Films
YAO Dong-Sheng, GE Shi-Hui, ZHOU Xue-Yun, ZHANG Bang-Min, ZUO Hua-Ping
Chin. Phys. Lett. 2010, 27 (6):
067502
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DOI: 10.1088/0256-307X/27/6/067502
(Fe65Co35)x(MgF2)1-x films with different metal volume fraction x are fabricated by magnetron sputtering. The results reveal that good soft magnetic properties can be obtained in a very wide x range (0.9> x >0.55) with Hc not exceeding 10 Oe, and high resistivity is also realized for the samples. Especially for the sample with x= 0.75, the coercivity in hard and easy axes is 1.6 Oe and 8.5 Oe, respectively, 4π Ms=14.1 kG and ρ reaches 1.16 mΩcdotcm. The dependence of complex permeability μ =μ- jμ'' on frequency shows that the real part μ' is more than 190 below 2.0 GHz and ferromagnetic resonance frequency fr reaches 2.43 GHz, implying that the film is promising for high frequency applications. High resolution transmission electron micrographs show that the films consists of bcc Fe65Co35 particles embedded uniformly in an amorphous insulating MgF2 matrix with particle size around a few nanometers. The excellent soft magnetic properties and high frequency properties are ascribed to exchange of coupling among magnetic granules, and the exchange coupling variation in a wide x range (0.9> x >0.55) is studied systematically byΔ M plots.
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Permanent Magnetic Properties of Melt-Spun YCo5Cx Ribbons
WANG Fei, YAN Yu, YUAN Zhou, BAI Xue, DU Xiao-Bo, WANG Wen-Quan, SU Feng, JIN Han-Min
Chin. Phys. Lett. 2010, 27 (6):
067503
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DOI: 10.1088/0256-307X/27/6/067503
Ribbons of nominal compositions YCo5Cx (x = 0, 0.2, 0.4, 0.6) are prepared by melt spinning at surface velocities v=5, 10, 15, 20, 25, 30 and 35 m/s. YCo5 ribbon is crystallized in a single YCo5 phase of hexagonal CaCu5 structure. A small quantity of YCoC2 phase appears in the ribbons with C addition besides the YCo5 phase. With the increase of x the lattice constant c increases and a along with the unit cell volume decreases. The largest values of iHc=888 kA/m and (BH)max =58.4 kJ/m3 at present for the YCo5 ribbon system were obtained with x=0.4 and v=20 m/s. The improvement of the permanent magnetic properties is rooted in the refinement of the microstructure and the appearance of the YCoC2 phase which can act as domain wall pinning centers.
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Static and Ultrafast Transient Photophysics of Mono- and Dual-Branched Triarylamines
LI Feng-Ming, MENG Fan-Shun, FENG Wen-Ke, WANG Shu-Feng**, TIAN He, GONG Qi-Huang
Chin. Phys. Lett. 2010, 27 (6):
068202
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DOI: 10.1088/0256-307X/27/6/068202
Mono- and dual-branched molecules, {4-[2-(4-benzothiazol-2-yl-phenyl)-vinyl]-phenyl}-(4-methoxy-phenyl)-phenyl-amine (BS1) and bis-{4-[2- (4-benzothiazol-2-yl-phenyl)-vinyl]-phenyl}-(4-methoxy-phenyl)-phenyl-amine (BS2), are investigated with one- and two-photon static spectroscopy, and the femtosecond fluorescence up-conversion technique. The molecules show branch-based fluorescence emission at low quantum yield. Ultrafast non-radiative decay on a picosecond time scale is found and is attributed to intramolecular charge-transfer bridged by the central triphenylamine. The two-photon absorption cross-sections of BS1 and BS2 are 19.1 and 19.4 GM, respectively.
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A Charge-Trap Memory Device with a Composition-Modulated Zr-Silicate High-k Dielectric Multilayer Structure
LV Shi-Cheng, GE Zhong-Yang, ZHOU Yue, XU Bo, GAO Li-Gang, YIN Jiang, XIA Yi-Dong, LIU Zhi-Guo
Chin. Phys. Lett. 2010, 27 (6):
068502
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DOI: 10.1088/0256-307X/27/6/068502
We report a novel charge-trap memory device with a composition-modulated Zr-silicate high-k dielectric multilayer structure prepared by using the pulsed laser deposition technique. The device employs amorphous (ZrO2)0.5(SiO2)0.5 as the tunneling and blocking oxide layers, and ZrO2 nanocrystals as the trapping storage layer. ZrO2 nanocrystals are precipitated from the phase separation of (ZrO2)0.8(SiO2)0.2 films annealed at 800\circC, and isolated from each other within the amorphous (ZrO2)0.5(SiO2)0.5 matrix. Our charge trapping device shows a memory window of 2.6 V and a stored electron density of 1×1013/cm2.
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Information Filtering via Improved Similarity Definition
PAN Xin, DENG Gui-Shi, LIU Jian-Guo,
Chin. Phys. Lett. 2010, 27 (6):
068903
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DOI: 10.1088/0256-307X/27/6/068903
Based on a new definition of user similarity, we introduce an improved collaborative filtering (ICF) algorithm, which could improve the algorithmic accuracy and diversity simultaneously. In the ICF, instead of the standard Pearson coefficient, the user-user similarities are obtained by integrating the heat conduction and mass diffusion processes. The simulation results on a benchmark data set indicate that the corresponding algorithmic accuracy, measured by the ranking score, is improved by 6.7% in the optimal case compared to the standard collaborative filtering (CF) algorithm. More importantly, the diversity of the recommendation lists is also improved by 63.6%. Since the user similarity is crucial for the CF algorithm, this work may shed some light on how to improve the algorithmic performance by giving accurate similarity measurement.
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76 articles
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