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Volume 30 Issue 8
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GENERAL
The Hamiltonian Structures of μ-Equations Related to Periodic Peakons
FU Wei, ZHANG Da-Jun
Chin. Phys. Lett. 2013, 30 (8): 080201 .   DOI: 10.1088/0256-307X/30/8/080201
Abstract   PDF(pc) (422KB) ( 605 )
The hierarchies of the μ-Camassa–Holm, two-component μ-Camassa–Holm and μ-modified Camassa–Holm equations are constructed from bi-Hamiltonian structures of the Korteweg-de Vries equation, the Ito equation and the modified Korteweg-de Vries equation. The key Hamiltonian operator that includes μ is ?x μ??3x, and the inner product used to define the Jacobi identity of the Hamiltonian operators is defined on the unit circle S1.
From Nothing to Something: Discrete Integrable Systems
LOU Sen-Yue, LI Yu-Qi, TANG Xiao-Yan
Chin. Phys. Lett. 2013, 30 (8): 080202 .   DOI: 10.1088/0256-307X/30/8/080202
Abstract   PDF(pc) (486KB) ( 503 )
Chinese ancient sage Laozi said that everything comes from 'nothing'. Einstein believes the principle of nature is simple. Quantum physics proves that the world is discrete. And computer science takes continuous systems as discrete ones. This report is devoted to deriving a number of discrete models, including well-known integrable systems such as the KdV, KP, Toda, BKP, CKP, and special Viallet equations, from 'nothing' via simple principles. It is conjectured that the discrete models generated from nothing may be integrable because they are identities of simple algebra, model-independent nonlinear superpositions of a trivial integrable system (Riccati equation), index homogeneous decompositions of the simplest geometric theorem (the angle bisector theorem), as well as the M?bious transformation invariants.
Application of the Störmer–Verlet-Like Symplectic Method to the Wave Equation*
QIU Yu-Fen, WU Xin
Chin. Phys. Lett. 2013, 30 (8): 080203 .   DOI: 10.1088/0256-307X/30/8/080203
Abstract   PDF(pc) (508KB) ( 618 )
A fourth-order three-stage symplectic integrator similar to the second-order St?rmer–Verlet method has been proposed and used before [Chin. Phys. Lett. 28 (2011) 070201; Eur. Phys. J. Plus 126 (2011) 73]. Continuing the work initiated in the publications, we investigate the numerical performance of the integrator applied to a one-dimensional wave equation, which is expressed as a discrete Hamiltonian system with a fourth-order central difference approximation to a second-order partial derivative with respect to the space variable. It is shown that the St?rmer–Verlet-like scheme has a larger numerical stable zone than either the St?rmer–Verlet method or the fourth-order Forest–Ruth symplectic algorithm, and its numerical errors in the discrete Hamiltonian and numerical solution are also smaller.
The -Dressing Method for the Sasa–Satsuma Equation with Self-Consistent Sources
ZHU Jun-Yi, GENG Xian-Guo
Chin. Phys. Lett. 2013, 30 (8): 080204 .   DOI: 10.1088/0256-307X/30/8/080204
Abstract   PDF(pc) (482KB) ( 421 )
The dressing method, based on the local 3×3 matrix ?-problem, is extended to study the Sasa–Satsuma equation with self-consistent sources. The explicit solutions, including one-soliton and two-soliton solutions, are given by virtue of the properties of the Cauchy matrix.
Synthetic Spin-Orbit Coupling in Two-Level Cold Atoms
ZHANG Qi, GONG Jiang-Bin, OH Choo-Hiap
Chin. Phys. Lett. 2013, 30 (8): 080301 .   DOI: 10.1088/0256-307X/30/8/080301
Abstract   PDF(pc) (479KB) ( 309 )
We theoretically and computationally show the simplest realization of SOC using two-level cold atoms interacting with only one laser beam. The underlying mechanism is based on the non-adiabatic nature of laser-atom interaction, with the Rabi frequency being not much larger than the kinetic energy of the atom. We use Zitterbewegung oscillation to further illustrate the effects of the synthesized SOC on the quantum dynamics of the two-level cold atoms. We expect our proposal to be of experimental interest in the quantum simulation of SOC-related physics.
Quantum Discord for a Qutrit-Qutrit System under Depolarizing and Dephasing Noise
YANG Yang, WANG An-Min
Chin. Phys. Lett. 2013, 30 (8): 080302 .   DOI: 10.1088/0256-307X/30/8/080302
Abstract   PDF(pc) (784KB) ( 473 )
The dynamics of quantum discord for a class of qutrit-qutrit states under depolarizing and dephasing noise are investigated using the geometric measure of quantum discord. We find that in the quantum discord for these states, a sudden change near the transition point exists from a bound-entangled to a free-entangled state, and that the sudden change point remains unchanged in later evolution under depolarizing noise. Moreover, the behavior of quantum discord is independent of the parameter of the given initial states in many regions.
Coherent Operation of the Collective Atomic Modes in the Coupled Cavity System
ZHONG Zhi-Rong
Chin. Phys. Lett. 2013, 30 (8): 080303 .   DOI: 10.1088/0256-307X/30/8/080303
Abstract   PDF(pc) (528KB) ( 236 )
We study the dynamics of a coupled cavity system composed of three cavities, and propose a scheme for the coherent manipulation of two collective atomic modes by a control atom. In the scheme, the control atom and two atomic ensembles interact with the local cavity mode, while the control atom is externally driven by a laser field. We show that under certain conditions, the dynamics of the whole system are reduced to an effective coherent coupling between the control atom and two collective atomic modes, while the cavity fields are only virtually excited. We also study the dynamics of the entanglement generation of the two distant collective atomic modes. The scheme provides a potential application for quantum-state engineering and quantum control.
The Enhanced Role of Shallow-Trench Isolation in Ionizing Radiation Damage of Narrow Width Devices in 0.2 µm Partially-Depleted Silicon-on-Insulator Technology
HUANG Hui-Xiang, BI Da-Wei, PENG Chao, ZHANG Yan-Wei, ZHANG Zheng-Xuan
Chin. Phys. Lett. 2013, 30 (8): 080701 .   DOI: 10.1088/0256-307X/30/8/080701
Abstract   PDF(pc) (687KB) ( 766 )
An anomalous total dose effect is observed in narrow-width devices fabricated in a 0.2 μm partially-depleted silicon-on-insulator (SOI) technology. The previous radiation-induced narrow channel effect manifests itself with obvious threshold voltage shift after the transistors are subjected to total dose radiation in bulk technology. Nevertheless, a sharply increasing off-state leakage current dominates the total dose effects in narrow devices of this partially-depleted SOI technology instead of threshold voltage shifts. A radiation-induced positive charge trapping model is introduced to understand this phenomenon. The enhanced role of shallow-trench oxide induced by compressive mechanical stress in narrow devices is discussed in detail in terms of modification of the edge impurity density and charge trapping characteristics, which affect the total dose sensitivity.
Stable Operation of the 2 K Cryogenic System for the Superconducting Accelerator at Peking University
LIN Lin, HAO Jian-Kui, XIE Hua-Mu, QUAN Sheng-Wen, WEN Xiao-Dong, ZHAO Kui, LIU Ke-Xin
Chin. Phys. Lett. 2013, 30 (8): 080702 .   DOI: 10.1088/0256-307X/30/8/080702
Abstract   PDF(pc) (823KB) ( 686 )
A superconducting energy recovery linac test facility (PKU-SETF) was built at Peking University, and a 2 K cryogenic system, which is the first closed-loop 2 K cryogenic system for a superconducting accelerator in China, was constructed for the 1.3 GHz 3+1/2 cell dc-SRF injector. The main accelerator consists of two nine-cell TESLA-type superconducting cavities of the PKU-SETF. The commissioning and stable operation of this 2 K cryogenic system was carried out. A helium pressure stability of better than ±0.1 mbar and a total refrigeration capacity of 65 W at a temperature of 2 K was reached.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Minimal Ward–Takahashi Vertices and Light Cone Pion Distribution Amplitudes from the GND Quark Model
LI Chuan, JIANG Shao-Zhou, WANG Qing
Chin. Phys. Lett. 2013, 30 (8): 081101 .   DOI: 10.1088/0256-307X/30/8/081101
Abstract   PDF(pc) (482KB) ( 198 )
The gauge-invariant, nonlocal, dynamical quark model is shown to generate minimal vertices that satisfy the Ward–Takahashi identities and the flat-like form of the light-cone pion distribution amplitudes. Non-flat form amplitudes can be produced only if we take a finite momentum cutoff and include nonzero pion mass corrections or go beyond the minimal vertices. A by-product of our investigation shows that the variable u appearing in light-cone pion distribution amplitudes is just the standard Feynman parameter in the Feynman parameter integrals.
NUCLEAR PHYSICS
The Role of Neck Evolution in the Synthesis of Superheavy Element 112
ZHU Min, FU Jun-Li, QU Zhen, LIU Zu-Hua, WANG Wen-Zhong
Chin. Phys. Lett. 2013, 30 (8): 082401 .   DOI: 10.1088/0256-307X/30/8/082401
Abstract   PDF(pc) (709KB) ( 270 )
The coupled and uncoupled Langevin equations in two-dimensional collective space are used to study the neck dynamics of the mass asymmetric system 48Ca+238U at the above barrier energy. The results show that the coupling between the neck and radial degrees of freedom delays the transition from dinucleus to mononucleus, and correspondingly increases the lifetime of the dinucleus system. The lifetime of the dinucleus for the asymmetric system48Ca+238U is about 11.6 and 13.0×10?22 s, obtained with uncoupled and coupled Langevin equations. We calculate the evaporation residue (ER) cross sections for the 3n and 4n evaporation channels in the 48Ca+238U reaction leading to the formation of 283112 and 282112 isotopes in three different approaches, i.e., coupled, uncoupled and frozen approximation, and compare them with the experimental data. It is found that the results of the uncoupled and frozen approximation are in close similarity, while the coupling between the radial and neck degrees of freedom reduces the ER cross section by about 30%, compared with the case of frozen approximation.
Charged Hadron Multiplicity at RHIC and LHC Energies from Color Glass Condensate
XIANG Wen-Chang, ZHANG Jun-Jie, CHEN Shi-Guo, LIU Wan-Song, ZHOU Dai-Cui
Chin. Phys. Lett. 2013, 30 (8): 082501 .   DOI: 10.1088/0256-307X/30/8/082501
Abstract   PDF(pc) (525KB) ( 300 )
We investigate charged hadron production at RHIC and LHC energies in the framework of color glass condensate. Our study gives a very good description of the experimental data of inclusive charged hadron production in proton–proton collisions at both RHIC and LHC energies. The saturation scale is treated as a free parameter, which will reduce the uncertainties from fitting low-energy experimental data and the modeling of the saturation momentum. We find a reasonable value of the saturation scale Qs1 GeV, which is consistent with the theoretical findings. The running coupling effect is taken into account, and it is found that it plays an important role in the description of the experimental data. We provide quantitative predictions of the rapidity dependence of the inclusive charged hadron production for the upcoming LHC experiment in proton–proton collisions at √s=14 TeV.
ATOMIC AND MOLECULAR PHYSICS
Spectroscopy of X-Ray-Boosted Photoionization with an Intense Laser Pulse
GE Yu-Cheng
Chin. Phys. Lett. 2013, 30 (8): 083201 .   DOI: 10.1088/0256-307X/30/8/083201
Abstract   PDF(pc) (748KB) ( 203 )
The present study shows that x-ray photoionization in the presence of an intense laser pulse has interesting energetic and statistical properties due to field modulation and interference between photoelectrons. The spectral cut-off energies, integral, and double integral reflect the strength, time, and interference of the laser field modulation. New methods are proposed for precise intense-laser-pulse measurement in situ. These methods have the advantages of accuracy, simplicity, speed, and large dynamic ranges.
Weak Electrostatic Field Orientation of Cold KRb Molecules Enhanced by a Shaped Laser Pulse
HUANG Yun-Xia, XU Shu-Wu, YANG Xiao-Hua
Chin. Phys. Lett. 2013, 30 (8): 083701 .   DOI: 10.1088/0256-307X/30/8/083701
Abstract   PDF(pc) (612KB) ( 271 )
We theoretically investigate the orientation of the cold KRb molecules in a weak electrostatic field assisted by a shaped laser pulse. The results show that the slow turn-on and rapid turn-off laser pulse can enhance the molecular orientation of KRb significantly, and a high degree of molecular orientation of more than 0.9 can be obtained when the electrostatic field is as low as 3 kV/cm. In addition, the influences of the electrostatic field strength and the parameters of the laser pulse are studied in detail.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Magnetic Measurements of a Third Harmonic Table-Top Undulator for Free Electron Lasers
Mona Gehlot, Geetanjali Sharma, G. Mishra, Hussain Jeevakhan, Sumit Tripathi
Chin. Phys. Lett. 2013, 30 (8): 084101 .   DOI: 10.1088/0256-307X/30/8/084101
Abstract   PDF(pc) (700KB) ( 242 )
We describe the measurement studies of a third harmonic undulator. The harmonic undulator is fabricated by placing shims at suitable locations along the length of a table-top six-period planar undulator. The undulator field is measured with a Hall probe and pulsed wire bench. The pulsed wire data show good agreement with the Hall probe data.
Influence of Feedback Level on Laser Polarization in Polarized Optical Feedback
WU Yun, TAN Yi-Dong, ZHANG Shu-Lian, LI Yan
Chin. Phys. Lett. 2013, 30 (8): 084201 .   DOI: 10.1088/0256-307X/30/8/084201
Abstract   PDF(pc) (703KB) ( 239 )
The influence of feedback level (or the amplitude of feedback light) on laser polarization in polarized optical feedback is investigated. A polarizer is placed in the feedback cavity to form the polarized feedback, and an attenuator is placed in the feedback cavity to tune the feedback level. The laser intensity and polarization vary dramatically at different transmissivities of the attenuator. According to the experimental phenomenon, the range of the attenuator transmissivity is divided into three zones: the flipping zone, monostable zone, and bistable zone. In the monostable zone, the laser polarization is always perpendicular to the axis of the polarizer in the feedback cavity. This may provide an effective way to choose or control laser polarization. A theoretical model based on the self-consistency of laser oscillation is presented to analyze the experimental results.
Raman Frequency Conversion of Picosecond Pulses in the YVO4 Crystal
XU Yang, CHEN Meng, LI Zheng-Wei, BAI Zhen-Xu, YANG Chao, CHEN Li-Yuan, LI Gang, LIU Yang
Chin. Phys. Lett. 2013, 30 (8): 084202 .   DOI: 10.1088/0256-307X/30/8/084202
Abstract   PDF(pc) (2158KB) ( 366 )
We compare the stimulated Raman scattering (SRS) performance of a-cut and c-cut YVO4 in a single-pass Raman experiment. The undoped YVO4 crystal shows its good SRS capability in a quasi-transient field. The non-axial scattering angles of Raman radiation are also studied, and the result is in good agreement with the physical model based on the phase matching condition. High-order Raman Stokes and anti-Stokes lights with good beam quality are obtained by means of Raman amplification. Our experiments show that Raman amplification is a practical way to avoid unexpected nonlinear effects and to obtain new wavelength picosecond lasers.
The Gordon–Mollenauer Effect in 112 Gbit/s DP-QPSK Systems
QIAO Yao-Jun, ZHOU Ji, QIAN Wen-Hui, JI Yue-Feng
Chin. Phys. Lett. 2013, 30 (8): 084203 .   DOI: 10.1088/0256-307X/30/8/084203
Abstract   PDF(pc) (622KB) ( 566 )
Gordon and Mollenauer (G-M) proposed in 1990 that the interplay between the nonlinear Kerr effect and amplified spontaneous emission noise can generate an enhanced level of noise and degrade the performance of optical phase-modulated systems. We systematically investigate the G-M effect in 112 Gbit/s coherent dual polarization quaternary phase shift keying (DP-QPSK) systems through comprehensive simulation. The results show that in the presence or absence of inline dispersion compensation, the G-M effect will seriously damage the system performance. Some of our important conclusions are listed as follows: with the increase in the input power into each span, the G-M effect is enhanced simultaneously; the smaller the span length, the stronger the G-M effect caused by more inter-span interaction; for non-zero dispersion-shifted fibers, different coefficient values will cause a similar amount of G-M effect penalty; by comparing the system performance with different dispersion compensation ratios, one can conclude that different residual dispersions of the same magnitude, no matter whether they are under-compensated or over-compensated, can derogate the overall system performance to a similar degree. In brief, the G-M effect cannot be ignored. We also have a short discussion on how to reduce and compensate for the G-M effect in DP-QPSK systems.
An Eight-Channel 400 GHz-Spacing Etched Diffraction Grating Multi/Demultiplexer on a Nanophotonic Silicon-on-Insulator Platform
SHEN Ao, QIU Chen, HU Ting, XU Chao, JIANG Xiao-Qing, LI Yu-Bo, YANG Jian-Yi
Chin. Phys. Lett. 2013, 30 (8): 084204 .   DOI: 10.1088/0256-307X/30/8/084204
Abstract   PDF(pc) (823KB) ( 398 )
An eight-channel 400 GHz-spacing planar waveguide multi/demultiplexer employing etched diffraction grating is designed and fabricated on a silicon-on-insulator platform with a 220 nm thick top layer. The design parameters are optimized by scalar diffraction simulation to obtain optimal performance with a small footprint of only 0.75 mm2. A bi-level adiabatic taper is used to connect the input/output waveguide and the slab waveguide so as to reduce the insertion loss and the broadening of the diffraction angle of the propagating light. The device is fabricated in a two-step process with E-beam lithography and dry etching, and the alignment accuracy is 10 nm or even better. Measurements show that the insertion loss is 7.35 dB and the crosstalk between adjacent channels is about ?15 dB. Ways to improve the performance are also investigated in detail.
Detection of Foreign Bodies and Bubble Defects in Tire Radiography Images Based on Total Variation and Edge Detection
ZHANG Yan, LI Tao, LI Qing-Ling
Chin. Phys. Lett. 2013, 30 (8): 084205 .   DOI: 10.1088/0256-307X/30/8/084205
Abstract   PDF(pc) (726KB) ( 948 )
We present the analysis and decomposition of tire radiography images by combining the total variation, curvelet transform based image enhancement, and Canny edge detection to detect foreign bodies and bubble defects in tires. Relying on the feature of total variation that images can be decomposed as texture parts and cartoon parts, we decompose the tire radiography image and select the cartoon part for defect detection since the textures are segmented and defect information is retained. The edges of the image are enhanced by modifying the curvelet coefficients before further edge detection operation. Furthermore, a Canny edge detection operator is used to detect the defects in which the eight-neighborhood bilinear interpolation non-maximum suppression method is employed to improve the detection performance. In our experiments, the Sobel operator and state-of-the-art methods such as the LoG operator and Canny edge detection algorithms are employed for comparison, and the experimental results are discussed briefly. The experimental results indicate that foreign bodies and bubbles in tires can be detected and located accurately by our proposed method.
Wide-Range Position-Tuning Lasers in Cholesteric Liquid Crystal
DAI Qin, LI Yong, WU Jie, ZHANG Meng, WU Ri-Na, PENG Zeng-Hui, YAO Li-Shuang
Chin. Phys. Lett. 2013, 30 (8): 084206 .   DOI: 10.1088/0256-307X/30/8/084206
Abstract   PDF(pc) (648KB) ( 264 )
A wedge liquid crystal (LC) cell is designed and manufactured, and a dye-doping cholesteric LC laser formed by mutual diffusion of the cholesteric LC with different pitches. A laser that is tunable in the 558–624 nm range is obtained under moderate optical pumping, with a tuning range of 66 nm and a laser spectral tuning resolution of 1 nm, so as to achieve the spatial position of a wide range of tunable lasers. The laser threshold varies at different positions in the device, and the lasing thresholds of the dye-doping cholesteric LC cell at 40 and 9 μm are 18 and 25 μJ/pulse, respectively. The density of the photonic states is simulated in the experimental sample, and the result is in good agreement with the photonic band gap in our experiment, which not only explains the low-threshold laser at the band gap edge, but also predicts the experiment.
Blue Upconversion Luminescence in Tm3+/Yb3+ Codoped CaWO4 Polycrystals
XU Yan-Ling, WANG Yun-Long, SHI Lian-Sheng, TAN Xiang
Chin. Phys. Lett. 2013, 30 (8): 084207 .   DOI: 10.1088/0256-307X/30/8/084207
Abstract   PDF(pc) (593KB) ( 343 )
We investigate the upconversion emission of CaWO4:Tm3+/Yb3+ polycrystals prepared by the high-temperature solid-state method. The crystal structure of the polycrystals is characterized by means of x-ray diffraction. Under the excitation of a 980 nm continuous wave diode laser, the samples show intense blue upconversion emissions centered at 473 nm, corresponding to the 1G43H6 transition of Tm3+. The dependence of the upconversion emission intensity on the pump power of a laser diode is measured, and the results indicate that the two-photon and three-photon processes contribute simultaneously to the blue upconversion emissions. The possible multi-photon upconversion process and upconversion mechanisms are discussed.
A Novel Scheme for Hundred-Hertz Linewidth Measurements with the Self-Heterodyne Method
PENG Yu
Chin. Phys. Lett. 2013, 30 (8): 084208 .   DOI: 10.1088/0256-307X/30/8/084208
Abstract   PDF(pc) (649KB) ( 564 )
We propose a novel scheme to accurately determine the hundred-hertz linewidth using the delayed self-heterodyne method, in which the delay time is far less than the coherence time of the laser. This exceeds the former understanding of the delayed self-heterodyne technique, which requires a prohibitively long fiber. The self-heterodyne autocorrelation function and power spectrum are evaluated, and by numerical analysis we ensure that ?3 dB of the power spectrum is applied to the self-heterodyne linewidth measurements. For a laser linewidth of less than 100 Hz, the linewidth can be measured directly by a 10 km fiber, and in a more general case, the linewidth can be deduced from ?20 dB or ?40 dB of the fitting Lorentzian curve.
Bubble Pulse Cancelation in the Time-Frequency Domain Using Warping Operators
NIU Hai-Qiang, ZHANG Ren-He, LI Zheng-Lin, GUO Yong-Gang, HE Li
Chin. Phys. Lett. 2013, 30 (8): 084301 .   DOI: 10.1088/0256-307X/30/8/084301
Abstract   PDF(pc) (623KB) ( 374 )
The received shock waves produced by explosive charges are often polluted by bubble pulses in underwater acoustic experiments. A method based on warping operators is proposed to cancel the bubble pulses in the time-frequency domain. This is applied to the explosive data collected during the Yellow Sea experiment in November 2000. The original received signal is first transformed into a warped signal by warping operators. Then, the warped signal is analyzed in the time-frequency domain. Due to the different features between the shock waves and the bubble pulses in the time-frequency domain for the warped signal, the bubble pulses can be easily filtered out. Furthermore, the shock waves in the original time domain can be retrieved by the inverse warping transformation. The autocorrelation functions and the time-frequency representation show that the bubble pulses can be canceled effectively.
Schlieren Visualization of Acoustic Propagation Characteristics in a One-Dimensional Phononic Crystal
JIANG Xue-Ping, QIAN Meng-Lu, CHENG Qian
Chin. Phys. Lett. 2013, 30 (8): 084302 .   DOI: 10.1088/0256-307X/30/8/084302
Abstract   PDF(pc) (1136KB) ( 1152 )
The acoustic propagation characteristics of a finite one-dimensional water-glass phononic crystal (PC) are studied using the Schlieren visualization method, which is fast and non-invasive. The band structures of this PC are measured experimentally with continuous acoustic waves incident on it using the Schlieren method, and the results are highly consistent with the theoretical calculations. The dynamic acoustic field in the PC at different frequencies is imaged and the resonance phenomena in the components of the PC are observed. The results show that the Schlieren method is an effective means of studying the interactions between acoustic waves and PCs.
The Shock Wave Refraction in Supersonic Planar Mixing Layers
ZHANG Yun-Long, WANG Bing, ZHANG Hui-Qiang
Chin. Phys. Lett. 2013, 30 (8): 084701 .   DOI: 10.1088/0256-307X/30/8/084701
Abstract   PDF(pc) (768KB) ( 301 )
We analyze the shock wave refraction in a spatially developing shocked mixing layer by means of direct numerical simulation. Both regular and Mach reflections can occur depending on the relative strength of the induced shock wave over the vorticity of interacting vortex in the mixing layer. The stronger incident shock wave frequently refracts Mach reflection. The shock polar diagram is used to determine the shock wave refraction patterns. Moreover, the vortices are deformed and compressed by the shock wave, and their vorticities are increased. The interaction of shock wave and coherent structure can be helpful to enhance the mixing process.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Self-Adjusting Characterization for Steady-State, Direct Current Cathode-Dominated Glow Discharge Plasmas at High Pressures
DING Fang, ZHENG Shi-Jian, KE Bo, TANG Zhong-Liang, ZHANG Yi-Chuan, YANG Kuan, XIE Xin-Hua, ZHU Xiao-Dong
Chin. Phys. Lett. 2013, 30 (8): 085201 .   DOI: 10.1088/0256-307X/30/8/085201
Abstract   PDF(pc) (1222KB) ( 243 )
A steady-state, direct-current high-pressure CH4-H2 glow discharge in a cup-shaped cathode parallel to anode configuration is investigated by using their VI characteristics and CCD images. The discharges display an abnormal glow feature, and an expansion of a negative glow is observed on the cathode sidewall with the increasing discharge current. There exists a dependence of voltage on gas pressure for different fixed currents. The voltage decreases with gas pressure initially, and then increases conversely, which is correlated with the glow states of the cathode sidewall. This study exhibits a self-adjusting characterization for plasmas in cathode fall, which is important for maintaining steady-state, abnormal glow discharge in a relatively high pressure range.
Numerical Examination of the Effects of Ion Thermal Flow on Plasma Sheath Characteristics
Mansour Khoramabadi, S. Farhad Masoudi
Chin. Phys. Lett. 2013, 30 (8): 085202 .   DOI: 10.1088/0256-307X/30/8/085202
Abstract   PDF(pc) (869KB) ( 397 )
The effects of ion thermal flow on the electric and hydrodynamic characteristics of a plasma sheath are examined using a multi-fluid model. In comparison with cold plasma, ion pressure is modeled by a power law dependence on the ion density in warm plasma. The pressure force on the ion depends on the ion density, ion temperature, and a nearly constant parameter called the ion polytropic coefficient. Two well-known quantities for this coefficient, γi =1 and 3, are considered, corresponding to isothermal and adiabatic flows, respectively. The numerical calculations show that increasing the ion temperature decreases the sheath thickness and increases the ion impact energy and ion saturation current at the wall. The ion polytropic coefficient has the same effect as the ion temperature and intensifies the ion temperature effects.
Laser Diagnostics of Combustion Enhancement on a CH4/Air Bunsen Flame by Dielectric Barrier Discharge
ZHANG Shao-Hua, YU Xi-Long, CHEN Li-Hong, ZHANG Xin-Yu
Chin. Phys. Lett. 2013, 30 (8): 085203 .   DOI: 10.1088/0256-307X/30/8/085203
Abstract   PDF(pc) (1971KB) ( 375 )
We investigate plasma-assisted combustion for premixed CH4/air Bunsen flames. Dielectric barrier discharge (DBD) is employed to produce non-equilibrium plasma for combustion enhancement. The transient planar laser induced fluorescence (PLIF) technique of CH and OH radicals is used to image reaction zones for enhancement measurement, and the emission spectra of the Bunsen flame are monitored to explore the kinetics mechanism. From the drift of radicals in PLIF images, the quantitative enhancement of plasma on the flame velocities of premixed methane/air flames is experimentally measured, and the data show that the flame velocities are increased by at least 15% in the presented equivalence ratio range. Furthermore, the well analyzed emission spectra of the Bunsen flame (300–800 nm) with/without DBD reveal that the emissions as well as the concentrations of the crucial radicals (like C2, CH, OH etc.) in combustion all are intensified greatly by the discharge. In addition, the appearance of excited spectral bands of N2 and N2+ during discharge indicates that the premixed gas is also heated and ionized partially by the DBD.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
A Novel Fabrication Method for Flexible SOI Substrate Based on Trench Refilling with Polydimethylsiloxane
ZHANG Cang-Hai, YANG Yi, WANG Yu-Feng, ZHOU Chang-Jian, SHU Yi, TIAN He, REN Tian-Ling
Chin. Phys. Lett. 2013, 30 (8): 086201 .   DOI: 10.1088/0256-307X/30/8/086201
Abstract   PDF(pc) (643KB) ( 288 )
Flexible arrays based on the flexible connection of double layers are demonstrated. Flexible sensor arrays are highly desired for many applications. Conventional flexible electronics are implemented by directly fabricating them on organic flexible substrates such as polyimide or polyethylene terephthalate, or forming on rigid substrates and then transferring them onto elastomeric substrates. For the first time, a novel process method based on trench refilling with polydimethylsiloxane to make flexible arrays is proposed. In this method, the sensors are directly fabricated on islands of the final bulk silicon. The performance of the sensor will not to be effected by bending and stretching operations. A one-dimensional flexible array shows good flexibility. Since the flexibility process is the last fabrication step, this method is compatible with many micro-electro-mechanical system fabrication technologies and has good yield.
Numerical Investigation of the Slow Acoustic Wave Modes in a One-Dimensional Phononic Crystal Plate
ZHANG Xu, AN Zhi-Wu
Chin. Phys. Lett. 2013, 30 (8): 086301 .   DOI: 10.1088/0256-307X/30/8/086301
Abstract   PDF(pc) (526KB) ( 469 )
The propagation of Lamb waves in a two-layered free standing plate composed of a one-dimensional photonic crystal thin layer coated on uniform substrates of different thicknesses is investigated numerically by the finite element method. We concentrate on the theoretical demonstration of the existence of very slow group velocity at the nearly flat band in specially designed phononic crystal plates and show that the group velocity can be tuned from positive to negative gradually as the thickness of the substrate layer increases. Potential applications in new acoustic devices are described.
Ground State Property of a One-Dimensional Bose–Hubbard Model Using Time-Evolving Body Decimation
OUYANG Sheng-De, LIU Jing, XIANG Shao-Hua, SONG Ke-Hui
Chin. Phys. Lett. 2013, 30 (8): 086701 .   DOI: 10.1088/0256-307X/30/8/086701
Abstract   PDF(pc) (754KB) ( 880 )
We study the ground state property of the one-dimensional Bose–Hubbard model using an imaginary time evolving body decimation algorithm. The single-particle density matrix is numerically calculated for a Mott insulating system and a superfluid system separately. By plotting the chemical potential versus the filling n=N/L for U/J=20 and U/J=0.1, we identify the Mott gap for U/J=20 in filling n=1. Lastly, we investigate the occupation number of the Bloch state with quasimomentum for a system deep in the Mott phase and in the superfluid phase respectively. The results indicate Bose condensation in the quasimomentum space.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Reduction of Efficiency Droop and Modification of Polarization Fields of InGaN-Based Green Light-Emitting Diodes via Mg-Doping in the Barriers
ZHANG Ning, LIU Zhe, SI Zhao, REN Peng, WANG Xiao-Dong, FENG Xiang-Xu, DONG Peng, DU Cheng-Xiao, ZHU Shao-Xin, FU Bing-Lei, LU Hong-Xi, LI Jin-Min, WANG Jun-Xi
Chin. Phys. Lett. 2013, 30 (8): 087101 .   DOI: 10.1088/0256-307X/30/8/087101
Abstract   PDF(pc) (543KB) ( 372 )
We demonstrate that the Mg-doping in barriers can partially screen the polarization fields of InGaN-based green light-emitting diodes. The photocurrent spectra show that the Mg-doping samples have smaller polarization fields and the blue shift of the peak with increasing current is observed. The reduction of polarization fields can be attributed to the screening of the impurity holes generated by the Mg atoms in the barriers. The efficiency droop is sensitive to the Mg-doping concentration in barriers, while the sample with Mg concentration of 5×1019 cm?3 exhibits the lowest efficiency degradation of 12.4% at a high injection current.
Spin-Polarized Currents in Double Quantum Dots with Rashba Spin-Orbit Interactions
LI Zhen-Shan, PAN Hui, LÜ Rong
Chin. Phys. Lett. 2013, 30 (8): 087102 .   DOI: 10.1088/0256-307X/30/8/087102
Abstract   PDF(pc) (806KB) ( 396 )
We propose a new scheme of realizing spin-polarized currents in a double quantum dot system. In the presence of Rashba spin-orbit coupling interactions and different Zeeman splittings of each quantum dot, the currents are spin-polarized. The polarization can be controlled by tuning the strength of Rashba spin-orbit coupling and external magnetic fields, which can produce nearly 100% spin-polarized currents. Furthermore, we explain and analyze the mechanism of the strongly spin-polarized currents. Lastly we give two phase diagrams to display our results.
Effects of the Bridging Bond on Electronic Transport in a D-B-A Device
LI Ming-Jun, LONG Meng-Qiu, XU Hui
Chin. Phys. Lett. 2013, 30 (8): 087201 .   DOI: 10.1088/0256-307X/30/8/087201
Abstract   PDF(pc) (978KB) ( 261 )
By using density functional theory combined with a nonequilibrium Green's functions approach, the electronic transport properties of different bridges connecting benzene-based heterojunction molecular devices are investigated. We focus on the effects of the bridging bond polarity and its bond length. Our results show that the polar bond plays a significant role in determining the overall conductance of the molecular devices. The effects of a current plateau and the negative differential resistance can be observed. These simulation results suggest that the proposed models may be helpful for designing practical molecular devices.
Magneto-Conductance in Tri-(8-Hydroxyquinoline) Aluminum-Based Organic Light Emitting Diodes
XU Kai, YANG De-Zhi, MA Dong-Ge
Chin. Phys. Lett. 2013, 30 (8): 087202 .   DOI: 10.1088/0256-307X/30/8/087202
Abstract   PDF(pc) (557KB) ( 421 )
The origin of magneto-conductance (MC) in tri-(8-hydroxyquinoline)-aluminum (Alq3)-based organic light emitting diodes is investigated. Our results clearly show that the generated MC is related to the singlet polaron pair dissociation. Further studies on the MC in an electron blocking layer N,N'-bis(lnaphthyl)-N,N'-diphenyl-l,l'-biphentl-4,4'-diamine (NPB) and a hole blocking layer 2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole (TPBi)-based devices indicate that the holes reaching the cathode from the dissociation of singlet polaron pairs on Alq3 are the main cause of the MC generation. It is found that the MC can be significantly reduced by doping a red fluorescence dye DCJTB as a hole trapper in Alq3.
A Win-Win Effect for Both the Ferromagnetism and the Dopability of p-Type Doping in ZnO:(Cu+N)
WEI Ling, ZHANG Wei-Feng
Chin. Phys. Lett. 2013, 30 (8): 087203 .   DOI: 10.1088/0256-307X/30/8/087203
Abstract   PDF(pc) (772KB) ( 241 )
We investigate the electronic structures and magnetic properties of ZnO doped with N, Cu, and (Cu+N) by using a first principles method and considering the strong correlation effect. It is interesting to compare these three systems. ZnO:N has weak p-type doping and unstable ferromagnetism, while ZnO:Cu becomes insulating due to the Jahn–Teller effect. Cu and N codoping can not only greatly improve the dopability of p-type doping accompanying the Jahn–Teller fading, but also enhance the ferromagnetism at the same time. The calculation results indicate that there is a win-win effect between N and Cu dopants in the ZnO:(Cu+N) system, which could possibly find applications in spintronics besides optoelectronics.
Strong Coupling of a Meta-Diatom to a Plasmonic Nanocavity
CHEN San, LU Hong-Yan, LIU Jian-Qiang, ZHU Yong-Yuan
Chin. Phys. Lett. 2013, 30 (8): 087301 .   DOI: 10.1088/0256-307X/30/8/087301
Abstract   PDF(pc) (839KB) ( 338 )
A strong coupling meta-diatom-plasmonic nanocavity is proposed and numerically investigated. When the meta-diatomic sizes are gradually increased, the meta-diatomic electric dipole and quadrupole resonances could strongly couple to those of the nanocavity. The characteristic anticrossing behaviors of three hybrid modes manifest the occurrence of the strong coupling from the transmission spectra, with Rabi-type splittings at about 40.8 meV and 128.4 meV for dipole interaction, and 11.8 meV and 72.7 meV for quadrupole interaction, respectively. We also present the coupling strength dependence on meta-atomic positions, in which one meta-atomic position is fixed and the other is changed. The average Rabi-type splittings of three polariton modes are used to evaluate the coupling strength of the meta-atomic position dependence. The corresponding Rabi-type oscillation in the time domain is also presented, which is obviously different from the one of a single meta-atom strongly coupling to a nanocavity.
Self-Assembled in-Plane-Gate Thin-Film Transistors Gated by WOx Solid-State Electrolytes
ZHU De-Ming, MEN Chuan-Ling, WAN Xiang, DENG Chuang, LI Zhen-Peng
Chin. Phys. Lett. 2013, 30 (8): 087302 .   DOI: 10.1088/0256-307X/30/8/087302
Abstract   PDF(pc) (798KB) ( 366 )
Low-voltage WOx gated indium-zinc-oxide thin-film transistors (TFTs) with in-plane-gate structures are fabricated by using an extremely simplified one-shadow mask method at room temperature. The proton conductive WOx solid-state electrolyte is demonstrated to form an electric-double-layer (EDL) effect associated with a huge capacitance of 0.51 μF/cm2. The special EDL capacitance of the WOx electrolyte is also extended to novel in-plane-gate structure TFTs as the gate dielectric, reducing the operating voltage to 1.8 V. Such TFTs operate at n-type depletion mode with a threshold voltage of ?0.5 V, saturation electron mobility of 13.2 cm2/V?s, ON/OFF ratio of 1.7×106, subthreshold swing of 110 mV/dec, and low leakage current less than 7 nA. The hysteresis window of the transfer curves is also explained by an unique reaction within the WOx electrolyte.
Characterization of HfSiAlON/MoAlN PMOSFETs Fabricated by Using a Novel Gate-Last Process
XU Gao-Bo, XU Qiu-Xia, YIN Hua-Xiang, ZHOU Hua-Jie, YANG Tao, NIU Jie-Bin, HE Xiao-Bin, MENG Ling-Kuan, YU Jia-Han, LI Jun-Feng, YAN Jiang, ZHAO Chao, CHEN Da-Peng
Chin. Phys. Lett. 2013, 30 (8): 087303 .   DOI: 10.1088/0256-307X/30/8/087303
Abstract   PDF(pc) (1295KB) ( 350 )
We fabricate p-channel metal-oxide-semiconductor-field-effect-transistors (PMOSFETs) with a HfSiAlON/MoAlN gate stack using a novel and practical gate-last process. In the process, SiO2/poly-Si is adopted as the dummy gate stack and replaced by an HfSiAlON/MoAlN gate stack after source/drain formation. Because of the high-k/metal-gate stack formation after the 1000°C source/drain ion-implant doping activation, the fabricated PMOSFET has good electrical characteristics. The device's saturation driving current is 2.71×10?4 A/μm (VGS=VDS=?1.5 V) and the off-state current is 2.78×10?9 A/μm. The subthreshold slope of 105 mV/dec (VDS=?1.5 V), drain induced barrier lowering of 80 mV/V and Vth of ?0.3 V are obtained. The research indicates that the present PMOSFET could be a solution for high performance PMOSFET applications.
The Microwave Characteristics of an In0.4Ga0.6As Metal-Oxide-Semiconductor Field-Effect Transistor with an In0.49Ga0.51P Interfacial Layer
LIU Gui-Ming, CHANG Hu-Dong, SUN Bing, LIU Hong-Gang
Chin. Phys. Lett. 2013, 30 (8): 087304 .   DOI: 10.1088/0256-307X/30/8/087304
Abstract   PDF(pc) (658KB) ( 280 )
A high microwave performance enhancement-mode (E-mode) In0.4Ga0.6As channel metal-oxide-semiconductor field-effect transistor (MOSFET) with a Si-doped In0.49Ga0.51P interfacial layer is fabricated. A 0.8-μm-gate-length In0.4Ga0.6As MOSFET with a 5-nm Al2O3 dielectric layer provides a current gain cutoff frequency of 16.7 GHz and a maximum oscillation frequency of 52 GHz. A semi-empirical small-signal-parameter extraction technique accounting for the low frequency anomaly of this MOSFET device is described, which is based on on-wafer S-parameter measurements. Excellent agreement between measured and simulated scattering parameters as well as the physically realistic circuit elements demonstrates the validity of this approach.
Effect of a Highly Metallic Surface State on the Magneto-Transport Properties of Single Crystal Bi Films
YIN Shu-Li, LIANG Xue-Jin, ZHAO Hong-Wu
Chin. Phys. Lett. 2013, 30 (8): 087305 .   DOI: 10.1088/0256-307X/30/8/087305
Abstract   PDF(pc) (729KB) ( 289 )
The magneto-transport properties of thin single crystal Bi films epitaxial grown on Si (111)-7×7 surfaces are investigated systematically as functions of film thickness (5–55 nm) and temperature. Under a perpendicular magnetic field, the positive magnetoresistance (PMR) effect is normally found, and its curve shapes are evolved systematically with film thickness. In contrast, under parallel magnetic fields the PMR effect observed for thinner Bi films develops into the negative magnetoresistance effect with the increasing magnetic field for the thicker Bi film. Our analysis indicates that there exists strong competition between the weak anti-localization effect in the surface states and the weak-localization effect in the bulk states of the Bi film, which induces the anomalous changes in the parallel magneto-resistance curves. The temperature-dependent experiments further demonstrate that the surface state plays an important role in the magneto-transport process of Bi films.
The Surface Photovoltage Mechanism of a Silicon Nanoporous Pillar Array
HU Zhen-Gang, TIAN Yong-Tao, LI Xin-Jian
Chin. Phys. Lett. 2013, 30 (8): 087801 .   DOI: 10.1088/0256-307X/30/8/087801
Abstract   PDF(pc) (593KB) ( 381 )
The surface photovoltage (SPV) mechanism of a silicon nanoporous pillar array (Si-NPA) is investigated by using SPV spectroscopy in different external electric fields. Through comparisons with the SPV spectrum of single crystal silicon (sc-Si), the silicon nano-crystallite (nc-Si)/SiOx nanostructure of Si-NPA is proved to be capable of producing obvious SPV in the wavelength range 300–580 nm. The SPV for the sc-Si layer and the nc-Si/SiOx nanostructure has shown certain contrary characters in different external electric fields. Through analysis, the localized states in the amorphous SiOx matrix are believed to dominate the SPV for the nc-Si/SiOx nanostructure.
Luminescence and Energy Transfer in Europium and Bismuth Codoped Trisodium Yttrium Silicates
XIE Guo-Bo
Chin. Phys. Lett. 2013, 30 (8): 087802 .   DOI: 10.1088/0256-307X/30/8/087802
Abstract   PDF(pc) (812KB) ( 488 )
Bi3+ and Eu3+ doped Na3YSi2O7 phosphors are prepared with solid state reactions. The luminescence properties of Bi3+ and Eu3+ in Na3YSi2O7 and the energy transfer (ET) from Bi3+ to Eu3+ are investigated in detail. The ET mechanism is also discussed. Bi3+ in Na3YSi2O7 emits near-ultraviolet (UV) light in a broad band peaking at 394 nm which can be attributed to the transition from excited states 3P0, 1 to ground state 1S0 under the excitation of UV light with a wavelength of 309 nm. Eu3+ in Na3YSi2O7 emits orange and red light. The co-doping of Bi3+ into Eu3+ doped Na3YSi2O7 introduces an intense absorption band from 270 to 350 nm due to ET from Bi3+ to Eu3+. The sensitization effect of Bi3+ on Eu3+ makes it possible that Bi3+ and Eu3+ co-doped Na3YSi2O7 could be used in AlGaN-based UV light emitting diodes as a red phosphor.
The Effect of Spin Fluctuations on the Exchange Field in Pr:YIG Crystal at Low Temperature
HU Feng, ZHANG Guo-Ying, YANG Dan, ZHANG Xue-Long, XUE Liu-Ping, ZHANG Lei
Chin. Phys. Lett. 2013, 30 (8): 087803 .   DOI: 10.1088/0256-307X/30/8/087803
Abstract   PDF(pc) (524KB) ( 332 )
Based on the temperature dependence of spin fluctuations of magnetic ions, the exchange field Hexch acting on the rare-earth ions in Pr-substituted yttrium iron garnet (Pr:YIG) is modified, which is expressed as Hexch=n0(1+γT+βeωT)MYIG. By means of the improved exchange field, the magnetic and magneto-optical properties of Pr:YIG are calculated. The calculated results are in good agreement with the experimental data in the temperature range of 4.2–300 K. Our study implies that the spin fluctuations of magnetic ions have an important influence on the magnetic and magneto-optical properties of Pr:YIG at low temperature.
Fabrication of Low-Density Long-Wavelength InAs Quantum Dots using a Formation-Dissolution-Regrowth Method
ZHANG Shi-Zhu, YE Xiao-Ling, XU Bo, LIU Shu-Man, ZHOU Wen-Fei, WANG Zhan-Guo
Chin. Phys. Lett. 2013, 30 (8): 087804 .   DOI: 10.1088/0256-307X/30/8/087804
Abstract   PDF(pc) (721KB) ( 255 )
Low-density (109cm?2), long-wavelength (more than 1300 nm at room temperature) InAs/GaAs quantum dots (QDs) with only 1.75-mono-layer (ML) InAs deposition were achieved by using a formation-dissolution-regrowth method. Firstly, small high-density InAs QDs were formed at 490°C, then the substrate temperature was ramped up to 530°C, and another 0.2 ML InAs was added. After this process, the density of the InAs QDs became much lower, and their size became much larger. The full width at half maximum of the photoluminescence peak of the low density, long-wavelength InAs QDs was as small as 27.5 meV.
Low-Threshold Surface Plasmon Lasing using the Band Edge Mode in a Bi-Periodic Groove Array
LI Jia-Qi, DONG Zheng-Gao, QIU Teng, ZHAI Ya
Chin. Phys. Lett. 2013, 30 (8): 087805 .   DOI: 10.1088/0256-307X/30/8/087805
Abstract   PDF(pc) (898KB) ( 379 )
We study surface plasmon lasing based on periodic and bi-periodic groove arrays etched on a silver substrate. It is interesting to find that the bi-periodic structure can open a clear band gap of surface plasmon polaritons near the first Brillouin zone boundary, and thus it is promising to utilize the band edge modes of surface plasmon polaritons. A low threshold for the surface plasmon lasing effect is demonstrated numerically, owing to the low group velocity of the band edge mode, which provides a feasible way to design surface plasmon lasers.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Growth and Scintillation Properties of La(Cl0.05Br0.95)3:Ce Crystal
BAO Han-Bo, QIN Lai-Shun, DING Yan-Guo, LI Zheng-Guo, SHI Hong-Sheng, SHU Kang-Ying
Chin. Phys. Lett. 2013, 30 (8): 088101 .   DOI: 10.1088/0256-307X/30/8/088101
Abstract   PDF(pc) (729KB) ( 510 )
The growth and scintillation properties of La0.97(Cl0.05Br0.95)3:Ce0.03 crystals are reported. A 1-inch-diameter as-grown crystal is achieved by applying the vertical Bridgman technique, and one machined single crystal with sizes 18 mm×8 mm×8 mm is acquired. The scintillation properties of La0.97(Cl0.05Br0.95)3:Ce0.03 crystals are presented. Under the excitation of UV (ultraviolet) light, the crystal exhibits two luminescent peaks centered at 358 nm and 382 nm. The light output is about 62000 ph/MeV while the energy resolution (ΔE/E) of this crystal at 662 keV is 4.55% of the full width at half-maximum. Additionally, the crystal photoluminescence decay time constant is 17.7 ns, which is significantly faster than that of LaBr3:Ce. The results indicate that the LaCl3 and the LaBr3 can form the anion solid solution crystal. The Lax(ClyBr1?y)3:Ce1?x crystal is potentionally a promising scintillator.
Oxygen Ion Implantation Enhanced Silicon-Vacancy Photoluminescence and n-Type Conductivity of Ultrananocrystalline Diamond Films
HU Xiao-Jun, LI Nian
Chin. Phys. Lett. 2013, 30 (8): 088102 .   DOI: 10.1088/0256-307X/30/8/088102
Abstract   PDF(pc) (638KB) ( 418 )
We report the enhanced silicon-vacancy (Si-V) photoluminescence (PL) intensity and n-type conductivity of ultrananocrystalline diamond (UNCD) films by oxygen ion (O+) implantation. With O+ dose increasing from 1014 to 1015 cm?2, the PL intensity and n-type conductivity significantly increase by 6 and 45 times, respectively, after 1000°C annealing. The secondary ion mass spectroscopy mapping measurements show that the content of oxygen is larger in the zone, which has larger content of silicon, indicating that oxygen tends to adhere to silicon. It is suggested that oxygen related Si-V defects are formed, which will enhance the PL intensity and n-type conductivity of UNCD films.
Splitting Process of Na-Birnessite Nanosheet via Transmission Electron Microscopy
LI Lin, MA Chao, YANG Huai-Xin, LI Jian-Qi
Chin. Phys. Lett. 2013, 30 (8): 088103 .   DOI: 10.1088/0256-307X/30/8/088103
Abstract   PDF(pc) (2576KB) ( 278 )
The intermediate phase of hydrothermal synthesis of the Na0.44MnO2 (NMO) nanowires is systematically investigated by means of transmission electron microscopy (TEM). The coexistence of Na-birnessite and NMO is commonly observed in the nanosheets. The NMO nanobelts in general have the width of 15 nm embedded in the (001) oriented Na-birnessite nanosheet. It is also found that the nanosheets of this intermediate phase often split along the NMO and Na-birnessite interface. Our structural study also shows that the NMO nanobelts prefer to grow along the [001] direction and gives rise to the [001] elongated NMO nanowires. Based on our TEM observations, the visible lattice mismatch and the resultant strain at the NMO/Na-birnessite interface play a critical role for formation of notable splitting structures in this kind of nanomaterial. The mechanism for the formation of the [001] NMO nanobelt is briefly discussed.
Microwave Transmissions through Superconducting Coplanar Waveguide Resonators with Different Coupling Configurations
ZHANG Si-Lei, LI Hai-Jie, WEI Lian-Fu, FANG Yu-Rong, WANG Yi-Wen, ZHOU Pin-Jia, WEI Qiang, CAO Chun-Hai, XIONG Xiang-Zheng
Chin. Phys. Lett. 2013, 30 (8): 088401 .   DOI: 10.1088/0256-307X/30/8/088401
Abstract   PDF(pc) (654KB) ( 416 )
We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates. Their microwave transmissions are measured at 20 mK. It is found that these two types of resonators possess significantly different loaded quality factors; one is 5.6×103 and the other is 4.0×104. The measured data are fitted well by classical ABCD matrix approach and consequently the coupling capacitances are determined. It is found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.
Differential Structure and Characteristics of a New-Type Silicon Magnetic Sensitivity Transistor
ZHAO Xiao-Feng, WEN Dian-Zhong, PAN Dong-Yang, GUAN Han-Yu, LV Mei-Wei, LI Lei
Chin. Phys. Lett. 2013, 30 (8): 088501 .   DOI: 10.1088/0256-307X/30/8/088501
Abstract   PDF(pc) (712KB) ( 280 )
A differential structure magnetic sensor is proposed. It is comprised of two new-type silicon magnetic sensitivity transistors (SMSTs) with similar characteristics and has a common emitter, two bases and two collectors. The sensor is fabricated by micro electromechanical system technology on a ?100? high resistivity silicon wafer. At room temperature, when supply voltage VDD=10.0 V, all the base currents Ib1 of SMST1 and Ib2 of SMST2 equal 6.0 mA, the absolute magnetic sensitivity for the two SMSTs are 46.8 mV/kG and 56.1 mV/kG, respectively, and the absolute magnetic sensitivity for the sensor is 102.9 mV/kG. Meanwhile, the temperature coefficient αV of the collector output voltage of the sensor is 0.044%/°C. The experimental results show that the magnetic sensitivity and the temperature characteristics of the sensor can be improved and ameliorated compared with a single SMST.
A Silicon Tunnel Field-Effect Transistor with an In Situ Doped Single Crystalline Ge Source for Achieving Sub-60 mV/decade Subthreshold Swing
LIU Yan, WANG Hong-Juan, YAN Jing, HAN Gen-Quan
Chin. Phys. Lett. 2013, 30 (8): 088502 .   DOI: 10.1088/0256-307X/30/8/088502
Abstract   PDF(pc) (778KB) ( 346 )
We report the demonstration of an n-channel lateral Si tunnel field-effect transistor (TFET) with a single crystalline Ge source fabricated using the gate-last process. The p Ge source was in situ doped and grown at 320°C. An abrupt interface between Ge source and Si channel with type-II band alignment and a steep source doping profile (1.5 nm/decade) formed the tunneling junction. This allows the realization of a TFET with a steep subthreshold swing of 49 mV/decade at room temperature and an ION/IOFF ratio of 107.
A High Figure-of-Merit SOI MOSFET with a Double-Sided Charge Oxide-Trench
FAN Yuan-Hang, LUO Xiao-Rong, WANG Pei, ZHOU Kun, ZHANG Bo, LI Zhao-Ji
Chin. Phys. Lett. 2013, 30 (8): 088503 .   DOI: 10.1088/0256-307X/30/8/088503
Abstract   PDF(pc) (1033KB) ( 355 )
A novel silicon-on-insulator (SOI) metal-oxide-semiconductor field effect transistor (MOSFET) with a high figure of merit (FOM) is proposed. The device features a double-sided charge oxide-trench (DCT) and a trench gate extended to the buried oxide. First, the oxide trench causes multiple-dimensional depletion in the drift region, which not only improves the electric field (E-field) strength, but also enhances the reduced surface field effect. Second, self-adaptive charges are collected in the DCT, which enhances the E-field strength of the trench oxide. Third, the oxide trench folds the drift region along the vertical direction, reducing the device cell pitch. Fourth, one side of the DCT regions acts as the body contact of p-well to reduce cell pitch and specific on-resistance (Ron, sp) further. Compared with a trench gate lateral double-diffused MOSFET, the DCT MOSFET increases the breakdown voltage (BV) from 53 V to 158 V at the same cell pitch of 3.5 μm, or reduces the cell pitch by 60% and Ron, sp by 70% at the same BV. The FOM (FOM=BV2/Ron, sp) of the proposed structure is 23 MW/cm2.
Brownian Markets
Roumen Tsekov
Chin. Phys. Lett. 2013, 30 (8): 088901 .   DOI: 10.1088/0256-307X/30/8/088901
Abstract   PDF(pc) (398KB) ( 347 )
Financial market dynamics are rigorously studied via the exact generalized Langevin equation. Assuming market Brownian self-similarity, the market return rate memory and autocorrelation functions are derived, which exhibit an oscillatory-decaying behavior with a long-time tail, similar to empirical observations. Individual stocks are also described via the generalized Langevin equation. They are classified by their relation to the market memory as heavy, neutral and light stocks, possessing different kinds of autocorrelation functions.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
A Generalized Semi-Holographic Universe
LI Hui, ZHANG Hong-Sheng, ZHANG Yi
Chin. Phys. Lett. 2013, 30 (8): 089801 .   DOI: 10.1088/0256-307X/30/8/089801
Abstract   PDF(pc) (521KB) ( 384 )
We study the semi-holographic idea in the context of decaying dark components. The energy flow between dark energy and the compensating dark matter is thermodynamically generalized to involve a particle number variable dark component with non-zero chemical potential. It is found that, unlike the original semi-holographic model, no cosmological constant is needed for a dynamical evolution of the universe. A transient phantom phase appears while a non-trivial dark energy-dark matter scaling solution stays at a later time, which evades the big-rip and helps to resolve the coincidence problem. For reasonable parameters, the deceleration parameter is well consistent with current observations. The original semi-holographic model is extended and it also suggests that the concordance model may be reconstructed from the semi-holographic idea.
COMMENTS AND ERRATA
Withdrawal of Chinese Physics Letters 29 (2012) 010503 "Size Segregation in Rapid Flows of Inelastic Particles with Continuous Size Distributions"
LI Rui
Chin. Phys. Lett. 2013, 30 (8): 089901 .   DOI: 10.1088/0256-307X/30/8/089901
Abstract   PDF(pc) (162KB) ( 364 )
57 articles