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Volume 30 Issue 3
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GENERAL
A New Multi-Symplectic Integration Method for the Nonlinear Schrödinger Equation
LV Zhong-Quan, WANG Yu-Shun, SONG Yong-Zhong
Chin. Phys. Lett. 2013, 30 (3): 030201 .   DOI: 10.1088/0256-307X/30/3/030201
Abstract   PDF(pc) (507KB) ( 1213 )

We propose a new multi-symplectic integration method for the nonlinear Schrödinger equation. The new scheme is derived by concatenating spatial discretization of the multi-symplectic Fourier pseudospectral method with temporal discretization of a symplectic Euler scheme and it is semi-explicit in the sense that it does not need to solve the nonlinear algebraic equations at every time step. We verify that the multi-symplectic semi-discretization of the Schrödinger equation with periodic boundary conditions has N semi-discrete multi-symplectic conservation laws. The discretization in time of the semi-discretization leads to N full-discrete multi-symplectic conservation laws. Numerical results are presented to demonstrate the robustness and the stability.

New Variable Separation Solutions for Two Nonlinear Evolution Equations in Higher Dimensions
XU Gui-Qiong, HUANG Xing-Zhong
Chin. Phys. Lett. 2013, 30 (3): 030202 .   DOI: 10.1088/0256-307X/30/3/030202
Abstract   PDF(pc) (401KB) ( 542 )

Based on the multi-linear variable separation approach, a new direct variable separation algorithm is proposed. The effectiveness of the algorithm is demonstrated by the applications of the (2+1)-dimensional modified Korteweg-de Vries equation and the (3+1)-dimensional BKP equation. The new variable separation solutions which include at least one arbitrary function are derived for these two equations with the aid of Maple.

Realization of Optimal Universal and Phase-Covariant Quantum Machines via Input-Output Cavities
WANG Cong-Rong, LI Da-Chuang, ZHANG Feng-Yuan, XU Rui-Min
Chin. Phys. Lett. 2013, 30 (3): 030302 .   DOI: 10.1088/0256-307X/30/3/030302
Abstract   PDF(pc) (428KB) ( 337 )

We present a scheme to realize a special quantum cloning machine via input-output cavities. The cloning machine can copy information from one atom to another distant atom. Choosing different parameters, the method can perform optimal symmetric (asymmetric) universal quantum cloning and optimal symmetric (asymmetric) phase-covariant cloning. Compared to previous schemes, our scheme is more insensitive to actual environmental noise and can get higher fidelity in a current cavity quantum electrodynamics system with an entangled state acting as a quantum channel than a single-photon pulse.

Various Correlations in the Anisotropic Heisenberg XYZ Model with Dzyaloshinski–Moriya Interaction
TURSUN Mamtimin, ABLIZ Ahmad, MAMTIMIN Rabigul, ABLIZ Ablimit, QIAO Pan-Pan
Chin. Phys. Lett. 2013, 30 (3): 030303 .   DOI: 10.1088/0256-307X/30/3/030303
Abstract   PDF(pc) (662KB) ( 372 )

Various thermal correlations as well as the effect of intrinsic decoherence on the correlations are studied in a two-qubit Heisenberg XYZ spin chain with the Dzyaloshinski–Moriya (DM) interaction along the z direction, i.e. Dz. It is found that tunable parameter Dz may play a constructive role on the concurrence C, classical correlation (CC) and quantum discord (QD) in thermal equilibrium while it plays a destructive role on the correlations in the intrinsic decoherence case. The entanglement and quantum discord exhibit collapse and revival under the phase decoherence. With a proper combination of the system parameters, the correlations can effectively be kept at high steady state values despite the intrinsic decoherence.

A Method of Measuring the Axial Secular Motion Temperature of Trapping Large Size Ion Clouds
YANG Yu-Na, LIU Hao, HE Yue-Hong, LI Hai-Xia, CHEN Yi-He, SHE Lei, CHEN Liang, LI Jiao-Mei
Chin. Phys. Lett. 2013, 30 (3): 030501 .   DOI: 10.1088/0256-307X/30/3/030501
Abstract   PDF(pc) (612KB) ( 310 )

A large cloud of 40Ca+ is successfully trapped and manipulated in a linear ion trap. The axial length of the ion cloud is measured under a series of end-cap voltages. We propose a method of measuring the axial secular motion temperature of the ion cloud by analyzing its image on an electron-multiplying CCD. The method is based on the Boltzmann equation that the axial density distribution of ions at secular motion temperature T satisfies. The axial secular motion temperature of the ion cloud is also obtained by measuring the Doppler broadened line width. For the same trapping parameters, the axial secular motion temperature by analyzing the image of ion cloud is 840 K and by fitting the experimental resonance line profile is 700 K.

Changes in the Dynamics of a Rössler Oscillator by an External Forcing
Amanda C. Mathias, Paulo C. Rech
Chin. Phys. Lett. 2013, 30 (3): 030502 .   DOI: 10.1088/0256-307X/30/3/030502
Abstract   PDF(pc) (2405KB) ( 429 )

We report some results indicating changes in the observed dynamics of the Rössler model under the influence of external sinusoidal forcing. By varying the control parameters of the external sinusoidal forcing, namely the amplitude and the angular frequency, we show, through numerical simulations which include parameter planes and Lyapunov exponents, that the external forcing can produce both chaos-order and order-chaos transitions. We also show that the sinusoidal forcing may generate hyperchaos.

A High-Spectral-Resolution Laser Raman System and Its Application in Shock–Compressed Benzene
ZHAO Bei-Jing, LIU Fu-Sheng, ZHANG Ning-Chao, FENG Li-Peng,WANG Wen-Peng, ZHANG Ming-Jian
Chin. Phys. Lett. 2013, 30 (3): 030701 .   DOI: 10.1088/0256-307X/30/3/030701
Abstract   PDF(pc) (436KB) ( 377 )

Raman measurements play an important role in examining the molecular changes associated with shock-induced structural and chemical changes in condensed materials. We combine a high spectra-resolution Raman system with a two-stage light gas gun to provide better quality data than the transient Raman system used previously. Representative measurements are presented for the shock compression of benzene. The high spectral resolution data have provided an insight into molecular changes that could not be obtained from time-resolved methods.

The Diagnosis of Human Liver Cancer by using THz Fiber-Scanning Near-Field Imaging
CHEN Hua, MA Shi-Hua, YAN Wen-Xing, WU Xiu-Mei, WANG Xiao-Zhou
Chin. Phys. Lett. 2013, 30 (3): 030702 .   DOI: 10.1088/0256-307X/30/3/030702
Abstract   PDF(pc) (507KB) ( 376 )
Based on a room-temperature-operated THz fiber-scanning near-field imaging system, we demonstrate the capability of THz imaging for diagnosing human liver cancer. By THz near-field mapping of the absorption constants of liver tissues, the acquired images can clearly distinguish cancer from normal tissues fast, automatically, and correctly without pathological H&E staining examination. Accordingly, the studied THz imaging system has valuable potential applications in clinical cancer diagnosis. With the help of THz imaging, we can expect to economize the use of hospital and human resources.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
An Inverse Laplace Transform on Lattice Spacing
Hirofumi Yamada
Chin. Phys. Lett. 2013, 30 (3): 031101 .   DOI: 10.1088/0256-307X/30/3/031101
Abstract   PDF(pc) (481KB) ( 293 )
An inverse Laplace transform on lattice spacing is introduced as a computational framework of the extrapolation of the strong coupling expansion to the scaling region. We apply the transform to the two-dimensional nonlinear O(N) model at N≥3 and show that the approximation of the continuum limit of the susceptibility agrees with the existing theoretical and Monte Carlo data.
The Statistical Origin of Constituent-Quark Scaling in QGP Hadronization
TANG Ze-Bo, YI Li, RUAN Li-Juan, SHAO Ming, LI Cheng, CHEN Hong-Fang, Bedanga Mohanty, XU Zhang-Bu
Chin. Phys. Lett. 2013, 30 (3): 031201 .   DOI: 10.1088/0256-307X/30/3/031201
Abstract   PDF(pc) (667KB) ( 309 )
Nonextensive statistics in a blast-wave model is implemented to describe the identified hadron production in relativistic p+p and nucleus-nucleus collisions. Incorporating the core and corona components within the TBW formalism allows us to describe simultaneously some of the major observations in hadronic observables at the Relativistic Heavy-Ion Collider (RHIC): the amount of constituent quark scaling (NCQ), the large radial and elliptic flow, the effect of gluon saturation, and the suppression of hadron production at high transverse momentum (pT) due to jet quenching. In this formalism, the NCQ scaling at the RHIC appears as a consequence of a non-equilibrium process. Our study also provides concise reference distributions with a least χ2 fit of the available experimental data for future experiments and models.
NUCLEAR PHYSICS
Variational Monte Carlo Study of ΛΛ4H
Bhupali Sharma
Chin. Phys. Lett. 2013, 30 (3): 032101 .   DOI: 10.1088/0256-307X/30/3/032101
Abstract   PDF(pc) (524KB) ( 244 )
Variational Monte Carlo calculations are carried out for ΛΛ4H to explore the possibility of its existence, using realistic NN, NNN, and phenomenological ΛN and ΛNN interactions. We also perform calculations using FGNNand NSC97 ΛN potentials, and demonstrate the effect of the exchange part of the two-body ΛN interaction and three-body ΛNN interaction on the binding energy of ΛΛ4H. Still the stability of ΛΛ4H remains an open question and this hypernuclear system has to be explored more theoretically.
Analysis of the Cooling Water Temperature Rise of Accelerating Electrodes in EAST Neutral Beam Injector Beam Extraction
XU Yong-Jian, HU Chun-Dong, XIE Yuan-Lai, LI Jun, LIU Sheng, XIE Ya-Hong, YU Ling, NBI Group
Chin. Phys. Lett. 2013, 30 (3): 032901 .   DOI: 10.1088/0256-307X/30/3/032901
Abstract   PDF(pc) (565KB) ( 429 )
Neutral beam injection is recognized as one of the most effective means of plasma heating. The preliminary data of beam power deposition in different electrodes during beam extraction are obtained on the EAST neutral beam injector test stand. The measurement of the cooling water temperature rise of accelerating electrodes is reported. The data given can guide the optimization of beam extraction parameters and decrease the damage to the accelerating electrodes following long pulse beam extraction.
ATOMIC AND MOLECULAR PHYSICS
Background-Free Doppler Cooling of Trapped Ions Using Quadrupole Transition
ZHOU Fei, XIE Yi, CHEN Liang, WAN Wei, WU Hao-Yu, FENG Mang
Chin. Phys. Lett. 2013, 30 (3): 033701 .   DOI: 10.1088/0256-307X/30/3/033701
Abstract   PDF(pc) (517KB) ( 341 )
We demonstrate experimentally the Doppler cooling of 40Ca+ ions using the S1/2 →D3/2 electric quadrupole transition, in which the scattering light that is much different from the exciting light makes it possible to collect background-free fluorescence. The idea excluding 397 nm excitation has the advantage of high-sensitivity detection and only employs lasers in red and infrared wavelengths, which should be practical for trapped-ion quantum information processing.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
A Modified MRTD Forward Model of Electromagnetic Scattering with an FDTD/PML Connection Absorbing Boundary Condition
CUI Shuai, ZHANG Xiao-Juan, FANG Guang-You
Chin. Phys. Lett. 2013, 30 (3): 034101 .   DOI: 10.1088/0256-307X/30/3/034101
Abstract   PDF(pc) (2582KB) ( 664 )
We derive the TE-mode two-dimensional multi-resolution time-domain (MRTD) iterative equations based on compactly supported wavelet basis functions as Haar, Daubechies and Coifman, and we develop a basis function selectable electromagnetic scattering forward model according to the derived equations. Meanwhile, we propose a new absorbing boundary named the FDTD/PML connection absorbing boundary condition to simplify the field calculation at the boundary area. Compared with the perfectly matched layer (PML), the proposed boundary can reduce the computing cost largely, especially for high order MRTD calculation. The simulation results show that the absorbing effect of the proposed boundary is good, and the model has higher computing accuracy and cost less time to achieve convergence compared to the finite-difference time-domain (FDTD) algorithm.
The Gain Equation of a Helical Wiggler Free Electron Laser with Ion-Channel Guiding and/or an Axial Magnetic Field
Taghi Mohsenpour, Hassan Ehsani Amri
Chin. Phys. Lett. 2013, 30 (3): 034102 .   DOI: 10.1088/0256-307X/30/3/034102
Abstract   PDF(pc) (460KB) ( 374 )
Electron motion in the combined ion-channel, helical wiggler and axial magnetic fields is analyzed in the absence of a radiation field. Detailed analysis of the gain equation in a free-electron laser is presented. Numerical calculations are made to illustrate the effects of the two electron-beam guiding devices on the gain when applied separately and simultaneously.
Multi-Wavelength Conversion Based on Single Wavelength Results in Phase Retardation Measurement
CHEN Wen-Xue, ZHANG Shu-Lian, LONG Xing-Wu
Chin. Phys. Lett. 2013, 30 (3): 034201 .   DOI: 10.1088/0256-307X/30/3/034201
Abstract   PDF(pc) (440KB) ( 307 )
We introduce an instrument for single wavelength measurement of phase retardation based on the laser feedback phenomenon. A method of multi-wavelength conversion for this instrument is proposed and the conversion results are analyzed. System calibration is used to eliminate the conversion error. The experimental results show that the maximum error after conversion is 0.26°. Through the present work, the application of laser feedback instrument for single wavelength measurement of a wave plate is expanded to the multi-wavelength range. This will expand the application area of the instruments.
A Linearly-Polarized Rubidium Vapor Laser Pumped by a Tunable Laser Diode Array with an External Cavity of a Temperature-Controlled Volume Bragg Grating
LI Zhi-Yong, TAN Rong-Qing, XU Cheng, LI Lin, ZHAO Zhi-Long
Chin. Phys. Lett. 2013, 30 (3): 034202 .   DOI: 10.1088/0256-307X/30/3/034202
Abstract   PDF(pc) (753KB) ( 353 )
A diode pumped alkali vapor laser has advantages in high quantum efficiency, excellent beam quality, and low thermal effect. We obtain a laser diode array (LDA) with linewidth of 0.20 nm and an external cavity of volume Bragg grating (VBG). Its central wavelength can be tuned from 779.30 nm to 780.10 nm by changing the VBG's temperature. Pumped by this LDA, a 2.1 W rubidium vapor laser is achieved with optical efficiency of 10.5% and slope efficiency of 22.7%.
Controlled Photonic Stop Bands in a Four-Level Atomic System of an Inhomogeneously Broad-End Solid
HAN Li-Li, ZHANG Xiao-Jun, LIU Cheng-Zhi, FAN Cun-Bo, HAN Xing-Wei, WU Jin-Hui, GAO Jin-Yue
Chin. Phys. Lett. 2013, 30 (3): 034203 .   DOI: 10.1088/0256-307X/30/3/034203
Abstract   PDF(pc) (731KB) ( 257 )
A neatly controllable photonic band gap formed in a four-level tripod system in the solid material, Pr3+-doped yttrium orthosilicate (Pr:YSO) is investigated. Driven by two standing waves, the sample is just like a photonic crystal to the weak probe. Based on the numerical simulation and the analytic result we present a clear and full-scale view on the induced band gap in the inhomogeneously broadened tripod system.
A Tm-Bi Co-Doped Fiber Laser with Dual Pumping Operation
N. Saidin, S. W. Harun, S. S. A. Damanhuri, S. M. M. Ali, H. Ahmad, A. Halder, M. C. Paul, S. Das, M. Pal, S. K. Bhadra
Chin. Phys. Lett. 2013, 30 (3): 034204 .   DOI: 10.1088/0256-307X/30/3/034204
Abstract   PDF(pc) (522KB) ( 411 )
We demonstrate an efficient fiber laser operating at 1901.6 nm using a newly developed thulium bismuth co-doped fiber (TBF) with dual pumping at 792 nm and 1552 nm. The fiber was fabricated using modified chemical vapor deposition and solution doping processes. The dopant concentrations (wt%) and compositions inside the core are 0.15 Bi2O3, 0.3 Tm2O3, 1.0 Al2O3 and 12.0 GeO2. The TBF laser operates at 1901.6 nm with a lasing efficiency of 33.2% and pump power threshold of 85 mW using a 2-m-long TBF in a linear cavity with two fiber Bragg gratings (FBGs). The high efficiency is attributed to the use of additional 1552 nm pump to complement 792 nm pumping. The maximum output power of 225 mW is achieved at the pump power of 820 mW with the optimum length of 2 m.
Two-Dimensional Atom Localization via Spontaneous Emission in an Inverted-Y System
WU Jian-Chun, LIU Zheng-Dong, ZHENG Jun, WANG Hui-Qin
Chin. Phys. Lett. 2013, 30 (3): 034205 .   DOI: 10.1088/0256-307X/30/3/034205
Abstract   PDF(pc) (2414KB) ( 365 )
We investigate the behavior of two-dimensional atom localization in an inverted-Y system driven by one coherent field and two standing-wave fields. The position probability distribution of the atom passing through the spatial-position-dependent standing-wave fields can be determined by measuring the spontaneously emitted photon. It is found that high-precision two-dimensional atom localization can be obtained by choosing appropriate system parameters.
The Generation of a Compact Azimuthally Polarized Vertical-Cavity Surface Emitting Laser Beam with Radial Slits
XU Bin-Zong, LIU Jie-Tao, CAI Li-Kang, HU Hai-Feng, WANG Qing, WEI Xin, SONG Guo-Feng
Chin. Phys. Lett. 2013, 30 (3): 034206 .   DOI: 10.1088/0256-307X/30/3/034206
Abstract   PDF(pc) (2178KB) ( 455 )
We propose the simple and efficient generation of a compact azimuthally polarized laser beam. Radial slits with annular distribution are patterned onto the output facet of a standard vertical-cavity surface emitting laser. Due to the polarization modulation of the surface plasmon polariton mode excited by the radial slits, a compact azimuthally polarized laser beam at 850 nm is experimentally demonstrated. The finite-difference time-domain method is introduced to analyze the polarization characteristics of the transmitted light through the radial slit, which agrees well with our experimental results.
A Resonantly Pumped Q-Switched Er:Lu2SiO5 Laser
YAO Bao-Quan, YU Xiao, LIU Xiao-Lei, DUAN Xiao-Ming, JU You-Lun, WANG Yue-Zhu
Chin. Phys. Lett. 2013, 30 (3): 034207 .   DOI: 10.1088/0256-307X/30/3/034207
Abstract   PDF(pc) (642KB) ( 356 )
We describe the cw and Q-switched actions of a novel erbium-doped crystal Er:Lu2SiO5 pumped by a MgO:PPLN-OPO at 1536 nm. An efficient 1580.9 nm cw laser with the output power of 608 mW is obtained when the incident power is 4.5 W, corresponding to a slope efficiency of 11.1%. In the Q-switched operation, the pulse energy up to 1.2 mJ is obtained at a repetition rate of 200 Hz.
Modified Hybrid Plasmonic Waveguides as Tunable Optical Tweezers
ZHANG Lu, YANG Shu
Chin. Phys. Lett. 2013, 30 (3): 034208 .   DOI: 10.1088/0256-307X/30/3/034208
Abstract   PDF(pc) (466KB) ( 371 )
We propose a series of modified hybrid plasmonic waveguide systems. It is found that their propagation distances and mode areas depend on their shapes notably. The optical trapping forces exerting on the dielectric nanoparticles are calculated, and the strength and range of the forces can be adjusted by altering the shapes of the waveguides. These features demonstrate the possibility of using the modified hybrid waveguide systems to design tunable nanoscale optical tweezers.
An Innovative Electro-Optic Q-Switch Technology in 1064 nm and 1319 nm Dual-Wavelength Operation of a Nd:YAG Laser
JIN Guang-Yong, WU Chun-Ting, CHEN Xin-Yu, YU Yong-Ji, WANG Chao
Chin. Phys. Lett. 2013, 30 (3): 034209 .   DOI: 10.1088/0256-307X/30/3/034209
Abstract   PDF(pc) (588KB) ( 715 )
An innovative electro-optic (EO) Q-switch technology in 1064 nm and 1319 nm dual-wavelength operation of a Nd:YAG laser is illustrated. Output energy of 4.6 mJ and pulse width of 400 ns for 1064 nm and output energy of 8.7 mJ and pulse width of 80 ns for 1319 nm are achieved simultaneously at the repetition rate of 1 Hz and pumping voltage of 750 V by using this bias voltage electro-optic Q-switched-technology when the voltage on LiNbO3 crystal is 2254 V. The strong line of 1064 nm in Q-switched operation is inhibited efficiently.
Ultracompact, Reflection-Free and High-Efficiency Channel Drop Filters Based on Photonic Crystal Nanobeam Cavities
YU Ping, HU Ting, QIU Chen, SHEN Ao, QIU Hui-Ye, WANG Fan, JIANG Xiao-Qing, WANG Ming-Hua, YANG Jian-Yi
Chin. Phys. Lett. 2013, 30 (3): 034210 .   DOI: 10.1088/0256-307X/30/3/034210
Abstract   PDF(pc) (549KB) ( 395 )
We propose an ultracompact channel drop filter (CDF) based on photonic crystal nanobeam cavities. The conditions for implementing such an ideal CDF are derived from the temporal coupled-mode equations governing the operation of the CDF. By considering the intercoupling of the two involved nanobeam cavities, some ambiguities of the previous equivalent circuit model analysis are cleared up. Practical configurations on silicon-on-insulator (SOI) for the proposed CDF are suggested with a typical length less than 15 μm . Finite difference time domain (FDTD) method calculations show that the proposed filter can achieve drop efficiency higher than 99% without any reflection. Compared to the λ/4-shifted Bragg grating resonators based CDF, the proposed CDF is more compact, high-efficient and reflection-free. It is also easy to implement a low-power tunable filter due to the ultrahigh quality factor Q and ultrasmall modal volume V of the involved photonic crystal nanobeam cavities.
A Sparse Representation Algorithm for the Mode Separation and SNR Improvement of Lamb Wave Signals
YU Yong-Ling, ZHANG Hai-Yan, SHI Fang-Fang, FENG Guo-Rui, MA Shi-Wei
Chin. Phys. Lett. 2013, 30 (3): 034301 .   DOI: 10.1088/0256-307X/30/3/034301
Abstract   PDF(pc) (536KB) ( 560 )
A matching pursuit method based on training an over-complete dictionary is investigated. By using the K-singular value decomposition (K-SVD) algorithm, an over-complete dictionary that describes the Lamb wave signals is trained. The results demonstrate that the method can effectively remove redundant information and separate multiple Lamb wave modes. The matching pursuit method with the K-SVD algorithm shows its efficiency for Lamb wave signal processing.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
A Computational Study of Radio Frequency Atmospheric Pressure Discharge in Nitrogen and Oxygen Mixture Gases
WANG Yi-Nan, LIU Yue, LIN Guo-Qiang
Chin. Phys. Lett. 2013, 30 (3): 035201 .   DOI: 10.1088/0256-307X/30/3/035201
Abstract   PDF(pc) (709KB) ( 365 )
The characteristics of radio frequency atmospheric pressure discharge in nitrogen and oxygen mixture gases are investigated by using a one-dimensional fluid model. The model consists of equations of particle continuity, Poisson's equation, and the electron energy equation. The effect of the concentrations of O2 in N2 on the discharge characteristics is analyzed. The results show that when the concentration of O2 in N2 is less than 12%, as the amount of O2 grows, the electron density and the N4+ ion density decrease; the main negative particles are electrons. When the concentration of O2 in N2 is greater than 12%, the electron density and the N4+ ion density increase with the increasing admixture of oxygen; the main negative particle is the O? ion. Moreover, the O? ion density, the O2+ ion density, the electron temperature and the mixture gases electronegativity increase with growth of O2 in the range from 4% to 20% and with density of O2 in N2.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
High Response in aTellurium-Supersaturated Silicon Photodiode
WANG Xi-Yuan, HUANG Yong-Guang, LIU De-Wei, ZHU Xiao-Ning, ZHU Hong-Liang
Chin. Phys. Lett. 2013, 30 (3): 036101 .   DOI: 10.1088/0256-307X/30/3/036101
Abstract   PDF(pc) (643KB) ( 363 )
Single crystalline silicon supersaturated with tellurium are formed by ion implantation followed by excimer nanosecond pulsed laser melting (PLM). The lattice damaged by ion implantation is restored during the PLM process, and dopants are effectively activated. The hyperdoped layer exhibits high and broad optical absorption from 400 to 2500 nm. The n+p photodiodes fabricated from these materials show high response (6.9 A/W at 1000 nm) with reverse bias 12 V at room temperature. The corresponding cut-off wavelength is 1258 nm. The amount of gain and extended cut-off wavelength both increase with increasing reverse bias voltage; above 100% external quantum efficiency is observed even at a reverse bias of 1 V. The cut-off wavelength with 0 V bias is shorter than the commercial silicon detector. This implies that the Burstein-Moss shift is due to hyperdoping. The amount of the extended cut-off wavelength increases with increasing reverse bias voltage, suggesting existence of the Franz–Keldysh effect.
Variation of Ti Valence with Lithium Content in Lithiated/Delithiated Li4Ti5O12 Studied by X-Ray Absorption near the Edge Structure
YU Peng-Fei, CUI Zhong-Hui, MENG Jian-Wei, GUO Xiang-Xin
Chin. Phys. Lett. 2013, 30 (3): 036102 .   DOI: 10.1088/0256-307X/30/3/036102
Abstract   PDF(pc) (716KB) ( 467 )
Synchrotron-based x-ray absorption near-edge structure (XANES) spectroscopy is applied to investigate the variation of Ti valence in the discharge and charge processes of Li4Ti5O12. Through analysis of the XANES data, the average valence of Ti can be calculated, which allows quantitative determination of the ratios of Ti3+/Ti4+ as a function of Li content in the electrodes. It is found that the ratios in the composites of Li4Ti5O12/acetylene black (AB)-carbon are larger than those in Li4Ti5O12/Ag/AB-carbon after the discharge to 1.1 V, indicating a larger amount of Li inserted into the former than that into the latter. This finding provides a good explanation for the fact that the Li4Ti5O12/AB-carbon samples exhibit larger storage capacities than the Li4Ti5O12/Ag/AB-carbon ones prepared in this work, concerning the larger Ti3+/Ti4+ ratio and the larger amount of Li+ inserted in the electrode for satisfying the charge neutralization requirement.
A Novel Micro-Scale Plastic Deformation Feature on a Bulk Metallic Glass Surface under Laser Shock Peening
WEI Yan-Peng, WEI Bing-Chen, WANG Xi, XU Guang-Yue, LI Lei, WU Xian-Qian, SONG Hong-Wei, HUANG Chen-Guang
Chin. Phys. Lett. 2013, 30 (3): 036201 .   DOI: 10.1088/0256-307X/30/3/036201
Abstract   PDF(pc) (629KB) ( 354 )
Laser shocking peening is a widely applied surface treatment technique that can effectively improve the fatigue properties of metal parts. We observe many micro-scale arc plastic steps on the surface of Zr47.9Ti0.3Ni3.1Cu39.3Al9.4 metallic glass subjected to the ultra-high pressure and strain rate induced by laser shock peening. The scanning electronic microscopy and atomic force microscopy show that the arc plastic step (APS) has an arc boundary, 50–300 nm step height, 5–50 μm radius and no preferable direction. These APSs have the ability to accommodate plastic deformation in the same way as shear band. This may indicate a new mechanism to accommodate the plastic deformation in amorphous metallic glass under high pressure, ultra-high strain rates, and short duration.
Effects of 3 GPa High Pressure Treatment on the β1α+β2 Phase Transition Dynamics of TC4 Titanium Alloy
WANG Hai-Yan, CHEN Yan, LIU Jian-Hua, WANG Wen-Kui
Chin. Phys. Lett. 2013, 30 (3): 036202 .   DOI: 10.1088/0256-307X/30/3/036202
Abstract   PDF(pc) (1094KB) ( 388 )
The temperature, duration, activation energy, and Avrami exponent of the solid phase transformation β1→α+β2 of TC4 titanium alloy treated at 3 GPa in a cooling process are calculated by means of differential scanning calorimetric curves. Then the effects of high pressure on the β1→α+β2 phase transformation dynamics of TC4 alloy in a cooling process are investigated. The results show that 3 GPa high pressure treatment can increase the activation energy of the TC4 alloy. The beginning time, end time, and duration of the β1→α+β2 phase transition of the 3 GPa high pressure treated TC4 alloy at the cooling rate of 10°C/min are increased by 2.90°C, 7.78°C and ?29.28 s respectively. It is known that 3 GPa high pressure treatment has little effect on the phase transition mechanism.
The Physical-Mechanism Based High-Temperature Thermal Contact Conductance Model with Experimental Verification
LIU Dong-Huan, SHANG Xin-Chun
Chin. Phys. Lett. 2013, 30 (3): 036501 .   DOI: 10.1088/0256-307X/30/3/036501
Abstract   PDF(pc) (904KB) ( 592 )
The physical-mechanism based high-temperature thermal contact conductance model is proposed, in which the temperature effect on the material properties and interface radiation effect are considered. A testing platform of high temperature thermal contact conductance is also established, and the thermal contact conductance between three-dimensional braid C/C composite material and superalloy GH600 is tested under different interface roughness and temperatures. Experimental results verify the rationality of the present model. Results also show that it is necessary to take the effect of temperature into account especially at high temperatures, and the interface radiation effect is negligible compared to spot conduction under 850 K.
Archimedes Spiral Cracks Developed in a Nanofilm/Substrate System
WU Dan, YIN Ya-Jun, XIE Hui-Min, DAI Fu-Long
Chin. Phys. Lett. 2013, 30 (3): 036801 .   DOI: 10.1088/0256-307X/30/3/036801
Abstract   PDF(pc) (534KB) ( 586 )
Perfect Archimedes spiral cracks at micrometer scales are found in a colloid film of several hundred nanometers in thickness coated on a glass substrate. To explain the formation of this kind of spiral crack, the relation between the geometrical properties of the Archimedes spiral and the growth kinematics of the spiral cracks are analyzed. Meanwhile, the initiation and propagation of the spiral cracks are speculated upon logically from the specific material system based on sufficient evidence. In addition, we introduce a new cracking phenomenon and provide an insight into the new mechanism for crack propagation in soft material nano films coated on stiff substrates.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Carrier Density and Electric Field Dependent Nonlinear Transport of Chemical Vapor Deposition Graphene
KHALIL Hafiz M. W., KELEKCI Ozgur, NOH Hwayong
Chin. Phys. Lett. 2013, 30 (3): 037201 .   DOI: 10.1088/0256-307X/30/3/037201
Abstract   PDF(pc) (527KB) ( 501 )
We report on the measurements of nonlinear current-voltage characteristics of graphene fabricated by chemical vapor deposition. The current-voltage characteristic is described by a power law with a superlinear dependence of the current on the voltage, and the nonlinearity depends on the carrier density and the excitation level. The nonlinearity is strongest at the Dirac point and becomes weaker as the carrier density increases. At the Dirac point, we also observe a crossover to a much stronger nonlinear transport when the electric field increases above 104 V/m.
Fabrication of P-Type ZnO:N Film by Radio-Frequency Magnetron Sputtering for Extremely Thin Absorber Solar Cell Applications
WANG Xiang-Hu, LI Rong-Bin, FAN Dong-Hua
Chin. Phys. Lett. 2013, 30 (3): 037202 .   DOI: 10.1088/0256-307X/30/3/037202
Abstract   PDF(pc) (612KB) ( 428 )
We successfully fabricate p-type ZnO:N films by using rf magnetron sputtering and in situ annealing in O2 atmosphere. These p-type ZnO:N films can be used as p-type window materials for extremely thin absorber (ETA) solar cells composed of quartz glass/p-ZnO:N/i-ZnO/CdSe/i-ZnO/n-ZnO:Al. The short-circuit photocurrent density, open circuit voltage, fill factor and conversion efficiency of the ETA solar cells can be determined to be 8.549 mA/cm2, 0.702 V, 0.437 and 2.623%, respectively, through measurements of photovoltaic properties under illumination with a 100 mW/cm2 at air-mass (AM) 1.5.
AlGaN/GaN Based Diodes for Liquid Sensing
LUO Wei-Jun, CHEN Xiao-Juan, YUAN Ting-Ting, PANG Lei, LIU Xin-Yu
Chin. Phys. Lett. 2013, 30 (3): 037301 .   DOI: 10.1088/0256-307X/30/3/037301
Abstract   PDF(pc) (694KB) ( 499 )
The characteristics of AlGaN/GaN Schottky diodes as polar liquid sensors are reported. Circular structures, with a gate metal diameter of 200 μm , are designed and fabricated by using a optical lithography process. Ni/Au and Ti/Al/Ni/Au metals are used as the Schottky contact and the ohmic contact, respectively. The Schottky diodes exhibit large changes in reverse leakage current at a bias of ?20 V in response to the surface exposed to various polar liquids, such as acetone and ethanol. The effective Schottky barrier height of the diodes is also changed with the polar liquids. The polar nature of the liquids leads to a change of surface charges, producing a change in surface potential at the semiconductor/liquid interface. The effect of the SiNx passivation layer thickness on the liquid sensing is also discussed. The results demonstrate that the AlGaN/GaN heterostructures are promising for polar liquids, combustion gas, biological, and strain sensing applications.
The Theoretical Electrical Characteristics of Organic Thin Film Transistors Based on Capacitance Modulation
CHEN Yue-Ning, XU Zheng, ZHAO Su-Ling, YIN Fei-Fei
Chin. Phys. Lett. 2013, 30 (3): 037302 .   DOI: 10.1088/0256-307X/30/3/037302
Abstract   PDF(pc) (482KB) ( 387 )
An electrical characteristic model of organic thin film transistors (OTFTs) is presented. The model is based on the capacitance modulation principle, i.e. the accumulated charges in the conductive channel are induced by the gate capacitance under an electric field. The current-voltage characteristics of the presented model are compared with the experimental data. According to the electrical characteristics of the model, it is explained that the operating process of OTFTs is actually modulated by the capacitance. The gate capacitance, the contact resistance, the contact barrier, and the field-effect mobility have a significant effect on the performance of OTFTs.
A High Performance In0.7Ga0.3As MOSFET with an InP Barrier Layer for Radio-Frequency Application
CHANG Hu-Dong, LIU Gui-Ming, SUN Bing, ZHAO Wei, WANG Wen-Xin, LIU Hong-Gang
Chin. Phys. Lett. 2013, 30 (3): 037303 .   DOI: 10.1088/0256-307X/30/3/037303
Abstract   PDF(pc) (755KB) ( 397 )
We demonstrate a high performance implant-free n-type In0.7Ga0.3As channel MOSFET with a 4-nm InP barrier layer fabricated on a semi-insulating substrate employing a 10-nm Al2O3 as gate dielectric. The maximum effective channel mobility is 1862 cm2/V?s extracted by the split CV method. Devices with 0.8 μm gate length exhibit a peak extrinsic transconductance of 85 mS/mm and a drive current of more than 200 mA/mm. A short-circuit current gain cutoff frequency fT of 24.5 GHz and a maximum oscillation frequency fmax of 54 GHz are achieved for the 0.8 μm gate-length device. The research is helpful to obtain higher performance In0.7Ga0.3As MOSFETs for radio-frequency applications.
An Improvement of the Thermal Stability of SnTe through Nitrogen Doping
XIA Meng-Jiao, RAO Feng, SONG Zhi-Tang, REN Kun, WU Liang-Cai, LIU Bo, FENG Song-Lin
Chin. Phys. Lett. 2013, 30 (3): 037401 .   DOI: 10.1088/0256-307X/30/3/037401
Abstract   PDF(pc) (949KB) ( 439 )
Nitrogen doping is applied to improve the thermal stability of SnTe. The crystallization temperature Tc of SnTe is below room temperature, which can be elevated to 216°C by 7.65at.% nitrogen doping. Nitrogen doping results in the formation of SnNx in the nitrogen doped SnTe (N-SnTe) materials, which hinders the movement of atoms and suppresses the crystallization, leading to a better thermal stability. The crystallization activation energy (Ea) and data retention for ten years of 7.65at.% N-SnTe are 1.89 eV and 81°C, respectively. Moreover, the voltage pulses have successfully triggered the SET and RESET operations of the N-SnTe based device at the voltage of 0.9 V and 2.6 V. The good thermal stability and reversible phase-change ability have proved the potential of N-SnTe for phase-change memory application.
Enhanced Giant Magnetoimpedance Effect in Rapid Heat-Treated Fe-Based Amorphous Ribbons
ZHANG Yi, DONG Juan, FENG Er-Xi, LUO Cai-Qin, LIU Qing-Fang, WANG Jian-Bo
Chin. Phys. Lett. 2013, 30 (3): 037501 .   DOI: 10.1088/0256-307X/30/3/037501
Abstract   PDF(pc) (3775KB) ( 468 )
An enhanced giant magnetoimpedance (GMI) effect of Fe-based amorphous ribbons is obtained by rapid heat treatment. The structural investigations on the ribbon reveal the presence of two phases, i.e. a fine grained Fe3Si phase and a residual amorphous phase on rapid heat treatment. The soft magnetic property is improved by rapid heat treatment; the crystal size and grain size of Fe3Si decrease. The maximum magnetoimpedance ratio obtained in the present study is 81% at 10 MHz, and the optimized heat-treated rate is 200°C/min. Separated GMI curves are observed after the simultaneous rapid heat treatment and magnetic field annealing. This suggests that tailoring of the nanocrystalline microstructures induced by optimum rapid heat treatment conditions can result in an excellent GMI effect.
Synthesis and Magnetotransport Properties of CrO2-TiO2 Composites
FAN Yin-Bo, ZHANG Cai-Ping, DU Xiao-Bo, WEN Ge-Hui, MA Hong-An, JIA Xiao-Peng
Chin. Phys. Lett. 2013, 30 (3): 037502 .   DOI: 10.1088/0256-307X/30/3/037502
Abstract   PDF(pc) (1250KB) ( 467 )
CrO2-TiO2 composites are synthesized by using a high temperature and high pressure method using CrO3 and H2TiO3 as precursors. The composites consist of large rod-like CrO2 crystals separated by small TiO2 grains. The CrO2 in the composites is very pure and its saturation magnetization is very close to the theoretical value (i.e., 2μB per formula unit). The composites exhibit a large negative magnetoresistance (MR) at 5 K. The MR in CrO2-TiO2 composites is mainly attributed to spin-polarized tunneling between CrO2 crystals. The conductivity of the composites is best described by a fluctuation-induced tunneling model below 230 K.
Spin-Peierls Instability in the Ferromagnetic Heisenberg Ladder
XU Yin-Jie, ZHAO Hui, CHEN Yu-Guang, YAN Yong-Hong
Chin. Phys. Lett. 2013, 30 (3): 037503 .   DOI: 10.1088/0256-307X/30/3/037503
Abstract   PDF(pc) (639KB) ( 337 )
A two-leg S=1/2 spin ladder with ferromagnetic rung coupling is investigated to reveal the phase transition between the Haldane and columnar dimer phase. The elastic lattice with the elastic force K is introduced into the system, which induces unstable spin chains towards the spontaneous dimerization. When the rung coupling is strong enough, the dimerization along the legs is suppressed and the spin ladder undergoes a phase transition. The dimerization amplitude is calculated self-consistently by the density-matrix renormalization group method. To determine the phase transition boundary, the spin gap, the columnar dimer order parameter and the block-block entanglement entropy are calculated. Our results show that the phase boundary between the columnar dimer phase and Haldane phase follows the power law Jt~K.
Bubble Motion in Transformer Oil under Non-Uniform Electric Fields
CAI Dan, LIU Lie, CHENG Guo-Xin, ZHANG Qiang, ZHAO Xue-Long, ZHAO Qi
Chin. Phys. Lett. 2013, 30 (3): 037701 .   DOI: 10.1088/0256-307X/30/3/037701
Abstract   PDF(pc) (925KB) ( 748 )
We investigate the bubble motion in transformer oil under a typical non-uniform electric field. Based on the principle of virtual work, an analytical equation is derived for the electric force putting on the bubbles. The bubble's visualized motion graphics are then obtained by using the finite-element method, which utilizes Comsol Multiphysics software. The effects of bubble radius and release position on the motion trajectory are studied. It is found that, under the non-uniform electric field, the bubbles have a long residence time between the electrodes. This accordingly can lead to a higher probability of forming a bubble-bridge along the bubble motion trajectory. The bubbles with a particular radius or release position are easier to form bubble-bridge between the electrodes. They can increase the chance of liquid breakdown.
Tunable Magneto-Optical Kerr Effect in Fe Films Underneath a Two-Dimensional Array of Polystyrene Spheres Covered by Au Nanocaps
ZHANG Xia, SHI Lei, LI Jing, XIA Yun-Jie, SHI Zhong, ZHOU Shi-Ming
Chin. Phys. Lett. 2013, 30 (3): 037801 .   DOI: 10.1088/0256-307X/30/3/037801
Abstract   PDF(pc) (819KB) ( 459 )
For Fe layers covered by two-dimensional arrays of hexagonal close-packed polystyrene spheres which are hemispherically covered by Au films on the top, fine structures are observed in reflection, magneto-optical Kerr rotation and ellipticity spectra. The Kerr rotation achieves peaks or exhibits a narrow resonance-like spectral lineshape near the reflection minima, depending on the mechanism of the reflection dips. The Kerr rotation peaks and the resonance-like lineshape both are shifted with the sphere diameters. These phenomena can be attributed to the excitation of surface plasmon resonance and Fabry–Pérot modes.
The Effect of the Oxygen Plasma Treatment for ITO and ZnO Nanorods on the Electroluminescence of ZnO Nanorod/MEH-PPV Heterostructure Devices
ZHAO Su-Ling, WANG Yong-Sheng, GAO Song, YANG Yi-Fan, XU Zheng
Chin. Phys. Lett. 2013, 30 (3): 037802 .   DOI: 10.1088/0256-307X/30/3/037802
Abstract   PDF(pc) (556KB) ( 556 )
Series devices of ITO/ZnO/ZnO nanorods/MEH-PPV/Al have been fabricated. ITO and ZnO nanorods of some devices are treated by O2 plasma. The electroluminescence of different devices is detected under different biases. UV electroluminescence of ZnO nanorods at 380 nm is observed in all the devices. The intensity of 380 nm increases when both ITO and ZnO nanorods are treated. The turn-on voltage of the treated device is lower than that of the non-treated device, and the EL power is enhanced. When the thickness of MEH-PPV is sufficiently thin, only 380 nm electroluminescence, besides a weak defect emission at 760 nm, is detected. The enhancement mechanism of the electroluminescence of the treated devices is discussed.
Large Active Area AlGaN Solar-Blind Schottky Avalanche Photodiodes with High Multiplication Gain
LI Jian-Fei, HUANG Ze-Qiang, ZHANG Wen-Le, JIANG Hao
Chin. Phys. Lett. 2013, 30 (3): 037803 .   DOI: 10.1088/0256-307X/30/3/037803
Abstract   PDF(pc) (603KB) ( 489 )
We report the fabrication and performance of solar-blind AlGaN Schottky avalanche photodiodes grown on sapphire substrates. An increased active donor density is found near the surface, leading to an enhanced electric field adjacent to the Schottky electrode. Multiplication gain over 2000 has been achieved in the fabricated devices with a mesa diameter of 200 μm. The measured dark IV curves at different temperatures show strong temperature dependence, suggesting that the gain mechanism in our devices is primarily due to impact ionization. Peak responsivity of 66.3 mA/W is obtained at 260 nm and at zero bias, corresponding to an external quantum efficiency of 31.6%.
The Influence of Strong Laser Fields on the Interaction between Fast B3+ Clusters and Plasmas
E Peng, WANG Gui-Qiu, YAO Li, GAO Hong, WANG Yao-Chuan, ZHONG Hai-Yang, LIU Wei, YANG Kun, SUN Min, XU Dian-Guo
Chin. Phys. Lett. 2013, 30 (3): 037901 .   DOI: 10.1088/0256-307X/30/3/037901
Abstract   PDF(pc) (788KB) ( 344 )
The influence of a high-intensity laser field on the inelastic interactions between a swift B3+ cluster ion and a plasma target is studied by means of the linearized Vlasov–Poisson theory. Excitations of the plasma are described by the classical plasma dielectric function. In the presence of the laser field, the general expressions for the induced potential in the target and the interaction force among the ions within the cluster are derived. Based on the numerical solution of the equations of motion for the constituent ions, the Coulomb explosion patterns and the cluster's energy losses are discussed for a range of laser parameters.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Single-Step Fabrication of Gd2O3@SiO2 Nanoparticles for use as MRI Contrast Agents by Pulsed Laser Ablation in Liquid
LUO Ning-Qi, HUANG Zhan-Yun, LI Li, SHAO Yuan-Zhi, CHEN Di-Hu
Chin. Phys. Lett. 2013, 30 (3): 038101 .   DOI: 10.1088/0256-307X/30/3/038101
Abstract   PDF(pc) (1033KB) ( 714 )
Gd2O3@SiO2 nanoparticles with a core-shell structure are synthesized by pulsed laser ablation in liquid (PLAL) in single steps. A Gd2O3 target immersed in tetraethyl orthosilicate (TEOS) is ablated by a microsecond Nd:YAG laser, which induces the generation of a Gd2O3 plasma plume and pyrolysis of the TEOS. We propose that the moment Gd2O3 nanoparticles are formed they will be coated immediately by SiO2 and directly synthesized Gd2O3@SiO2 core-shell nanoparticles. These particles obtain high r1 relaxivity of 5.26 s?1mM?1 and are used as T1-weighted magnetic resonance imaging contrast agents. It is shown that the PLAL technique is promising for fabricating core-shell structure nanomaterial with potential medical applications.
Fabrication of a 10 Gb/s InGaAs/InP Avalanche Photodiode with an AlGaInAs/InP Distributed Bragg Reflector
YUE Ai-Wen, WANG Ren-Fan, XIONG Bing, SHI Jing
Chin. Phys. Lett. 2013, 30 (3): 038501 .   DOI: 10.1088/0256-307X/30/3/038501
Abstract   PDF(pc) (646KB) ( 1731 )
A new planar InGaAs/InP avalanche photodiode (APD) is proposed and fabricated, which incorporates a high reflective AlGaInAs/InP distributed Bragg reflector (DBR) to improve its responsivity. The fabricated APD exhibits a low dark current of less than 3 nA at M=10 and high responsivity of 0.92 A/W at M=1. The gain bandwidth product of the device is above 80 GHz. The APD receiver exhibits a sensitivity of over ?26 dBm at BER = 10?12, which is sufficient for 10 Gb/s communication systems.
A Continuous Current Model of Accumulation Mode (Junctionless) Cylindrical Surrounding-Gate Nanowire MOSFETs
JIN Xiao-Shi, LIU Xi, KWON Hyuck-In, LEE Jong-Ho
Chin. Phys. Lett. 2013, 30 (3): 038502 .   DOI: 10.1088/0256-307X/30/3/038502
Abstract   PDF(pc) (714KB) ( 940 )
A continuous current model of accumulation mode or so-called junctionless (JL) cylindrical surrounding-gate Si Nanowire metal-oxide-silicon field effect transistors (MOSFETs) is proposed. The model is based on an approximated solution of Poisson's equation considering both body doping and mobile charge concentrations. It is verified by comparing with three-dimensional simulation results using SILVACO Atlas TCAD which shows good agreement. Without any empirical fitting parameters, the proposed continuous current model of JL SRG MOSFETs is valid for all the operation regions.
Improvement of Ni Silicide Thermal Stability By Using Vanadium Elements
LIU Hai-Long, LIU Yan, LIU Min, WANG Tao, A. Tuya
Chin. Phys. Lett. 2013, 30 (3): 038503 .   DOI: 10.1088/0256-307X/30/3/038503
Abstract   PDF(pc) (560KB) ( 1097 )
Ni silicide thermal stability is improved by the use of a Ni-V (nickel vanadium) alloy target. The relationship between the formation temperature and the thermal stability of Ni silicide is investigated. The sheet resistance after the formation of Ni silicide with the Ni-V shows stable characteristics up to a rapid-thermal-process temperature of 700°C, while degradation of sheet resistance starts at that temperature in the case of pure-Ni. Moreover, the thermal stability improvement is demonstrated by the post-silicidation annealing. It is considered that the thermal robustness of Ni-V silicide is highly dependent on the formation temperature. With the increasing silicidation temperature (around 700°C), more thermally stable Ni silicide is formed in comparison to the low-temperature case using the Ni-V. A Ni-V alloy target is utilized to form Ni silicide. The V and the V-trap complexes are explained to block the transformation from NiSi to NiSi2 so as to improve the Ni silicide thermal stability.
The Efficiency Improvement of Blue InGaN Multiple Quantum-Well Light-Emitting Diodes with AlGaN/InGaN Superlattice Barriers
LUO Da-Feng, CHEN Cui-Ping, PENG Ju
Chin. Phys. Lett. 2013, 30 (3): 038504 .   DOI: 10.1088/0256-307X/30/3/038504
Abstract   PDF(pc) (569KB) ( 618 )
The characteristics of blue InGaN light emitting diodes with AlGaN/InGaN superlattice barriers are investigated. The efficiency droop can be improved when AlGaN/InGaN superlattice barriers are used. This improvement can be attributed to the reduced polarization effect in the active region by using AlGaN/InGaN superlattice barriers.
First-Principles Study of Hydrogen Binding Property in Alkaline-Earth (Be, Mg, Ca) Metal-Doped Closo-Boranes
REN Juan , ZHANG Hong, CHENG Xin-Lu
Chin. Phys. Lett. 2013, 30 (3): 038801 .   DOI: 10.1088/0256-307X/30/3/038801
Abstract   PDF(pc) (721KB) ( 313 )
Using the first-principles method based on density functional theory (DFT), we investigate the stability of alkaline-earth (AE) metal-doped (AE = Be, Mg, and Ca) dodecaborane(12) and the interactions of H2 molecules with the B12H12Be, B12H12Mg, and B12H12Ca clusters. Our calculated results show that the metal sites carry a partial negative/positive charge. The binding energies of metal cations and the boron framework are calculated to be 28.21, 21.92, and 18.79 eV, respectively, which are large enough to prevent metal atoms clustering and ensure the stability toward recyclability. These charge surfaces created at the metal site, which can induce a dipole in the molecular hydrogen, can bind to the hydrogen molecule through the ion-quadrupole as well as through ion-induced dipole interactions. The results show that B12H12Mg and B12H12Ca complexes can store up to 3.52 and 5.26wt% hydrogen, respectively. These studies may provide guidance for designing new 3D hydrogen storage materials with the icosahedra twelve-member boron cluster doped with AE metals as the building blocks.
Long Division Unites or Long Union Divides: a Model for Social Network Evolution
JIANG Jian, WANG Ru, Pezeril Michel, Wang Qiuping Alexandre
Chin. Phys. Lett. 2013, 30 (3): 038901 .   DOI: 10.1088/0256-307X/30/3/038901
Abstract   PDF(pc) (679KB) ( 262 )
A remarkable phenomenon in the time evolution of many networks such as cultural, political, national and economic systems is the recurrent transition between the states of union and the division of nodes. We propose a phenomenological modeling, inspired by the maxim "long union divides and long division unites" to investigate the evolutionary characters of these networks composed of the entities whose behaviors are dominated by these two events. The nodes are endowed with quantities such as identity, ingredient, richness (power), openness (connections), age, distance, and interaction, which determine collectively the evolution in a probabilistic way. Depending on a tunable parameter, the time evolution of this model is mainly an alternative domination of union or division state, with a possible state of final union dominated by one single node.
COMMENTS AND ERRATA
Comment on "A Quantum Network System of QSS-QDC Using χ-Type Entangled States" [Chin. Phys. Lett. 29 (2012) 050303]
LIU Zhi-Hao, CHEN Han-Wu, LIU Wen-Jie, XU Juan
Chin. Phys. Lett. 2013, 30 (3): 039901 .   DOI: 10.1088/0256-307X/30/3/039901
Abstract   PDF(pc) (338KB) ( 359 )
Two quantum secret sharing (QSS) protocols in a multiuser quantum direct communication (QDC) network system were put forward by Hong et al. [Chin. Phys. Lett. 29 (2012) 050303]. However, we find that either agent (Bob or Charlie) alone can obtain half the information about the sender's secret without collaboration with the other, which does not satisfy the security requirement of QSS. Moreover, the secret message sent by Alice in the second protocol can be eavesdropped on or its communication can be disturbed by the builder of quantum channels (Trent).
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