Current Issue

Volume 20 Issue 3
Online Date:
Previous Issue    Next Issue
Original Articles
An Automated Algebraic Method for Finding a Series of Exact Travelling Wave Solutions of Nonlinear Evolution Equations
LIU Yin-Ping, LI Zhi-Bin
Chin. Phys. Lett. 2003, 20 (3): 317-320 .  
Abstract   PDF(pc) (206KB) ( 1257 )
Based on a type of elliptic equation, a new algebraic method to
construct a series of exact solutions for nonlinear evolution equations is proposed, meanwhile, its complete implementation TRWS in Maple is presented. The TRWS can output a series of travelling wave solutions entirely automatically, which include polynomial solutions, exponential function solutions, triangular function solutions, hyperbolic function solutions, rational function solutions, Jacobi elliptic function solutions, and Weierstrass elliptic function solutions. The effectiveness of the package is illustrated by applying it to a variety of equations. Not only are previously known solutions recovered but also new solutions and more general form of solutions are obtained.
Classical Electromagnetic Field Theory in the Presence of Magnetic Sources
LI Kang, CHEN Wen-Jun, NAÓ, N Carlos M.
Chin. Phys. Lett. 2003, 20 (3): 321-324 .  
Abstract   PDF(pc) (210KB) ( 452 )
Using two new well-defined four-dimensional potential vectors, we formulate the classical Maxwell field theory in a form which has manifest Lorentz covariance and SO(2) duality symmetry in the presence of magnetic sources. We set up a consistent Lagrangian for the theory. Then from the action principle we obtain both Maxwell’s equation and the equation of motion of a dyon moving in the electro-magnetic field.
Simplified Scheme for Cloning and Telecloing Quantum States near a Given State
ZHENG Shi-Biao
Chin. Phys. Lett. 2003, 20 (3): 325-327 .  
Abstract   PDF(pc) (178KB) ( 480 )
We describe a simple protocol to produce two approximate copiers of an input state in the neighbourhood of a particular state. We show that the scheme can be realized in the framework of cavity quantum electrodynamics. We also present a scheme for telecloning this kind of states.

Entropy in the Bak-Sneppen Model for Self-Organized Criticality
YANG Chun-Bin
Chin. Phys. Lett. 2003, 20 (3): 328-330 .  
Abstract   PDF(pc) (248KB) ( 434 )
The distributions of fitness on the sites of the one- and two-dimensional lattices are studied for the nearest-neighbour Bak-Sneppen model on self-organized criticality. The distributions show complicated behaviour showing that the system is far from equilibrium. By introducing the “energy”of a site, the entropy flow from the system to its environment is investigated.

Chaos and Fractals in a (2+1)-Dimensional Soliton System
ZHENG Chun-Long, , ZHANG Jie-Fang, SHENG Zheng-Mao
Chin. Phys. Lett. 2003, 20 (3): 331-334 .  
Abstract   PDF(pc) (729KB) ( 471 )
Considering that there are abundant coherent soliton excitations in high dimensions, we reveal a novel phenomenon that the localized excitations possess chaotic and fractal behaviour in some (2+1)-dimensional soliton systems. To clarify the interesting phenomenon, we take the generalized (2+1)-dimensional Nizhnik-Novikov-Vesselov system as a concrete example. A quite general variable separation solutions of this system is derived via a variable separation approach first, then some new excitations like chaos and fractals are derived by introducing some types of lower dimensional chaotic and fractal patterns.
Variable Separation Solutions for the (2+1)-Dimensional Burgers Equation
TANG Xiao-Yan, LOU Sen-Yue,
Chin. Phys. Lett. 2003, 20 (3): 335-337 .  
Abstract   PDF(pc) (672KB) ( 846 )
Considering that the multi-linear variable separation approach has been proven to be very useful to solve many (2+1)-dimensional integrable systems, we obtain the variable separation solutions of the Burgers equation with arbitrary number of variable separated functions. The Y-shaped soliton fusion phenomenon is revealed.
Shear Force Detection Using Single-Tine Oscillating Tuning Fork for Scanning Near-Field Optical Microscopy
TAN Xiao-Jing, SUN Jia-Lin, LIU Sheng, GUO Ji-Hua, SUN Hong-San
Chin. Phys. Lett. 2003, 20 (3): 338-341 .  
Abstract   PDF(pc) (279KB) ( 460 )
We propose a new method to detect near-field by using a single-tine oscillating tuning fork with mechanically asymmetric excitation that exhibits the sensitivity and stability better than that by using a double-tine oscillating one. Comparison of shear forces for the two methods demonstrate that the single-tine oscillating tuning fork provides a simpler and more sensitive method for near-field measurements. A theoretical analysis is presented for explanation to the greater sensitivity. The method is demonstrated by imaging a sparse-packed layer of micro-spheres in size of 200 nm.
Further Analysis of ππ Scattering Dispersion Relations
XIAO Zhi-Guang, ZHENG Han-Qing
Chin. Phys. Lett. 2003, 20 (3): 342-345 .  
Abstract   PDF(pc) (218KB) ( 341 )
The naive use of higher order perturbation theory leads to the left-hand cut integrals in ππ dispersion relations [Phys. Lett. B 536 (2002) 59; B 549 (2002) 362; Nucl. Phys. A 695 (2001) 273] to be divergent. This problem is discussed and solved. We point out that the Adler zero condition imposes three constraints on the dispersion relations. The σ pole position is determined using the improved method, Mσ = 483±13 MeV, Γσ = 705±50 MeV. The scattering length parameter is found to be in excellent agreement with the experimental result.
Structure of the Semi-decoupled π 1/2[411] Band in Odd Proton Nucleus 169Ta
SONG Hai, YANG Chun-Xiang, , SUN Hui-Bin, DENG Fu-Guo, WU Xiao-Guang, LU Jing-Bin, ZHAO Guang-Yi, HAN Guang-Bing, PENG Chao-Hua, YIN Li-Chang, WEN Shu-Xian, LI Guang-Sheng, YUAN Guan-Jun, LIU Yun-Zuo, ZHU Li-Hua, SHAO Li-Qin, ZHOU Hong-Yu,
Chin. Phys. Lett. 2003, 20 (3): 346-349 .  
Abstract   PDF(pc) (533KB) ( 440 )
High spin states of the odd proton-nucleus 169Ta have been populated in the reaction 155Gd(19F, 5n) with beam energies of 97 MeV. Rotational band based on d3/2 proton 1/2[411] Nilsson state has been pushed up to 39/2+ in the α = 1/2 decay sequence. Its signature partner, the α = -1/2 decay sequence with four link transitions has been established and 1/2[411] band in 169Ta was reassigned to be a semi-decoupled band. The systematics of the signature splitting in the K = 1/2 bands in the rear-earth region and the accidental degeneracy conclusion given by the angular projection shell model were discussed.
Collective Bands in Neutron-Rich 110Ru Nucleus
JIANG Zhuo, ZHU Sheng-Jiang, J. H. Hamilton, A. V. Ramayya, J. K. Hwang, ZHANG Zheng, XU Rui-Qing, XIAO Shu-Dong, CHE Xing-Lai, YU Yong-Nan, W. C. Ma, J. D. Cole, M. W. Drigert, I. Y. Lee, J. O.Rasmussen, Y. X. Luo,
Chin. Phys. Lett. 2003, 20 (3): 350-353 .  
Abstract   PDF(pc) (1082KB) ( 401 )
High spin states in neutron-rich 110Ru nucleus have been investigated by measuring high-fold prompt γ-ray coincidence events of the spontaneous fission of 252Cf with the Gammasphere detector array. The ground-state band and the γ-vibrational band have been confirmed and extended with spin up to 18ħ and 13ħ, respectively. The other three side bands, two proposed as two-quasiparticle bands and one proposed as a four-quasiparticle band,have been observed for the first time. The possible configurations for the quasi-particle bands are discussed. The cranked shell model calculations show that 110Ru nucleus may have oblate triaxial deformation with parameters β2 = -0.30 and γ = 24°, and the band crossing in the yrast band is due to the alignment of a pair of h11/2 neutrons.

Total Reaction Cross Section in an Isospin-Dependent Quantum Molecular Dynamics Model
WEI Yi-Bin, CAI Xiang-Zhou, SHEN Wen-Qing, , MA Yu-Gang, ZHANG Hu-Yong, ZHONG Chen, GUO Wei, CHEN Jin-Gen, MA Guo-Liang, WANG Kun
Chin. Phys. Lett. 2003, 20 (3): 354-357 .  
Abstract   PDF(pc) (373KB) ( 397 )
The isospin-dependent quantum molecular dynamics (IDQMD) model is used to study the total reaction cross section σR. The energy-dependent Pauli volumes of neutrons and protons have been discussed and introduced into the IDQMD calculation to replace the widely used energy-independent Pauli volumes. The modified IDQMD calculation can reproduce the experimental σR well for both stable and exotic nuclei induced reactions. Comparisons of the calculated σR induced by 11Li with different initial density distributions have been performed. It is shown that the calculation by using the experimentally deduced density distribution with a long tail can fit the experimental excitation function better than that by using the Skyrme-Hartree-Fock calculated density without long tails. It is also found that σR at high energy is sensitive to the long tail of density distribution.
Pseudospin Symmetry in Relativistic Framework with Harmonic Oscillator Potential and Woods-Saxon Potential
CHEN Ti-Sheng, LÜ, Hong-Feng, MENG Jie, , ZHANG Shuang-Quan, ZHOU Shan-Gui,
Chin. Phys. Lett. 2003, 20 (3): 358-361 .  
Abstract   PDF(pc) (470KB) ( 725 )
Based on the Dirac equation, we discuss the exact pseudospin symmetry and some examples are presented. For harmonic oscillator potential there exist bound states under the condition of the exact pseudospin symmetry, Vs+Vv = 0, and even usual intruder orbits will have degenerated pseudospin partners. Apart from the harmonic oscillator potential, a Woods-Saxon potential is introduced to eliminate the redundant degeneracies due to the speciality of harmonic oscillator potential except the pseudospin degeneracy.

Calculation of Chiral Lagrangian Coefficients
WANG Zhi-Gang
Chin. Phys. Lett. 2003, 20 (3): 362-365 .  
Abstract   PDF(pc) (219KB) ( 323 )
We present a systematic way to combine the global color model and the instanton liquid model to calculate the chiral Lagrangian coefficients. Our numerical results are in agreement well with the experimental values.
Coupled-Channel Investigation of the Collision of Protons and Antiprotons with Hydrogen-Like Atoms in the 2s States
Reda S. Tantawi
Chin. Phys. Lett. 2003, 20 (3): 366-369 .  
Abstract   PDF(pc) (644KB) ( 370 )
The influence of the electric charge of both the projectile and the target nucleus on the cross section of the inelastic collision of protons and antiprotons with atoms is investigated at energies ranging from 1 to 2500 KeV. The impact parameter method is used to analyse the cross sections of the excitation of the n = 3 states of H atom and He+, Li2+ ions being initially in the excited 2s states. The calculated cross sections for hydrogen atoms are compared with the other theoretical results based on coupled-channels methods.

Temporal Skewness of Electromagnetic Pulsed Waves Propagating Through Random Media with Embedded Irregularity Slab
XU Zheng-Wen, WU Jian, HUO Wen-Ping, WU Zhen-Se
Chin. Phys. Lett. 2003, 20 (3): 370-373 .  
Abstract   PDF(pc) (374KB) ( 293 )
Electromagnetic pulsed waves can be distorted in the propagation through random media, and their energy distributions change along the leading and trailing edge of the waveform, which can be presented by the temporal skewness. The skewness presents asymmetry and is treated by the third order temporal moment, in which an analytic solution for the two-frequency mutual coherence function is obtained recently. Then, transionospheric pulses are discussed in details. Both theoretical analysis and numerical computation indicate that the contributions from scattering and dispersion of irregularities dominate over those of background, so the latter can be neglected in most cases. Also, the temporal skewness of a transionospheric pulse is negative and energy is shifted to the leading edge.
Experimental and Theoretical Analysis of Gradient-Index Lens Diffraction by Matrix Optics
SUN Xiao-Hong, MA Hui, MING Hai, ZHENG Zhi-Qiang, YANG Ji-Wen, ZHANG Yong-Sheng, XIE Jian-Ping
Chin. Phys. Lett. 2003, 20 (3): 374-376 .  
Abstract   PDF(pc) (337KB) ( 542 )
We present the diffraction patterns observed in the gradient-index (GRIN) lens sensor experiment. Then the diffraction pattern of radial GRIN lens is explored by using matrix optics. The theoretical results agree with the experimental results of 27.9-mm-long GRIN lens with 2-mm diameter diffraction patterns.

Multiplexing Nonvolatile Holograms in LiNbO3:Cu:Ce Crystals
ZHAO Jian, WANG Jian-Gang, LIU Guo-Dong, HE Qing-Sheng, WU Min-Xian, JIN Guo-Fan
Chin. Phys. Lett. 2003, 20 (3): 377-378 .  
Abstract   PDF(pc) (342KB) ( 419 )
A practical experimental system for two-center recording by angular multiplexing and 90°geometry is designed with red and blue light. The erasure mechanism of lithium niobate crystals doubly doped with copper and cerium for two-center recording is discussed and a modified decremental recording schedule for angular multiplexing is proposed subsequently. Finally, 50 nonvolatile holograms with almost the same diffraction efficiency are recorded.
Novel Atomic Mirror with a Blue-Detuned Semi-Gaussian Beam
ZHENG Ping, GAO Wei-Jian, YIN Jian-Ping,
Chin. Phys. Lett. 2003, 20 (3): 379-382 .  
Abstract   PDF(pc) (503KB) ( 373 )
A novel and simple atomic mirror composed of a blue-detuned
semi-Gaussian beam is proposed. From the Fresnel diffraction theory, the intensity distributions of a collimated Gaussian laser beam diffracted by the straight edge of a semi-infinite opaque plate are studied. The optical potential of the semi-Gaussian beam for 85Rb atoms and its spontaneous emission probability are calculated and compared with the performance of the evanescent-wave mirror. Our study shows that the blue-detuned semi-Gaussian beam, as a novel atomic mirror, can be used to reflect atomic beam efficiently, and under the same beam parameters and lower normal atomic velocity, the performance of the semi-Gaussian-beam mirror is better than that of the evanescent-wave mirror.

Structure of Vortex Dislocations in a Wake-Type Flow
LING Guo-Can, ZHAO Hong-Liang,
Chin. Phys. Lett. 2003, 20 (3): 383-385 .  
Abstract   PDF(pc) (212KB) ( 379 )
Structure and dynamical processes of vortex dislocations in a kind of wake-type flow are described clearly by vortex lines, which are directly constructed from data of three-dimensional direct numerical simulations of the flow evolution.

Helium-Charged Titanium Films Deposited by Pulsed Laser Deposition in an Electron-Cyclotron-Resonance Helium Plasma Environment
JIN Qin-Hua, HU Pei-Gang, LING Hao, WU Jia-Da, SHI Li-Qun, ZHOU Zhu-Ying
Chin. Phys. Lett. 2003, 20 (3): 386-388 .  
Abstract   PDF(pc) (266KB) ( 435 )
Titanium thin films incorporated with helium are produced by pulsed laser deposition in an electron cyclotron resonance helium plasma environment. Helium is distributed evenly in the film and a relatively high He/Ti atomic ratio (~20%) is obtained from the proton backscattering spectroscopy. This high concentration of helium leads to a surface blistering which is observed by scanning electron microscopy. Laser repetition rate has little influence on film characters. Substrate bias voltage is also changed for the helium incorporating mechanism study, and this is a helium ion implantation process during the film growth. Choosing suitable substrate bias voltage, one can avoid the damage produced by ion implantation, which is always present in general implantation case.

Measurement of Specimen Thickness by Using Electron Holography and Electron Dynamic Calculation with a Transmission Electron Microscope
WANG Yan-Guo, LIU Hong-Rong, YANG Qi-Bin, ZHANG Ze
Chin. Phys. Lett. 2003, 20 (3): 389-391 .  
Abstract   PDF(pc) (272KB) ( 858 )
A method of transmission-electron microscopy for accurate measurement of specimen thickness has been proposed based on off-axis electron holography along with the dynamic electron diffraction simulation. The phase shift of the exit object wave with respect to the reference wave in vacuum, resulting from the scattering within the specimen, has been simulated versus the specimen thickness by the dynamic electron diffraction formula. Off-axis electron holography in a field emission gun transmission electron microscope has been used to determine the phase shift of the exit wave. The specimen thickness can be obtained by match of the experimental and simulated phase shift. Based on the measured phase shift of the [110] oriented copper foil, the thickness can be determined at a good level of accuracy with an error less than ~10%.

Entropy of Baker’s Transformation
LUAN Chang-Fu
Chin. Phys. Lett. 2003, 20 (3): 392-394 .  
Abstract   PDF(pc) (213KB) ( 316 )
Four theorems about four different kinds of entropies for Baker’s transformation are presented. The Kolmogorov entropy of Baker’s transformation is sensitive to the initial flips by the time. The topological entropy of Baker’s transformation is found to be logk. The conditions for the state of Baker’s transformation to be forbidden are also derived. The relations among the Shanonn, Kolmogorov, topological and Boltzmann entropies are discussed in details.

Viscosity Measurements of Fe-Si-BCu-Nb-C Metallic Glass Melts by an Oscillating Crucible Method
LI Cheng-Dong, TIAN Xue-Lei, CHEN Xi-Chen, A.G. Ilinsky
Chin. Phys. Lett. 2003, 20 (3): 395-397 .  
Abstract   PDF(pc) (356KB) ( 544 )
Dependence of the dynamic viscosity of new type of Fe-based
amorphous alloy (Fe68.5Si13.5B9Cu1Nb3C5) melt on temperature is investigated by using a torsional oscillation viscometer. The temperature dependence of the viscosity can be fitted by the Arrhenius relation and Fulcher expression as lnη = 0.082+ 1463.48/T and lnη = 6.75 x 10-5+954.71/(T-608.36), where η is the viscosity in units of cP and T is the temperature in units of K. The results show that the Arrhenius relation is more suitable in high temperature region, while the Fulcher expression is more appropriate in undercooled region. Combining the Differential scanning calorimetry data and free-volume model, the glass forming ability of Fe68.5Si13.5B9Cu1Nb3C5 alloy is discussed.

Etch Pits and Threading Dislocations in GaN Films Grown by Metal-Organic Chemical Vapor Deposition
LU Min, , CHANG Xin, LI Zi-Lan, , YANG Zhi-Jian, , ZHANG Guo-Yi, , ZHANG Bei,
Chin. Phys. Lett. 2003, 20 (3): 398-400 .  
Abstract   PDF(pc) (262KB) ( 1731 )
High quality epitaxial GaN films on (0001) sapphire substrates were grown by a commercial metal-organic chemical vapor deposition system. The etch-pits and threading dislocations in GaN films is studied by a scaning electron microscope (SEM) and a transmission electron microscope (TEM). The SEM images of GaN films etched in mixed acid solution (H3PO4:H2SO4 = 1:3) and molten KOH exhibit notably different etching pit densities of 5 x 108/cm2 and 4 x 107/cm2, respectively, which probably indicate that more kinds of etching pits were revealed when etched in mixed acid solution (H3PO4:H2SO4 = 1:3). Cross section TEM of GaN films with different g vectors showed the portions of different threading dislocations. Theoretical calculation indicates that the lattice and thermal expansion coefficient mismatch may be the main origins of pure edge threading dislocations.
Blue Cathodoluminescence from Highly Er-Doped ZnO Thin Films Induced by the Phonon Bottleneck Effect
ZHANG Xi-Tian, LIU Yi-Chun, MA Jian-Gang, LU You-Ming, SHEN De-Zhen, XU Wub, ZHONG Guo-Zhu, FAN Xi-Wu
Chin. Phys. Lett. 2003, 20 (3): 401-403 .  
Abstract   PDF(pc) (192KB) ( 384 )
The room-temperature blue cathodoluminescence (CL) from highly Er-doped ZnO thin films has been studied by using different electron beam currents (EBCs). The ZnO:Er thin films used in our experiment were prepared by simultaneous evaporation from two sources. The x-ray diffraction spectra show that the thin films have a strong preferential c-axis (0002) orientation with a hexagonal crystalline structure. The blue emission at 455 nm originating from the intra-4f shell transition (4F5/2.4I15/2) in Er3+ ions was observed at room temperature. The nonlinear dependence of the CL intensity on the EBC shows a more intense blue emission above the threshold EBC of 0.6μA, which is attributed to the phonon bottleneck effect.

First-Principle Calculations for Scanning-Tunneling-Microscopic Images of a Monolayer Graphite Surface
CHEN Xiang-Rong, OSHIYAMA Atsushi, OKADA Susumu, GOU Qing-Quan
Chin. Phys. Lett. 2003, 20 (3): 404-407 .  
Abstract   PDF(pc) (945KB) ( 375 )
We have applied first-principle total-energy electronic structure calculations in the local density approximation to calculate the scanning tunneling microscopy images of a monolayer graphite surface near the Fermi level. The results obtained agree well with the observation, which has not been interpreted before.

Evaluation of Spectroscopic Properties of Yb3+ in Silicate-Based Heavy Metal Oxide Glasses
DAI Neng-Li, HU Li-Li, DAI Shi-Xun, YANG Jian-Hu, LIN Ao-Xiang
Chin. Phys. Lett. 2003, 20 (3): 408-410 .  
Abstract   PDF(pc) (264KB) ( 412 )
The absorption, stimulated emission cross section and potential
laser parameters of heavy metal silicate glasses doped with Yb3+ ions have been investigated. The emission cross section has been evaluated by using the measured absorption spectra and principle of reciprocity. It is found that Yb3+ in SiO2-Bi2O3-B2O3 glass has high stimulated emission cross section of 0.9 pm2 for the 2F5/22F7/2 transition and exists short measured fluorescence lifetime of 0.78 ms. On the other hand, the stimulated emission cross section of Yb3+-doped SiO2-PbO glass was 0.49 pm2. Its measured fluorescence lifetime was 2.00 ms. Evaluated from the good potential laser parameters, Yb3+-doped SiO2-PbO glass may be a good candidate for fibre laser applications.
A Possible Explanation to Paradox in Horse Spleen Ferritins
KOU Su-Peng, LIANG Jiu-Qing
Chin. Phys. Lett. 2003, 20 (3): 411-413 .  
Abstract   PDF(pc) (230KB) ( 299 )
There are contradicting opinions about the tunneling experiments in horse-spleen ferritin particles. By distinguish the coherent and incoherent tunneling processes, we give a unified explanation to different experiments. As a result, a possible explanation to the paradox is proposed.
Growth of Structured Non-crystalline Boron-Oxygen-Nitrogen Films and Measurement of Their Electrical Properties
CHEN Guang-Chao, LU Fan-Xiu, J. -H. Boo
Chin. Phys. Lett. 2003, 20 (3): 414-416 .  
Abstract   PDF(pc) (237KB) ( 455 )
The boron-oxygen-nitrogen (BON) films have been grown on Si wafer by the low-frequency rf-plasma-enhanced metal-organic chemical vapor deposition method. The homogeneous film structure of completely amorphous BON is first fabricated on a low-temperature-made buffer at 500°C with N2 plasma and is observed with a high-resolution electron microscope by the transmission electron diffraction. The results show that the interfaces among substrate/buffer/film are clear and straight in the structured film. A heterogeneous film containing nano-sized crystalline particles is also grown by a routine growth procedure as a referential structure. The C-V characteristic is measured on both the amorphous and crystal-containing films by using the metal-oxide-semiconductor structure. The dielectric constants of the films are, therefore, deduced to be 5.9 and 10.5 for the amorphous and crystal-containing films, respectively. The C-V results also indicate that more trapped charges exist in the amorphous film. The binding energy of the B, O, and N atoms in the amorphous film is higher than that in the crystal-containing one, and the N-content in the latter is found to be higher than that in the former by x-ray photo-electron spectroscopy. The different electrical property of the films is thought to originate from the energy state of the covalent electrons.
Submergence and Control of Dark Soliton in a Dispersion-Managed System with Random Dispersion Map
LI Hong, HUANG De-Xiu
Chin. Phys. Lett. 2003, 20 (3): 417-419 .  
Abstract   PDF(pc) (570KB) ( 344 )
Random dispersion map is considered in a dispersion-managed dark soliton system, its influence on soliton propagation and interaction is discussed. It is found that the random dispersion map results in large sidebands, leads to submergence of dark soliton, and enhances the interaction between solitons. Finally nonlinear gain is introduced to suppress the influence effectively.
A New Kind of Buffer Layer of TiO2 Self-Assembled Material in Organic Electroluminescent Devices
BAI Feng, DENG Zhen-Bo, ZHANG Meng-Xin, ZOU Wei-Yan, CAI Qiang
Chin. Phys. Lett. 2003, 20 (3): 420-422 .  
Abstract   PDF(pc) (353KB) ( 383 )
A new kind of TiO2 self-assembled nanometer material has been fabricated and is used as a hole-injecting buffer layer in organic electroluminescent devices. The luminance and the efficiency of a device individually rises from 1500 cd/m2 to 5000 cd/m2 and from 2.0 cd/A to 3.92 cd/A at the current density of 100 mA/cm2. The enhancements in brightness and efficiency are attributed to an improved balance of hole and electron injections due to blocking of the injected holes by the buffer layer and a more homogeneous adhesion of the hole transporting layer to the anode.
An a-C:F:H Film with High Thermal Stability by Electron Cyclotron Resonance Chemical Vapor Deposition at Room Temperature
XIN Yu, XU Sheng-Hua, NING Zhao-Yuan, LU Xin-Hua, JIANG Mei-Fu, HUANG Song, DU Wei, CHEN Jun, YE Chao, CHENG Shan-Hua
Chin. Phys. Lett. 2003, 20 (3): 423-426 .  
Abstract   PDF(pc) (501KB) ( 422 )
Using CHF3/C6H6 gases, amorphous fluorinated hydrocarbon films (a-C:F:H) were deposited by electron cyclotron resonance (ECR) chemical vapor deposition at room temperature. Dependence of the film properties on variable flow ratios R[CHF3]/{[CHF3]+[C6H6]} was investigated by infrared absorption, x-ray photoelectron spectroscopy, measurements of the film thickness and dielectric constant. Evidences show that the film deposition rate decreases linearly with the increasing flow ratios R and the adding of C6H6 source gas to ECR plasma enhances structural cross-linking in the a-C:F:H films. In order to obtain good structural stability of these films, it is necessary to reconcile configurations between C-C bond and H or F terminal atoms carefully. The experimental results indicate that an a-C:F:H film with low dielectric constant (k < 3) and high thermal stability ( > 400°C) has been deposited successfully at R = 56.3%.
Behaviour of Internal Stress in Melt-Spun Ni-Mn-Ga Ribbons
ZHAO Wei-Ren, LI Jian-Liang, QI Yan, WANG Xin-Lin
Chin. Phys. Lett. 2003, 20 (3): 427-429 .  
Abstract   PDF(pc) (512KB) ( 325 )
We investigate the martensitic transition of melt-spun Ni-Mn-Ga ribbons, during which an abrupt release of internal stress occurs. The release results in the appearance of two peaks on the curve of field-induced strains versus temperature. During and after the transformation, a large lag of field-induced strains was observed, indicating a competition between the stress energy and Zeemann energy. The lag leads to an unusual relation of the strains to the inducing field.

A Light-Activated SiC Darlington Transistor Using SiCGe as Base Layer
CHEN Zhi-Ming, PU Hong-Bin, Fred R. BEYETTE Jr.
Chin. Phys. Lett. 2003, 20 (3): 430-432 .  
Abstract   PDF(pc) (408KB) ( 344 )
If a Darlington transistor is triggered by the photocurrent output from an individual photodiode, the electromagnetic interference (EMI) problem may still exist because the direct input of the Darlington is an actually electronic signal. To eliminate the EMI problem completely, we propose an absolutely light-activated Darlington transistor made of SiC, in which p-SiCGe/n-SiC heterojunction is employed to produce a base current by means of optical illumination. Performance of the novel light-activated power switch was simulated using MEDICI tools, which has shown that the light-activated device has very good switching characteristics especially for a triggering light intensity greater than 0.23 W/cm2. For a relatively weak light, the device can be switched to the ON state only for a higher bias voltage.
Gamma-Ray Pulsars Expected in the Outer Gap Model of Gamma-Ray Emission
ZHANG Li, WU Jie, JIANG Ze-Jun, MEI Dong-Cheng
Chin. Phys. Lett. 2003, 20 (3): 433-435 .  
Abstract   PDF(pc) (376KB) ( 487 )
We study the possibility of high-energy gamma-ray emission from the known 1130 radio pulsars based on the outer gap model of high energy emission from pulsars. We estimate the fractional size of outer gap, the integrated flux, the gamma-ray luminosity for each known radio pulsar, and find that only 14% of the known radio pulsars are gamma-ray emitters according to the outer gap model. In the sample of possible 156 gamma-ray pulsars, our statistical analysis indicates that the distributions of the spin-down powers and the ages of these pulsars concentrate mainly on 1033.5-1039 erg/s and 103-107 y, respectively. The predictions of gamma-ray pulsars detected by the AGILE and GLAST missions are given.
Softness of Nuclear Matter and the Production of Strange Particles in Neutron Stars
CHEN Wei, WEN De-Hua, LIU Liang-Gang
Chin. Phys. Lett. 2003, 20 (3): 436-439 .  
Abstract   PDF(pc) (398KB) ( 297 )
In the various models, we study the influences of the softness of nuclear matter, the vacuum fluctuation of nucleons and σ mesons on the production of strange particles in neutron stars. We find that the stiffer the nuclear matter is, the more easily the strange particles is produced in neutron stars. The vacuum fluctuation of nucleons has large effect on strange particle production while the one of σ meson has little effect on it.
Reissner-Nordstrom Black Hole Entropy Inside and Outside the Brick Wall
LIU Wen-Biao
Chin. Phys. Lett. 2003, 20 (3): 440-443 .  
Abstract   PDF(pc) (202KB) ( 650 )
Applying the generalized uncertainty relation to the calculation of the free energy and entropy of a Reissner-Nordstrom black hole inside the brick wall, the entropy proportional to the horizon area is derived from the contribution of the vicinity of the horizon. This is compared with the entropy calculated via the original brick wall model. The entropy given by the original brick wall model comes from the outside of the brick wall seemingly. The inside result using generalized uncertainty relation is similar to the outside result using original uncertainty relation, and the divergence inside the brick wall disappears. It is apparent that the cutoff is something related to the quantum theory of gravity.
37 articles