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Volume 19 Issue 3
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Original Articles
Probabilistic Preparation of N-particle Cat States via Entanglement Swapping and Entanglement Concentration
YAO Chun-Mei, LI Min, YE Liu, GUO Guang-Can
Chin. Phys. Lett. 2002, 19 (3): 289-291 .  
Abstract   PDF(pc) (222KB) ( 479 )
We discuss two different schemes for the probabilistic preparation of N-particle cat states using pure multiparticle entangled states via entanglement swapping and entanglement concentration. at the center of distribution A, Alice performs all of the operations required to achieve our goal.
Quantum-Mechanical Simulation of an Atomic Beam Focused by an Optical Standing Wave
HE Ming, WANG Jin, TU Xian-Hua, JIANG Kai-Jun, WANG Yi, ZHAN Ming-Sheng
Chin. Phys. Lett. 2002, 19 (3): 292-294 .  
Abstract   PDF(pc) (438KB) ( 332 )
Recent experiments have demonstrated that the light pressure force from an optical standing wave (SW) focuses an atomic beam to sub-micrometer dimensions. We start from a two-dimensional time-dependent Schrödinger equation and reduce it to a one-dimensional equation by a paraxial approximation. We calculate some theoretical limits on the focusing of an atomic beam by an SW optical field. It is found that two parameters, the atomic velocity and intensity of laser beam play an important role in determining the deposition quality.
O(N) Quintessence with a Cosine-Type Potential
LI Xin-Zhou, LIU Dao-Jun, HAO Jian-Gang
Chin. Phys. Lett. 2002, 19 (3): 295-298 .  
Abstract   PDF(pc) (245KB) ( 446 )
We propose a quintessence model with a cosine-type potential, in which the scalar field Фa possesses an O(N) internal symmetry. The most prominent feature of this model is that it will not reduce to a cosmological constant even when |Фa| is spatially uniform and time-independent. Since different value of the potential parameter will lead to different cosmic microwave background anisotropies which may be detectable in the future satellite experiments, one can decide by observations whether the cosine-type quintessence consists of one scalar field or many fields with a symmetry constraint.
Stochastic Resonance in Coupled Array Without Periodic Driving
QIAN Min, ZHANG Xue-Juan,
Chin. Phys. Lett. 2002, 19 (3): 299-301 .  
Abstract   PDF(pc) (393KB) ( 422 )
We manifests a stochastic resonance in a two-dimensional square array of coupled oscillators subjected only to white noise and constant driving forces. The result shows that the coherent output of every single oscillator plays a role of the periodic input to its neighbours. Even without periodic driving, the cooperation of the white noise and the coupling can also result in the array enhanced stochastic resonance effect. In our investigation, global as well as local noise perturbation is taken into account.
Channel Equalization for Chaos-Based Communication Systems
FENG Jiu-Chao, LU Rui-Hua
Chin. Phys. Lett. 2002, 19 (3): 302-305 .  
Abstract   PDF(pc) (446KB) ( 338 )
We suudy the equalization of the channel for chaotic communication systems. A channel equalizer is designed and realized by a modified recurrent neural network for eliminating channel distortions. The results from computer simulations demonstrate the effectiveness of the equalizer as applied to a chaotic communication system.
Search for the Halo Effect in the 1H(6He, 6Li)n Reaction
LI Zhi-Hong, LIU Wei-Ping, BAI Xi-Xiang, WANG You-Bao, LIAN Gang, LI Zhi-Chang, SHEN Qing-Biao, LIN Cheng-Jian, ZENG Sheng, FU Chang-Bo
Chin. Phys. Lett. 2002, 19 (3): 306-308 .  
Abstract   PDF(pc) (441KB) ( 681 )
The angular distributions of the charge exchange reaction 1H(6He, 6Li)n were measured in reverse kinematics with a secondary 6He beam at the energy of 4.17 A MeV. The data were analysed in the context of a microscopic calculation. It is shown that both the ground state of 6He and the second excited state of 6Li (3.563MeV, 0+) have a halo structure.
Statistical Properties of the Realistic Model Spectra for Doubly-Odd Nuclei
CHENG Nan-Pu, CHEN Zhi-Qian, CHEN Hong
Chin. Phys. Lett. 2002, 19 (3): 309-311 .  
Abstract   PDF(pc) (375KB) ( 411 )
The statistical properties of the energy levels calculated for the doubly-odd nuclei 84Y, 124Cs and 156Tb within the quasiparticle plus axially symmetric rotor model are studied by means of the two standard statistical tests of random-matrix theory, i.e. the distribution function p(s) of the nearest-neighbor level spacings and the spectral rigidity (Δ3 statistics). We also investigate the Brody distribution function pB(s) with a single parameter that describes the chaotic degree of the systematic dynamics and the transition behaviour of the spectral fluctuations between Poisson and gauss orthogonal ensemble limits.
Giant Neutron Halo in Exotic Calcium Nuclei
ZHANG Shuang-Quan, , MENG Jie, , ZHOU Shan-Gui, , ZENG Jin-Yan,
Chin. Phys. Lett. 2002, 19 (3): 312-314 .  
Abstract   PDF(pc) (356KB) ( 631 )
The properties of even-even Ca isotopes are studied using the
relativistic continuum Hartree-Bogoliubov theory. The calculations reproduce very wwell the experimental binding energies E and two neutron separation energies S2n. The predicted neutron drip nuclei is 72Ca. From the analysis of S2n, the neutron radii and neutron density distribution, giant neutron haloes are predicted in Ca isotopes with A > 60.
Description of Superdeformed Bands of the Nuclei in A ~ 80 Mass Region
LIU Yu-Xin, , MU Liang-Zhu, WANG Jia-Jun
Chin. Phys. Lett. 2002, 19 (3): 315-318 .  
Abstract   PDF(pc) (458KB) ( 510 )
Within the supersymmetry scheme including many-body interactions and a perturbation possessing the SO(5) (or SU(5)) symmetry on the rotational symmetry, the superdeformed (SD) bands of the nuclei in the A ~ 80 mass region are investigated systematically. Quantitatively good results of the γ-ray energy spectra and the dynamical moments of inertia are obtained. It is shown that the supersymmetry approach is powerful to describe not only the generic rotational property, but also the characteristic of the triaxial SD band simultaneously.
Rotation-Vibration Coupling in the Geometric Representation of the Interacting Boson Model
DI Yao-Min
Chin. Phys. Lett. 2002, 19 (3): 319-320 .  
Abstract   PDF(pc) (163KB) ( 367 )
We discuss rotation-vibration coupling in the geometric representation of the interacting boson model (IBM). The Hamiltonian, the relations between the IBM parameters and geometric parameters, and the method of calculation are given so that practical applications of geometric representation may become possible.
Isospin Effect on Nuclear Stopping in Intermediate Energy Heavy Ion Collisions
LI Qing-Feng, LI Zhu-Xia,
Chin. Phys. Lett. 2002, 19 (3): 321-323 .  
Abstract   PDF(pc) (447KB) ( 387 )
By using the isospin-dependent quantum molecular dynamics model, we study the dependence of nuclear stopping QZZ/A and R in intermediate energy heavy ion collisions on system size, initial N/Z, isospin symmetry potential and the medium correction of two-body cross sections. We find the effect of initial N/Z ratio, isospin symmetry potential on stopping is weak. The excitation function of QZZ/A and R depends on the form of medium correction of two-body cross sections, the equation of state of nuclear matter. Our results show the behaviour of the excitation function of QZZ/A and R can provide clearer information of the isospin dependence of the medium correction of two-body cross sections.
Structure and Thermodynamic Properties of Liquid Transition Metals with Different Embedded-Atom Method Models
WANG Jin-Zhao, CHEN Min, GUO Zeng-Yuan
Chin. Phys. Lett. 2002, 19 (3): 324-326 .  
Abstract   PDF(pc) (322KB) ( 990 )
Pair distribution functions and constant-volume heat capacities of liquid copper, silver and nickel have been calculated by molecular dynamics simulations with four different versions of embedded-atom method (EAM) model, namely, the version of Johnson, Mei Cai and Pohlong. The simulated structure properties with the four potential models show reasonable agreements with experiments and have little difference with each other. While the calculated heat capacities with different EAM versions show remarkable discrepancies. Detailed analyses of the energy of liquid metallic system show that an EAM model to predict successfully the heat capacity should match the state equation first proposed by Rose.
Atomic Magnetic Lattices and Their Applications
YIN Jian-Ping, GAO Wei-Jian, HU Jian-Jun, LIU Nan-Chun
Chin. Phys. Lett. 2002, 19 (3): 327-330 .  
Abstract   PDF(pc) (859KB) ( 446 )
We propose a novel scheme to construct one-, two- or three-dimensional (1D, 2D or 3D) atomic magnetic lattices by using various arrays of microscopic magnetic traps, which are composed of some arrays of current-carrying wires. The magnetic field distributions from 1D, 2D and 3D arrays of the current-carrying wires are calculated, and some interesting and periodic magnetic microstructures are found. Our study shows that these magnetic lattices may be used to prepare 1D, 2D or 3D photonic crystals and so on.
Transmission Probability of an Ultracold Atom in the Presence of Atomic Coherence
XIONG Jin, CHU Kai-Qin, ZHANG Zhi-Ming
Chin. Phys. Lett. 2002, 19 (3): 331-333 .  
Abstract   PDF(pc) (290KB) ( 282 )
We investigate the transmission probability of an ultracold V-type three-level atom passing through a micromaser cavity, in the presence of atomic coherence which is established by a coherent driving field. We show that the transmissibility of this micromaser system with the atomic coherence is better than that of the ordinary micromaser system without atomic coherence. When the driving field is strong enough, for any cavity length the ultracold atom can pass through the micromaser cavity freely.
Experimental Observation of Constructive Quantum Interference via Hybrid Excitation in an Na2-Na System
YANG Xi-Hua, LI Yong-Fang, SUN Zhen-Rong, DING Liang-En, WANG Zu-Geng
Chin. Phys. Lett. 2002, 19 (3): 334-337 .  
Abstract   PDF(pc) (497KB) ( 465 )
We report on an experimental observation of constructive quantum interference between two atomic transition pathways 3P1/2-5S (or 4D) and 3P3/2-5S (or 4D) via equal-frequency hybrid excitation and collision-aided radiative excitation in an Na2-Na system. Through the special excitation processes, constructive quantum interference is realized for a Λ-type quantum-beat configuration with a widely-spaced doublet (about 17 cm-1) in the excited sodium atom driven by one laser. The dependences of quantum interference on the argon buffer gas pressure and sample temperature are also examined.
Transparency and Strong Gain Without Population Inversion in Photonic Bandgap Crystals
DU Chun-Guang, HU Zheng-Feng, HOU Chun-Feng, LI Shi-Qun
Chin. Phys. Lett. 2002, 19 (3): 338-341 .  
Abstract   PDF(pc) (424KB) ( 371 )
Without using the weak-field approximation, we investigate the transient properties of a Λ-type atom with one transition near resonant with a photonic bandgap edge. Whatever the initial state of the atom is, the atom can become transparent to a probe field, and strong gain without population inversion is also possible if the atom has been pre-excited. The defect mode formed by atomic doping can have strong effect on the absorption properties of the atom.

Performance of the Self-Q-Switched Cr,Yb:YAG Laser
DONG Jun, DENG Pei-Zhen, LIU Yu-Pu, ZHANG Ying-Hua, HUANG Guo-Song, GAN Fu-Xi
Chin. Phys. Lett. 2002, 19 (3): 342-344 .  
Abstract   PDF(pc) (461KB) ( 520 )
We report on the spectral properties of Cr,Yb:YAG crystal co-doped with 0.025 at.% Cr and 10 at.% Yb are reported. Using a continuous wave Ti:sapphire laser as a pumping source, We have demonstrated the self-Q-switched Cr,Yb:YAG laser has been at room temperature. We obtained an average output power as much as 75mW at 1.03μm with a pulse width (FWHM) as short as 0.4 μs. The laser experiment demonstrated that the Cr,Yb:YAG crystal exactly combines the Cr4+ saturable absorber and Yb3+ gain medium. The Cr,Yb:YAG crystal can be a most promising self-Q-switched laser crystal for compact and efficient solid-state lasers.
Spatial Interference Effect of Two-Photon in Femtosecond-Pulse Pumped Spontaneous Parametric Down-Conversion
LU Shu-Long, SUN Bao-Quan, LIU Bo, JIANG De-Sheng, XU Zhong-Ying
Chin. Phys. Lett. 2002, 19 (3): 345-347 .  
Abstract   PDF(pc) (308KB) ( 422 )
We have used the transverse correlated properties of the entangled photon pairs generated in the process of spontaneous parametric down-conversion, which is pumped by a femtosecond pulse laser, to perform Young's interference experiment. Different from the case of continuous wave laser pump, broadband pulse laser pump can submerge an interference pattern. In order to obtain high visibility interference pattern, we used a lens with tunable focal length and two interference filters to eliminate the effects of broadband pump laser. It is proved that the process of two-photon direct interference is a post-selection process.
Phase Dependence of Few-Cycle Pulsed Laser Propagation in a Two-Level Atom Medium
XIAO Jian, WANG Zhong-Yang, XU Zhi-Zhan
Chin. Phys. Lett. 2002, 19 (3): 348-350 .  
Abstract   PDF(pc) (382KB) ( 429 )
The phase-dependent feature of few-cycle pulsed laser propagation in a resonant two-level atom medium is demonstrated by solving the full Maxwell-Bloch equations. Even in the perturbative region, the propagating carrier field and the corresponding spectra of few-cycle pulsed laser are sensitive to the initial phase due to the self-phase modulation. For the larger pulse area, the fact that the carrier-wave reshaping comes from the carrier-wave Rabi flopping is also responsible for this sensitivity, and the phase dependent feature is more evident.
High Gain Lateral Semi-Insulating GaAs Photoconductive Switch Triggered by 1064 nm Laser Pulses
SHI Wei, ZHANG Xian-Bin, LI Qi, CHEN Er-Zhu, ZHAO Wei
Chin. Phys. Lett. 2002, 19 (3): 351-354 .  
Abstract   PDF(pc) (421KB) ( 539 )
We report on the experimental results of a lateral semi-insulating GaAs photoconductive switch, with a gap of 8mm between two electrodes, triggered by 1064nm laser pulses at the wavelength beyond the GaAs absorption edge. Both the linear and nonlinear modes of the switch were observed when it was triggered by light pulses with energy of 1.9mJ and the pulse width of 60ns, and operated at high voltage of 3 and 5kV. The results show that when the semi-insulating GaAs photoconductive switch operates under an electrical field of 4.37kV/cm, it will enter into the linear mode first, and then the switch will undergo the nonlinear mode (lock-on) after a delay of about 20-100ns. It is worth noticing that the delay time under high light energy is longer than that in the low optical energy. The non-intrinsic absorption mechanism is discussed. EL2 deep level defects and double-photon absorption in GaAs may play a key part in the absorption process.
Focusing Ultrasonic Field of Holed Cap Spherical Shell Transducer Using the Spheroidal Beam Equation
XIA Rong-Min, SHOU Wen-De, CHEN Guo-Ping, WANG Hong-Zhang
Chin. Phys. Lett. 2002, 19 (3): 355-357 .  
Abstract   PDF(pc) (667KB) ( 599 )
A large aperture transducer with an inner hole has been used to validate the feasibility of using the spheroidal beam equation to solve the acoustic field of the inner holed transducer. The numerical results several harmonics are presented for the nonlinear field.

Lattice Boltzmann Model and Geophysical Hydrodynamic Equation
FENG Shi-De, YANG Jing-Long, GAO Xian-Lin, JI Zhong-Zhen
Chin. Phys. Lett. 2002, 19 (3): 358-361 .  
Abstract   PDF(pc) (0KB) ( 272 )
A lattice Boltzmann equation model in a rotating system is developed by introducing the Coriolis force effect. The geophysical hydrodynamic equation can be derived from this model. Numerical computations are performed to simulate the cylindrical annulus experiment and Benard convection. The numerical results have shown the flow behaviour of large-scale geostrophic current and Benard convection cells, which verifies the applicability of this model in both theory and experiment.
L-Shell Absorption Spectrum Measurement and Simulation of the Mg Laser Plasma
LIU Hong-Jie, ZHANG Bao-Han, ZHANG Ji-Yan, YANG Guo-Hong, YANG Jia-Min, LI Jun, WANG Yao-Mei, ZHANG Wen-Hai
Chin. Phys. Lett. 2002, 19 (3): 362-364 .  
Abstract   PDF(pc) (528KB) ( 384 )
We report on the measurement of the L-shell absorption spectrum of Mg laser plasma. The resonance absorption lines of Li-like and Be-like ions are clearly observed. The electron density is sufficiently high so that our sample plasma is in nearly complete local thermodynamic equilibrium. At the determined electron temperature 56±4eV and mass density 0.01±0.002g/cm3, the predicted transmission spectrum is calculated. The simulation result is in good agreement with the experiment.
Does the Decay Wave Propagate Forwards in Dusty Plasmas?
XIE Bai-Song
Chin. Phys. Lett. 2002, 19 (3): 365-367 .  
Abstract   PDF(pc) (192KB) ( 424 )
The decay interaction of the ion acoustic wave in a dusty plasma with variable-charge dust grains is studied. Even if strong charging relaxation for dust grains and the short wavelength regime for ion waves are included, it is found that the decay wave must be backward propagating.
Current Filamentation and Resonant Transport of the Relativistic-Electron-Beam in Dense Plasmas
YIN Yan, CHANG Wen-Wei, MA Yan-Yun, YUE Zong-Wu, CAO Li-Hua
Chin. Phys. Lett. 2002, 19 (3): 368-371 .  
Abstract   PDF(pc) (2667KB) ( 413 )
The transport of a relativistic electron beam in dense plasmas
with a cold return electron current is examined by two-dimensional particle-in-cell simulation. The filamentation and coalescence of currents and related magnetic field patterns, caused by the electromagnetic-beam-plasma instability, are observed. In the later simulation time, the electrons of the relativistic electron beam are trapped into the potential wells of the wave excitated by the instability, and transport resonantly with the wave.
Structural Characteristics and Photoluminescence of Zinc Oxide Nanocrystals
DU Yu-Lei, ZHANG Ming-Sheng, DENG Yu, CHEN Qiang, YIN Zhen, CHEN Wan-Chun
Chin. Phys. Lett. 2002, 19 (3): 372-374 .  
Abstract   PDF(pc) (516KB) ( 740 )
We have prepared zinc oxide nanocrystals using a new type of solid-state reaction. The nanosized grains were obtained by changing the heat treatment temperature and the sizes were determined to be from 10 to 42 nm. The lattice vibrational Raman spectra were measured and assigned at different grain sizes. We observed a strong visible emission centered at 580 nm in the nanosized ZnO at room temperature. We have investigated the photoluminescence properties under different grain sizes after annealing. The weakening of the luminescence is attributed to the decrease of intrinsic structural defects, mainly, oxygen vacancies and the increase of the grain size in the nanocrystals.
Microstructures of GaN Films Laterally Overgrown on Si(111) by Hydride Vapor Phase Epitaxy
CHEN Zhi-Zhong, ZHANG Rong, ZHU Jian-Min, QIN Zhi-Xin, SHEN Bo, GU Shu-Lin, WANG Feng, ZHENG You-Dou, ZHANG Guo-Yi, LI Zhi-Feng, L. F. KUECH
Chin. Phys. Lett. 2002, 19 (3): 375-377 .  
Abstract   PDF(pc) (1002KB) ( 524 )
We have investigated the microstructures of GaN films laterally epitaxially overgrown (LEO) on Si (111) substrates by hydride vapor phase epitaxy. The threading dislocation density in the LEO GaN is reduced by about two orders. Different etching angles of the two sidewalls of SiO2 masks (66°and 90°) lead to the asymmetry of the LEO and cause the particular microstructures of LEO GaN. In micro-Raman spectra, the intensities vary weakly periodically about 5μm perpendicular to the mask stripes. The indistinction selective growth in the top surface is discussed.
Mechanism of Long-Range Penetration of Low-Energy Ions in Botanic Samples
LIU Feng, WANG Yu-Gang, XUE Jian-Ming, WANG Si-Xue, DU Guang-Hua, YAN Sha, ZHAO Wei-Jiang
Chin. Phys. Lett. 2002, 19 (3): 378-380 .  
Abstract   PDF(pc) (708KB) ( 389 )
We present experimental evidence to reveal the mechanism of long-range penetration of low-energy ions in botanic samples. In the 100 keV Ar+ ion transmission measurement, the result confirmed that low-energy ions could penetrate at least 60μm thick kidney bean slices with the probability about 1.0 x 10-5. The energy spectrum of 1 MeV He+ ions penetrating botanic samples showed that there existed peak of count of ions with little energy loss. The probability of the low-energy ions penetrating the botanic sample is almost the same as that of the high-energy ions penetrating the same samples with little energy loss. The results indicate that there are some micro-regions with the mass thickness less than the projectile range of low-energy ions in the botanic samples and they result in the long-range penetration of low-energy ions in botanic samples.
Grain Boundary Peak in a Foamed Zn-Al Eutectoid Alloy
WEI Jian-Ning, CHENG He-Fa, GONG Chen-Li, ZHOU Zheng-Cun, LI Zhi-Bin, HAN Fu-Sheng
Chin. Phys. Lett. 2002, 19 (3): 381-384 .  
Abstract   PDF(pc) (428KB) ( 456 )
We study experimentally the temperature spectra of internal friction (IF) and relative dynamic modulus (RDM) in a foamed Zn-Al eutectoid alloy. The specimens with macroscopic pores (0.5--1.0mm) were prepared in an air pressure infiltration process. The damping behaviour of the foamed Zn-Al eutectoid alloy is characterized by IF. The IF and RDM measurements at maximum surface shear strain of 20 x 10-6 have been made by using a multifunction internal friction apparatus at frequencies of 0.5, 1.0, and 3.0 Hz from room temperature to equilibrium eutectoid isotherm of 277°C, while continuously changing the temperature cycle. At low frequency, an IF peak is observed in the IF-temperature curve. The IF peak is of a grain boundary, which is associated with the diffusive flux on a crystalline boundary between the like-phases of Al/Al. Its activation energy has been calculated to be 1.10±0.06eV and the pre-exponential factor τ0 is 10-14s in the IF measurements.
Preparation and Annealing-Induced Structural Transition of Self-Organized Nanostripes on the Electropolished Aluminum Surface
GUO Deng-Zhu, HOU Shi-Min, SHEN Zi-Yong, ZHAO Xing-Yu, LIU Wei-Min, XUE Zeng-Quan
Chin. Phys. Lett. 2002, 19 (3): 385-388 .  
Abstract   PDF(pc) (2082KB) ( 579 )
Self-organized nanostripe patterns with a wavelength of 100 nm and an amplitude 4-5 nm were formed on the surface of high-purity aluminum by electropolishing. The thermal stability of the nanostripe patterns was investigated experimentally by using a needle-sensor atomic force microscope in an ultrahigh vacuum after annealing the sample in a high vacuum. We found that the originally highly ordered nanostripe structures had transformed into many domains separated by various boundaries, and different nanostripe patterns had formed, especially the belt-like boundaries formed “cross”patterns on the surface. We also found that the vacuum annealing had the tendency to efface the nanostripe structures.
Computer Modelling of Metal Dissolution in the Presence of Aqueous Electrolyte
R. I. Eglitis, M. R. Philpott
Chin. Phys. Lett. 2002, 19 (3): 389-390 .  
Abstract   PDF(pc) (259KB) ( 333 )
The semi-empirical Hartree-Fock intermediate neglect of differential overlap (INDO) method was used to explore the potential energy surface of adsorbed water molecules and to speculate, using fairly simple cluster models, on the reaction path followed by metal ions leaving the surface. As an example, INDO calculations were used to calculate the potential energy curve for a metal atom leaving the surface and entering into a solvation cage composed of tetrahedral arranged water molecules. The effect of adding a NaCl ion pair to the system with the halide ion above the dissolving atom was also explored.
Microstructural Models of Alumina Nanotubes and Anodic Porous Alumina Film Formed in Sulfuric Acid
PU Lin, CHEN Zhi-Qiang, TAN Chao, YANG Zheng, ZOU Jian-Ping, BAO Xi-Mao, FENG Duan, SHI Yi, ZHENG You-Dou
Chin. Phys. Lett. 2002, 19 (3): 391-394 .  
Abstract   PDF(pc) (1350KB) ( 474 )
Electrochemical stepwise-anodization of aluminum in dilute sulfuric acid results in the formation of alumina nanotubes (ANTs) which is due to hexagonal split of anodic porous alumina (APA) film along the cell boundaries containing many voids, that is, the ANTs are the completely detached cell of the APA film. The inner diameters of the ANTs are in the range of 10-20nm, and the aspect ratio (inner diameter/length) of the ANTs can be about 80. The relations found for pore diameter, cell diameter and barrier layer thickness are around 1, 2.7 and 0.85 nm/V, respectively. Transmission electron microscope (TEM) reveals that the ANT wall has a three-shell structure: an outer shell (metal/oxide interface) consisting of pure alumina oxide, a middle shell of the hydrated oxide or/and hydroxide and an inner shell (oxide/electrolyte interface) of anion incorporated oxide with the thickness ratio of 1:1:2. The structural change of ANTs induced by e-beam irradiation in TEM indicates that the thermal instability of the hydrated oxide or/and hydroxide within the cell wall might be an alternative origin contributing to the self-organization of the cells, leading to a densely packed triangular cell lattice of the APA film.

High-Quality ZrO2 Thin Films Deposited on Silicon by High Vacuum Electron Beam Evaporation
ZHANG Ning-Lin, WAN Qing, SONG Zhi-Tang, SHEN Qin-Wo, ZHU Xiang-Rong, LIN Cheng-Lu
Chin. Phys. Lett. 2002, 19 (3): 395-397 .  
Abstract   PDF(pc) (500KB) ( 1032 )
Zirconium oxide films were deposited on p-type Si (100) substrates using high vacuum electron beam evaporation (HVEBE) at room temperature. X-ray photoelectric spectroscopy shows that the dominating chemical state of zirconia thin films is in the fully oxidized state of Zr4+, no matter whether annealed in oxygen. The structure information from x-ray diffraction shows that zirconia thin films deposited at room temperature by HVEBE were completely amorphous before and after the annealing. The spreading resistance profile indicates that ZrO2 thin films have excellent insulation property (with resistance of more than 108Ω) and the thickness is 800Å. After thermal treatment at 600°C in O2 ambient, the root-mean-square roughness changed from 8.09Å of the as-deposited film to 13.8Å across an area of 1 x 1μm2.
Dependence of Tunnel Resistance on the Injection Current of Magnetic Tunnel Junctions
LIU Cun-Ye, LI Jian, CHEN Jian-Yong, XU Qing-Yu, NI Gang, DU You-Wei
Chin. Phys. Lett. 2002, 19 (3): 398-401 .  
Abstract   PDF(pc) (473KB) ( 467 )
Anomalous transport behaviour, i.e., the dependence of the tunnel resistance on the injection current, has been discovered in Ta/Co/Al2O3/FeNi tunnel junctions. The zero field voltage-current characteristic of the magnetic tunneling junction obeys the transport principle of the normal tunnel junction at low injection current, but it exhibits the negative resistance behaviour when the injection current is raised to the breakover current level. The physics of the restorable electric breakdown has been initially studied.
Universal Class of Criticality of Diluted Strongly Frustrated Systems
K. Afif, A. Benyoussef, M. Hamedoun
Chin. Phys. Lett. 2002, 19 (3): 402-405 .  
Abstract   PDF(pc) (446KB) ( 646 )
Using Monte Carlo simulations, We study the universal classes of criticality associated to the superlattices CddMn1-dTe/CdTe and the spinels ZndCd1-dCr2S[Se]4. Both systems are diluted frustrated antiferromagnets. The ratio d of dilution or substitution is found to be of great influence on the nature of criticality. The effect of dimensionality in spin glass transitions is also investigated.
Multi-photon Absorption Induced Fluorescence of a Novel Compound
ZHANG Jun-Xiang, CUI Yi-Ping, XU Chun-Xiang, WANG Ming-Liang, LIU Ju-Zheng
Chin. Phys. Lett. 2002, 19 (3): 406-408 .  
Abstract   PDF(pc) (367KB) ( 430 )
The linear and nonlinear fluorescence spectra of 5-(9-anthryl)-3-(4-nitrophenyl)-1-phenyl-2-pyrazoline (ANPP) have been studied in different polarity solvents. The linear fluorescence spectrum of ANPP has two emission bands originating from the anthryl and pyrazoline moieties of ANPP on excitation at 355nm, respectively. The nonlinear two-photon and three-photon fluorescence from these two moieties are observed simultaneously when ANPP is excited at 1064 nm due to the proximity of the absorption bands of these two moieties to λ/3 and λ/2 of the exciting wavelength. The similar spectrum structure indicates that the nonlinear and linear fluorescence originates from the same relaxation process.
Atomic and Electronic Structures of Submonolayer In on Cu(111)
WANG Peng, XUN Kun, JIA Jin-Feng, GAO Xing, QIAN Hai-Jie, LIU Feng-Qin, Ibrahim Kurash, ZHOU Yu-Mei, XUE Qi-Kun, WU Si-Cheng
Chin. Phys. Lett. 2002, 19 (3): 409-412 .  
Abstract   PDF(pc) (1295KB) ( 398 )
We have studied the atomic and electronic structures of submonolayer In on Cu(111) using synchrotron radiation photoemission and scanning tunnelling microscopy (STM). At very low coverage, In atoms were favorable to occupy substitutional sites and to be distributed evenly on Cu(111) surface. At higher coverage of 0.33 and 0.50 ML, two ordered reconstructure phases of (√3 x√3)R30°and (2 x 1) have been observed for the first time. The two dimensional states of In induced valence bands in the (√3 x√3)R30°phase were measured by angle-resovled photoemission. The result is in good agreement with theoretical calculations.
Behaviour of Oxygen-Implanted and Hydrogen-Implanted SiGe/Si Heterostructure
AN Zheng-Hua, ZHANG Miao, MEN Chuan-Ling, SHEN Qin-Wo, LIN Zi-Xin, LI Kai-Cheng, LIN Cheng-Lu
Chin. Phys. Lett. 2002, 19 (3): 413-415 .  
Abstract   PDF(pc) (532KB) ( 418 )
For SiGe-on-insulator fabrication, a 100nm SiGe film with uniform germanium composition was grown on Si (100) substrate using a molecular beam epitaxy system without a graded SiGe buffer layer. The samples were implanted by oxygen ions at an energy of 45 keV and a dose of 3 x 1017cm-2, and annealed for five hours at 1250°C in flowing (Ar + 5% O2) atmosphere with a 100 nm oxide protective layer. The result indicates that a buried oxide layer was successfully formed at the interface of SiGe and Si on the substrate. Furthermore, hydrogen was implanted into SiGe at the energy of 62 keV and the dose of 6 x 1016cm-2 to perform a blistering study, which confirmed the feasibility of H-induced layer splitting in SiGe layer.
Electron Field Emission of CNx Thin Films Prepared by Low Pressure Plasma Enhanced Chemical Vapor Deposition
LU Xian-Feng, LI Jin-Chai, GUO Huai-Xi, ZHANG Zhi-Hong, YE Ming-Sheng
Chin. Phys. Lett. 2002, 19 (3): 416-418 .  
Abstract   PDF(pc) (351KB) ( 345 )
CNx thin films were prepared using low pressure plasma enhanced chemical vapor deposition (LP-PECVD), and then bombarded by low energy N+2. The compositions before and after N+2 bombardment were compared by using x-ray photoelectron spectroscopy. The electron field emission characteristics of CNx thin films before and after N+2 bombardment were studied under the pressure of 10-6Pa. For the samples, the turn-on emission field decreased from 2.5V/μm to 1.2V/μm while the stable current density increased from 0.5mA/cm2 to a value larger than 1mA/cm2 before and after the bombardment. Our results illustrated that the field emission characteristics were improved after the bombardment of N+2.
Interface Instability of Diamond Crystals at High Temperature and High Pressure
YIN Long-Wei, LI Mu-Sen, XU Bin, CUI Jian-Jun, HAO Zhao-Yin
Chin. Phys. Lett. 2002, 19 (3): 419-421 .  
Abstract   PDF(pc) (975KB) ( 509 )
Diamond growth instability at high temperature and high pressure (HPHT) has been elucidated by observing the cellular interface in diamond crystals. The HPHT diamond crystals grow layer by layer from solution of carbon in the molten catalyst. In the growth of any other crystals from solution, the growth interface is not stable and should be of the greatest significance further to understand the diamond growth
mechanism. During the diamond growth, the carbon atoms are delivered to the growing diamond crystal by diffusion through a diamond crystal-solution boundary layer. In front of the boundary layer, there exists a narrow constitutional supercooling zone related to the solubility difference between diamond and graphite in the molten catalyst. The diamond growth stability is broken, and the flat or planar growth interface transforms into cellular interface due to the light supercooling. The phenomenon of solute trails in the diamonds was observed, the formation of solute trails was closely associated with the cellular interface.
Physical Properties of Diamond Coatings on a WC-6%Co Substrate
LIU Sha, YI Dan-Qing, YU Zhi-Ming
Chin. Phys. Lett. 2002, 19 (3): 422-424 .  
Abstract   PDF(pc) (1493KB) ( 484 )
We have investigated the physical properties, including the morphology, texture, adhesion and chemical quality, of high-frequency chemical vapour deposited diamond coatings on WC-6%Co substrates which were pre-treated by a two-step etching method. The results indicate that the increasing Co content from 0.12 to 3.05% within the etching depth of 5μm caused a morphology transformation from prism diamond to spherulitic diamond, and a texture one from a {111} orientation to a {110} orientation. The Raman spectrum shows that the spherulitic diamond film contains more non-diamond phases (graphite, amorphous carbon and diamond-like carbon, etc) and has lower chemical quality of diamond films on a WC-6%Co substrate. The diamond coating grain sizes became smaller about 4 times when the deposition temperatures on the substrate surface were reduced from 1000 to 900°C. Compared with spherulitic diamond films, the prism diamond films exhibit better adhesion on the WC-6%Co substrate.
Structure-Dependent Electronic and Optical Properties of the Martensitic Alloys TiAu
ZHU Zi-Zhong, YE Yi-Ying
Chin. Phys. Lett. 2002, 19 (3): 425-428 .  
Abstract   PDF(pc) (411KB) ( 569 )
The atomic and electronic structures together with the optical properties of TiAu in the low-temperature B19 and B11 phases are calculated by using first principles local density functional approaches. Our results show that the B11 structure is more stable than B19 for TiAu alloy in ordered equiatomic composition (Ti : Au = 50 : 50). In low temperature, the B11 structure should exist as a binary alloy from the energetic consideration. The accurate atomic positions in the unit cell have been given by fully force relaxed calculations. The calculated optical conductivities of B19 and B11 phases show drastic change in the region of 1.5 to 3.5eV.

Characteristics of Photoelectron Decay of Silver Halide Microcrystal Illuminated by a Short Pulse Laser
YANG Shao-Peng, LI Xiao-Wei, HAN Li, FU Guang-Sheng
Chin. Phys. Lett. 2002, 19 (3): 429-431 .  
Abstract   PDF(pc) (416KB) ( 598 )
A YAG supershort pulse laser (355nm, 35ps) is used as an exposure source and the microwave dielectric spectrum technique is used to quickly detect the photoelectron decay process in AgX microcrystals, because the free photoelectron lifetime and decay process can decide the sensitivity and other efficiency of silver halide material. The result shows that the free photoelectron average lifetimes of Kodak-100 and Fuji-100 colour film samples are 8.5 and 9.5 ns, respectively.
A Silicon-Based Ferroelectric Capacitor for Memory Devices
REN Tian-Ling, ZHANG Lin-Tao, LIU Li-Tian, LI Zhi-Jian
Chin. Phys. Lett. 2002, 19 (3): 432-433 .  
Abstract   PDF(pc) (301KB) ( 538 )
We study a silicon-based PbTiO3/Pb(Zr0.53Ti0.47)O3/PbTiO3 capacitor, prepared by an improved sol-gel method. The ferroelectric capacitor, with high remanent polarization of 15μC/cm2 at a coercive field of about 30kV/cm, an ultra-low leakage current density of 0.1nA/cm2, and almost fatigue free properties, It can be used as a promising candidate for ferroelectric memory devices.
Nonlinear Dynamics Approach to the Correlation Analysis of Protein Sequences
Chin. Phys. Lett. 2002, 19 (3): 434-436 .  
Abstract   PDF(pc) (344KB) ( 345 )
To clarify the randomness of protein sequences, we make a detailed analysis to a set of typical protein sequences representing each fold by using nonlinear prediction method developed in nonlinear dynamics theory. No deterministic structures are found in these protein sequences and this implies that they behave as random chains. We also explain the controversial results obtained in the previous investigations.
Experiments and Models of DNA Nano-Catenary Patterns Manipulated by Liquid Flow
ZHANG Yi, HU Jun, WU Shi-Ying, AI Xiao-Bai, LI Min-Qian
Chin. Phys. Lett. 2002, 19 (3): 437-440 .  
Abstract   PDF(pc) (954KB) ( 424 )
Individual DNA molecules were first stretched by a centrifugal force and adsorbed on a modified mica surface. Then, a liquid flow was guided across the surface along a direction perpendicular to the aligned DNA strands. Some nano-catenary-like patterns of DNA molecules were formed, which were revealed by atomic force microscope. A physical mechanism called the “s-suspension bridge” model has been presented, by which the features of the catenary-like patterns of DNA molecules can be understood quantitatively quite well.
A Procedure for Modeling Shallow Dislocation Sources with Tensional Component
HE Yu-Mei, WANG Wei-Min, YAO Zhen-Xing
Chin. Phys. Lett. 2002, 19 (3): 441-444 .  
Abstract   PDF(pc) (404KB) ( 338 )
The source terms of a tensile dislocation are presented in terms of the wave number and circular frequency. Expressions for displacements on the surface of a half-space due to an arbitrary oriented dislocation are also obtained by using the generalized ray method. The result shows that the far-field waveforms contributed by tensile source are different from other sources. Considering that not all large earthquakes can be explained with the shear dislocation model, these expressions may be efficient in analysing some earthquakes.
Biot/Squirt Model in Viscoelastic Porous Media
CHENG Yuan-Feng, YANG Ding-Hui, YANG Hui-Zhu
Chin. Phys. Lett. 2002, 19 (3): 445-448 .  
Abstract   PDF(pc) (645KB) ( 462 )
Viscoelastic wave equations are derived for both the Biot flow and squirt-flow involved. The relationship between phase velocity or attenuation of viscoelastic wave and macro parameters of the reservior is clarified in a porous extensive dilatancy anisotropy medium. Numerical models clearly demonstrate that the viscoelastic property of rocks, not the squirt-flow, causes the dispersion and attenuation in the low-frequency range. The attenuation of the quasi SV-wave, SH-wave and the quasi P-wave depend strongly on the directions of permeabilities. Furthermore, the trends of attenuation of the quasi P-wave fast and the quasi SV-wave are inversed in both the high-frequency range and the low-frequency range. Our numerical result is in agreement with the experimental result that was carried out for the Biot/Squirt model by Jorge [Geophys. 65(2000) 202].
48 articles