Vol. 49, No. 11 (2000)
2000-06-05
GENERAL
2000, 49 (11): 2113-2117.
doi: 10.7498/aps.49.2113
Abstract +
Three types of similarity reductions are obtained for nonlinear wave equation with damping term utt-2buxxt+αuxxxx=β(unx)x(α>0,β≠0,n≥2)by the use of the direct reduction method due to Clarkson and Kruskal.It is shown that this equation is not integrable under the sense of Ablowitz's conjecture by analysing the Painlevé properties of these reduction equations.In addition,four families of exact solutions are found for this equation(n=2).
2000, 49 (11): 2118-2122.
doi: 10.7498/aps.49.2118
Abstract +
Quantum theory of double-wave function description (DWFD) is applied to describe the motion of spinning electron in both perpendicular uniform electromagnetic field and two-dimensional harmonic oscillator potential field.The time evolution equations of related mechanical quantities are derived.Furthermore,DWFD of spin-zero electron in the same fields is also given,and it is found that their classical limit results correspond to those of classical mechanics.
2000, 49 (11): 2123-2128.
doi: 10.7498/aps.49.2123
Abstract +
This paper proposes an approach to control chaos based on occasional linear feedback.This scheme is composed of control and non-control phases.The different stable periodic orbits are obtained by adjusting the feedback coefficients and the time duration which the control phase occupies.We also simulate acousto-optic bistable model and Henon-like attactor.The results from the numerical simulation show that the method can switch effectively the system to the desired periodic orbits.
2000, 49 (11): 2129-2132.
doi: 10.7498/aps.49.2129
Abstract +
Compressional and shear wave velocities have been measured as functions of pressure up to 2 GPa for float glass and SiO2+8.4wt%TiO2 glass using pulse superposition method.The compressional wave velocities for float glass are found to increase first,then decrease with increasing pressure.This phenomenon is different from that of other glasses.The shear wave velocities of float glass and both compressional and shear wave velocities of SiO2+8.4wt%TiO2 decrease with increasing pressure as general SiO2 glass.The experimental results are discussed.And the state parameters in Murnaghan equation have been calculated.
ATOMIC AND MOLECULAR PHYSICS
2000, 49 (11): 2133-2138.
doi: 10.7498/aps.49.2133
Abstract +
Based on relativistic Hartree-Fock-Slater self-consistent average atomic model,atomic structure for mixture is studied by summing up component volumes in mixture.Algorithumic procedure for solving both the group of Thomas-Fermi equations and the self-consistent atomic structure is presented in detail,and,some numerical results are discussed.
2000, 49 (11): 2139-2145.
doi: 10.7498/aps.49.2139
Abstract +
The Rayleigh-Ritz variational method is used with a multiconfiguration-interaction function and restricted variation method to obtain the energies of 2p2np4So(n=2—4)and 1s2pmp4Ｐ(m=2,3)in lithium-like ions,including the mass polarization and relativistic corrections.Oscillator strengths,transition rates,lifetimes and wavelengths are also calculated.The results are compared with other theoretical and experiment data in the literature.
2000, 49 (11): 2146-2150.
doi: 10.7498/aps.49.2146
Abstract +
By analyzing the phase of transition probability amplitude,a formula for level shift induced by the time-dependent perturbation of quantum transition is given.AC-Stark shifts of the levels in two-level atoms are calculated,which are induced by mono-mode quantized field.The calculated results indicate that the quantum statistic property can directly influence the atomic level shift.
LASER-INDUCED FLUORESCENCE EXCITATION SPECTRUM OF NO2 IN THE REGION OF 500—532nm AT ROOM TEMPERATURE
2000, 49 (11): 2151-2158.
doi: 10.7498/aps.49.2151
Abstract +
The high-resolution fluorescence excitation spectrum was measured in the region of 500—532nm at room temperature.Though the spectrum was rather congested,we could determine the molecular constants such as band origins and rotational and spin-rotation constants for 25 vibronic bands in the two most intense absorption regions 505—510nm and 513—520nm.Among the vibronic bands assigned there were 5 new bands observed and reported in this work.All rotational structures analyzed were of the parallel type.It was shown from the experiment that the high lying vibration levels of ground state X～2Ａ1 had heavily perturbed the electronic excited state A～2Ｂ2.
CLASSICAL AREA OF PHENOMENOLOGY
2000, 49 (11): 2159-2164.
doi: 10.7498/aps.49.2159
Abstract +
The squeezing and coherence properties of the light in the system of two-mode squeezing vacuum field interacting with two coupling-atoms are studied in the framework of quantum theory.The relation between the quantum properties of the light and the characteristics of the system itself is discussed.
2000, 49 (11): 2165-2170.
doi: 10.7498/aps.49.2165
Abstract +
Characteristics and response times of the stimulated photorefractive scattering self-pumped phase conjugator(SPS-SPPC) in the series of Rh-doped and Ce-doped BaTiO3 crystals are investigated.The experimental results show that the SPS-SPPC has higher reflectivity and faster response rate at greater incident angle.The phenomenon was properly analysed using characteristics of two-wave mixing.By the way,the phase conjugation reflectivity of Ce:BaTiO3 is higher than that of Rh:BaTiO3 crystals'.
2000, 49 (11): 2171-2175.
doi: 10.7498/aps.49.2171
Abstract +
This paper discusses the design of a kind of fractal film set showing good absorption for electromagnetic waves. Based on a simplified model, we have calculated analytically the reflectivity of the film set, and obtained a group of criterions for selection of suitable materials for the set layers so as to decrease the reflectivity. Numerical simulations have been done to obtain the reflectivity of some film sets constructed by ideal or practical materials selected according to the criterions. The results show that the reflectivity of the set decreases when the total degree number of the fractal increases. The lowest reflectivity obtained is 0.01.
2000, 49 (11): 2176-2179.
doi: 10.7498/aps.49.2176
Abstract +
Theoretical calculation shows that electrorheological fluids with dielectric coating conductive particles as a dispersed phase will give high shear stress. We has coated graphite particles with TiO2 using sol-gel technique. Rutile phase TiO2 coating graphite composite particles have been got. The shear stress of composite particles/silicone oil electrorheological fluid is one order higher than that of the TiO2/silicone oil. When the electric field strength is 1.7kV/mm, the shear stress of composite particles/silicone oil electrorheological fluid reaches 1.25kPa， and electric current density is less than 10μA/cm2.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
2000, 49 (11): 2180-2185.
doi: 10.7498/aps.49.2180
Abstract +
Charge separation electric fields and magnetic fields induced by superthermal electrons escaping from the plasmas have been evaluated using a very simple model. The magnitude and configuration of magnetic fields have been obtained. Generally the circular-shaped magnetic fields are weak because of the charge separation electric field and the followed finite number of the escaping superthermal electrons, and they are mainly distributed over the laser focus near the surface of the plasma because of the transverse motion of the escaping superthermal electrons. Only when electron current is very strong (about 103A through the cross-section with 1μm radius) a 102T magnetic field can be obtained.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2000, 49 (11): 2186-2190.
doi: 10.7498/aps.49.2186
Abstract +
By mass-selected low energy ion beam deposition, amorphous carbon film was obtained. X-ray diffraction, Raman and Auger electron spectroscopy depth line shape measurements showed that such carbon films contained diamond particles. The main growth mechanism is subsurface implantation. Furthermore, it was indicated in a different way that ion bombardment played a decisive role in bias enhanced nucleation of chemical vapor deposition diamond.
2000, 49 (11): 2191-2195.
doi: 10.7498/aps.49.2191
Abstract +
The Ag-BaO photocathode with internal field-assisted structure was successfully fabricated through depositing silver electrode on the surface of Ag-BaO thin film. Photoemission enhancement was observed when the internal field-assisted bias was applied to the Ag-BaO thin film. Theoretical analysis shows that enhanced photoemission can be attributed to the decrease of interfacial barrier between Ag particles and BaO matrix, and the degradation of vacuum level at the surface.
2000, 49 (11): 2196-2200.
doi: 10.7498/aps.49.2196
Abstract +
BayFexCo4-xSb12(x=0—3.0，y=0—0.7) were synthesized by a two-step solid state reaction method. The results of Rietveld refinement demonstrated that BayFexCo4-xSb12 synthesized possesses a filled skutterudite structure. The filling fraction of Ba obtained by Rietveld refinement agreed well with the composition obtained by inductively coupled plasma emission spectroscopy. Thermal parameters (B) of Ba was larger than that of Sb, and Fe/Co, indicating that Ba “rattles”in Sb-icosahedron voids. The lattice constants of BayFexCo4-xSb12 increased with increasing Ba filling fraction and Fe content. The maximum filling fraction of Ba (ymax) in BayFexCo4-xSb12 increased with increasing Fe content, and was found to be rather greater than that of Ce of La in LnyFexCo4-xSb12. The ymax varied from 0.35 to near 1.0 when Fe content (x) changed from 0 to 4.0.
2000, 49 (11): 2201-2209.
doi: 10.7498/aps.49.2201
Abstract +
We have determined 10 ordered structure types and 14 perfect ordered structures of binary alloys with hexagonal close-packed lattice by using concentration-wave theory, and proposed an explanation for several typical experimental results.
2000, 49 (11): 2210-2213.
doi: 10.7498/aps.49.2210
Abstract +
Carbon ions with concentration of (0.6—1.5)% were implanted into silicon crystals at room temperature and Si1-xCx alloys were grown by solid phase epitaxy with high temperature annealing. The formation and characteristics of Si1-xCx alloys under different implanted carbon doses were studied. If the implanted carbon atom concentration was less than 0.6%, carbon atoms would tend to combine with the defects produced during implantation and it was difficult for Si1-xCx alloys to form during annealing at 850—950℃. With the increase of implanted C concentration, almost all implanted carbon atoms would occupy substitution positions to form Si1-xCx alloys, but only part of implanted carbon atoms would occupy the substitution position to form Si1-xCx alloys as the implanted dose increased to 1.5%. Most Si1-xCx alloy phases would vanish as the annealing temperature was increased higher.
2000, 49 (11): 2214-2219.
doi: 10.7498/aps.49.2214
Abstract +
The dependence of the probability of the supercooled water freezing from homogeneous nucleation on the volume, time and temperature was deduced based on the “continuum” model of water structure put forward by Stanley and Teixeira. The homogeneous nucleation rate of supercooled water freezing was then calculated. The results agreed with the experimental measurements. The calculation of the pre-exponential factor, which is a key for the classical nucleation theory and the density functional method,is not needed for this method.
2000, 49 (11): 2220-2224.
doi: 10.7498/aps.49.2220
Abstract +
TiN/Ti film was fabricated by deposition on the chromium layer electrodeposited on the copper substrate by means of multi-arc ion plating technique under different conditions.The interface formation,microstructure and constituents,and morphology for TiN/Ti and Cr/Cu contact system are investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques.The XRD measurements showed that in addition to the TiN,Ti2N multi-crystallized phases,there was a lot of Cr-Ti,intermetallic compounds on the surface of TiN/Ti film.It is evident that the Ti2N phase was formed.The SEM observation indicated that the surface film prepared at 90℃,had a structure similar to the form of branches and an inhomogeneous crystallization had occurred.As the temperature was increased to 170℃,the XRD peak intensity became stronger and a fine TiN/Ti surface was obtained.
2000, 49 (11): 2225-2229.
doi: 10.7498/aps.49.2225
Abstract +
Two-dimensional growth of thin films is simulated using the Monte Carlo method.The effect of the interaction between particles on the morphology of the films at the preliminary stage has been investigated using Morse potential.The growth of films consists of four stages,including formation of critical nucleus,growth of clusters,formation of maze structure and appearance of continuous film.The simulated results indicate that the percentage of particles,with monomers being not included,decreases with the increase of the number of adatoms,which is in agreement with the actual conditions.
2000, 49 (11): 2230-2234.
doi: 10.7498/aps.49.2230
Abstract +
InAs self-assembled quantum dots(QDs) covered by 3-nm-thick InxGa1-xAs(0≤x≤0.3) capping layer have been grown on GaAs(100) substrate.Transmission electron microscopy shows that InGaAs layer reduces the strain in the InAs islands,and atomic force microscopy evidences the deposition of InGaAs on the top of InAs islands when x=0.3.The significant redshift of the photoluminescence (PL) peak energy and the reduction of PL linewidth of InAs quantum dots covered by InGaAs are observed.In addition,InGaAs overgrowth layer suppresses the temperature sensitivity of PL peak energy.Based on our analysis,the strain-reduction and the size distribution of the InAs QDs are the main cause of the redshift and temperature insensitivity of the PL respectively.
2000, 49 (11): 2235-2239.
doi: 10.7498/aps.49.2235
Abstract +
An aluminum film system,deposited on the silicone oil drop surfaces by vapor deposition method,has been fabricated and its surface morphologies as well as growth mechanism have been investigated by means of scanning electron microscopy.The granular size of Al film on oil surface is smaller than that of Al film on the silicon substrate.It is observed that the granular size distribution is inhomogeneous and the surface fluctuation is moderately large in the film samples.Furthermore,we find that the perpendicular fluctuation of the lower surface is more remarkable than that of the upper surface of the Al film.Near the edge of the silicone oil drop,an anomalous wedge shaped structure with a slope of 10-4—10-5 spontaneously forms and its growth mechanism can be interpreted as thethermal expansion of the liquid substrates.
2000, 49 (11): 2240-2246.
doi: 10.7498/aps.49.2240
Abstract +
The friction and adhesion characteristics of the self-assembled film of octadecyltrime-thoxysilane (OTE SAM) on the surface of SiO2 under the relative humidity of 5%—99% were studied using atomic force microscopy/friction force microscopy(AFM/FFM). Experimental results indicate that OTE SAM can not only improve the tribological properties of SiO2 surface,but also show well anti-wear properties under the pressure of the load of 200nN, or Hertz pressure of 0.8GPa. Due to the strong hydrophilicity, the friction force between the FFM tipe and SiO2 surface increases with the relative humidity when it is lower than 50%HR and then decreases sharply. However, due to the well hydrophobe property of OTE SAM, the friction force between FFM tipe and the surface of OTE SAM is much lower than that of the FFM/SiO2 surface and slightly decrease with relative humidity. Therefore, OTE SAM will be a good boundary lubricant of high speed recording system.
2000, 49 (11): 2247-2253.
doi: 10.7498/aps.49.2247
Abstract +
The adhesion characteristic of surfaces of SiO2 and the self-assembled film of octadecyltrime-thoxysilane (OTE SAM) on the surface of SiO2 under the relative humidity of 5%—99% were studied using atomic force microscopy/friction force microscopy.Experimental results indicate that the adhesion force of SiO2 increases first with the relative humidity and then decreases sharply.However,the adhesion force of OTE SAM surface hardly changes with the relative humidity due to its strong hydrophobe property.The mechanism of the adhesion force changing with the relative humidity has been analyzed from the viewpoint of surface tension,van der Walls force,and basic bond forces.
2000, 49 (11): 2254-2260.
doi: 10.7498/aps.49.2254
Abstract +
We present a model calculation,using the tight-binding approach,of a one-dimensional heterostructure consisting of regular alternation of two different halogen-bridged transition-metal compounds (MX compounds).Superlattice and multi-quantum-well properties can be detected depending on the well-barrier alternation sequence.We prove the possibility of developing new multi-quantum-well devices based upon MX compounds.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2000, 49 (11): 2261-2263.
doi: 10.7498/aps.49.2261
Abstract +
The non-Fermi liquid behavior of electrons with one-body impurity potential has been investigated.The electrons in an n(=3,2,1) dimensional system may have non-Fermi liquid properties,whether the electrons are in bound state or not,when a single-impurity model is introduced.
2000, 49 (11): 2264-2270.
doi: 10.7498/aps.49.2264
Abstract +
Polarons and bipolarons in mixed halide MX compounds were studied in the frame work of the two-band extended Peierls-Hubbard model.Different from the isolated MX chains,it was found that the segments tend to select impurities in mixed halide compounds.Then the charge confinement and the effect of electron-electron interactions were investigated.Finally the properties of impurities in mixed halide compounds with spontaneous charge transfer were also discussed.
2000, 49 (11): 2271-2275.
doi: 10.7498/aps.49.2271
Abstract +
Starting from the classical equation of motion for a mesoscopic capacitance coupling circuits,the quantum fluctuations of charge and current of the circuits in a displaced squeezed Fock state are investigated.It is found that the quantum fluctuations of charge and current in each component circuit depend on the device of the two loop circuits and squeezing parameters,while the fluctuation does not depend on displacement parameters.
2000, 49 (11): 2276-2280.
doi: 10.7498/aps.49.2276
Abstract +
Taking into account the exchange interaction in the ferromagnet and the interface scattering effect, within Blonder-Tinkham-Klapwijk scattering formalism, we have calculated the quasiparticle transport coefficients and the tunneling spectrum in the ferromagnet-insulator-d wave superconductor junction. It is found that the ferromagnetic exchange interaction can suppress the Andreev reflection, and consequently the Andreev reflected quasiparticle shows an evanescent-wave behavior depending on the injection angle of the quasiparticle. The tunneling spectrum exhibits some novel features.
2000, 49 (11): 2281-2286.
doi: 10.7498/aps.49.2281
Abstract +
The Nd10Fe84-xB6Inx(x=0，1) ribbon magnets were prepared with the melt-spun method. Influences of boundary feature on exchange coupling and hardening were investigated by means of indium addition and evaporation. It was found that hoth coercivity and remanence were affected by the grain boundary but in quite different way. Some boundary features affect hardening remarkably, while others strongly influence the exchange coupling.
2000, 49 (11): 2287-2289.
doi: 10.7498/aps.49.2287
Abstract +
A calculation of the exchange interaction constant between the R moment and the T moment in rare-earth (R) transition-metal (T) compounds of the type R2Fe17 has been discussed using molecular field theory combining with the results of neutron diffraction or X-ray diffraction. The calculated values for R2Fe17-xAlx (R=Tb,Dy,Ho,Er and Gd,x=7,8) have been given and they are in agreement with the experimental results .
2000, 49 (11): 2290-2295.
doi: 10.7498/aps.49.2290
Abstract +
The magnetic and transport properties of two series of sputtered ［Ni80Co20(L)/Fe(tFe)］N multilayers (MLs) with different Fe layer thickness of tFe=0.1 and 2nm, and varying L were studied and compared with each other. An enhanced anisotropic magnetoresistance (AMR) peak around L=10nm was observed for annealed films with tFe=0.1nm. The position of the enhanced AMR peak is the same as that of transversal MR peak for the deposited MLs with tFe=2nm. For the as-deposited films with impurity Fe layers, when L becomes lower than the electron mean free path of Ni80Co20 alloy, the zero-field resistivity ρ increases with decreasing L and the increase of ρ will exceed that of AMR (Δρ). The L dependence of ρ can be described by Fuchs-Sondheimer theory. The coercivity Hc of the as-deposited films with tFe=0.1nm increases rapidly with increasing L for L＜15nm and is almost saturated for L＞15nm. The dependence of Hc on Ｌ may be related to the interface structure of MLs, which is indicated by a big drop of Hc in the annealed films. Our experimental data show that the interface scattering in MLs may increase AMR; the magnetic alloy interfacial layers in MLs may change the domain structure and enhance transverse MR and AMR.
2000, 49 (11): 2296-2299.
doi: 10.7498/aps.49.2296
Abstract +
By using the transverse-field Ising model, the possible contribution of the quantum effect to the ferroelectric behaviors for BaTiO3 was described. It is found that the quantum effect can reduce the ferroelectric polarization obviously. The theoretical results based on the new model are in good agreement with the experimental ones.
2000, 49 (11): 2300-2303.
doi: 10.7498/aps.49.2300
Abstract +
Microstructure and electrical properties of lanthanum-modified Pb(Zr,Sn,Ti)O3(PZST) antiferroelectric (AFE) ceramics have been investigated by weak field dielectric, pyroelectric response, strong field polarization, and X-ray diffraction (XRD) techniques at different temperatures. Diffused phase transition and dielectric frequency dispersion (0.1—100kHz) have been observed within the temperature range of -100—50℃. However, XRD indicates that AFE ceramics are of tetragonal phase within the above-mentioned temperature range. Under a strong electric field, AFEt will be switched to a metastable ferroelectric (MFE) state, accompanying with the disappearance of dielectric frequency dispersion. Then the MFE state changes to AFE state again as temperature increases, producing a strong pyroelectric current peak. A new model considering compositional fluctuation on a nanometer scale in PZST antiferroelectric ceramics has been suggested to explain the polar relaxation in AFE state.
2000, 49 (11): 2304-2306.
doi: 10.7498/aps.49.2304
Abstract +
Raman scattering from InAs nanocrystals embedded in SiO2 thin films has been measured and studied. Raman spectra of InAs nanocrystals have a similar feature with that of bulk InAs crystal. Broadened and red-shifted Raman scattering peaks were observed from the nanocrystals; this has been attributed to the phonon confinement effect. A compressive stress in the interface between InAs nanocrystals and the SiO2 matrix was also taken into account to interpret the red shift.
2000, 49 (11): 2307-2309.
doi: 10.7498/aps.49.2307
Abstract +
Terbium-doped zinc oxide nanoparticles have been prepared by hydrolyzing zinc acetate and terbium acetate. Nanoparticle-matrix-facilitated photoluminescence which is related to Tb3+ ions has been observed for ZnO:Tb nanoparticles. The dependence of emission intensity on doping concentration of Tb3+ ions has been investigated. An energy transfer from excited states of ZnO hosts to dopants is disclosed by the fact that the emission intensity of Tb3+ centers increases with increasing Tb content at the expense of emission from defect states in ZnO matrix.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
2000, 49 (11): 2310-2314.
doi: 10.7498/aps.49.2310
Abstract +
Microstructure and adhesion properties of nitrogen-doped diamond-like amorphous carbon (DLC) film deposited by r f plasma-enhanced chemical vapor deposition method is studied by atomic force microscope, Auger electron spectroscopy (AES) and micro-indentation analysis. Results show that, with the increase of nitrogen content, particles of tens of nanometer in size appear in the film. The atomic lateral force microscope and AES analyses show that these nano particles are nitrogen-rich amorphous carbon nitride CNx, where x is larger than 0.126. Micro-indentation measurement shows that this DLC/CNx nano-composite structure reduces the residual stress of the film and improves the adhesion between DLC film and Si substrate.
