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Acta Physica Sinica  
  Acta Physica Sinica--2001, 50 (11)   Published: 15 November 2001
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LETTERS

GIANT TUNNELING MAGNETORESISTANCE IN NANOSTRUCTURED ZnxFe3-xO4-α-Fe2O3 POLYCRYSTALLINE MATERIAL

DU YOU-WEI, CHEN PENG, ZHU JIAN-MIN, XING DING-YU
Acta Physica Sinica. 2001, 50 (11): 2275 doi: 10.7498/aps.50.2275
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Giant tunneling magnetoresistance effect (TMR) as large as 1280% at 4.2K and 158% at 300K was observed in Zn0.41Fe2.59O4-α-Fe2O3 polycrystalline sample. The Zn0.41Fe2.59O4 grains are separated by insulating α-Fe2O3 thin layer boundaries, The pattern of nanostructure has been verified by TEM and HREM and the thickness of α-Fe2O3 boundary is about 6-7nm. The huge TMR is attributed to the high spin-polarization of Zn0.41Fe2.59O4 grains and insulating antiferromagnetic α-Fe2O3 thin layer. The ZnxFe3-xO4 ferrite is a new type half-metallic material with a huge TMR at room temperature is interesting to further study in future.
CLASSICAL AREA OF PHENOMENOLOGY

PHOTONIC FORBIDDEN BAND IN VOLUME HOLOGRAMS

ZHENG JUN, YE ZHI-CHENG, TANG WEI-GUO, LIU DA-HE
Acta Physica Sinica. 2001, 50 (11): 2144 doi: 10.7498/aps.50.2144
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Volume holograms are theoretically treated as a photonic crystal. The band gap structures in volume holograms are calculated. The properties of volume holograms can be explained based on the structures of band gaps. Experimental verifications were implemented by using elementary reflection holograms. The analysis of the band gap for volume holograms is in good agreement with the experimental results.

CONTROL OF THE PHOTOREFRACTIVE TWO-WAVE MIXING IN LiNbO3∶Fe AND LiNbO3∶Fe∶In WITH AN INCOHERENT BACKGROUND BEAM

ZHAO HONG-E, LIU SI-MIN, GUO RU, JIANG YING, LI FEI-FEI, CHEN XIAO-HU, WANG DA-YUN, WEN HAI-DONG, XU JING-JUN
Acta Physica Sinica. 2001, 50 (11): 2149 doi: 10.7498/aps.50.2149
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We have analysed the results of the photorefractive two-wave mixing in LiNbO3∶Fe and LiNbO3∶Fe∶In controlled by an incoherent beam, and performed related experiments. Experimental results showed that the incoherent beam can effectively control the photorefractive two-wave coupling gain in a large range, suppress the fanning effect, increase the signal-to-noise ratio, and shorten the setup time of the two-wave mixing grating.

INFLUENCE OF RELATIVE PHASE ON THE ENHANCED IONIZATION BEHAVIOUR OF LINEAR MULTIATOMIC MOLECULAR IONS IN TWO-COLOR LASER FIELDS

WANG XUN-CHUN, QIU XI-JUN, ZHENG LI-PING
Acta Physica Sinica. 2001, 50 (11): 2155 doi: 10.7498/aps.50.2155
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The enhanced ionization(EI) behaviour of linear multiatomic molecular ions is studied in two-color(fundamental radiation:780 nm, the second harmonic:390 nm) laser fields by the numerical solution of the time-dependent Schrdinger equation with the symmetrical splitting of the short-time exponential propagator. The influence of the relative phase between the two-color laser fields on the ionization probability is given. The numerical results demonstrate that the influence of the relative phase on the ionization probability is the strongest in the range of the inter-nuclear distance where the EI occurs. The influence can be explained in terms of the field-induced over-the-barrier ionization model.

SPATIAL SOLITONS IN PHOTOREFRACTIVE ORGANIC POLYMERS

HOU CHUN-FENG, ABDURUSUL, DU CHUN-GUANG, SUN XIU-DONG, LI SHI-QUN
Acta Physica Sinica. 2001, 50 (11): 2159 doi: 10.7498/aps.50.2159
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The bright, dark and grey soliton solutions for optical wave evolution equations are presented in photorefractive polymer under a steady-state condition. The polarization property of these different soliton states and the dependence of the width of these polymeric solitons on external bias field are discussed in detail.

ONE-DIMENSIONAL DARK SOLITONS IN PHOTOVOLTAIC MEDIA WITH A POSITIVE PERTURBATION REFRACTIVE INDEX

SHE WEI-LONG, WANG XIAO-SHENG, HE GUO-GANG, TAO MENG-XIAN, LIN LI-PING, LEE WING-KEE
Acta Physica Sinica. 2001, 50 (11): 2166 doi: 10.7498/aps.50.2166
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We present a theory of photovoltaic(PV) spatial solitons(SS's), that includes the PV contribution of a background beam(BB). The theory predicts that a dark or a bright SS can be formed in the same crystal with positive refractive index perturbation (Δn). If the ratio (R) of the effective Glass constants(EGC) of the BB to that of the signal beam(SB) is<1, a bright SS can be formed. A dark SS can be formed if R>1. We have formed a one-dimensional dark PV SS in a crystal, as predicted.

AN EIGEN MATRIX METHOD FOR OBTAINING THE BAND STRUCTURE OF PHOTONIC CRYSTALS

WANG HUI, LI YONG-PING
Acta Physica Sinica. 2001, 50 (11): 2172 doi: 10.7498/aps.50.2172
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An eigen matrix method is reported to obtain the band structure of one-dimensional(1D) photonic crystals. Using this method, we have calculated the band structures of 1D crystals consisting of components with different dielectric constants and geometric structures. It can also be extended to a case where the dielectric constant is dependent on the frequency of the incident light.

ELECTROMAGNETIC ADJOINT TRANSFORMATION AND MODE ANALYSIS FOR GUIDED WAVES IN AN OPTICAL FIBER

YU SHOU-MIAN, YU TIAN
Acta Physica Sinica. 2001, 50 (11): 2179 doi: 10.7498/aps.50.2179
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The adjoint transformation of electromagnetic fields for uniform isotropic dielectric is considered for guided waves in an optical fiber. The necessary and sufficient condition for two solutions to be a pair of partners is derived. The modes of guided waves are analyzed under this condition. It is proved that the dispersive normal modes do not exist in the case of non-axial symmetry. The guided modes in such cases are modes of critical refraction, which has a discrete spectrum. The dispersive normal modes exist in axial symmetrical cases. Theoretical predictions are comparable with the experiment data. The behaviour of the fundamental mode shows that it is a mode of critical refraction rather than a dispersive normal mode as is predicted by the theory.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

STUDIES OF THE IMPURITY EFFECTS ON CRYSTALLINE QUALITY BY HIGH-RESOLUTION X-RAY DIFFRACTION

LI CHAO-RONG, WU LI-JUN, CHEN WAN-CHUN
Acta Physica Sinica. 2001, 50 (11): 2185 doi: 10.7498/aps.50.2185
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Sr(NO3)2 single crystals with different impurities doped were grown from aqueous solutions. The distribution of impurities in Sr(NO3)2 crystals were investigated by electron probe micoranalysis. Results show that the distribution of impurities illustrates a compositional zoning behaviour. The Ba2+ has a higher concentration in the {100} growth sectors than in the {111} sectors. On the contrary, Pb2+ has a higher concentration in {111} growth sectors than in {100} sectors. The crystalline perfection of the pure and Ba2+ or Pb2+ doped Sr(NO3)2 crystals was studied by high-resolution X-ray rocking curve technique. The high-resolution X-ray rocking curve of the ideal Sr(NO3)2 crystal was theoretically calculated based on the dynamical X-ray diffraction theory. High-resolution X-ray diffraction results show that the crystalline quality in the growth sectors of the pure Sr(NO3)2 crystal is fairly high, since its experimental rocking curve is very close to the theoretical calculation. However, in the areas of the sector boundary the full width at half maximum of the rocking curve gets broader due to the lattice stress in the boundary area. The doping of impurities will deteriorate the quality of the crystal and induce an inhomogeneity behaviour of the crystalline quality. As for the Ba2+ doped Sr(NO3)2 crystal, the crystalline quality in {111} growth sectors is higher than that in {100} sectors. On the contrary, the crystalline quality in {100} growth sectors is higher than that in {111} sectors for Pb2+ doped Sr(NO3)2 crystal. This coincides well with the composition distributions of the dopants.

STUDY ON MICROSTRUCTURE AND CRYSTALLIZATION OF AMORPHOUS Cu56Zr44 ALLOY BY MEANS OF ISOTHERMAL ANNEALING

WANG HUAN-RONG, TENG XIN-YING, SHI ZHI-QIANG, YE YI-FU, MIN GUANG-HUI
Acta Physica Sinica. 2001, 50 (11): 2192 doi: 10.7498/aps.50.2192
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The microstructure and crystallization process of an amorphous Cu56Zr44 alloy at isothermal annealing were studied by using the X-ray diffraction, differential scanning calorimetry and transmission electron micrograph techniques. The experimental results seem to show that the short-range order of amorphous Cu56Zr44 alloy at room temperature is of hard sphere random dense packing. It is found that the crystallization products of amorphous Cu56Zr44 alloy annealed at 703K within its supercooled liquid range is mainly Cu8Zr3 phase in an annealing time of 3min, and when the time is 6min, Cu8Zr3 phase disappears completely and Cu10Zr7 phase precipitates a lot, while if the time is longer than 30min, several kinds of phases such as Cu10Zr7, CuZr2 and Cu8Zr3 will form. Based on the above the diffusion mechanism of amorphous Cu56Zr44 alloy at isothermal annealing is presented.

SIZE EFFECT ON ABSORPTION EDGES OFULTRA-FINE SnO2 NANOPARTICLES

KANG JUN-YONG, S.TSUNEKAWA, A.KASUYA
Acta Physica Sinica. 2001, 50 (11): 2198 doi: 10.7498/aps.50.2198
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Aqueous sols containing nanocrystalline SnO2 particles with sizes less than 2 nm were prepared by ultra-filtration from original acidic and alkaline sols with SnO2 particles. The sizes of SnO2 nanocrystallines were determined by dynamic light scattering, X-ray diffraction, and computer analysis of nanocrystalline images of transmission electron microscopy. Blue shifts of absorption edges of the nanocrystallines were observed in both the ultra-filtrated acidic and alkaline sols. The results show that the blue shifts of the SnO2 nanocrystallines are mainly attributable to the size decrease for the same kind of nanocrystallines.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

FIRST-PRINCIPLES STUDY ON THE ELECTRONIC AND MAGNETIC PROPERTIES OF PEROVSKITE RUTHENATE SrRuO3

TAN MING-QIU, TAO XIANG-MING, HE JUN-HUI
Acta Physica Sinica. 2001, 50 (11): 2203 doi: 10.7498/aps.50.2203
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We report a self-consistent full-potential linear muffin tin orbitals(LMTO) band structure calculation on the electronic and magnetic properties of Ru-based perovskite SrRuO3(SRO) in this article. For the assumed simple cubic SRO with lattice constant a=0.392nm, the calculated spin moment per SrRuO3 unit is 1.29μB. Most part of this spin moment (approximately 65%) is located on the Ru site within a unit cell. The density of states (DOS) of electrons near the Fermi energy is 43.5 (states/Ryd/f.u.). For real orthorhombic SRO, our LSDA calculation predicts a ferromagnetic ground state with 1.08μB moment per unit formula. The Sommerfeld constant is 10.60mJ/mol·K2 deduced from the calculated DOS near the Fermi energy. All these findings showed that SRO is an itinerant ferromagnet with wide energy bands.

THE ULTRAVIOLET AND GREEN LUMINESCENCE CENTERS IN UNDOPED ZINC OXIDE FILMS

LIN BI-XIA, FU ZHU-XI, JIA YUN-BO, LIAO GUI-HONG
Acta Physica Sinica. 2001, 50 (11): 2208 doi: 10.7498/aps.50.2208
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Undoped ZnO films were deposited on Si substrates by DC reactive sputtering. The samples were annealed in air, pure O2 (1atm) and pure N2 (1atm) at 850℃,950℃,1000℃ for 1h. The X-ray diffraction patterns of the as-deposited and annealed samples all have a widened diffraction peak of ZnO (002). It is evident that all the films we used are ZnO films with [001] orientation. The photoluminescence (PL) spectra of these samples include two emission peaks, centered at 3.18eV (ultraviolet, UV) and 2.38eV (green). It is fount that the intensities of these peaks vary with annealing temperature and atmosphere. At same annealing temperature, the intensity of green peak increases evidently with the increase of oxygen partial pressure, and the intensity of UV peak is also increased somewhat. In the same atmosphere, the intensity of green peak enhances sharply with the increase of annealing temperature, but the intensity of UV peak increases slowly and approaches a maximum value at 950℃, then decreases as the annealing temperature increases.; We investigated the dependence of the crystallization and also the intrinsic defects in ZnO film, such as zinc vacancy VZn, oxygen vacancy VO, interstitial zinc Zni, interstitial oxygen Oi and anti-sited oxygen OZn on the annealing conditions. Compared with the calculated data of these intrinsic defects, it is suggested that the UV radiation of ZnO is due to band-edge exciton transition, and the green emission corresponds to the transition from the bottom of the conduction band to the local level composed of oxide misplaced defects.

INFLUENCE OF CH3CSNH2 PASSIVATION ON INTERFACE DIFFUSION BETWEEN FERROMAGNETIC METALS AND GaAs

ZHU CHUAN-GANG, XU PENG-SHOU, LU ER-DONG, XU FA-QIANG, PAN HAI-BIN
Acta Physica Sinica. 2001, 50 (11): 2212 doi: 10.7498/aps.50.2212
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The influence of CH3CSNH2 passivation on diffusion at interface between ferromagnetic metals and GaAs has been studied. The experimental results show that sulfur passivation can change the chemical environment of As element , prevent As from diffusing into ferromagnetic metal overlayer, weaken the reaction of As with ferromagnetic metals and enhance the magnetism of the interface. Furthermore, we discussed the reason that S passivation can prevent As atoms diffusion.

SPONTANEOUS MAGNETIZATION IN HIGH-Tc SUPERCONDUCTING π RINGS

DENG PENG, MENG SHU-CHAO, WANG FU-REN, XIE FEI-XIANG, MA PING, DAI YUAN-DONG
Acta Physica Sinica. 2001, 50 (11): 2217 doi: 10.7498/aps.50.2217
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We analyzed and calculated the spontaneous magnetization in High-Tc superconducting YB2Cu3O7-δ 1-junction and 3-junction rings which contained a π junction. We also deduced the temperature dependence of the spontaneous magnetization in 3-junction π ring. The theoretic results fit the experimental data fairly well.

SCALING BEHAVIOURS OF VORTEX TRANSPORT IN 2H-Nb0.9Ta0.1Se2

ZHANG BO, TIAN MING-LIANG, ZHANG YU-HENG
Acta Physica Sinica. 2001, 50 (11): 2221 doi: 10.7498/aps.50.2221
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The field dependence of voltage V(H) in a 2H-Nb0.9Ta0.1Se2 single crystal at various currents was measured and converted to current-voltage data V(I). Then the scaling law V=α(I-Ic)β was applied to extract the critical current Ic(H) and differential resistance Rd(H). The results show a peak on the differential resistance vs.H curve near Hc2 when the applied current is high, but for a lower current it appears near the onset of peak effect region. This indicates that the new types of pinning centers generated by doped Ta significantly alter the dynamic properties of the vortex system.

INVESTIGATION OF THE RELATIONSHIP BETWEEN THE CONSISTENCE AND MICROSTRUCTURE OF SINTERED Nd-Fe-B MAGNETS

CHENG WEN-HAO, LI WEI, LI CHUAN-JIAN, PAN WEI
Acta Physica Sinica. 2001, 50 (11): 2226 doi: 10.7498/aps.50.2226
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One of the most important factors that lower the consistence is the appearance of regions where the technological parameters deviate from the points where the sensors are located. In this paper this was investigated on the basis of the relationship between the intrinsic coercivity and the microstructure parameters of sintered Nd-Fe-B magnets. It is found that the magnet with a fairly good microstructure will have higher consistence than the magnet with a relatively poor microstructure under the same technological conditions. This indicates that the more effective approach to enhance the consistence of a magnet is to optimize its microstructure other than to rigorously enforce the technological conditions. The results obtained show some directive for improving the consistence of the magnetic properties of sintered Nd-Fe-B magnets.

EFFECT OF Ta AND Ta/Cu BUFFERS ON THE EXCHANGE BIAS FIELD OFNiFe/FeMn BILAYERS

LI MING-HUA, YU GUANG-HUA, JIANG HONG-WEI, CAI JIAN-WANG, ZHU FENG-WU
Acta Physica Sinica. 2001, 50 (11): 2230 doi: 10.7498/aps.50.2230
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The NiFe/FeMn bilayers with different buffer layers (Ta or Ta /Cu) and Ta cover layers were prepared by magnetron sputtering. The results showed that the exchange bias field of NiFe/FeMn films with the Ta buffer was higher than that of the films with the Ta/ Cu buffer .We investigated the crystallographic texture, surface roughness and surface segregation, and demonstrated that the decrease of the exchange coupling field was caused by the Cu surface segregation in NiFe/FeMn films with Ta/ Cu buffer layers.

STRUCTURE AND MAGNETIC PROPERTIES OF Fe62Co8-x(Cr,Mo)xNb4Zr6B20 AMORPHOUSALLOY WITH A WIDE SUPERCOOLED LIQUID REGION

RONG CHUAN-BING, ZHAO YU-HUA, XU MIN, ZHAO HENG-HE, CHEHG LI-ZHI, HE KAI-YUAN
Acta Physica Sinica. 2001, 50 (11): 2235 doi: 10.7498/aps.50.2235
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Fe62Co8-xCrxNb4Zr6B20 and Fe62Co8-xMoxNb4Zr6B20(x=0,2,4, atomic percent) alloy series were chosen to study in this paper based on the three empirical rules of making bulk amorphous alloy. The ribbons, 30μm thick and 5mm wide, were produced by single-roller rapid quenching. The thermal stability, amorphous structure and magnetic properties of these alloys were studied by differential thermal analysis, X-ray diffraction, Faraday magnetic balance and static magnetic measurement. The supercooled liquid region ΔTx of the alloy, which contains 2at% Cr, reaches 85K, but the saturation magnetization σs of these alloys decreases distinctly with increasing Cr or Mo. The saturation magnetization σs and coercive force Hc increase rapidly for the alloys of this series annealed at 973K for 900s because of the precipitation of α-Fe.

LASER-INDUCED LATTICE DEFORMATION OF POROUS SILICON REVEALED BY RAMAN AND PHOTOLUMINESCENCE SPECTROSCOPIES

LIANG ER-JUN, CHAO MING-JU
Acta Physica Sinica. 2001, 50 (11): 2241 doi: 10.7498/aps.50.2241
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Raman and photoluminescence spectroscopies fo the porous silicon prepared in a hydrothermal solution with addition of titanium have been studied. Only a sharp single band near 520cm-1 appears in the Raman spectrum of the porous silicon when the exciting laser power is low and shifts to the red side with the increase of the laser power. If the laser power is increased to a critical value, the Raman band splits into two bands while the photoluminescence band splits also and the intensity of it increases enormously. We assign the two Raman bands to the lattice deformation-induced non-degeneracy of the LO and TO phonons. The laser-induced lattice deformation may result in the transformation of the porous silicon from a linear to a nonlinear optical material with a large laser-induced nonlinear optical absorption coefficient. It is found that the laser-induced transformation in the porous silicon is a reversible process. This may implicate some new applications of this material.

THE EFFICIENCY OF THE FORMATION AND FISSION OF POLARON-EXCITONS IN POLYMER LIGHT-EMITTING DEVICES

LI HONG-JIAN, PENG JING-CUI, XU XIE-MEI, QU SHU, XIA HUI
Acta Physica Sinica. 2001, 50 (11): 2247 doi: 10.7498/aps.50.2247
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The processes of formation and fission of polaron-excitons in polymer light-emitting devices are investigated in detail. A theoretical model and a complete analytic function for polaron-excitions fission is proposed. The influences of applied bias, temperature and dopant concentrations on recombination internal quantum efficiency are thoroughly studied. This theoretical model could explain the experimental phenomena.

THE SIZE EFFECT ON OPTICAL AND MAGNETO-OPTICAL PROPERTIES IN Fe-Ag GRANULAR FILMS

WANG SONG-YOU, JU XIAO-HUA, LI HE-YIN, XU XU-DONG, ZHOU PENG, ZHANG RONG-JUN, YANG YUE-MEI, ZHOU SHI-MING, CHEN LIANG-YAO
Acta Physica Sinica. 2001, 50 (11): 2252 doi: 10.7498/aps.50.2252
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A series of FexAg1-x(x=18, 45, 81) samples were prepared by ion beam sputtering and post-annealed in vacuum at different temperatures for one hour. X-ray diffraction, optical and magneto-optical measurement were performed and the structure, optical and magneto-optical Kerr effect properties for different annealing temperatures have been studied. Results show that the magneto-optical Kerr effects are closely related to the particle size.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

DEPOSITION OF HIGH-QUALITY c-BN FILM ENHANCED BY PULSED DC BIAS TECHNIQUE

TIAN JING-ZE, Lü FAN-XIU, XIA LI-FANG
Acta Physica Sinica. 2001, 50 (11): 2258 doi: 10.7498/aps.50.2258
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Cubic boron nitride (c-BN) films were synthesized using magnetically enhanced active reaction evaporation system in which pulsed DC technique was employed to enhance the formation of c-BN film. The effect of pulsed DC bias, plasma discharge current, Ar/N2 flow ratio, substrate temperature on the formation of c-BN films was investigated. The friction of c-BN phase in the film increased with the increase of pulsed DC negative bias and discharge current.Almost single phase c-BN films were obtained when deposited at-155V of pulsed DC bias,15A of discharge current,500℃ of substrate temperature and 10 of Ar/N2 flow ratio.

CARBON NITRIDE THIN FILMS PREPARED BY PULSED XeCl EXCIMERLASER DEPOSITION ASSISTED BY DC GLOW DISCHARGE

FU GUANG-SHENG, YU WEI, WANG SHU-FANG, LI XIAO-WEI, ZHANG LIAN-SHUI, HAN LI
Acta Physica Sinica. 2001, 50 (11): 2263 doi: 10.7498/aps.50.2263
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Carbon nitride thin films are deposited by combining XeCl pulsed laser deposition with additional dc glow discharge. The morphology, composition, structure and bonding status of the films are analyzed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy. The results show that the deposited films are mainly composed of crystalline carbon nitride and amorphous silicon nitride. The carbon nitride in the film exist in mixed phases of α- and β-C3N4 and the crystalline grain size is in the range of 40—60nm, The XPS studies indicate that carbon atoms of the films are mainly bonded to nitrogen in sp3 C—N bonds while most of the nitrogen atoms are in N—Si bonds.
GENERAL

A FIELD METHOD FOR SOLVING THE EQUATIONS OF MOTION OF A ROTATIONAL REALTIVISTIC BIRKHOFFIAN SYSTEM

LUO SHAO-KAI, GUO YONG-XIN, CHEN XIANG-WEI, FU JING-LI
Acta Physica Sinica. 2001, 50 (11): 2049 doi: 10.7498/aps.50.2049
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A field method for solving the equations of motion of a rotational relativistic Birkhoffian system is obtained.An example to illustrate the application of the method is given.

INTEGRATION THEORY OF THE DYNAMICS OF A ROTATIONAL RELATIVISTIC SYSTEM

LUO SHAO-KAI, GUO YONG-XIN, CHEN XIANG-WEI
Acta Physica Sinica. 2001, 50 (11): 2053 doi: 10.7498/aps.50.2053
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The basic integration theory of the dynamics of a rotational relativistic system is constructed.Firstly,the first integrals of the system are given.Secondly,the order of the equation of motion is reduced by using cyclic integrals and energy integrals,and thus the generalized Routh equation and generalized Whittaker equation are obtained.Thirdly,the canonical equation and variational equation of the system are established,and the integral invariant is constructed by using the first integrals.Fourthly,the integral variants and integral invariants of the Poincaré-Cartan type are given.Finally,some deductions are given.

CONNEXION OF FIRST INTEGRALS WITH PARTICULAR SOLUTIONS OF THE VARIATIONAL EQUATIONS FOR SYSTEMS OF GENERALIZED CLASSICAL MECHANICS

ZHANG YI
Acta Physica Sinica. 2001, 50 (11): 2059 doi: 10.7498/aps.50.2059
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This paper presents the variational equations for systems of generalized classical mechanics and studies the connexion of their solutions with the first integrals of the systems. By using a first integral, a particular solution of the variational equations is obtained and an example is given.

EXPLICIT EXACT SOLUTIONS TO NONLINEARCOUPLED DIFFERENTIAL EQUATIONS

LI ZHI-BIN, YAO RUO-XIA
Acta Physica Sinica. 2001, 50 (11): 2062 doi: 10.7498/aps.50.2062
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A method for constructing explicit exact solutions of coupled ordinary nonlinear differential equations by using the special solutions of Riccati equations is proposed.Two coupled nonlinear differentiall equations are studied using this method,and several new solutions (either functional or parametrical) are explicitly obtained,in addition to rederiving all known solutions in a systematic way.

EXPANSION METHOD ABOUT THE JACOBI ELLIPTIC FUNCTION ANDITS APPLICATIONS TO NONLINEAR WAVE EQUATIONS

LIU SHI-KUO, FU ZUN-TAO, LIU SHI-DA, ZHAO QIANG
Acta Physica Sinica. 2001, 50 (11): 2068 doi: 10.7498/aps.50.2068
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A Jacobi elliptic function expansion method is proposed to construct the exact periodic solutions of nonlinear wave equations. This new method contains the hyperbolic tangent expansion method, and the periodic solutions obtained by this method, include the shock wave solutions and the solitary wave solutions.

THE SOLITARY WAVE SOLUTIONS TO KdV-BURGERS EQUATION

Lü KE-PU, SHI YU-REN, DUAN WEN-SHAN, ZHAO JIN-BAO
Acta Physica Sinica. 2001, 50 (11): 2073 doi: 10.7498/aps.50.2073
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The study on the hyperbola function method has been done and the application of the method was extended.Furthermore, with the aid of computer algebraic system Mathematica, two kink solitary wave solutions to KdV-Burgers equation were successfully derived.

LEWIS-RIESENFELD PHASES AND BERRY PHASES IN THEQUANTUM SYSTEM OF TIME-DEPENDENT HARMONICOSCILLATOR WITH A MOVING BOUNDARY

LI LING, LI BO-ZANG, LIANG JIU-QING
Acta Physica Sinica. 2001, 50 (11): 2077 doi: 10.7498/aps.50.2077
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Using the Lewis-Riesenfeld′s quantum invariant theory,the Lewis-Riesenfeld phases for a time-dependent frequency harmonic oscillator,which is confined in an infinite well with a moving wall,are calculated.We find that the geometric part of the Lewis-Riesenfeld phases are identical with the “non-adiabatic Berry phases” described by D.Y.Liu in Acta Phys.Sin.It may be important that our results,at least for the system with a sinusoidally oscillating boundary,do not show any non-trivial Berry phase acquired.

DISENTANGLEMENT OF 3-PAETICLE SYSTEMS

FENG JIAN, WANG JI-SUO, GAO YUN-FENG, ZHAN MING-SHENG
Acta Physica Sinica. 2001, 50 (11): 2083 doi: 10.7498/aps.50.2083
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Three kinds of definitions of disentanglement of 3-particle systems are given. Three basic regulations of a 3-particle system pure-state disentanglement are completely analyzed. It is shown that there are some sets of 3-particle entangled states that can be disentangled into product states or 1-particle product and 2-particle separable states or fully separable states, but a universal disentangling machine into product states or 1-particle product and 2-particle separable states or fully separable states cannot exist.

EXTERNAL GRAVITATIONAL FIELD OF THE KASUYA DYONMETRIC IN A MAGNETIC FIELD

SU CHENG-YUE
Acta Physica Sinica. 2001, 50 (11): 2089 doi: 10.7498/aps.50.2089
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Using the Ernest's method and adopting the Harrison transform under the linear condition, we obtained an expression of the exterior metric associated with the Kasuya dyon, q≠-2B 0J, in a magnetic field. There is an arbitrary parameter B0 in the expression, it expresses a homogeneously weak magnetic field. While r→∞, the metric approaches asymptotically the Melvin magnetic universe, it is reasonable that the metric does not become asymptotically flat in a homogeneously magnetic field.

NONLINEAR ADAPTIVE PREDICTIVE TARGETING CONTROL OF THE CONTINUOUS CHAOTIC SYSTEMS

ZHANG JIA-SHU, XIAO XIAN-CI
Acta Physica Sinica. 2001, 50 (11): 2092 doi: 10.7498/aps.50.2092
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The sigmoid-Volterra adaptive predictors are used to perform nonlinear adaptive predictive targeting control of chaos in continuous chaotic systems based on the nonlinear adaptive predictive principle of chaotic time series, where the nonlinear adaptive controller acts on only one-dimensional time series coming from the chaotic state of the controlled system. This adaptive predictive targeting controller can control the system to any desired state by means of adaptive cancellation. Computer simulation results on the Lorenz and Rǒssler systems are shown to demonstrate the effectiveness of this nonlinear adaptive predictive targeting control method. The advantages of this new method are that it does not need to know the accurate equations or to identify the system′s model of the controlled chaotic systems.

A CIRCUIT EXPERIMENT FOR CONTROLLING HYPERCHAOS BY MEANS OF PROPORTIONAL PERIODIC PULSE PERTURBATION TO THE SYSTEM VARIABLES

YUE LI-JUAN, CHEN YAN-YAN, PENG JIAN-HUA
Acta Physica Sinica. 2001, 50 (11): 2097 doi: 10.7498/aps.50.2097
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The control of hyperchaos in the circuit by means of proportional periodic pulse perturbation to the system variables (PP-SV) has been realized. By using a single output signal of the system as the feedback variable, we and not only replace the system variable by itself, but also add the feedback signal to other system variables, and thus achieve good control results. The results of numerical simulation are in good agreemend with the experimental data.

CONTROLLING CHAOS IN CHAOTIC NEURAL NETWORK

HE GUO-GUANG, CAO ZHI-TONG
Acta Physica Sinica. 2001, 50 (11): 2103 doi: 10.7498/aps.50.2103
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In this paper, a pinning control method focused on a chaotic neural network (CNN) is proposed. The chaos of the CNN can be controlled by using this method, and the output of the CNN is fixed stably in its stored pattern. In this way, the information search in the CNN is realized. In addition, the factors which affect the control of the CNN are discussed.

THE ADAPTIVE CONTROL OF CHEN’S CHAOTIC SYSTEM

GUAN XIN-PING, FAN ZHENG-PING, PENG HAI-PENG, WANG YI-QUN
Acta Physica Sinica. 2001, 50 (11): 2108 doi: 10.7498/aps.50.2108
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The control of Chen's chaotic system when its parameters are known a priori or unknown is studied by means of a simple linear state feedback method. When the parameters are known a priori, we show the variation range of feedback gain; and when the parameters are unknown, an adaptive controller is designed, which overcomes the drawback that the control is discontinuous in a common adaptive controller. Finally the simulation results vertify the effectiveness of our proposed method.

NEURAL NERWORK BASED ROBUST ADAPTIVE SYNCHRONIZATION OF A CHAOTIC SYSTEM

GUAN XIN-PING, TANG YING-GAN, FAN ZHENG-PING, WANG YI-QUN
Acta Physica Sinica. 2001, 50 (11): 2112 doi: 10.7498/aps.50.2112
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Based on the neural network, the synchronization of two chaotic systems with uncertainties is studied.The results show that the approach proposed in this paper can overcome effectively the disruption of perturbation. Lorenz system is used to vertify the effectiveness of the proposed method, and the simulation results confirm it.

THE TRANSVERSE PATTERN OF LASER OSCILLATION OUTPUT IN A RING CAVITY AND THE TRANSITION TO OPTICAL TURBULENCE

ZHANG XU, SHEN KE
Acta Physica Sinica. 2001, 50 (11): 2116 doi: 10.7498/aps.50.2116
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Based on the earlier theoretical work on the bifurcation and chaos of laser oscillation output in a ring cavity, we present in this paper a study of transverse effects in the spatially extended system. Numerical simulations show that the spatially extended system has the homogeneous stationary states, the traveling wave solutions and the spatiotemporal chaos states with the change of its parameters. We also find a transition to turbulence via symmetry breaking at the definite system parameters when considering incident light as plane wave (homogeneous distribution).

CHAOTIC SYNCHRONIZATION SECURE COMMUNICATIONS BASED ON THE EXTENDED CHAOTIC MAPS SWITCH

ZHANG JIA-SHU, XIAO XIAN-CI
Acta Physica Sinica. 2001, 50 (11): 2121 doi: 10.7498/aps.50.2121
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A chaotic synchronization secure communication method based on chaotic maps switch is proposed. The extended chaotic model is first built to generate many kinds of chaotic signals based on changing parameters during different time durations. In the transmitter, the modulation is implemented by adding the information signal to chaotic carriers, taking a modular operation on the sum, and embedding the result of the modular operation in the iteration of the extended chaotic generating systems. In the receiver, the chaotic carriers are retrieved from the received signals by using the corresponding nonlinear dynamical system, and then the information signals are recovered. The simulation results show that this chaotic synchronization secure communication method based on chaotic maps switch has the good immunity to interference and can be realized easily. It is also shown that this chaotic secure communication system is better in security than that based on single chaotic map.

FRACTAL AND MULTIFRACTAL DESCRIPTION OF SURFACE TOPOGRAPHY

SUN XIA, WU ZI-QIN
Acta Physica Sinica. 2001, 50 (11): 2126 doi: 10.7498/aps.50.2126
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Six regular surfaces with same root-mean-square(rms) roughness are constructed by six typical generators. Variation method is used to calculate the fractal dimensions of these surfaces. The results suggest that fractal dimension can describe total topography of a surface quantitatively and can distinguish the surfaces which have same rms roughness. Multifractal method is further used in the analysis of surface. It is found that multifractal spectrum can reflect the overall characteristic of the distribution of probability of a surface. The width of multifractal spectrum can characterize the degree of the undulation of a surface quantitatively. The difference of the fractal dimensions between the maximum probability and the minimum probability subsets can give a statistical result of the ratio between the numbers of lowest and highest sites.

THE PREFERENTIAL ADSORPTION OF Ge ON Si(111)7×7 SURFACE

YAN LONG, ZHANG YONG-PING, PENG YI-PING, PANG SHI-JIN, GAO HONG-JUN
Acta Physica Sinica. 2001, 50 (11): 2132 doi: 10.7498/aps.50.2132
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Ge preferential adsorption on Si(111)7×7 surface at the initial stage has been investigated by ultra-high vacuum scanning tunneling microscopy (UHV-STM). We demonstrate that there is a critical nucleus for the adsorbed Ge clusters on Si(111) 7×7 surface. The center sites of the Ge clusters are located in the areas encircled by three adatoms. Moreover, on the Ge clusters the local density of states near the Fermi level is drastically reduced, compared with that far from the Fermi level.
ATOMIC AND MOLECULAR PHYSICS

A THEORETICAL STUDY ON ELECTRON ANGULAR DISTRIBUTIONS FOR (e,2e) PROCESSES ON HYDROGEN

ZHANG SUI-MENG, WU XING-JU
Acta Physica Sinica. 2001, 50 (11): 2137 doi: 10.7498/aps.50.2137
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In this work the triple differential cross sections for electron impact ionization of atomic hydrogen at different energies are calculated by use of 3C and DS3C models. The structure of the cross sections is analysed. It is seen that the angular distribution basically consists of two peaks which can be assigned to the binary and recoil peaks. The shape and position of the two peaks depend sensitively on the detection geometry and the energy shared between the two electrons. Furthermore, the final-state electron-electron repulsion contributes significantly to the form of the observed angular distributions. For different collision geometry, the three-body interactions will control the interference pattern of various scattering amplitudes by different weighting between these amplitudes. In addition, the direct and exchange amplitudes are also considered.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

AN EXPERIMENTAL STUDY ON THE FLUORESCENCE CORRELATIONSPECTROSCOPY IN LASER GRADIENT FIELD

DING YAO, MENG FAN-BO, CHEN BO, MA HUI, JIN LEI, CHEN DIE-YAN
Acta Physica Sinica. 2001, 50 (11): 2269 doi: 10.7498/aps.50.2269
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This work studies experimentally the influence of a laser gradient field on fluorescence correlation spectroscopy measurements.Results show that the derived diffusion time for particles across the detection volume increases almost linearly with the strength of the gradient field.The derived number of fluorescing particles in the detection volume also increases with the field.The larger the polarizability of the particles,the bigger the effects of the gradient field.
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