Table of Content

20 October 1994, Volume 3 Issue 10 Previous Issue    Next Issue

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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TWO-PARTICLE BOUND STATES IN THE QUANTUM SINE-GORDON FIELD THEORY IN (D+1) DIMENSIONS LU WEN-FA, XU BO-WEI, ZHANG YU-MEI 1994, 3 (10):  721-729.  doi: 10.1088/1004-423X/3/10/001 Abstract ( 0 )   PDF (225KB) ([an error occurred while processing this directive])   The two-particle states of the quantum sine-Gordon fields are studied variationally in (D+1) dimensions using the Gaussian wave functional approach. In both (1+1) and (2+1) dimensions, there exist two-particle bound states for certain ranges of coupling constant, where the vacuum states are stable. In the higher dimensions (D > 2), this approximation indicates that the two-particle states may be only the states consisting of two free particles, which is conformable to the triviality of the sine-Gordon field theory previously obtained in recent literatures.

NUCLEAR PHYSICS

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NMR STUDIES OF HYDROGEN MICROSTURUCTURES IN HYDROGENATED AMORPHOUS SILICON FILMS QU XUE-XUAN, CHEN KUN-JI, CHEN MAO-RUI, HU CHENG, LI ZHI-FENG, FENG DUAN 1994, 3 (10):  730-735.  doi: 10.1088/1004-423X/3/10/002 Abstract ( 0 )   PDF (167KB) ([an error occurred while processing this directive])   Four kinds of a-Si: H films deposited in the PECVD system with different Ts are studied by 1H NMR technique. Direct evidence is given to confirm hydrogen atoms in the diluted and clustered phases. The local bonding configurations for hydrogen and the density of dangling bonds are analyzed by ESR and infrared absorption spectroscopy. The behaviour of hydrogen in a-Si; H films is discussed.

CLASSICAL AREAS OF PHENOMENOLOGY

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THEORETICAL STUDY ON THE DIRECT RECONSTRUCTION OF LLFT X-RAY HOLOGRAM WITH VISIBLE LIGHT XIAO TI-QIAO, CHEN JIAN-WEN, XU ZHI-ZHAN, ZHU PEI-PING, KOU LEI-GANG, WANG ZHI-JIANG 1994, 3 (10):  736-745.  doi: 10.1088/1004-423X/3/10/003 Abstract ( 0 )   PDF (284KB) ([an error occurred while processing this directive])   Reconstructing X-ray hologram with visible light, without enlargement of it, can sim-plify the process of its reconstrution greatly. For lensless Fourier transform (LLFT) X-ray holography, there is no spherical aberration in it and the spacing of its interference fringes is relatively large. Therefore, it is possible to reconstruct hologram of this type directly with visible light. The effects of aberrations and emulsion shrinkage on the resolution of LLFT X-ray hologram, the conditions for perfect reconstructing of the recorded information are analyzed, and the results of corresponding numerical analyses are also given. As a result, the legibility for direct reconstructing of LLFT X-ray hologram with visible light is verified theoretically, In addition, the longitudinal resolution in X-ray holography is analyzed, and the conditione for longitudinal resolving in X-ray holography are given from the relationship between longitudinal and transverse resolution.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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BEHAVIOR OF Ar PLASMA FORMED IN A HIGH DENSITY PLASMA SOURCE-AN ECR REACTOR WU HAN-MING, D.B. GRAVES, R.K PORTEOUS, LI MING 1994, 3 (10):  746-757.  doi: 10.1088/1004-423X/3/10/004 Abstract ( 0 )   PDF (349KB) ([an error occurred while processing this directive])   In order to develop the ultra-large scale integration(ULSI), low pressure and high density plasma apparatus are required for etching and deposit of thin films. To understand critical parameters such as the pressure, temperature, electrostatic potential and energy distribution of ions impacting on the wafer, it is necessary to understand how these parameters are influenced by the power input and neutral gas pressure. In the present work, a 2-D hybrid electron fluid-particle ion model has been developed to simulate one of the high density plasma sources-an Electron Cyclotron Resonance (ECR) plasma system with various pressures and power inputs in a non-uniform magnetic field. By means of numerical simulation, the energy distributions of argon ion impacting on the wafer are obtained and the plasma density, electron temperature and plasma electrostatic potential are plotted in 3-D. It is concluded that the plasma density depends mainly on both the power input and neutral gas pressure. However, the plasma potential and electron temperature can hardly be affected by the power input, they seem to be primarily dependent on the neutral gas pressure. The comparison shows that the simulation results are qualitatively in good agreement with the experiment measurements.

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THE ION CURRENT BEHAVIOR IN ECR ARGON PLASMA YAO XIN-ZI, JIANG DE-YI, REN YU-FENG 1994, 3 (10):  758-763.  doi: 10.1088/1004-423X/3/10/005 Abstract ( 0 )   PDF (184KB) ([an error occurred while processing this directive])   The ion current density as a function of various system parameters, such as pressure, magnetic field, and microwave power, has been studied by using Faraday cup. The bistability of plasma was observed and discussed.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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A NEUTRON POWDER DIFFRACTION STUDY OF THE STRUCTURE IN Nd2Fe17Nx(x = 2.5, 3.0, 5.5) YAN QI-WEI, ZHANG PAN-LIN, SUN XIANG-DONG, WEI YU-NIAN, SUN KE, HU BO-PING, WANG YI-ZHONG, LIU GUI-CHUAN, GOU CHENG, CHENC YU-FEN, CHEN DONG-FENG 1994, 3 (10):  764-768.  doi: 10.1088/1004-423X/3/10/006 Abstract ( 0 )   PDF (118KB) ([an error occurred while processing this directive])   The crystallographic and magnetic structures of Nd2Fe17Nx(x = 2.5, 3.0, 5.5) at room temperature were refined by Rietveld analysis of neutron powder diffraction data. We found that Nd2Fe17Nx has a Th2Zn17 type structure (S.G. R3m) and the nitrogen atoms occupy both 9e and 18g sites simultaneously and at different rates.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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QUANTUM PERCOLATION AND BALLISTIC CONDUCTANCE IN A SYSTEM OF DOUBLE-COUPLED CHAINS FAN XU-DONG, GU BEN-YUAN, YANG GUO-ZHEN, LIN ZONG-HAN 1994, 3 (10):  769-779.  doi: 10.1088/1004-423X/3/10/007 Abstract ( 0 )   PDF (321KB) ([an error occurred while processing this directive])   The quantum-mechanical calculation of electronic conductance in double-coupled chains as a function of the interchain bonding probability p is presented. The calculated results show that one still can see the basic plateaus in the ensemble-averaged conductance curves as a function of the Fermi energy for the weak disorder. In addition, dense irregularly oscillating structures are superimposed upon each plateau. The characteristics of the conductance are very sensitive to the presence of the interchain broken bonds. For the strong disorder (p≈0.5) the conductance quantization breaks down. The accuracy of the quantization conductance rapidly drops down as the value of p approaches 0.5. The ensemble-averaged value of the logarithmic conductance as a function of the sample length exhibits a linear variation, determining a localization length. Both the localization length and the root-mean- square (RMS) value of the conductance fluctuations depend on p and the Fermi energy of electrons. The variations of the localization length and RMS with p are both of an approximate parabolic function around p≈0.5. No percolation transition is found for this quasi-one-dimensional system, as expected.

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TEMPERATURE DEPENDENCE OF ANISOTROPY IN Co/X(Pt, Au, Ag, Ni) MULTILAYER FILMS ZHANG HUI-YUN, WANG YIN-JUN 1994, 3 (10):  780-787.  doi: 10.1088/1004-423X/3/10/008 Abstract ( 0 )   PDF (260KB) ([an error occurred while processing this directive])   Temperature dependences of effective perpendicular anisotropy (PA) Ku and inter-face energy Ks for Co/X(Pt, Au, Ag, Ni) multilayer films(MFs) as well as of spontaneous magnetization Ms for Co/Pt and Co/Au MFs are reported. The dependence of Ks on T dis-tinguishes between Go/Au, Co/Ni and Co/Pt, Co/Ag MFs, i.e., Ks of the former decreases with the increase of T, but it increases for the latter. Co/Pt MFs with the perpendicular anisotropy possess a large enhancement of Ms at low temperature, but there is not any en-hancement for Co/Au MFs. We have discussed the source of PA in Co/Au and Co/Pt MFs and speculated that the strain due to the lattice mismatch may be the main cause of PA in Co/Au MFs, but it is not for Co/Pt MFs.

CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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A MODIFIED METHOD OF DETERMINING FRACTAL DIMENSIONS OF POLYMERS AND BIOPOLYMERS XIAO YI, YAO KAI-LUN 1994, 3 (10):  788-792.  doi: 10.1088/1004-423X/3/10/009 Abstract ( 0 )   PDF (136KB) ([an error occurred while processing this directive])   A modified method of calculating the end-to-end distance of segments with a given number of units in a single polymer chain is presented and numerical studies of some fractals by using Havlin and Ben-Avraham's and our methods are given. The results show that our method can remove the fluctuations in the end-to-end distances of the segments arising in Havlin and Ben-Avraham's method.