Table of contents

20 February 1996, Volume 5 Issue 2 Previous issue    Next issue

CLASSICAL AREAS OF PHENOMENOLOGY

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PHOTODIFFRACTIVE EFFECTS IN SEMICONDUCTOR MICROSTRUCTURES PAN SHI-HONG (潘士宏), GUO RU (郭儒), XIE MING-MIN (谢明敏), ZHANG GUANG-YIN (张光寅) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  81-89.  DOI: 10.1088/1004-423X/5/2/001 Abstract ( 1112 )   PDF (230KB) ( 413 )   We have investigated the photodiffractive effect induced by resonant excitations in semiconductor microstructures by means of the multiple wave coupling method. We have derived set of multiple wave coupling equations for photodiffractions in the case of coexistence of refraction and absorption gratings. Numerical results of the equations for a few typical cases have been analysed in detail, and their physical significance is also discussed.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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ELECTRON DIFFUSION IN A NON-UNIFORM ELECTRIC FIELD AND A UNIFORM MAGNETIC FIELD WEI HE-LIN (魏合林), LIU ZU-LI (刘祖黎), YU BO-MING (郁伯铭), LI ZAI-GUANG (李再光) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  90-99.  DOI: 10.1088/1004-423X/5/2/002 Abstract ( 1203 )   PDF (294KB) ( 441 )   A Monte Carlo simulation technique has been used to model the electron transport beharlot, especially the electron diffusion motion, in the cathode fall region of a glow discharge under the influence of a non-uniform electric field and a transverse magnetic field perpen-dicular to the cathode sheath electric field. Three types of collisions (elastic, excitation and ionization) are taken into account in our model. The electron free flying time is determined by the electron-neutral atom collision frequency. We focus attention on the electron diffusion distance and velocity. The electron-neutral atom collision processes and the electron drift velocity are also studied. The results indicate that with the increase of the magnetic field the electron diffusion distance increases and the electron diffusion velocity decreases. The results Mso show that the collision processes are enhanced by the magnetic field, this is in agreement with the experimental result. However, the axial magnetic field does not affect the electron transport behavior.

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ELECTRON TRANSPORT BEHAVIOR IN NORMAL AND ABNORMAL DIRECT CURRENT DISCHARGE CATHODE SHEATH WEI HE-LIN (魏合林), LIU ZU-LI (刘祖黎), LIU DA-MIANG (刘大明), LI ZAI-GUANG (李再光), LU DONG-SHENG (陆冬生) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  100-112.  DOI: 10.1088/1004-423X/5/2/003 Abstract ( 1227 )   PDF (369KB) ( 860 )   This paper studies the electron transport behavior in normal and abnormal helium direct current (dc) glow discharges using a Monte Carlo simulation, in which the influences of the electron initial energy and cathode surface reflection on the electron swarm behavior are considered. The electron-neutral atom collision processes and the electron swarm parameters (such as the number of collisions, collision rates, ionization coefficient, mean drift velocity, electron density, etc.) are analyzed. The results show that the variations of the initial energy of the electron emitted from the cathode and the cathode reflection cause a weak effect on the electron transport parameters in the two discharges. The results also indicate that the electron transport parameters are quite different in normal and abnormal discharges.

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

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SYNTHESIS AT AMBIENT PRESSURE AND SUPERCONDUCTIVITY OF Hg-DOPED TI-BASED DOUBLE [(T1, Hg)-O]-LAYERED CDPHATES CHEN ZU-YAO (陈祖耀), WEI QIN-QIAO (魏青桥), CAO GUANG-HAN (曹光旱), QIAN YI-TAI (钱逸泰), ZHANG YONG-JIAN (张永健), WANG CHENG-YOU (汪成友), WANG NAN-LING (王楠林), CAO LIE-ZHAO (曹烈兆), CHEN ZHAO-JIA (陈兆甲) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  113-119.  DOI: 10.1088/1004-423X/5/2/004 Abstract ( 1090 )   PDF (211KB) ( 399 )   The Hg-doped T1-based 2201 and 2212 phase layered cuprates have been successfully syn-thesized at ambient pressure and identified by X-ray powder diffraction and electron diffraction analysis. Compared with pure T1-based 2212 phase compound, there are indications that the corresponding Hg-doped T1-based compound (T11.8Hg0.2)Ba2CaCu2Oz exhibits much higher Tc (> 132K).

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INFLUENCE OF IN-PLANE FIELD ON THE CRITICAL TEMPERATURE FOR THE BREAKDOWN OF VERTICAL BLOCH LINE CHAINS HAN BAO-SHAN (韩宝善), HUO SHU-GUO (霍素国), ZHANG HONG-YUAN (张宏愿), MENG GUANG-QING (孟广庆) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  120-125.  DOI: 10.1088/1004-423X/5/2/005 Abstract ( 1166 )   PDF (188KB) ( 393 )   The influence of in-plane field Hip on the critical temperature T0 for the breakdown of vertical Bloch line (VBL) chains of hard domains in garnet bubble films has been inves-tigated experimentally. It was found that T0 can be significantly reduced by the increase of Hip. Besides, the critical in-plane field H′ip for the breakdown of VBL chains was measured as a function of temperature T for the same sample. As a result, the correlation between these two critical parameters, T0 and H′ip, was found. By introducing an effective in-plane field (Hip)e, the positive definiteness of the system of VBL pairs with two-dimemsional magnetization distribution was analyzed, giving rise to a theoretical expression of H′ip(T): H′ip(T) =|4$\pi$MsQ(a0+a1Q +a2Q2+a3Q3+ a4Q4)|T(T0(Hip=0)), where ai are constants. It agrees well with the experiments.

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MAGNETIC POLARIZATION OF Pd SPACERS AND OSCILLATORY EXCHANGE COUPLING BETWEEN Fe AND Pd LAYERS IN Fe/Pd MULTILAYERS MEI LIANG-MO (梅良模), LI MIN (李民), XIE SHI-JIE (解士杰), LIU YI-HUA (刘宜华), XU RONG-LI (徐荣历) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  126-142.  DOI: 10.1088/1004-423X/5/2/006 Abstract ( 1190 )   PDF (407KB) ( 416 )   Ay oscillatory behavior in specific saturation magnetization of Fe/Pd multilayers is observed. The conversion electron M$\ddot{\rm o}$ssbauer spectroscopy and other experiments indicate that this behavior is caused by the magnetic polarization of Pd spacers, which alternates between positive and negative polarization with respect to the magnetic moments of Fe layers. The interlayer coupling between two Fe layers always keeps ferromagnetic. Then, the interlayer couplings in ferromagnetic metal/nearly ferromagnetic metal multilayers were calculated By using the model of Barnas. The results of calculation prove that the above phenomenon might appear under some condition. The influence of magnetic polarization potential of spacers and interface chemical potential on the interlayer couplings is also discussed.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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GROWTH OF PREFERENTIALLY ORIENTED CUBIC BORON NITRIDE FILMS BY CHEMICAL VAPOR DEPOSITION GUO YONG-PING (郭永平), SONG ZHI-ZHONG (宋志忠), LI GONG-CHUAN (李公川), CHEN GUANG-HUA (陈光华) Acta Physica Sinica (Overseas Edition), 1996, 5 (2):  143-150.  DOI: 10.1088/1004-423X/5/2/007 Abstract ( 945 )   PDF (245KB) ( 332 )   Preferentially oriented cubic boron nitride films on nickel substrates have been grown using hot-filament-assisted rf plasma chemical vapor deposition method. X-ray photoelectron spectroscopy shows that the cubic boron nitride films are stoichiometric. Scanning electron microscopy and X-ray diffraction show that the films are of high quality with well-faceted and (220) preferentially oriented grains, without X-ray diffraction detectable hexagonal boron nitride phase. The nucleation and growth process has been investigated. After 40min deposition, well aligned, well faceted cubic boron nitride nuclei can be seen on the substrnies, and after 2 h deposition, the rectangular grains can be seen on the substrate with their corresponding edges parallel to each other in scanning electron microscopic images. The ratio of the diffraction peak height of (220) face to that of (111) face is about 5.2 in the X-ray diffraction pattern, but the corresponding value of the random cubic boron nitride crystallites is only 0.06.