Table of contents

20 November 1993, Volume 2 Issue 11 Previous issue    Next issue

ATOMIC AND MOLECULAR PHYSICS

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STUDIES ON HYPERFINE STRUCTURE AND ISOTOPE SHIFT OF SOME EXCITED STATES IN Yb AND Tm ATOMS JIANG ZHAN-KUI (蒋占魁), PENG WEI-XIAN (彭慰先), GUO CHUAN (郭川), YU YING-NING (于英宁), YU HUA (于华) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  801-806.  DOI: 10.1088/1004-423X/2/11/001 Abstract ( 1336 )   PDF (159KB) ( 451 )   The hyperfine structures and isotope shifts in some excited states of Yb and Tm have been measured using laser-atomic beam interaction, stepwise excitation and fluorescence detection techniques. From the experimental results, magnetic dipole hyperfine constants A and electric quadrupole hyperfine constants B have been derived. So for as we know, the A factor of [4f125d6s6p]9/2 level in Tm is given for the first time.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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DEPOSITION OF HIGH QUALITY AMORPHOUS SILICON FILMS WITH STRONG HYDROGEN DILUTED SILANE AS REACTANT GAS SOURCE HE YU-LIANG (何宇亮), LIU XIANG-NA (刘湘娜), YIN CHENG-ZHONG (殷晨钟), ZHANG YU (张昱) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  807-815.  DOI: 10.1088/1004-423X/2/11/002 Abstract ( 1286 )   PDF (235KB) ( 518 )   By using strongly hydrogen diluted silane as a reactant gas source [C(=SiH4/(SiH4+H2))<5%] in a conventional diode PECVD system, we have deposited high quality a-Si:H films which exhibit almost no Steable-Wronski (S-W) effect, The [H] radical in rf plasma erodes the growing surface and eliminates the weak Si-Si bonds, thus re-ducing the density of metastable defects of a-Si:H films and causing the amorphous network to be more perfect. Our results show that as C value decreases from 5.4 % to 0.8 %, the peak location of TO mode in Raman spectra changes from 480 to 500 cm-1, the average distortion of bond angles $\Delta\theta$, which is calculated from the width of half full height of TO peaks, reduces from 9.0° to 3.8°. The hydrogen content CH of the samples which show almost no S-W effect is less than 10at%.

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ELLIPSOMETRIC SPECTRA OF CONDUCTING POLYANILINE LIN YONG-YAO (林永耀), MO DANG (莫党), GONG KE-CHENG (龚克成), ZHANG GUI-PING (张贵萍) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  816-824.  DOI: 10.1088/1004-423X/2/11/003 Abstract ( 1220 )   PDF (231KB) ( 412 )   We report the ellipsometric spectrum studies on a new kind of conducting polymers, polyaniline. In the UV-visible range (1.4-4.8eV photon energy region) the absorption coef-ficient, the complex dielectric function and the refractive index of polyaniline as functions of photon energy are obtained. The spectra of nonconducting and fully conducting polyaniline have been analyzed and discussed. The experimental results show that the emeraldine base form of polyaniline has a large energy gap (Eg～3.6eV) and its absorption spectrum shows a broad exciton absorption peak centered at 2 eV. The absorption spectrum of emeraldine salt after protonation have four absorption peaks centered at 1.5, 1.83, 3.0 and 3.88eV. We also investigated the spectrum evolution of the samples from nonconducting ($\sigma$<10-9$\Omega$-1·cm-1) to conducting ($\sigma$≈10+1$\Omega$-1·cm-1) states, and give the dielectric function and the refractive index of the samples.

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THE THERMAL BEHAVIOR OF TWO-COMPONENT PIEZOELECTRIC SINGLE CRYSTAL ALUMINIUM GALLIUM PHOSPHATE Al1-xGaxPO4 XIA HAI-RUI (夏海瑞), ZOU ZHI-QIANG (邹志强), ZHANG PEI-LIN (张沛霖), QIN ZI-KAI (秦自楷) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  825-832.  DOI: 10.1088/1004-423X/2/11/004 Abstract ( 1361 )   PDF (183KB) ( 422 )   The temperature properties of elastic, piezoelectric and dielectric constants for the single crystal Al0.88Ga0.12PO4 have been studied in detail over a temperature range from 150 to 410K. And two crystal plates with different orientations which have zero temperature coefficient are introduced. As might have been expected, the single crystal Al1-xGaxPO4 is a new kind of materials applicable to the surface acoustic wave devices.

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A STUDY ON SECONDARY DEFECTS IN SELF-ION IMPLANTED Si TIAN REN-HE (田人和) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  833-840.  DOI: 10.1088/1004-423X/2/11/005 Abstract ( 1208 )   PDF (284KB) ( 436 )   By using the cross-sectional transmission electron microscopy (XTEM), Rutherford backscattering (and channeling) spectrometry (RBS) and high-energy electron beam irra-diation technology with a high voltage electron microscope (HVEM), secondary defects in self-ion implanted Si has been studied. The result shows that the depths of secondary de-fect bands are related to the implantation energies, and the values of depths are slightly greater than the projected ranges of self-ions implanted into Si. In the higher energy region (>1MeV), the former exceeds the latter by nearly 0.2-0.4μm. Experiments indicate that the pre-implantation damage (the primary defect), on one hand, will superpose on the primary defects of post-implantations and make secondary defects increase, and on the other hand, it will also provide an enhanced-diffusion region for vacancies and interstitials created by the post-implantation and reduce the formation of secondary defects. Experiments also show that dislocation loops in secondary defect bands of self-implanted Si are interstitial in nature.

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STUDY ON PREPARATION OF UV CROSS-LINKING FILMS OF POLYURETHANE-LiClO4 COMPLEXES AND THEIR IONIC CONDUCTIVITY WU CHENG-PEI (吴承佩), LIU WAN-YU (刘皖育), LI XU-HUI (厉旭辉), XU KUI (徐葵), YU WEN-HAI (俞文海) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  841-849.  DOI: 10.1088/1004-423X/2/11/006 Abstract ( 1202 )   PDF (220KB) ( 411 )   The complexes of polyurethane containing double bonds with LiClO4 were formed, and cross-linked films were produced by UV radiation, All of the films were uniform, transparent, flexible and smooth-faced with a considerable mechanical strength. The ionic conductivities of the films of several series of polymers with different molecule weights of PEG segment were measured, of which the highest is 8.09×10-5S·cm-1 at 300K under anhydrous atmosphere. Also the conductivity is deeply influenced by the molecule weight of the soft segment PEG of the polyurethane and the content of LiClO4. The transport number of Li+ is about 0.57. Structure characteristic measurement much as DSC, XRD, IR etc., have been done and the conductive mechanism is discussed.

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

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POSITRON LIFETIME STUDIES OF Y1-xCaxBa2Cu3O7-$\delta$ AND Y1-xCaxBa2Cu3-xFexO7-$\delta$ XU ZHU-AN (许祝安), CAI MENG (蔡盟), ZHANG XIAO-JUN (张小俊), ZHANG QI-RUI (张其瑞), ZHOU XIAN-YI (周先意) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  850-856.  DOI: 10.1088/1004-423X/2/11/007 Abstract ( 1384 )   PDF (189KB) ( 359 )   In this paper it is reported that the measurement of the bulk positron lifetime as a function of substitution content x in the temperature range from 70 to 220K was performed in two high-Tc superconducting systems, Y1-xCaxBa2Cu3-xFexO7-$\delta$ and Y1-xCaxBa2Cu3O7-$\delta$. It was found that $\tau$B of both systems decreases significantly with x and the temperature dependence of $\tau$B is very weak in normal state. In lower temperature region (Tc), a dramatic x-dependent temperature variation of $\tau$B was observed in the Ca-substituted system: from a decrease of $\tau$B with decreasing T to an increase of $\tau$B. With increasing x, the temperature dependence of $\tau$B remains weak in the Ca- and Fe- substituted systems. Compared with the experimental data of positron lifetime in other substituted systems and the calculation of the positron density distribution, the authors suggest that positron bulk lifetime spectra behaviour can be interpreted by the physical model based on the transfer of electron density between the CuO2 planes and Cu-O chains. Therefore, the study of positron lifetime spectra provides a useful means to detect the local charge density and to study the correlation between the electronic structure and the high-Tc superconductivity.

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CRITICAL CURRENT DENSITY OF Y-Ba-Cu-Sn-O SUPERCONDUCTORS FENG YONG (冯勇), ZHOU LIAN (周廉), WANG KE-GUANG (王克光), DU MING-HUAN (杜明焕), ZHANG YU-HENG (张裕恒), LU YA-FENG (卢亚锋), JIN XIN (金新), ZHANG YI-TONG (张贻瞳), JIN JI-RONG (金继荣), YAO XI-XIAN (姚希贤) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  857-862.  DOI: 10.1088/1004-423X/2/11/008 Abstract ( 979 )   PDF (136KB) ( 470 )   The magnetic curves of bulk Y-Ba-Cu-Sn-O have been studied in the temperature range 60-77K and in fields up to 2.4T. The results indicate that Jc varies with the magnetic field as a power law and decreases exponentially with temperature. The critical current density Jc can be improved by the substitution of Sn for Cu.

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ANNIHILATION OF VERTICAL-BLOCH-LINE CHAINS IN THE WALLS OF THE SECOND KIND OF DUMBBELL DOMAINS SUBJECTED TO AN IN-PLANE FIELD TANG GUI-DE (唐贵德), NIE XIANG-FU (聂向富), SUN HUI-YUAN (孙会元), MENG GUANG-QING (孟广庆), HAN BAO-SHAN (韩宝善) Acta Physica Sinica (Overseas Edition), 1993, 2 (11):  863-869.  DOI: 10.1088/1004-423X/2/11/009 Abstract ( 1153 )   PDF (234KB) ( 461 )   An experiment was statistically performed on the annihilation of vertical-Bloch-line (VBL) chains in the walls of the second kind of dumbbell domains (ⅡDs) subjected to an in-plane field Hip. It was again confirmed that there is a critical in-plane field H′ip, above which all VBL chains of hard domains in garnet bubble films, including ⅡDa, disappear. Just like ordinary hard bubbles (OHBs), it was also found that there exists a critical range of Hip, from (Hip)ID to H′ip, for ⅡD softening. Over this range, with the increase of Hip, more and more ⅡDs are softened, accompanied by the successive appearance of the first kind of dumbbell domains, OHBs and soft bubbles. In addition, for the five samples tested, the ratio, H′ip/(Hip)ID, is obviously greater than 21/2.