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Volume 5 Issue 4
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Original Articles
A SIMULATION STUDY OF LOW ENERGY SPUTTERING ANGULAR DISTRIBUTION
ZHENG Liping*, **, CUI Fuzhai**, ***
Chin. Phys. Lett. 1988, 5 (4): 145-148 .  
Abstract   PDF(pc) (42KB) ( 457 )
The low energy sputtering angular distributions are simulated in inert gas ion-metal target combinations. It is found that the angular distribution of PKAs trends to an under-cosine shape, while the angular distribution of SKAs shows either a cosine one or an over-cosine one: the formation of the under-cosine sputtering angular distribution seems to come from the smaller mass ratio and the lower incident energy.
ANALYSIS OF THE INSTABILITY AND PHASE TRANSITION OF THE COMPOUND La2CuO4
ZHANG Min*, TAO Ruibao, ZHOU Shixun**
Chin. Phys. Lett. 1988, 5 (4): 149-152 .  
Abstract   PDF(pc) (40KB) ( 428 )
The phase transition for La2CuO4 changing from I4/mmm to Cmca with cell-doubling has been analysed within the frame work of Landau's theory. It is a second order transition via softening of the optical breathing mode, coupling with a slight lattice distortion arising from the softening elastic mode based on electron-phonon interaction.


THERMAL EXPANSION COEFFICIENT OF SINGLE PHASE SUPERCONDUCTOR YBa2Cu3O7-δ
RUAN Yaozhong, LI Liping, HU Xuelong, MAO Xianglei MENG Guangyao*, PENG Dingkung*, HU Junbao*, ZHANG Yuheng
Chin. Phys. Lett. 1988, 5 (4): 153-156 .  
Abstract   PDF(pc) (42KB) ( 404 )
The thermal expansion coefficient of single phase superconductor YBa2Cu3O7-δ was measured by the method of differential parallel-plate capacitance. An obvious decrease of volume near 205K and a small jump of the thermal expansion coefficient at Tc were observed. The pressure effect was also estimated.


EFFECT OF SULPHUR AND CARBON SEGREGATION ON CHEMICAL BONDING OF GRAIN BOUNDARIES IN BCC METAL IRON
WU Xijun, HU Bin, ZHENG Qingqi
Chin. Phys. Lett. 1988, 5 (4): 157-160 .  
Abstract   PDF(pc) (49KB) ( 433 )
The effect of sulphur and carbon impurity segregation on chemical bonding of grain boundaries for b.c.c. metal iron was investigated using the self-consistent field Xα discrete variational method. A relaxed trigonal-prism cluster was used as one of the structural units of the grain boundaries. The grain boundary embrittlement, which is caused by impurity segregation, is interpreted by the electron charge transfer from neighbouring iron atoms onto impurity atoms, and by the characteristics of empty levels in the energy bands of the segregated grain boundaries.

FAR INFRARED REFLECTION MEASUREMENT OF THE ENERGY GAP OF YBa2Cu3O9-δ
YE Hongjuan, LU Wei, YU Zhiyi, SHEN Xuechu(S.C.Shen), MIAO Baicai*, CAI Yiming*, QIAN Yongjia*
Chin. Phys. Lett. 1988, 5 (4): 161-164 .  
Abstract   PDF(pc) (52KB) ( 380 )
The superconducting energy gap of YBa2Cu3O9-δ(Tc=90K) has been measured by means of far infrared reflection spectra. The value of 2Δ /kTc is between 2.2 and 3.4. According to the analysis of the dielectric function derived from K-K relations, we suggest that the energy gap value would be less than 18.8meV( 150cm-1). The temperature dependence of the energy gap Δ(T) is also obtained.
THEORETICAL INVESTIGATIONS ON COMPOSITION AND PRESSURE DEPENDENCES OF SUPERCONDUCTIVITY FOR VARIOUS OXIDE SYSTEMS
ZHAO Guomeng, WANG Ruilan, LI Hongcheng, DONG Ziwen, LI Lin
Chin. Phys. Lett. 1988, 5 (4): 165-168 .  
Abstract   PDF(pc) (0KB) ( 109 )
On the basis of band calculation results and a universal superconducting mechanism for oxide systems proposed previously by the authors, the superconducting transition temperatures are calculated for Ba(Pb1-xBix)O3 with x=0 and 0.1, which are in good agreement with experimental results. The composition and pressure dependences of Tc and normal state resistivity in various oxide systems can be interpreted.
WORK FUNCTION AND ELECTRONIC STRUCTURE OF Co OVERLAYERS ON THE ION SPUTTERED BASAL FACE OF MoS2 SINGLE CRYSTAL
HU Yongjun, LIN Zhangda, XIE Kan, WU Naijuan
Chin. Phys. Lett. 1988, 5 (4): 169-172 .  
Abstract   PDF(pc) (45KB) ( 372 )
Work function and photoemission spectroscopy have been applied to the study of the interaction of Co overlayers with the ion sputtered basal face of MoS2(0001). The experimental results show that upon Co deposition the work function of the MoS2 substrate drops rapidly and reaches a minimum value of -0.65eV for ΔФ, and then increases to the metal Co work function at coverages greater than a monolayer. The Fermi level pinning at 2.2eV above the Mo 4dz2 peak has been found at a low submonolayer coverage.
NUCLEATION AND GROWTH OF ULTRAFINE PARTICLES AND CONDITIONS OF EPITAXY
WU Quande
Chin. Phys. Lett. 1988, 5 (4): 173-176 .  
Abstract   PDF(pc) (42KB) ( 289 )
The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates. The physical picture of ultrafine particle growth are explained., Conditions of epitaxial growth are also discussed.
EXPERIMENTAL STUDY OF SELF QUENCHING STREAMER DISCHARGE
LI Zhongzhen, TANG Xiaowei*
Chin. Phys. Lett. 1988, 5 (4): 177-180 .  
Abstract   PDF(pc) (50KB) ( 401 )
A systematic experimental study on the self quenching streamer discharge has been performed. The dependence of the charge developed in the discharge on the high voltage can be approximated by a linear relation. The concentration of quenching gas and anode diameter have little influence on the slope of this linear relation.
POSITRON ANNIHILATION STUDY ON HIGH TC SUPERCONDUCTORS Y-Ba-CU-O
ZHU Jingsheng, YANG Zhongjin*, SONG Jian xian, ZHOU Xianyi, WANG Jun, WANG Yanfang
Chin. Phys. Lett. 1988, 5 (4): 181-184 .  
Abstract   PDF(pc) (53KB) ( 348 )
The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated. The lineshape parameters as a function of temperature were measured from 85K to 300K. Anomalous dependence of lineshape parameters on temperature was first observed in polyphase samples, i. e., the lineshape parameters occurred catastrophe for some narrow temperature regions (90K. 107K, 115K and 180K). This anomaly is probably due to the migration and redistribution of oxygen vacancies in the samples during superconducting transition.
LOW AND AUDIO FREQUENCY INTERNAL FRICTION IN HIGH Tc Y-Ba-Cu-O SYSTEM
CHEN Tingguo, ZHANG Jihua, HUANG Ji, CHEN Yuan, YANG Minjie, XIE Xiaoming, LI Tingwei, Xie Leiming
Chin. Phys. Lett. 1988, 5 (4): 185-188 .  
Abstract   PDF(pc) (44KB) ( 366 )
Low and audio frequency internal friction ( IF) measurements in Y1Ba2Cu3O7-x system showed five IF peaks at 110, 200(2430Hz), 220, 393 and 477K( ~ 1Hz )respectively. The 477K peak rises gradul1y with the escaping of oxygen atoms from the specimen during measuring process in vacuum and shifts to higher temperature with increasing frequency. The 477K peak is attributed to the diffusional relaxation process of oxygen atoms related to the one-dimensional Cu-O chains in the orthorhombic phase.
THE ANOMALOUS HALL EFFECT IN THE METAL-TYPE AMORPHOUS InSb FILM
CAO Xiaowen, ZHAO Dianfeng, ZHANG Yuheng*
Chin. Phys. Lett. 1988, 5 (4): 189-191 .  
Abstract   PDF(pc) (32KB) ( 472 )
An anomalous Hall effect was found experimentally in the metaltype amorphous InSb in which the carrier concentration was about 1018 - 1019 cm-3.The result showed that electron-electron interaction was found experimentally in amorphous metal for the first time. It also means that the conduction electrons are magnetic-frozen out. It is surprising that the magnetic field at which the conduction electrons are frozen out is only about 1kG.

12 articles