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Volume 9 Issue 9
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Original Articles
A Transition from DBM to FractaIs Generated by Random Successive Nuclelation Model
ZHAO Yadun, WU Ziqin*
Chin. Phys. Lett. 1992, 9 (9): 449-452 .  
Abstract   PDF(pc) (188KB) ( 379 )
We present a random successive nucleation model to simulate the formation of the dense branching morphology (DBM) found in amorphous Al-Ge alloys. Our simulation shows that the DBM is obtained when the parameter K accounting for the structures of alloy films is small, and that a transition from DBM to
fractals is found as K increases.

Limits on Heavy Neutrino Mass from Neutrinoless ββ Decays of 76Ge and 82Se
WU Huifang, SONG Changliang
Chin. Phys. Lett. 1992, 9 (9): 453-455 .  
Abstract   PDF(pc) (163KB) ( 410 )
With calculated nuclear shell-model wave functions, the nuclear matrix elements of the 0vββ decay mediated by heavy Majorana neutrino in 76Ge and 82Se are discussed. The results show that the lower limit of heavy neutrino mass is about α2 x l06 GeV with a mixing parameter α.

Modified Eikonal Approximation for K-Shell Capture in Asymmetric Ion-Atom Collisions
KUANG Yurang(KUANG Yu-Rang)*, YANG Qifeng, GUAN Hanqing
Chin. Phys. Lett. 1992, 9 (9): 456-458 .  
Abstract   PDF(pc) (136KB) ( 327 )
A modified eikonal approximation is developed by introducing an eikonal phase factor into the previous model-potential Oppenheimer-Brinkman-Kramers (MPOBK) approximation. The present calculation shows an obvious improvement on the MPOBK calculation for H+-Ne collisions at intermediate energies.

Spin Polarization Electrons of Elastically Scattered from Hg Atom
YUAN Jianmin, ZHANG Zhijie
Chin. Phys. Lett. 1992, 9 (9): 459-462 .  
Abstract   PDF(pc) (194KB) ( 408 )
Calculations on differential cross sections and spin polarization parameters of elastical electron scattering with Hg atoms are performed for electrons in the energy range from 0.5 to 150eV. Dirac equation is used to describe the motion of scattered electrons in the target field, which includes static, exchange and correlation-polarization interactions. The agreement between theory and experiment is generally good.
Xenon Flash Lamp Pumped Self-Frequency Doubling NYAB Q-Switched Laser
ZHANG Xingyu, ZHAO Shengzhi, WANG Qingpu, LIU Hua, LU Baosheng*, PAN Hengfu*
Chin. Phys. Lett. 1992, 9 (9): 463-466 .  
Abstract   PDF(pc) (178KB) ( 806 )
By using xenon flash lamp as pumping light source and BDN dye film as passive Q-switch or KD*P crystal as active Q-switch, we have, for the first time, realized Q-switching run from 1.06μm to 0.53μm in the NdxY1-xAl3 (BO3)4(NYAB) self-frequency doubling laser and obtained MW/cm2 giant pulse out-put at 0.53μm wavelength. Meanwhile, the green light output energy and pulse duration were measured under the conditions of different resonator lengths and pumpings. The experimental results are in agreement with the numerical solutions of the Q-switching coupling wave rate equations. Moreover, the ways of improving the green laser output peak power are proposed.

Electric Conductivity Profile Determination in Tokamak with Modulated Weak Toroidal Electric Field
XU Yan, HAN Gonghe, ZHENG Shaobai
Chin. Phys. Lett. 1992, 9 (9): 467-470 .  
Abstract   PDF(pc) (158KB) ( 458 )
In this paper the analytical relations between the electric conductivity profile of plasma in tokamak and the measured ac conductance are given with which the electric conductivity profile of CT-6B tokamak is determined.

Discussion of Solid C60 Upon Lennard-Jones Potential
JIANG Zongfu, LAI Wuyan
Chin. Phys. Lett. 1992, 9 (9): 471-474 .  
Abstract   PDF(pc) (219KB) ( 1050 )
The properties of solid C60 (fcc C60) are discussed based upon Lennard-Jones potential U(R) = ε[(σ/R)12 - (σ/R)6]. The magnitude of the constant ε is estimated by using the standard result of electrostatics for the interaction of two dipole moments of C60 molecules. The cohesive energy and bulk modulus of the solid fullerenes are calculated by classical theory.

Light Induced Rapid Thermal Diffusion of Boron Atom in Silicon
SHI Wanquan, HOU Qingrun, LIU Xuejun, LIU Shixiang, FU Zhengqing, LU Liwu*, LI Yuanjing*
Chin. Phys. Lett. 1992, 9 (9): 475-478 .  
Abstract   PDF(pc) (151KB) ( 397 )
We have studied the light induced rapid thermal diffusion of boron atom in silicon. The samples were heated by the rapid thermal processor. We have carried out spreading resistance and deep level transient spectroscopy (DLTS) measurements. The impurity distribution profile is much shallower and steeper than that of conventional thermal diffusion and the diffusion depth can be con-trolled to 0.1μm. Several peaks in the deep level transient spectra were detected and the density of these defects ranges from 0.5 x 10 12 to 5.6 x 10 12/cm3. The passivation and annihilation of these defects have been studied. We have also made the planar diode whose diameter is 500μm. The reverse current and the back breakdown voltage of the planar diode are 10 -9 A and 80V respectively.
Trap Behaviors of Constant Electric Field Stressing in Thin Oxynitride and Re-oxidized Oxynitride Films
YANG Bingliang (B. L. Yang), LIU Baiyong (B. Y. Liu), H. Wong*, Y. C. Cheng*
Chin. Phys. Lett. 1992, 9 (9): 479-482 .  
Abstract   PDF(pc) (218KB) ( 532 )
The behaviors of constant electric field stressing of the thin (200Å) oxynitride and re-oxidized oxynitride films are investigated. The flat-band shift is not a simple function of the stressing field. The observed phenomena are attributed to the significance of trap filling, electronic tunneling and trap generation at different stressing field strengths. Re-oxidized sample is found to have high resistant to the electron tunneling and trap generation.
Photoemission Evidence for Dilute K-doped Phase Kx C60 with x<0.2
WANG Zuquan, LIU Fengqin, DENG Junzhuo, YAO Jun, XUN Kun, LÜ, Sihua, WU Sichengi, JIANG Mingluo, GU Zhengnan, ZHOU Xihuang
Chin. Phys. Lett. 1992, 9 (9): 483-486 .  
Abstract   PDF(pc) (211KB) ( 497 )
A shift about 0.3eV to higher binding energy is reported in the valence band and Cls core level of Kx C60(x<0.2). Analysis shows that the result could not be interpreted by a mixture of C60 and K3 C60. A dulite K-doped phase and fermi level pinning near the lowest unoccupied molecular orbital derived band
caused by K-doping are proposed.

Oscillatory Interlayer Magnetic Exchange Coupling Through Chromium Layers
PENG Chubing, DAI Chen, DAI Daosheng
Chin. Phys. Lett. 1992, 9 (9): 487-490 .  
Abstract   PDF(pc) (244KB) ( 482 )
The evidences o f antiferromagnetic interlayer exchange coupling in Ni80Fe20/Cr multilayers are reported. In Ni80Fe20/Cr multilayers, both the magnitude of the interlayer magnetic exchange coupling and the saturation rnagnetoresis-tance were found to oscillate with the Cr spacer layer thickness with a period of about 13Å. Moreover, temperature dependence of magnetization shows a much larger thermal hysteresis for an antiferromagnetically coupled film than that for a ferromagnetically coupled film; in addition, zero magnetization occurs at 1.5 K in small magnetic field of 100 Oe for an antiferromagnetic film.

Low Energy Positron Beam Apparatus for Near-surface Studies and Its Application
GUO Xuezhe, WENG Huimin, HAN Rongdian
Chin. Phys. Lett. 1992, 9 (9): 491-494 .  
Abstract   PDF(pc) (234KB) ( 594 )
A low-energy positron beam apparatus has been designed and constructed. The beam can deliver a current of 4X 104e+/s to a target when a 7.3mCi 22Na source is used. The energy range,available at present is between 25eV and 16keV. We have applied it to study initially on the dynamic process of WSix film formation and on the distribution defects produced by N+ ion in nickel.
On Electronegativity of the High-Tc Oxide Superconductor
ZHANG Liyuan
Chin. Phys. Lett. 1992, 9 (9): 495-497 .  
Abstract   PDF(pc) (202KB) ( 531 )
Using a very useful quantity in physics and chemistry, the electronegativity, we have found that for nearly 70 high-Tc oxide superconductors (HTOS), the average electronegativity is in a narrow range 2.5-2.7. The difference of bond character between the HTOS and the conventional superconductors has been discussed. Finally, two categories of superconductors in terms of the group average electronegativity are suggested.

Electrical Properties and Superconductivity of MSr2Nd2-xCexCu2O10-δ (M = Ta, Nb)
ZHU Yingjie, QIAN Yitai, LI Rukang, WANG Shiwei, CHEN Zuyao, CHEN Zhaojia*, WANG Nanling*, ZHOU Guien**
Chin. Phys. Lett. 1992, 9 (9): 498-500 .  
Abstract   PDF(pc) (143KB) ( 478 )
A new series of layered cuprate compounds MSr2Nd2-xCexCu2O10-δ (M = Ta,Nb) have been synthesized. The structure of the compounds is similar to that of Tl-1222. A peak in the R-T curve for the sample of TaSr2Nd1.3Ce0.7Cu2O10-δ has been observed at about 50K. For the sample of NbSr2Nd1.45Ce0.55Cu2O10-δ, metal-like conductivity behaviour has been observed. We have found superconductivity at about 13.2K in the samples of NbSr2Nd2-xCexCu2O10-δ ( x= 0.49, 0.50, 0.51, 0.52).

A Universal Method Determining Hawking Effect in Spherically Symmetric or Plane-Symmetric Non-static Space-Times
ZHAO Zheng
Chin. Phys. Lett. 1992, 9 (9): 501-504 .  
Abstract   PDF(pc) (129KB) ( 476 )
A universal proof to the new method determining the location and the temperature of event horizons is given. The method is valid to every non-static spherically symmetric or plane-symmetric space-time. An additional term appears in the standard form of wave equation near the event horizon in the spherically symmetric case. The coefficient of this term is just the relative change rate of entropy of the black hole.

15 articles