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Volume 13 Issue 10
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Original Articles
A Uqp(u1,1) Model for Vibrational Molecular Spectra
ZHOU Huan-qiang, ZHANG Xin-ming
Chin. Phys. Lett. 1996, 13 (10): 721-723 .  
Abstract   PDF(pc) (147KB) ( 516 )
A Uqp(u1,1) model is presented for describing vibrational spectra of diatomic molecules. The model is tested on the vibrational spectra in the X1Σ g+ state of H2 obtained through the Rydberg-Klein-Rees method.

Giant Monopole Resonance with Boltzmann-Nordheim-Vlasov Model
WEN Wan-xin*, ZHONG Ji-quan, JIN Gen-ming
Chin. Phys. Lett. 1996, 13 (10): 724-726 .  
Abstract   PDF(pc) (185KB) ( 424 )
The Boltzmann-Nordheim-Vlasov (BNV) model was employed to investigate the giant monopole resonance (GMR) built on very excited residula nuclei formed in heavy-ion collisions. Roughly speaking the GMR energy of BNV model is very similar to the value given by the empirical formual EGMR = 31.2A-l/3 + 20.6A-l/6 and hardly changes with impact parameter and bombarding energy.

Coherence Rotation in the Reaction 19F+51V
WANG Qi, LU Jun, XU Hu-shan, LI Song-lin, ZHU Yong-tai, ZHANG Yu-hu, LI Zhi-chang*
Chin. Phys. Lett. 1996, 13 (10): 727-729 .  
Abstract   PDF(pc) (143KB) ( 444 )
Excitation functions of the dissipative products in the reaction 19F+51V have been measured from 102.25 to 109.50MeV by 250keV steps at θl = 21.7°, 36.1°and 40.5°. The rotation angular velocities ω and the energy coherence widths Γ of the corresponding dinuclear systems were extracted. The coherence rotation and its importance in the reaction process have been discussed.

Pion and Kaon Production in Heavy-Ion Reactions at 1GeV/Nucleon
ZHENG Yu-ming, CHU Zi-li
Chin. Phys. Lett. 1996, 13 (10): 730-733 .  
Abstract   PDF(pc) (213KB) ( 406 )
The pion and kaon production in heavy-ion reactions at 1GeV/nucleon has been investigated in the relativistic Vlasor-Uehling-Uhlenbeck model, which has been generalized to include the effect of nuclear medium on kaon and pion. The calculated results show that the attractive pion optical potential not only enhances apparently the yield of pions with low transverse momenta, leading to a reasonable fit to the experimental data, but also increases the kaon abundance.

Generation of Intensity Squeezing in Laser Diodes by Weak External Cavity Feedback
ZHANG Tian-cai, HOU Zhan-jia, WANG Jun-min, XIE Chang-de, PENG Kun-chi
Chin. Phys. Lett. 1996, 13 (10): 734-736 .  
Abstract   PDF(pc) (208KB) ( 468 )
We report the generation of intensity squeezing in a single-mode laser diode by weak external cavity feedback. The measurable squeezing of the output beam is 4.7%, corrected to 8.9% for the actual squeezing. This proves that intensity squeezing can be obtained by weak feedback.
Waveguides Written and Stored by Photovoltaic Dark Spatial Solitons in LiNbO3:Fe Crystals
LIU Si-min, ZHANG Guequan, SUN Qian, XU Jing-jun, ZHANG Guang-ying, TONG Yi-cheng*
Chin. Phys. Lett. 1996, 13 (10): 737-740 .  
Abstract   PDF(pc) (263KB) ( 450 )
To our knowledge, we have demonstrated for the first time that (2+1)-dimension photorefractive waveguides can be written and stored by light using the (2+1)-dimension photovoltaic dark spatial solitons in LiNbO3:Fe crystals. It can guide a probe beam of the same wavelength as that of the writing beam.

Blue and Violet Cerenkov Second Harmonic Generation of Laser Diodes in Proton Exchanged MgO:LiNbO3 Optical Waveguide
MU Xiao-dong, SHAO Zong-shu, ZHANG Heng-li, KONG Qing-yu, JIANG Min-hua
Chin. Phys. Lett. 1996, 13 (10): 741-743 .  
Abstract   PDF(pc) (176KB) ( 605 )
Using the Cerenkov second harmonic generation, 478 nm blue and 402nm violet light are generated by direct frequency doubling of 956 and 804 nm diode lasers in a same proton exchanged MgO:LiNbO3 waveguide. Under the low fundamental guide wave power of less than 1mW, the estimated value of the output blue and violet light power is in the order of 0.1-0.01μW.

A New Method for Fabrication of Chirped Fiber Gratings
ZHAO Yu-cheng, JIANG Shui-sheng, AN Gui-ren*, LI Li*, GE Huang*, WANG Wei*
Chin. Phys. Lett. 1996, 13 (10): 741-743 .  
Abstract   PDF(pc) (176KB) ( 541 )
A technique for chirped-period fiber gratings with etching method is reported. An analysis is presented for the behavior of the chirped gratings as a function of wavelength, the angle between the illuminating beams, as well as the position of the gratings. Experimentally, chirped fiber gratings have been etched on the D-fiber. Results obtained are in good agreement with theoretical analysis.
Self-Generated Magnetic Fields in Plasmas
ZENG Gui-hua, YU Wei, SHEN Bai-fei, XU Zhi-zhan
Chin. Phys. Lett. 1996, 13 (10): 747-749 .  
Abstract   PDF(pc) (177KB) ( 488 )
The self-generated magnetic field induced by an ultraintense short laser pulse propagating in a uniform underdense plasma is investigated. The magnetic fields are strong and associated with the plasma wave wake field. Some properties of dc magnetic field in two extreme laser pulse regime are described.
Roles of Low Energy Electrons in the Fabrication Process Using Scanning Tunnelling Microscope
WANG Chen, BAI Chun-li, LI Xiao-dong, SHANG Guang-yi, QIU Xiao-hui
Chin. Phys. Lett. 1996, 13 (10): 750-752 .  
Abstract   PDF(pc) (183KB) ( 584 )
The effects of low energy electrons in scanning tunnelling microscope operations are explored, with the emphasis on its role in the fabrication processes. A simple model based on the continuum electron diffusion is proposed to account for the observed sub-surface characteristics of the nanoscale features. The results suggest that the local transport properties could affect the outcome of such operations.
Very Low Pressure Nucleation of Diamond on Mirror-Smooth Silicon in Hot Filament Chemical Vapor Deposition System
LIN Zhang-da (Zhangda Lin), CHEN Yan, CHEN Qi-jin, S. T. Lee*, Y. W. Lam*
Chin. Phys. Lett. 1996, 13 (10): 750-752 .  
Abstract   PDF(pc) (183KB) ( 579 )
Under very low pressure (0.1 Torr) the high density nucleation of diamond on mirror-smooth silicon in hot filament-chemical vapor deposition system was obtained. The nucleation density of order of 1010-1011cm-2 was achieved, the same achievement which obtained in microwave plasma-chemical vapor deposition system with negative bias. In this paper the nucleation technique and the effect of low pressure on diamond nucleation were discussed in detail based on the molecular dynamics.
Cu-Doped KNSBN Single Crystals
XIA Hai-rui, WANG Cheng-jian, CHEN Huan-chu, YANG Zhao-he
Chin. Phys. Lett. 1996, 13 (10): 757-760 .  
Abstract   PDF(pc) (215KB) ( 460 )
The preparation procedure, the transmissivity, and the two-wave coupling properties of coppermodified potassium sodium strontium barium niobate (KNSBN) crystals are reported. The Cu ions doped in KNSBN can form two deep energy levels. This means that they are able to act as centers for free charge carrier stimulation and recombination. The two-wave coupling gain coefficient of KNSBN: Cu is two times larger than that of KNSBN. The photorefractive sensitivity of KNSBN: Cu is estimated to be in the order of 10-3cm2/J.
Sound Speed in a Shocked Tungsten Alloy: Its Significance in Studying “Softening” Mechanism to Multiphase Alloys
ZHOU Xian-ming, JING Fu-qian, HU Jin-biao
Chin. Phys. Lett. 1996, 13 (10): 761-764 .  
Abstract   PDF(pc) (193KB) ( 697 )
Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the speed increases with pressure, then a bulk“softening” process occurs at 250 to 340 GPa, afterwards the speed again rises with pressure and coincides with the calculated bulk sound speed, showing a fluid-like behavior for this alloy. Lindemann melting law calculations were made for both the binder and the tungsten. The results showed that 250 GPa corresponds approximately to the pressure for the binder beginning to melt, and 340GPa corresponds to that for tungsten. Therefore, we believe that the shock-induced “softening” mechanism for this kind of multiphase alloys can be attributed to the binder melting.
Raman Scattering from Fine Zn Particles Coated with ZnO
XU Jian-feng, CHENG Guang-xu, DU You-wei
Chin. Phys. Lett. 1996, 13 (10): 765-767 .  
Abstract   PDF(pc) (172KB) ( 715 )
Raman scattering from Zn fine spheric particles coated with ZnO of variable thickness is measured, and a broad line can be found. The Raman line shifts to lower frequency side with the increase of oxide thickness. A theoretical analysis based on the existence of surface phonon mode has been made. Agreement between experiment and theory is good.
Optical Interface Phonon in Thin Layer Inserted Quantum Well Structure
GU Bing-lin, DUAN Wen-hui, XIONG Shi-ying
Chin. Phys. Lett. 1996, 13 (10): 768-771 .  
Abstract   PDF(pc) (209KB) ( 486 )
The dependence of optical interface phonon on structure was demonstrated for thin layer inserted GaAlAs quantum well structures. It was found that the dispersion is sensitive to the Al-content of the inserted layer but almost independent of the position of the layer. The results showed that phonon modes can be modulated by adjusting the well parameters, which is useful for some device applications.
Structural and Critical Behaviors of Ag Rough Films Deposited on Liquid Substrates
YE Gao-xiang, FENG Chun-mu, ZHANG Qi-rui, GE Hong-liang, ZHANG Xuan-jia
Chin. Phys. Lett. 1996, 13 (10): 772-774 .  
Abstract   PDF(pc) (234KB) ( 574 )
A new Ag rough film system, deposited on silicone oil surfaces by rf-magnetron sputtering method, has been fabricated. The chrysanthemum-like surface morphology at micron length scale is observed. It is proposed that the anomalous critical behavior mainly results from the relative shift between the Ag atom clusters and the substrate. The discussion of the deposition mechanism is also presented.
Preparation and Characterization of the BaTiO3/YBa2Cu3O7/SrTiO3 Heteroepitaxial Films
MA Kun, LI Chun-ling, CUI Da-fu, ZHOU Yue-liang, LIU Yan-wei, LÜ, Hui-bin, ZHANG Dao-fan, WU Fei, CHEN Hong, LI Lin
Chin. Phys. Lett. 1996, 13 (10): 775-778 .  
Abstract   PDF(pc) (199KB) ( 343 )
BaTiO3(BTO)/YBa2Cu3O7 (YBCO) heteroepitaxial films have been fabricated on (100) SrTiO3 substrates by pulsed laser ablation. X-ray characterizations show the BTO/YBCO bilayer films have a highly epitaxial nature. Rocking curves for the BTO (002) and YBCO (005) peaks have full width at half maximum values of 0.36°and 0.32°, respectively. The Ф scan plots indicate good in-plane alignments of these epitaxial films. The ferroelectric properties of the B TO/YBCO heteroepitaxial films were evaluated by capacitance-voltage measurement in metal-ferroelectric-metal configuration.

Epitaxial Growth of High Quality Diamond Film on the Cubic Boron Nitride Surface by Chemical Vapor Deposition
GAO Chun-xiao, ZHANG Tie-chen, ZOU Guang-tian, JIN Zeng-sun, YANG Jie*
Chin. Phys. Lett. 1996, 13 (10): 779-781 .  
Abstract   PDF(pc) (379KB) ( 478 )
High quality diamond epitaxial film has been obtained on high pressure synthesized cubic boron nitride crystal surface by dc glow discharge chemical vapor deposition. The growth characteristics of the epitaxial film have been investigated by scanning electron microscope. The quality of the film has been confirmed by Raman spectroscope to be close to that of natural diamond.

Two Crystal Phases of C3N4 Found in Carbon Nitride Films Prepared by Ion Implantation
GU You-song, PAN Li-qing, ZHAO Min-xue, CHANG Xiang-rong, TIAN Zhong-zhuo, XIAO Ji-mei
Chin. Phys. Lett. 1996, 13 (10): 782-785 .  
Abstract   PDF(pc) (190KB) ( 492 )
CNx films prepared by high dose ion implantation and post-annealing were studied by Auger electron spectroscopy, x-ray photoelectron spectroscopy and x-ray diffraction. A nearly uniform CNx layer was formed. Carbon and nitrogen were found covalently bonded in the films. X-ray diffraction results showed that two crystal phases of C3N4, β-C3N4 and p-C3N4, have been formed in the matrix of carbon.
Band Gap Behaviors of (α-GaN) / (α-AIN) Superlattice and (β-GaN)/(β- A1N) Superlattice
KE San-huang, ZHANG Kai-ming, XIE Xi-de
Chin. Phys. Lett. 1996, 13 (10): 786-789 .  
Abstract   PDF(pc) (261KB) ( 386 )
By using an ab initio calculation, it is found that the variation of the fundamental band gap of (α-GaN)n / (α-AlN))n (0001) superlattices is remarkably different from that of (β-GaN))n / (β- A1N))n (001) superlattices. The difference in band gap behaviors was shown to be due to the internal electric fields induced by the spontaneous polarizations in α-GaN and α-AlN. In addition, the valence-band offsets at the interfaces of these superlattices are also determined. The results are in good agreement with those available from experimental data.

Influence of the Energy Level Matching on the Performances of Organic/Polymeric Electroluminescent Devices
TIAN Wen-jing, HUANG Jin-song, WU Fang, SUN Chang-qing, LIU Xiao-dong, MA Yu-guang, LIU Shi-yong, SHEN Jia-cong
Chin. Phys. Lett. 1996, 13 (10): 790-793 .  
Abstract   PDF(pc) (232KB) ( 493 )
The performances such as the operating-voltage and the brightness of three types of devices: single-layer device, double-layer device and three-layer device, were examined. It is demonstrated that the I-V characteristics of single-layer device depends not on the applied voltage but instead on the electric-field strength, and the brightness increased by a factor of 50 and the operating-voltage decreased when introducing one electron transporting layer or an electron transporting layer and one hole blocking layer between the light emitting layer and the negative electrode. In fact, it is imperative to match the energy level of each layer in the electroluminescent device in order to improve its comprehensive performances.

Photoluminescence and Electroluminescence from Plasma Ploymerized Naphthalene Films
ZHANG Hai-feng, MA Yu-guang, TIAN Wen-jing, SHEN Jia-cong, TANG Jian-guo*, LIU Shi-yong*
Chin. Phys. Lett. 1996, 13 (10): 794-796 .  
Abstract   PDF(pc) (184KB) ( 421 )
A polymer thin film electroluminescence (EL) device has been prepared by using plasma polymerization technique. Its basic structure consists of an emitting layer of plasma polymerized naphthalene (PPN) which is sandwiched between two metal electrodes. A uniform blue emission is observed under 8-20 V. Some electrical and optical properties of the device are described. The possible explanations for the blue EL from PPN are discussed.

Quantum Confinement in GaAs Microcrystallites Embedded in SiO2 Thin Film
SHI Wang-zhou, LIN Kui-xun, LIN Xuan-ying, QI Zhen-zhong
Chin. Phys. Lett. 1996, 13 (10): 797-800 .  
Abstract   PDF(pc) (288KB) ( 430 )
Semiconductor GaAs microcrystallites were embedded in SiO2 thin films by magnetron rf cosputtering technique. Structures of the thin films were characterized by transmission electron microscopy, x-ray diffraction and x-ray photoelectron microscopy. Average size of microcrystallites, depending on the substrate temperature during deposition, is 3-10nm. Absorption spectra of the films were measured. Blue shift of absorption edge was observed and discussed according to quantum confinement effect.
23 articles