Table of contents

20 March 1994, Volume 3 Issue 3 Previous issue    Next issue

CLASSICAL AREAS OF PHENOMENOLOGY

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TRANSIENT BEHAVIOR OF THE SELF-PUMPED PHASE CONJUGATE BEAM BY THE CHANGE OF INCIDENT BEAM INTENSITY HONG YAN-HUA (洪艳华), XIE PING (谢平), DAI JIAN-HUA (戴建华), ZHANG HONG-JUN (张洪钧) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  161-168.  DOI: 10.1088/1004-423X/3/3/001 Abstract ( 1103 )   PDF (222KB) ( 465 )   We have studied the transient behavior of thc self-pumped phase conjugation when the incident beam is below the saturation intensity. We found that, when the incident beam intensity is changed abruptly, the intensity of the conjugate beam always decreases at first and then gradually increases to its stable value. This is due to the fact that the positions of the two coupled interaction regions are changed.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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GEOMETRIC AND ELECTRONIC STRUCTURES OF Ti8C12 CLUSTER YANG JIN-LONG (杨金龙), ZHANG MAN-HONG (张满红), XIA SHANG-DA (夏上达), WANG KE-LIN (汪克林) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  169-175.  DOI: 10.1088/1004-423X/3/3/002 Abstract ( 1269 )   PDF (215KB) ( 376 )   The electronic structure of Ti8C12 clusters with three possible geometric structures suggested in the literature is studied using the discrete-variational local-density-functional method. The results show that the ground states of the clusters are all degenerate, which means further Jahn-Teller distortions for the geometric structures of clusters. The results also indicate that the distorted dodecahedral Ti8C12 cluster, which is proposed by Guo et al. and optimized by the first principle calculations, is the most stable one among the clusters we considered and its electronic structure can explain the experimental observations. In this cluster, there is a strong pd bonding between Ti and C atoms, and the density of states at the Fermi energy is high.

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INFLUENCE OF $\gamma$-RADIATION ON THE DIELECTRIC CHARACTERISTICS IN Rb2ZnCl4 SINGLE CRYSTALS AT INCOMMENSURATE-COMMENSURATE PHASE TRANSITION ZHANG DAO-FAN (张道范), ZHU YONG (朱镛), YANG HUA-GUANG (杨华光), MA WEN-YI (马文漪), GU BEN-YUAN (顾本源) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  176-181.  DOI: 10.1088/1004-423X/3/3/003 Abstract ( 1085 )   PDF (162KB) ( 389 )   In this paper the influence of $\gamma$-radiation on the dielectric constants of Rb2ZnCl4 crystal at incommensurate-commensurate phase transition (hereafter abbreviated as INC-C transition) are studied. The thermal hysteresis occurs upon both cooling and heating runs, irrespective of whether the samples have been treated with $\gamma$-radiation or not. For the $\gamma$-irradiated sample, its transition point, Tc, between the INC and C phases is not changed, but the peak value of the dielectric constant at Tc increases abruptly, compared with that before $\gamma$-irradiation, When this sample is annealed at 40℃, the peak value restores to the incipient value for the sample free from $\gamma$-irradiation. The origin of the phenomenon of the thermal hysteresis of the dielectric constant may be due to the pinning effect of dejects or impurities in the samples.

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MICROSTRUCTURE AND LUMINESCENCE PROPERTIES OF GaxIn1-xP/GaAs HETEROSTRUCTURE ZHANG SHU-YUAN (张庶元), LI FAN-QING (李凡庆), ZUO JIAN (左健), TAN SHUN (谭舜), XU CUN-YI (许存义), LU BIN (陆斌), CHEN ZHI-WEN (陈志文) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  182-189.  DOI: 10.1088/1004-423X/3/3/004 Abstract ( 1265 )   PDF (233KB) ( 400 )   The GaxIn1-xP/GaAs heterostructures with different x values have been investigated by photoluminescence (PL), energy dispersive spectrum (EDS), and transmission electron microscopy (TEM). Experimental results suggested that the composition of epitaxial layers evidently affected the microstructure of the heterostructures. When x value was close to 0.5, the defects in the epitaxial layer decreased, and the lattice match between film and sub-strate approached optimum, Meanwhile, the heteroatructure provided a high luminescence efficiency.

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

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EFFECT OF THE SUBSTITUTION OF Ga AND Sn FOR Cu ON THE ELECTRONIC STRUCTURE AND SUPERCONDUCTIVITY OF La1.85Sr0.15CuO4 FENG XIAO-BING (冯小兵), HAO XUE-JUN (郝学军), ZHANG LI-YUAN (章立源), WANG HUAI-YU (王怀玉) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  190-199.  DOI: 10.1088/1004-423X/3/3/005 Abstract ( 1155 )   PDF (302KB) ( 422 )   The electronic structure of La1.85Sr0.15CuO4， as well as the two cases of substitution of Ga and Sn for Cu, has been studied by the recursion method. The change of hole concentration and the effective local magnetic moment have also been calculated. Our calculations show that Ga and Sn destroy the two-dimensional character of the CuO2 plane and lead to the disorder of the electronic structure, accompanied by the migration of electrons which canines the decrease of the hole concentration in the CuO2 planes. From our point of view, these changes may be responsible for the destruction of superconductivity of the Ga and Sn-doped systems.

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SIMULATION OF OCCUPATION FUNCTION FOR THERMALLY STIMULATED CONDUCTIVITY IN AMORPHOUS SEMICONDUCTORS ZHU MEI-FANG (朱美芳), DING YI-BING (丁亦兵), ZONG JUN (宗军), LIU HONG (刘红) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  200-207.  DOI: 10.1088/1004-423X/3/3/006 Abstract ( 1009 )   PDF (198KB) ( 380 )   The occupation functions for the general condition f(E,T), for the high field approx-imation (HTSC) fH(E,T) and for the steady state photoconductivity (SSPC) fP(E,T) in the thermally stimulated conductivity (TSC) of amorphous semiconductors have been inves-tigated. It was found that the occupation function f(E,T) in TSC is in excellent agreement with the occupation function in SSPC fP(E,T) under the condition of $\sigma$TSC(T) = $\sigma$P(T).There is a large difference between fP(E,T) and fH(E,T), which can be much reduced by introducing an effective attempt to escape frequency νeff in the calculation of fH (E, T). The results show that the mobility-lifetime product ($\mu$$\tau$) in TSC obtained from SSPC measure-ments under the above condition is valid. For high field approximation TSC, the simulated νeff is found to be temperature dependent.

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PHOTOELECTRON SPECTROSCOPIC STUDY OF THE EFFECT OF Cs INTRALAYER ON THE BAND LINEUP OF Ge/InP(100) HETEROJUNCTION XU SHI-HONG (徐世红), XU PENG-SHOU (徐彭寿), ZHU JING-SHENG (朱警生), LIU XIAN-MING (刘先明), ZHANG YU-HENG (张裕恒), XU ZHEN-JIA (许振嘉) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  208-215.  DOI: 10.1088/1004-423X/3/3/007 Abstract ( 1094 )   PDF (209KB) ( 376 )   The formation and band lineup of the Ge/InP(100) interface with or without alkali metal Cs intralayer (IL) are studied by means of X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). It is found that the Cs atoms do not react with or diffuse into the subatrate and the Ge overlayer. The thin Cs IL will induce an increase of the valence band offset ($\Delta$Ev) for the Ge/InP(100) heterojunction. The changes of $\Delta$Ev are proportional to the IL thickness and them saturate for IL thickness of about one half of a monolayer of Cs IL. Without the IL, $\Delta$Ev of the Ge/InP(100) heterojunction is equal to 0.70eV, and $\Delta$Ev with one half of monolayer IL is up to 0.90eV. These results show that the interface dipole plays a major role in the band lineup at the heterojunction interface.

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ELECTROREFLECTANCE SPECTRA OF GexSi1-x/Si STRAINED LAYER MULTIPLE-QUANTUM WELLS PAN SHI-HONG (潘士宏), HUANG SHUO (黄硕), WANG ZHONG-HE (汪忠和), CHEN WEI (陈卫), ZHANG CUN-ZHOU (张存洲), SHENG CHI (盛篪), WANG XUN (王迅) Acta Physica Sinica (Overseas Edition), 1994, 3 (3):  216-229.  DOI: 10.1088/1004-423X/3/3/008 Abstract ( 1247 )   PDF (388KB) ( 353 )   We have investigated the optical transitions above the fundamental gap of a set of GexSi1-x/Si strained layer multiple-quantum wells by electroreflectance (ER). The sam-ples were grown by molecular beam espitaxy (MBE). The thickness of the strained layer of GexSi1-x was 5nm with Ge concentration x in the range from 0.4 to 0.5, and the Si barrier layer greater than 16nm. Considering the energy shift caused by strain and quantum well confinement, we were able to clearly recognize the transitions from different quantum well structures associated with the critical points E0, E′0, and E1. The transitions of the critical points E0 and E′0, which are very weak in bulk mateials, are apparently enhanced in the quantum well structures.