Table of contents

20 June 1997, Volume 6 Issue 6 Previous issue    Next issue

GENERAL

Select

UNCOOLED GaInAsSb INFRARED DETECTORS GROWN BY METALORGANIC CHEMICAL VAPOR DEPOSITION LI SHU-WEI (李树玮), JIN YI-XIN (金亿鑫), ZHANG BAO-LIN (张宝林), ZHOU TIAN-MING (周天明), JIANG HONG (蒋红), NING YONG-QIANG (宁永强) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  401-405.  DOI: 10.1088/1004-423X/6/6/001 Abstract ( 1256 )   PDF (152KB) ( 375 )   The GaInAsSb as one of the most important semiconductor alloy systems for infrar ed detectors is well established. Samples of GaInAsSb alloys have been grown by atmospheric pressure metalorganic chemical vapor deposition on n-GaSb (Te-doped ) substrates. The properties of GaInAsSb layers were characterized by single-crystal X-ray diffraction, doublecrystal X-ray rocking curve and scanning elec tron acoustic microscopy. The spectral responses of p+-GaInAsSb/p-GaInAsSb/n-GaSb detectors showed cut-off wavelength at 2.4μm,detectivity D=1.2×109 cmHz0.05/W at room temperature,and quantum efficiency 40%.

CLASSICAL AREAS OF PHENOMENOLOGY

Select

MAGNETIC FIELD DISTRIBUTIONS OF A PLANAR PULSE MICROWIGGLER XU YONG (徐勇), LIU QING-XIANG (刘庆想), KE ZUN-PING (柯尊平) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  406-412.  DOI: 10.1088/1004-423X/6/6/002 Abstract ( 1158 )   PDF (193KB) ( 357 )   Magnetic field distributions of a planar pulse microwiggler are studied analytically and numerically. An exact solution of two-dimensional magnetic field is derived in detail,and the formula shows that along the electron axis the field has a variation close enough to a sine wave. Effects of ends of the microwiggler on magnetic field are also investigated with the help of numerical methods.

Select

THEORY OF PHOTOREFRACTIVE EFFECT FOR DOUBLE CARRIERS WITH TWO DEEP TRAPS AND A SHALLOW HOLE TRAP LI YAN-QIU (李艳秋), LIU SHU-TIAN (刘树田), SUN WAN-JUN (孙万均), XU KE-BIN (许克彬), HONG JING (洪晶) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  413-421.  DOI: 10.1088/1004-423X/6/6/003 Abstract ( 1166 )   PDF (233KB) ( 384 )   We propose a new theoretical model of photorefractivity which consists of both electron and hole carriers with two deep traps and a shallow hole trap. The model predicts that,if the shallow trap accumulates a large density of charge carriers,the photoconductivity will be a sublinear (or superlinear) function of light intensity,and the space charge field will increase (or decrease) to a saturated value as the light intensity increases,depending on the sign of the dominant carrier. The comparison of this model with previous ones shows that it provides a more common description about the dependences of photoconductivi ty and space charge field on the light intensity.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Select

THE WIDTH EFFECT OF ELECTRODE IN THE FREEDERICKSZ TRANSITION OF NEMATIC LIQUID CRYSTALS WANG CUN-DAO (王存道), YANG GUO-CHEN (杨国琛) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  422-428.  DOI: 10.1088/1004-423X/6/6/004 Abstract ( 1170 )   PDF (176KB) ( 446 )   The Freedericksz transition of nematic liquid crystals with limited width of ele ctrode on substrates of the cell is investigated. Solving two-dimensional nonli near partial differential equations by means of numerical method, we obtained the sp ace distribution of the director of the liquid crystal. The threshold voltage is found to depend on the ratio of the electrode width l to the thickness of the liquid crystal layer d. The deflect angle $\theta$ of the director lapses near the edge of the electrode and the width of this lapsing area are discussed.

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

Select

INFLUENCE OF HIGH PRESSURE ON EMISSION SPECTRA AND CRYSTAL FIELD STRENGTH FOR Eu3+ IN GdOBr CHI YUAN-BIN (池元斌), LIU SHEN-XIN (刘慎薪), LI HONG-NIAN (李宏年), ZHAO XU-YI (赵绪义), WANG LI-ZHONG (王立中) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  429-439.  DOI: 10.1088/1004-423X/6/6/005 Abstract ( 1198 )   PDF (274KB) ( 363 )   The emission spectra of the Eu3+ ion in GdOBr∶Eu3+ were measured in the range of pressure from 0 GPa to 12.4 GPa. The energy level schemes establis hed from the spectra show that the splittings of the 7F1,7F3 and 5D1 multiplets decrease obviously with increasing pressure. The crystal-field parameters Bkq and the crystal-field strength parameter S versus Bkq were determined at different pressures. With pressurization S reduces and the J-mixings of the state functions for the Eu3+ ion decrease, which is in agreement with the decrease of the multiplet splittings. This shows that for Eu3+ in REOX∶Eu3+ the diminution of the crystal-field strength with pressure, the authenticity of which is under suspicion for several years, is certain.

Select

MAGNETIC PROPERTIES OF Dy2Fe17-xCrx AND Er2Fe17-xCrx(x=0-3)COMPOUNDS HAO YAN-MING (郝延明), YAN QI-WEI (严启伟), ZHANG PAN-LIN (张泮霖), SUN XIANG-DONG (孙向东), WANG FANG-WEI (王芳卫), SHEN BAO-GEN (沈保根) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  440-444.  DOI: 10.1088/1004-423X/6/6/006 Abstract ( 1135 )   PDF (132KB) ( 348 )   The crystal structure and magnetic properties of R2Fe17-xCrx(R=Dy,Er,0≤x≤3) compounds have been investigated by me ans of X-ray diffraction and magnetization measurements. These compounds have hexagonal Th2Ni17-type structure. The unit-cell volumes decrease with the increase of Cr concentration x. The Curie temperature Tc of the Er2Fe17-xCrx compounds increases from 320 K for x=0 to 403 K for x=1.0 and then decreases with further increase of x. The Cur ie temperat ure Tc of Dy2Fe17-xCrx compounds increases from 364 K for x=0 to 435 K for x=1.0 and then decreases with further increase of x. The saturation magnetization of these compounds shows an approximately linear decrease with the increase of x. Spin reorientation transitions occur s in Er2Fe17-xCrx(x=2.0 and 3.0).

Select

FORMATION AND MAGNETIC PROPERTIES OF NEW COMPOUNDS R3Fe29-xCrx (R=Y,Ce,Nd,Sm,Gd,Tb,and Dy) HAN XIU-FENG (韩秀峰), YANG FU-MING (杨伏明), LIU HONG-LI (刘洪利), PAN HONG-GE (潘洪革) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  445-455.  DOI: 10.1088/1004-423X/6/6/007 Abstract ( 1458 )   PDF (306KB) ( 406 )   A systematic investigation of structure and magnetic properties of the new R3Fe29-xCrx compounds(R=Y,Ce,Nd,Sm,Gd, Tb,and Dy)has been performed. The Curie temperature of R3Fe29-xCrx increased with increasing atomic number from R=Ce to Gd and de creased from Gd to Dy. The saturation magnetization of R3Fe29-xCrx at 4.2 K decreased gradually with increasing atomic number from R=Y to Dy,except for Ce. The spin reorientations of the easy magnetization direction were observed at around 230 K for Nd3Fe24.5Cr4.5 and 180 K for Tb3Fe28.0Cr1.0, and the magnetohistory effects were obser ved for Nd3Fe24.5Cr4.5 and Sm3Fe24.0Cr5.0 in a low field of about 0.04 T. First order magnetization process occurs in magnetic field of around 2.3 T at room temperature for Tb3Fe28.0Cr1.0. The saturation magnetization of Y3Fe27.2Cr1.8 at 4.2 K is 52.2μB/f.u., which corresponds to an average magnetic moment of 1.92μB per each Fe atom.

Select

MAGNETIC POLARIZATION OF SPACER Pd LAYER AND MAGNETIC PROPERTIES OF Co/Pd MULTILAYERS MEI LIANG-MO (梅良模), LI MIN (李民), MA XIAO-DING (马小丁), LIU YI-HUA (刘宜华), ZHENG MIN (郑敏), GU YOU-SONG (顾有松), MAI ZHEN-HONG (麦振洪), ZHAO JIAN-GAO (赵见高), T.P.MA, R.C.BARKER Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  456-465.  DOI: 10.1088/1004-423X/6/6/008 Abstract ( 1175 )   PDF (306KB) ( 428 )   Magnetic multilayers［Co(1.5 nm)/Pd(x nm)］40 grown by rf sputtering were studied by X-ray diffraction,vibrating sample magnetometer,torque magnetomet er and magnetoresistance measurements.The dependences of the interfacial roughne ss and the structure perfectness of Co/Pd multilayers on the spacer Pd layer thi ckness have been revealed from X-ray diffraction data.An oscillatory variation of saturation magnetization versus the thickness of the Pd spacer was observed.A similar oscillatory behavior in the dependence of its magnetic anisotropy on the thickness of the Pd spacer was observed.It is suggested from these two phenomen a that the magnetic polarization of Pd spacers oscillates between ferromagnetic and antiferromagnetic polarization with the increase of Pd spacer thickness under a RKKY-like interaction.Evidence is found for the antiferromagnetic polarization of the inner part of the Pd spacer.The antiferromagnetic coupling between two Co layers and giant magnetoresistance effect in Co/Pd multilayer system were not observed.The relationship among structure,interlayer coupling and magnetic polarization effect of the Pd spacer was discussed.

Select

VIOLET LIGHT-EMISSION FROM Ge+-IMPLANTED SiO2 FILMS ON Si SUBSTRATE GAO TING (高婷), BAO XI-MAO (鲍希茂), YAN FENG (阎锋), TONG SONG (佟嵩), CHEB YI-JUN (陈逸郡) Acta Physica Sinica (Overseas Edition), 1997, 6 (6):  466-470.  DOI: 10.1088/1004-423X/6/6/009 Abstract ( 1170 )   PDF (134KB) ( 420 )   Germanium ions were implanted into SiO2 films which were thermally grown on crystalline Si at an energy of 60 keV and with doses of 1×1015 and 1×1016 cm-2.Under an ultraviolet excitation of ～5.0 eV,the implanted f ilms annealed at various temperatures exhibit intense violet luminescence with a peak at 396 nm.It is ascribed to the T1→S0 transition in GeO,which was formed during implantation and annealing process.