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Vol. 50, No. 12 (2001)

2001-06-20
Topics
GENERAL
STUDY OF RELATIVE DOSE-ENHANCEMENT EFFECTS ON CMOS DEVICE IRRADIATED BY STEADY-STATE AND TRANSIENT PULSED X-RAYS
ZHANG YI-MEN, GUO HONG-XIA, CHEN YU-SHENG, ZHOU HUI, GONG JIAN-CHENG, HAN FU-BIN, GUAN YING, WU GUO-RONG
2001, 50 (12): 2279-2283. doi: 10.7498/aps.50.2279
Abstract +
The results are presented with emphasis on the relative dose-enhancement factor for complementary metal-oxide semiconductor (CMOS) devices irradiated by steady state and transient pulsed X-rays. With the help of experimental study, sensitive parameter threshold voltage as a function of irradiation dose was obtained. So the equivalent relation of total dose damage is eslablished by comparing the response of devices irradiated by 60Co γ-rays and X-rays. By employing the X-ray transient pulsed sources, the research of X-rays transient upset enhancement effects is carried out using bi-laminate structure. Upset enhancement factor of X-rays are measured. These methods are provided for X-ray radiation hardening technology an effective evaluation method.
THE ORBITAL PRECESSION EFFECT IN THE MASS QUADRUPOLE MOMENT FIELD
WANG YONG-JIU, TANG ZHI-MING
2001, 50 (12): 2284-2288. doi: 10.7498/aps.50.2284
Abstract +
In this paper,we calculate the orbital precession effect on the experiment body in a mass quadrupole moment field by the parameterized post Newton method.We obtain some interesting results in astrophysics preferred frame effect and the limits on some PPN parameters.
STUDY ON DYNAMICS OF RELATIVISTIC BIRKHOFF SYSTEMS
LUO SHAO-KAI, CHEN XIANG-WEI, WANG XIN-MIN, FU JING-LI, CHEN LI-QUN
2001, 50 (12): 2289-2295. doi: 10.7498/aps.50.2289
Abstract +
The Birkhoffian, the Birkhoff's functions, the Pfaff action, the Pfaff-Birkhoff principle and the Birkhoff equations of relativistic Birkhoff systems are given. The Birkhoff representation of relativistic dynamical systems is studied. Then the theory of Noether symmetries and Lie symmetries of the relativistic Birkhoff systems is obtained by the invariance of relativistic Pfaff action and relativistic Birkhoff equations under infinitesimal transformations. Finally the algebraic structure and Poisson integrals for the relativistic Birkhoff systems are studied.
ERROR ANALYSIS FOR DELAY SYNCHRONIZATION OF CHAOTIC SYSTEM
HUANG WEI, XU JIAN-XUE, HUANG XIAN-GAO, ZHU FU-CHEN
2001, 50 (12): 2296-2302. doi: 10.7498/aps.50.2296
Abstract +
We analyzed the delay synchronization errors in Pecora and Carroll's chaotic self synchronizing scheme. The delay synchronization errors are simulated using the masking scheme of Lorenz chaotic system on computer. Given system parameters, the relational curves of the mean square error vs sampling step length are presented for different delay time. Given system parameters and delay time, the error curves of chaotic time series are given for different sampling step lengths. Given sampling step lengths, the scale changes of chaotic time series are obtained for different system parameters. And given delay time, the relational curves of mean square error vs sampling step length are shown for different system parameters. Then some ways of decreasing the delay synchronization errors are proposed. Some new results obtained in this paper are useful for practical applications of chaos synchronization and chaos control.
ANALYSIS OF STABILITY FOR EQUILIBRIUM OFCELLULAR NEURAL NETWORKS
WANG HONG-XIA, YU JUE-BANG
2001, 50 (12): 2303-2306. doi: 10.7498/aps.50.2303
Abstract +
This paper discusses in detail the expressions, distribution and stability of equilibria for cellular neutral networks. Some useful conclusions are obtained. The network can be stable via choosing different connection-weight matrices based on special regions. The example shows the conditions are concise and easy to use.
A NOVEL CONTROL METHOD FOR DISCRETE MAP CHAOTIC SYSTEM
YU JUE-BANG, GU TIAN-XIANG, WANG GAI-YUN
2001, 50 (12): 2307-2310. doi: 10.7498/aps.50.2307
Abstract +
Based on the delayed feedback control idea, a novel prediction feedback control method for discrete chaotic system is presented. The method is illustrated in detail and the computer simulation is carried out. The simulation result is compared with that of delayed feedback control and it is shown that the proposed method is more effective for controlling fixed point of chaotic system.
CALCULATION OF THE LARGEST LYAPUNOV EXPONENT IN THE DISCRETE DYNAMICAL SYSTEM WITH WAVELET ANALYSIS
LIU HAI-FENG, ZHAO YAN-YAN, DAI ZHENG-HUA, GONG XIN, YU ZUN-HONG
2001, 50 (12): 2311-2317. doi: 10.7498/aps.50.2311
Abstract +
The largest Lyapunov exponent is an important parameter of detecting and characterizing chaos produced from a dynamical system. Based on simulative calculation, it has been found that the largest Lyapunov exponent of the small scale wavelet transform modulus of a discrete dynamical system is the same as the system's. At the same time, the calculated results show that calculating the largest Lyapunov exponent with the small scale wavelet transform modulus can efficiently eliminate the effect of strong large scale noiss because of the high pass filtering characteristic of small scale wavelet transform.
OUTPUT FEEDBACK SYNCHRONIZATION FOR A CLASS OF CHAOTIC LUR'E SYSTEMS
LIU FENG, REN YONG, SHAN XIU-MING, QIU ZU-LIAN
2001, 50 (12): 2318-2321. doi: 10.7498/aps.50.2318
Abstract +
A new synchronization theorem for a class of chaotic Lur'e systems is proposed. With the last state variable of the drive system as the driving signal,it is proved that the global asymptotic stable synchronization can be attained by a simple linear output error feedback.Taking Chua's chaotic oscillator as an example,simulation results demonstrated the effectiveness of the present control rule.
PREPARATION OF OPTICAL PROBES FOR SCANNING NEAR-FIELD INFRARED MICROSCOPY BY ETCHING METHOD
ZHANG LI-YUAN, LI YONG-GUI, WANG QIAN-
2001, 50 (12): 2322-2326. doi: 10.7498/aps.50.2322
Abstract +
The infrared probe is the pivotal part of scanning near-infrared microscopy. The fabrication methods of it are different according to the different kinds of materials, most popular up to now is the adiabatic pulling of optical fibers during heating with CO2 laser and afterwards chemical etching. In this paper, a method of etching is presented; how to deal with the polymer and to strip away the Se-S layer, and how to etch inner core into a high quality tip are introduced in details. The production of large cone angles and smooth probe is further studied, Finally, we use the Beijing free electron laser as light source, The spectrum signals of GaN varying with different wavelengths were detected and analyzed under the near field condition, and obtained the primary result.
EFFECTS OF ANNEALING CONDITIONS ON THE CRYSTALLIZATION QUALITIES OF Cd1-xZnxTe SLICES
LI YU-JIE-, ZHANG XIAO-NA, JIE WAN-QI
2001, 50 (12): 2327-2334. doi: 10.7498/aps.50.2327
Abstract +
Defects such as point defects, dislocations, impurities and Te precipitates always exist in Cd 1-xZnxTe ( x =0.04) crystals obtained by Bridgman and accelerated crucible rotation technique-Bridgman bulk crystal growth methods. It is important to anneal CdZnTe slices in Cd vapor to eliminate these defects. In this paper, the solid-vapor equilibrium for CdZnTe crystals is first discussed extensively based on the phase diagrams of Cd-Te and the P-T plot of Cd0.96Zn0.04Te. Through the annalysis, the annealing conditions for Cd1-xZnxTe crystals are optimized. Experimental results show that the Zn partial vapor pressure, which is higher than the equilibrium pressure within a certain range, can enhance the diffusion process of the excess Te towards the surface of the slices and thus eliminate Te precipitates. However, saturated Zn pressure causes Zn and Te concentration in surface layers of the slices far away from the stoichiometry. Intensive exchange of atoms between the slice surface and the vapor under this condition would lead to severe damage to the crystallization quality on the surface. The inter diffusion of Zn also inhibits the outer-diffusion of impurities during annealing. Thus a lower Zn partial pressure, but still lies in the solid vapor equilibrium area of the P-T plot, can help to drive out the impurities. According to the crystallization quality and the concentration distribution of slices annealed under different conditions, the annealing of CdZnTe wafers is classified into three kinds, namely de-precipitate annealing, de-impurity annealing and homogenizing annealing. The favorable annealing process should be a multi-step and multi period procedure.
ATOMIC AND MOLECULAR PHYSICS
POPULATION TRAPPING PHENOMENA IN A TWO-LEVEL SYSTEM
LONG DE-SHUN, NING XI-JING
2001, 50 (12): 2335-2340. doi: 10.7498/aps.50.2335
Abstract +
The critical criterion for realizing population trapping is deduced for a two-level system driven by a frequency-modulated laser field in terms of dressed atom model, followed by demonstrating the various population trapping behaviours under different conditions. Detailed numerical solutions of time-dependent Schr?idinger equation are found to be in good agreement with the analytical results.
CLASSICAL AREA OF PHENOMENOLOGY
PHOTOREFRACTIVE LIGHT-INDUCED BACKWARD SCATTERING IN c-CUT LiNbO3∶Fe CRYSTALS
LI FEI-FEI, XU JING-JUN, LIU SI-MIN, QIAO HAI-JUN, ZHANG GUANG-YIN
2001, 50 (12): 2341-2344. doi: 10.7498/aps.50.2341
Abstract +
We propose a new theoretical calculation by which photorefractive quasi-periodic light-induced backward scattering in c -cut LiNbO3∶Fe crystals induced by inhomogeneity of the photovoltaic current is studied. And our calculated results give quite well explanations on the formerly observed experimental ones.
MICROMASER INJECTED WITH ULTRA-COLD V-TYPE THREE-LEVEL ATOMS:EFFECTS OF ATOMIC COHERENCE ON PHOTON STATISTICS
LIANG WEN-QING, CHU KAI-QIN, ZHANG ZHI-MING, XIE SHENG-WU
2001, 50 (12): 2345-2355. doi: 10.7498/aps.50.2345
Abstract +
The effects of the atomic coherence on the photon statistics of the micromaser injected with ultra-cold V-type three-level atoms are studied.In the plot of the atomic emission probability versus the cavity length, there are resonance peaks and non-resonance platforms, which can be adjusted by the atomic coherence parameters.These features of emission probability affect the properties of photon statistics directly. In the plot of the mean number of photons versus the cavity length, there are resonance peaks and non-resonance platforms,too. Given a cavity length, with the change of the atomic coherence parameters, the distribution of photon numbers can move towards the large or small photon numbers, and the mean number of photons increases or decreases accordingly.We also find, with appropriate atomic coherence parameters, that the photon statistics are sub-Poissonian in large region of the cavity length.
SOLVING THE EIGENVALUE EQUATION OF AN ISOTONIC OSCILLATOR BY PSEUDO-ANGULAR-MOMENTUM METHOD
LI WEN-BO
2001, 50 (12): 2356-2362. doi: 10.7498/aps.50.2356
Abstract +
A rigorous solution of Schr?idinger equation of an isotonic oscillator is studied by pseudo-angular-momentum method. The effect of the parameter g in the centripetal potential barrier on the domain of effective values for formation of stationary bounded states and the effect of domain of the parameter g on the energy spectrum are discussed in detail. An appropriate and comprehensive formulation of the energy spectrum and analytic expressions of the corresponding eigenstates are presented. The different treatments in the literatures are clarified.
PERIODIC ENTANGLEMENT BETWEEN THE INTERNAL AND EXTERANL DEGREE OF FREEDOM OF A TRAPPED ION IN A STANDING WAVE LASER
FANG MAO-FA, LIU XIANG
2001, 50 (12): 2363-2368. doi: 10.7498/aps.50.2363
Abstract +
We have investigated the quantum entropy and entanglement of the internal and external degrees of freedom of a trapped ion in a standing wave laser by transforming the Hamiltonian to that in the Jaynes-Cummings system for the bare basis of the trapped ion under the Lamb-Dicke limit. Under the off-resonant condition, we have found the periodic entanglement between the internal and external degrees of freedom of a trapped ion.
COMPARISON BETWEEN THE THEORIES OF SIX-TEMPERATURE MODEL AND THE RATE EQUATION FOR Q-SWITCHED CO2 LASER
TIAN ZHAO-SHUO, WANG QI, LI ZI-QIN, WANG YU-SAN
2001, 50 (12): 2369-2374. doi: 10.7498/aps.50.2369
Abstract +
The theories of rate equation and six-temperature model for CO2 lasers are used to describe the process of the dynamic emission in the electrooptically Q switched CO2 laser. The peak power and delay time of Q switched laser calculated by the two theories are well consistent with the experiments. The calculated pulse width of Q switched laser using the theory of rate equation is narrow and the tailing is too short. However, a theoretical analysis by using the six-temperature model is consistent with the measured waveform and the tailing is obvious. In addition, the processes of energy-transfer of all kinds of molecular levels are considered in the six-temperature model. So compared to the rate equation, the six-temperature model makes a better analysis.
THE DYNAMIC MODULATION FOR GAIN PERFORMANCE IN MULTI-SEGMENT Nd:GLASS DISK LASER AMPLIFIERS
ZHANG HUA, FAN DIAN-YUAN
2001, 50 (12): 2375-2381. doi: 10.7498/aps.50.2375
Abstract +
Based upon the instantaneous output spectra of a xenon flashlamp, we have constructed a unique dynamic modeling program to predict the gain performance of multi segment Nd:glass laser amplifiers. The model, which includes all the dynamic modulations from flashlamp discharging to laser output, may be used in the laser amplifier system optimization. The gain uniformity in the horizontal direction is investigated with the modeling program. The amplified spontaneous emission inside a laser slab first increases the overall decay rate and thereby decreases the stored energy at the slab edges. The stored energy density at the slab center is higher than that at the slab edges when the explosion fraction of the flashlamp becomes large. The influences of the disk thickness and Nd2O3 doping level on gain performance are also studied with the modeling program. The stored fluence is determined by the doping-thickness products (Nd ion concentration ×slab thickness)in the multi-segment amplifiers slab, and the details are also given.
FABRICATION OF LARGE CONE ANGLE OPTICAL FIBER PROBE BY DYNAMIC CHEMICAL ETCHING METHOD
SUN JIA-LIN, TIAN GUANG-YAN, LI QIN, ZHAO JUN, GUO JI-HUA, XIE AI-FANG, ZHANG ZE-BO
2001, 50 (12): 2382-2386. doi: 10.7498/aps.50.2382
Abstract +
According to the hydraulic transmission principle, a device for fabricating large cone angle near-field optical fiber probe by means of dynamic chemical etching is developed. The results indicated that in the course of traditional fabrication of optical fiber probes by chemical etching, the configuration and the cone angle of the taper can be controlled efficiently through controlling the velocity of the lifting of etching fluid. Furthermore, The advantage of controlling the displacement between optical fiber probe and etching fluid step by step in the fabrication of large cone angle optical fiber probe is also described in this paper. A large cone angle near-field optical fiber probe in scanning near-field optical microscopy is applied to measuring the sphere with a diameter 200nm. Its force images show that this probe has high topography resolution (~50nm).
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
STUDIES OF OUTWARD-EMITTING COAXIAL VIRCATOR
SHAO HAO, LIU GUO-ZHI
2001, 50 (12): 2387-2392. doi: 10.7498/aps.50.2387
Abstract +
As a novel concept of vircator geometry proposed in this paper, the outward-emitting coaxial vircator (OECV) is at the cutting edge in the field of high-power microwave (HPM) source researches. Theoretical analyses are carried out to study the space-charge-limiting current in coaxial configuration and the terms of virtual cathode formation. According to the simulation results, OECV has the advantages in energy conversion efficiency and bears the potentialities in increasing the high-power microwave pulse width, as well as in generating HPM in relatively low bands. Two kinds of geomtries for HPM emission are also given in this paper.
DEALING WITH ABEL INVERSION BY USING LENGENDRE EXPANSIONS
RUAN HUAI-LIN, WAN BAO-NIAN, ZHANG XIAN-MEI, LIU JIAN-KUN
2001, 50 (12): 2393-2397. doi: 10.7498/aps.50.2393
Abstract +
A new method is presented for dealing with weakly asymmetrical Abel inversion in this paper. We separate the integrated quantity into odd and even parts by using Yasutomo′s method. The asymmetric local value is expressed as the product of a weight function and a symmetric local value. The symmetric distribution is expanded into Fourier Lengendre series, and the coefficients of the series are determined by using a least-square-fitting method.
DYNAMICAL MODEL OF THE RADIO-FREQUENCY PLASMA SHEATH
DAI ZHONG-LING, WANG YOU-NIAN, MA TENG-CAI
2001, 50 (12): 2398-2402. doi: 10.7498/aps.50.2398
Abstract +
A self-consistent model for the dynamics of the capacitive radio-frequency (RF) plasma sheath driven by a sinusoidal current source is obtained under the assumptions of time-dependent,collisionless ion motion and inertialess electrons. The model consists of fluid equations describing the charge transport in the sheath coupled to an equivalent circuit model of the sheath to predict the characteristics of it at any RF frequency. Some numerical results have been obtained for the instantaneous sheath thickness, the instantaneous voltage and the ion flux density on the substrate, etc. It has been shown that when the RF frequency is less than the ion plasma frequency, the ion flux density will strongly depend on the time.
PLASMA DIAGNOSIS OF RF DISCHARGE BY USING IMPEDANCE MEASUREMENT
YU JIAN-HUA, HUANG JIAN-JUN
2001, 50 (12): 2403-2407. doi: 10.7498/aps.50.2403
Abstract +
It is presented in this paper that the method known from network analysis with home-made probe and experimental setup to measure current, voltage and phase angle of RF discharge in He gas more accurately. The sheath thickness and the real and imaginary parts of the plasma impedance were obtained by using the equivalent circuit model and taking account stray capacitances of the set-up. In addition, making use of Godyak′s RF discharge simple model, the electron density in the discharge was calculated at different pressure and current density.
DT FUEL AREAL DENSITY DIAGNOSTIC IN DIRECT-DRIVEN IMPLOSIONS
YANG HONG-QIONG, YANG JIAN-LUN, WEN SHU-HUAI, WANG GEN-XING, GUO YU-ZHI, TANG ZHENG-YUAN, MU WEI-BING, MA CHI
2001, 50 (12): 2408-2412. doi: 10.7498/aps.50.2408
Abstract +
The diagnostic of DT fuel plasma areal density in the direct-driven implosion experiments on SG-Ⅱ laser facility has been performed by measuring the number of recoil D and T produced by 14MeV neutron′s scattering. The particles of recoil D and T were detected by CR39 solid-state nuclear track detector. The experimental results indicate that the uniformity of laser illuminating affects the compression to a certain extent. The areal density of exploding pusher target is about one order lower than that of ablative-driven target. This means that the compression of ablative-driven target is better than exploding pusher target. There is a strong relationship between areal density and suprathermal electron heating.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
ELECTRODEPOSITION OF DIAMOND-LIKE CARBON FILMS FROM ORGANIC SOLVENTS AND EFFECTS OF ANNEALING ON THE FILM STRUCTURE
GUO DONG, CAI KAI, LI LONG-TU, GUI ZHI-LUN
2001, 50 (12): 2413-2417. doi: 10.7498/aps.50.2413
Abstract +
After analyzing the molecular structure of several organic solvents we select methanol, N,N-dimethylformamide (DMF) and acetonitrile as the carbon source to deposit diamond-like carbon (DLC) films on Si plate with a pulse-modulated power. The deposition reaction can be facilitated by increasing temperature or by decreasing separation between the electrodes. The films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy sequentially. The results showed that the films were typical hydrogenated DLC films. Hydrogen was removed and the primary bonding in the films changed gradually from sp3-bonded carbon to sp2-bonded carbon as annealing proceeded, i.e. the film underwent a graphitization process. Comparing the results of different solvents, we discover that the methyl group of the solvents seems to be the functional group in forming the DLC films.
THE MICROSTRUCTURE AND ITS HIGH-TEMPERATURE ANNEALING BEHAVIOURS OF a-Si∶O∶H FILM
YANG FU-HUA, WANG YONG-QIAN, CHEN CHANG-YONG, CHEN WEI-DE, DIAO HONG-WEI, XU ZHEN-JIA, ZHANG SHI-BIN, KONG GUANG-LIN, LIAO XIAN-BO
2001, 50 (12): 2418-2422. doi: 10.7498/aps.50.2418
Abstract +
The microstructure and its annealing behaviours of a Si∶O∶H film prepared by PECVD are investigated in detail using micro Raman spectroscopy, X-ray photoelectron spectroscopy and Infrared absorption spectroscopy. The results indicate that the as deposited a-Si∶O∶H film is structural inhomogeneous, with Si-riched phases surrounded by O-riched phases. The Si-riched phases are found to be nonhydrogenated amorphous silicon (a-Si) clusters, and the O riched phases SiOx∶H ( x ≈1.35) are formed by random bonding of Si, O and H atoms. By high temperature annealing at 1150℃, the SiOx∶H ( x ≈1.35) matrix is shown to be transformed into SiO2 and SiOx (x ≈0.64), during which all of the hydrogen atoms in the film escape and some of silicon atoms are separated from the SiOx∶H ( x ≈1.35) matrix;The separated silicon atoms are found to be participated in the nucleation and growth processes of solid phase crystallization of the a Si-clusters, nano-crystalline silicon (nc-Si) is then formed. The microstructure of the annealed film is thereby described with a multi shell model, in which the nc- Si clusters are embedded in SiOx (x =0.64) and SiO2. The former is located at the boundaries of the nc-Si clusters, with a thickness comparable with the scale of nc-Si clusters, and forms the transition oxide layer between the nc-Si and the SiO2 matrix.
NUMERICAL SIMULATION OF DENDRITIC GROWTH IN UNDERCOOLED MELT USING PHASE-FIELD APPROACH
C. BECKERMANN, A. KARMA, YU YAN-MEI, YANG GEN-CANG, ZHAO DA-WEN, Lü YI-LI
2001, 50 (12): 2423-2428. doi: 10.7498/aps.50.2423
Abstract +
Using the phase-field approach, the dendritic growth in the undercooled pure metal melt is simulated, and the dependence of dendritic growth upon the anisotropy,interfacial kinetics,thermal diffusivity and surface energy is investigated.The calculated results indicate that the heat noise can trigger the growth of side-branches;however this dose not influence the selection of the tip operating state.The dimensionless tip velocity increases and the tip radius decreases with the increase of anisotropy. Correspondently,the dimensionless tip velocity decreases and tip radius increases when the interfacial kinetics or thermal diffusivity (when the interface kinetic coeffiecient is less than 1) inreases. The surface energy tends to increase the size of dendrite and keeps the stability of interface under the disturbance of heat noise.The greater the surface energy,the weaker the tendency to form side-branches.
XPS AND AES INVESTIGATION OF GaN FILMS GROWN BY MBE
XU ZHUO, CHEN GUANG-DE, YUAN JIN-SHE, QI MING, LI AI-ZHEN
2001, 50 (12): 2429-2433. doi: 10.7498/aps.50.2429
Abstract +
The surface composition of GaN grown by plasma-assisted MBE was investigated using X-ray photoelectron spectroscopy and Auger election emission spectroscopy(AES), while the depth profile was analyzed by AES with Ar iron sputtering. The experimental results indicated that unintentional doped semi-in salating films formed by plasma-assisted MBE had a rich-gallium surface. It was found that the impurity carbon was chiefly adsorbed onto the surface while oxygen diffused into the bulk to distribute in a certain depth. Consequently, the oxygen-related impurity band and an acceptor level could be simultaneously formed in the layer. This influenced the optical and electrical properties of the films.
RADIATION EFFECTS OF MOS DEVICE AT LOW DOSE RATE AND LOW TEMPERATURE
ZHANG TING-QING, LIU CHUAN-YANG, LIU JIA-LU, WANG JIAN-PING, HUANG ZHI, XU NA-JUN, HE BAO-PING, PENG HONG-LUN, YAO YU-JUAN
2001, 50 (12): 2434-2438. doi: 10.7498/aps.50.2434
Abstract +
Effects of irradiation dose rates and irradiation temperature are investigated for MOS device under γ-rays. Threshold voltage shift is compared after the MOS devices are radiated at different dose rates and different temperatures. At low dose rate,interface trap formation is affected by the irradiation time and H+ induced in the oxide,the longer the device is radiated and the greater the number of induced H+,the more the interface trap. The effects of temperature on radiation response are related to the time of interface trap formation,it takes more time to form interface trap at low temperatures.
ATOMIC STRUCTURE OF THE Ge(112)-(4×1)-In RECONSTRUCTION
TU XIU-WEN, GAI ZHENG
2001, 50 (12): 2439-2445. doi: 10.7498/aps.50.2439
Abstract +
We have studied the Ge(112)-(4×1)-In reconstruction with scanning tunneling microscopy (STM). Based on our bias dependent STM images and the characteristic electronic structure of stable submonolayer group Ⅲ-metal/group-Ⅳ-semiconductor interfaces, we propose an atomic model of this reconstruction for further investigation. The adsorption sites of In atoms are the same as In atoms' adsorption sites in the Si(112)-(7×1)-In reconstruction, but are different from the adsorption sites of Al and Ga atoms on the Si(112) surface. We suggest that this difference in adsorption sites is mainly due to the longer covalent bond length of In atoms. We further propose that, due to the smaller misfit, Al and Ga atoms may form longer nano wires along the step edges on the Ge(112) surface.
EFFECT OF LOW-ENERGY DEPOSITION PARTICLES ON INITIAL STAGE OF THIN FILM
WEI HE-LIN, LIU ZU-LI, YAO KAI-LUN, CHEN MIN
2001, 50 (12): 2446-2451. doi: 10.7498/aps.50.2446
Abstract +
The effect of low-energy deposition particles on the initial stage of thin film growth is studied by Monte Carlo simulation in this paper. The energy range of deposition particles is from 0 to 0.7eV. Three processes are considered: atom deposition, adatom diffusion and re evaporation. The effect of nearest adatoms and next near adatoms is also considered. The results show that the low-energy ion irradiation strongly affects the island film growth process at low temperature. Morphologies and size distributions of islands have significantly changed with the increase of incident ion energy.
SiC NANOWIRES GROWN ON SILICON(100) WAFER BY MPCVD METHOD
HU YING
2001, 50 (12): 2452-2455. doi: 10.7498/aps.50.2452
Abstract +
Silicon carbide nanowires have been grown on single crystal silicon wafers by using microwave plasma chemical vapor deposition method. The nanowires are analyzed by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy and low-energy electron diffraction methods. The growth mechanism of nanowires is proposed.
MECHANISM FOR THE ORIENTATIONAL PHASE TRANSITION OF K3C60
XU YA-BO, LI HAI-YANG, CHEN XIAO, LI HONG-NIAN, BAO SHI-NING, WU TAI-QUAN, QIAN HAI-JIE, I. KURASH, LIU FENG-QIN
2001, 50 (12): 2456-2460. doi: 10.7498/aps.50.2456
Abstract +
Conduction band structure of K3C60 single crystal films was studied at temperatures near 200 K. Band dispersions along the [111] direction could be observed at 190 K using synchrotron radiation photoemission spectra technique. When the sample temperature increased to 220 K, most subpeaks of the conduction band vanished and the dispersions could not be observed. This result coincides with the existence of an orientational phase transition occurring at 200 K. The fcc nearest-neighbor antiferromagetic Ising model was adopted to analyze the temperature dependence of the band structure. The phase transition is due to the one-dimensional-disordered structure (1DDS) at lower temperatures, which turns to a mixture of bi-directional structure domains and disordered molecules at higher temperatures. The number of disordered molecules was deduced to be about 40 percent of the total molecules at 220 K.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
C-V CHARACTERISTICS OF Bi2Ti2O7 THIN FILMS ON n-Si(100)
WANG HONG, WANG DONG, WANG MIN, LU WEI, SHEN XUE-CHU, WANG SHAO-WEI
2001, 50 (12): 2461-2465. doi: 10.7498/aps.50.2461
Abstract +
We report the growth of Bi2Ti2O7 thin films on n type Si substrates by the chemical solution decomposition technique. Both the X-ray double-crystal diffraction and atomic force micro spectroscopy measurements are used to check the film properties. It is shown that the film is a multi crystal film dominated by the Bi2Ti2O7 phase. The C-V measurements are also performed on Au/Bi2Ti2O7/n-Si(100) MOS structure. It is revealed that both the fixed and mobile negative charges are contained in the film. The mobile negative charge results in the hysteresis loops on C-V curve.
ANOMALOUS MAGNETIZATION PEAK EFFECT IN Bi2Sr2CaCu2O8 SINGLE CRYSTALS
WANG WEN-HU, XIONG YU-FENG, LI SHI-LIANG, CHEN ZHAO-JIA, WEN HAI-HU
2001, 50 (12): 2466-2470. doi: 10.7498/aps.50.2466
Abstract +
Magnetic hysteresis loops were measured on Bi2Sr2CaCu2O8 single crystals with a vibrating sample magnetometer. An anomalous second magnetization peak was observed between 20 and 40K. The magnetic fields showing peak effect in over-doped crystal were observed to be higher than the optimally doped samples. The disorder-driven transition shifted to lower fields with increasing point disorder. At lower temperatures the quasilattice transformed into a disordered solid as the field was increased above the second magnetization peak. There was not any transition from the ordered solid quasilattice to a disordered solid below 20K in schematic vortex matter phase diagram in BSCCO. The peak effect was a complicated function of magnetic field, temperature and material disorder.
MICROWAVE PERMITTIVITY OF NANO Si/C/N OMPOSITE POWDERS
ZHOU WAN-CHENG, WAN WEI, ZHAO DONG-LIN
2001, 50 (12): 2471-2476. doi: 10.7498/aps.50.2471
Abstract +
The microwave permittivity of nano Si/C/N composite powders suspended in paraffin wax has been studied at the frequency range of 8.2—18GHz. The nano Si/C/N composite powders were synthesized from hexamethyldisilazane ((Me3Si)2NH) (Me:CH3) by a laser induced gas phase reaction. The dissipation factors of the nano Si/C/N composite powders are high at the microwave frequencies. The microwave permittivity of the mixture of nano Si/C/N composite powders and paraffin wax (or other dielectric materials) can be tailored by the content of the composite powders. And ε′, ε″ and tan δ increase with the volume filling factor ( v ) of nano Si/C/N composite powders. The ε′ and ε″ can be effectively modeled using second order polynomials ( ε′, ε″=Av2+Bv+C ). The ε′ and ε″ of the nano Si/C/N composite powders decrease with frequency at the frequency range of 8.2—18GHz. The difference being the microwave resonance is not sharply peaked but rather smeared out over a large frequency range. The promising features of nano Si/C/N composite powders would be due to more complicated Si, C, and N atomic chemical environment than in a mixture of pure SiC and Si3N4 phase. The SiC microcrystallines in the nano Si/C/N composite powders dissolve a great deal of nitrogen. The local structure around Si atoms changes by introducing N into SiC. Carbon atoms around Si are substituted by N atoms. So there exist a large number of charged defects and dangling bonds in the nano Si/C/N composite powders. Thus charged defects and quasi free electrons move in response to the electric field, diffusion or polarization current resulting from the field propagation. The high ε″ and dissipation factor tan δ(ε″/ε′) of Si/C/N composite powders are due to the dielectric relaxation.
DYNAMICS THEORY OF FERROELECTRIC POLARONS
LI ZHI-QIANG, CHEN MIN, SHEN WEN-BIN, LI JING-DE
2001, 50 (12): 2477-2481. doi: 10.7498/aps.50.2477
Abstract +
Dynamics theory of ferroelectric polarons, which was developed from the shielding theory of ferroelectricity, is used to explain the polarization switch of ferroelectricity. The theoretical results are well consistent with the experimental results of TGS crystal. Based on this theory, the basic physics process of electron emissions from ferroelectricity can be studied.
NONLINEARLY OPTICAL-INDUCED BIREFRINGENCE IN AZO LIQUID CRYSTAL POLYMERS
MING HAI, WANG PEI, ZHANG JIANG-YING, LONG YUN-ZE, XIA YONG, XIE JIAN-PING, ZHANG QI-JIN, LIANG ZHONG-CHENG
2001, 50 (12): 2482-2486. doi: 10.7498/aps.50.2482
Abstract +
We introduce the experimental results of nonlinearly optical induced birefringence in azo liquid crystal polymer P-CN. The nonlinear nature of the photochemical process in P-CN was verified by the use of Z scan technique. Based on the analysis of the photo isomerization mechanism, a nonlinearly optical method is proposed to induce the birefringence in azo liquid crystal polymers by optical optical isomerization cycle.
ROOM-TEMPERATURE 1.54μm Er3+ PHOTOLUMINESCENCE FROM Er-DOPED SILICON-RICH SILICON OXIDE FILM GROWN BY MAGNETRON SPUTTERING
RAN GUANG-ZHAO, CHAN YUAN, ZHANG BO-RUI, QIAO YONG-PING, FU JI-SHI, QIN GUO-GANG, YUAN FANG-CHENG, MA ZHEN-CHANG, ZONG WAN-HUA
2001, 50 (12): 2487-2491. doi: 10.7498/aps.50.2487
Abstract +
Room temperature photoluminescence (PL) has been observed from Er doped silicon rich silicon oxide films grown by magnetron sputtering. For all kinds of silicon rich silicon oxide films grown with different excess Si contents, each PL spectrum has two peaks at 1.54 and 1.38μm, which originate from Er3+ and a certain kind of defects, respectively, in the silicon rich silicon oxide. It was found that 1.54 and 1.38μm PL peak intensities are correlated with each other. The PL intensity-dependence on the excess-Si content and annealing temperature was studied in detail.
INFRARED ANALYSIS OF BOND CONFIGURATION FOR THE a-C∶F∶H FILMS DEPOSITED AT VARIABLE CHF3/CH4 FLOW RATIOS
LU XIN-HUA, XIN YU, NING ZHAO-YUAN, GAN ZHAO-QIANG, FANG LIANG, CHENG SHAN-HUA
2001, 50 (12): 2492-2496. doi: 10.7498/aps.50.2492
Abstract +
a-C∶F∶H films are prepared by microwave ECR plasma-enhanced chemical vapor deposition method at variable CHF3/CH4 gas flow raitos. The results from the Fourier transform-infra-red abserption for these films have shown that a structural evolution of the a-C∶F∶H film occurs at variable flow ratios R =[CHF3]/([CHF3]+[CH4]). The main structure of the films is diamond-like carbon (DLC) characteristics for R less than 64%. The film presents a structure of PTFE-like as R is larger than 64%, where the dominant structural monomer is —CF2. Meanwhile, this structural evolution has also an influence on optical gap of the films. Optical gap decreases with the increase of flow ratios in the region of DLC-like characteristics, while increasing in the PTFE-like region. The transmittance of the a-C∶F∶H film is close to 100% for R larger than 92%.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
ESTIMATION OF POST-NEWTONIAN APPROXIMATION OF GRAVITY THAT AFFECTS SATELLITES OF PLANET
ZHONG MING-QIAN
2001, 50 (12): 2497-2500. doi: 10.7498/aps.50.2497
Abstract +
The post-Newtonian approximation in general relativity will be used to estimate gravity for the jovian system and the comet shoemaker-Levy 9 that collided with Jupiter. We calculate and discuss the post-Newtonian corrections to the gravity of Jupiter and precessions of its satellites, which are compared with the Earth-Moon system.
LETTERS
THE INFLUENCE OF InAs QUANTUM DOTS ON THE TRANSPORT PROPERTIES OF SCHOTTKY DIODE
LI HONG-WEI, WANG TAI-HONG
2001, 50 (12): 2501-2505. doi: 10.7498/aps.50.2501
Abstract +
In the temperature range from 77 to 292 K, we investigated the transport properties of metal-semiconductor-metal diode containing InAs quantum dots. With increasing temperature, the current hysteresis loops, which were caused by charged quantum dots, reduced gradually. The resonant tunneling process, which may occur in some Schottky barriers, could induce steps on the I-V curves in the measured temperature range and diminish the hysteresis loops intensively. We have calculated the saturation current density and ideality factor of the Schottky barrier with reverse characteristics. We found that the resonant tunneling process would shift the Schottky barrier away from the ideality status, while the charging effect mainly influenced the barrier height and therefore influenced the saturation current density.
CURRENT TRANSPORT THROUGH STACKED InAs QUANTUM DOTS EMBEDDED IN A SCHOTTKY BARRIER
LI HONG-WEI, WANG TAI-HONG
2001, 50 (12): 2506-2510. doi: 10.7498/aps.50.2506
Abstract +
We have investigated the transport properties of a metal-semiconductor-metal structure containing multi-layers of InAs quantum dots from 77 K to room temperature. Three distinct phenomena are observed in the current voltage( I-V ) curves:the hysteresis loops, current jumps and voltage offsets. Because of the coupling between the multi layered quantum dots, the devices made of these quantum dots exhibit much more complicated phenomenon than the devices containing single-layer quantum dots. The devices may undergo many metastable states and relaxation processes. These processes would induce current jump structures and noise in the I-V curve.