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Multiparty Quantum Secret Sharing of Classical Message using Cavity Quantum Electrodynamic System
HAN Lian-Fang, LIU Yi-Min, ZHANG Zhan-Jun,
Chin. Phys. Lett. 2006, 23 (8):
1988-1991
.
An experimental feasible scheme of multiparty secret sharing of classical messages is proposed, based on a cavity quantum electrodynamic system. The secret messages are imposed on atomic Bell states initially in the sender's possession by local unitary operations. By swapping quantum entanglement of atomic Bell states, the secret messages are split into several parts and each part is distributed to a separate party. In this case, any subset of the entire party group can not read out the secret message but the entirety via mutual ooperations. In this scheme, to discriminate atomic Bell states, additional classical fields are employed besides the same highly-detuned single-mode cavities used to prepare atomic Bell states. This scheme is insensitive to the cavity decay and the thermal field, and usual joint Bell-state measurements are unnecessary.
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Quantum Effects of Many Atoms in Spinor Bose--Einstein Condensates
YU Zhao-Xian, LIANG Jiu-Qing, JIAO Zhi-Yong
Chin. Phys. Lett. 2006, 23 (8):
2004-2007
.
We have studied the evolutions of the population transfer, tunnelling current and antibunching effects between spin-(+1) and spin-(-1) in the case of the strong laser pulses. It is found that the population transfer and tunnelling current exhibit periodical oscillation. For the same Rabi frequency, the larger the atom number, the longer the oscillation period is. For the spin-(-1) component, when the atomic numbers are N=4 and 10, the antibunching effect can appear. For different atomic numbers, the appearing regions are very different. For spin component +1, the antibunching effect can always appear for different atomic numbers.
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Non-Equilibrium Quantum Transport of Bosons through a Quantum Dot
CHEN Zuo-Zi, Lü Rong, ZHAI Hui, CHANG Lee
Chin. Phys. Lett. 2006, 23 (8):
2008-2011
.
The quantum dot coupled to reservoirs is known as a typical mesoscopic setup to manifest the quantum characteristics of particles in transport. In analogue to many efforts made on the study of electronic quantum dots in the past decades, we study the transport of bosons through such a device. We first generalize the formula which relates the current to the local properties of dot in the bosonic situation. Then, as an illustrative example, we calculate the local density of state and lesser Green function of the localized boson with a bosonic Fano--Anderson model. The current--voltage (I-V) behaviour at zero temperature is presented, and in the bosonic dot it is the I-V curve, in contrast to the differential conductance in the electronic dot, which is found to be proportional to the spectral function.
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Unpredictability of Iteration Destination in an Integrate-and-Fire Circuit
DAI Jun, HU Chin-Kun, CHU Xiang-Sheng, HE Da-Ren,
Chin. Phys. Lett. 2006, 23 (8):
2023-2026
.
Based on our previous study that discovered a new mechanism of the riddled-like basin appearance in piecewise continuous and noninvertible links of two conservative mappings, and the mechanism being the mixing of different attraction basins on a fat-fractal set, which was addressed as the forbidden region net [Phys. Rev. E 72 (2005) 025201(R)], we show numerically that the riddled-like attraction basins and the new mechanism appear in an integrate-and-fire circuit that can be described by piecewise continuous and noninvertible links of two dissipative mappings. This leads to the fact that vast increase of the precision of the initial condition results in practically no improvement in predictability of the iteration destination. Predictability is usually characterized by examining how error probability in the prediction, f(ε), scales with the precision ε under the initial condition. Typically, f(ε) ~ εα with 0 ≤ α ≤ 1 being the uncertainty exponent. For riddled-like basins, α should be zero, which is in good agreement with the numerical simulation results.
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Theoretical Study on Negative Parity States of 191,193,195,197Au in Particle Triaxial-Rotor Model
CHEN Guo-Jie, LIU Yu-Xin, , CAO Hui, SONG Hui-Chao
Chin. Phys. Lett. 2006, 23 (8):
2042-2045
.
By taking the particle triaxial-rotor model with variable moment of inertia, we investigate the energy spectra, the deformation and the single particle configuration of the negative-parity states in nuclei 191,193,195,197Au systemically. The calculated energy spectra agree well with experimental data. The obtained results indicate that the negative-parity states in 191,193,195,197Au originate from the proton-hole h11/2 configuration coupled to a triaxial oblate Hg core. Meanwhile the main single particle configuration of the bands 1, 2 and 3 are identified to be |5h11/2 1/2 > (α= - 1/2), |5h11/2 > (α= 1/2) and |5h9/2 7/2>;, respectively.
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Tritium Burn-up Depth and Tritium Break-Even Time
LI Cheng-Yue, DENG Bai-Quan, HUANG Jin-Hua, YAN Jian-Cheng
Chin. Phys. Lett. 2006, 23 (8):
2056-2058
.
Similarly to but quite different from the xenon poisoning effects resulting from fission-produced iodine during the restart-up process of a fission reactor, we introduce a completely new concept of the tritium burn-up depth and tritium break-even time in the fusion energy research area. To show what the least required amount of tritium storage is used to start up a fusion reactor and how long a time the fusion reactor needs to be operated for achieving the tritium break-even during the initial start-up phase due to the finite tritium breeding time that is dependent on the tritium breeder, specific structure of breeding zone, layout of coolant flow pipe, tritium recovery scheme, extraction process, the tritium retention of reactor components, unrecoverable tritium fraction in breeder, leakage to the inertial gas container, and the natural decay etc., we describe this new phenomenon and answer this problem by setting up and by solving a set of equations, which express a dynamic subsystem model of the tritium inventory evolution in a fusion experimental breeder (FEB). It is found that the tritium burn-up depth is 317g and the tritium break-even time is approximately 240 full power days for FEB designed detail configuration and it is also found that after one-year operation, the tritium storage reaches 1.18kg that is more than the least required amount of tritium storage to start up three of FEB-like fusion reactors.
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A Compact Nanosecond-Pulse Shaping System Based on Pulse Stacking in Fibres
SUI Zhan, LIN Hong-Huan, WANG Jian-Jun, ZHAO Hong-Ming, LI Ming-Zhong, QIAN Lie-Jia, ZHU He-Yuan, FAN Dian-Yuan
Chin. Phys. Lett. 2006, 23 (8):
2074-2076
.
We demonstrate a compact pulse shaping system based on temporal stacking of pulses in fibres, by which synchronized pulses of ultrashort and nanosecond lasers can be obtained. The system may generate shape-controllable pulses with a fast rise time and high-resolution within a time window of ~2.2ns by adjusting variable optical attenuators in the 32 fibre channels independently. With the help of optical amplifiers, the system delivers mJ-level pulses with a signal-to-noise ratio of ~35dB.
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Characteristics of Nd:GdVO4 Laser with Different Nd-Doping Concentrations
ZHANG Ling, ZHANG Chun-Yu, WEI Zhi-Yi, ZHANG Zhi-Guo, Stephan Strohmaier, Hans J. Eichler
Chin. Phys. Lett. 2006, 23 (8):
2088-2091
.
We report the properties of a compact diode-pumped continuous-wave Nd:GdVO4 laser with a linear cavity and different Nd-doped laser crystals. In a 0.2at.% Nd-doped Nd:GdVO4 laser, 1.54W output
laser power is achieved at 912nm wavelength with a slope efficiency of 24.8% at an absorbed pump power of 9.4W. With 0.3at.% Nd-doping concentration, we can obtain the either single-wavelength emission at 1064nm or 912nm or the dual-wavelength emission at 1064nm and 912nm by controlling the incident pump power. From an incident pump power of 11.6W, the 1064nm emission between 4F3/2 and 4I11/2 is suppressed completely by the 912nm emission between 4F3/2 and 4I9/2. We obtain 670mW output of the 912nm single-wavelength laser emission with a slope efficiency of 5.5% by taking an incident pump power of 18.4W. Using a Nd:GdVO4 laser with 0.4at.% Nd-doping concentration, we obtain either the single-wavelength emission at 1064nm or the dual-wavelength emission at both 1064nm and 912nm by increasing the incident pump power. We observe a strong competition process in the dual-wavelength laser.
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Realization of Stable Narrow Linewidth Dual-Wavelength Lasing in an Erbium-Doped Fibre Laser by Cleaving the Wavelength-Selective Filter Spectrum
JIA Xiu-Jie, LIU Yan-Ge, SI Li-Bin, GUO Zhan-Cheng, FU Sheng-Gui, LIU Feng-Nian, YUAN Shu-Zhong, DONG Xiao-Yi
Chin. Phys. Lett. 2006, 23 (8):
2092-2094
.
We propose and demonstrate a new concept of stable narrow-line-width and close wavelength spacing dual-wavelength lasing in an Er-doped fibre ring laser (EDFRL) by cleaving the spectrum with a wavelength-selective component in the EDFRL. A fibre loop mirror (FLM) combining with a polarization controller (PC) acts as the cleaver. The cleaver can produce a fine pectinate spectrum. By adjusting the PC, the fine pectinate spectrum can be so changeable that cleaving the spectrum of a fibre Bragg grating (FBG) into two parts. As a result, we obtain the dual-wavelength fibre lasering with a bandwidth of only 0.03nm and a wavelength spacing of only 0.07nm. Furthermore, the laser can also perform stable switchable single wavelength or stable different-bandwidth dual-wavelength by carefully adjusting the PC at room temperature.
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Compact Single-Stage Femtosecond Multipass Ti:Sapphire Amplifier at 1kHz with High Beam Quality
ZHAO Wei, WANG Yi-Shan, CHENG Zhao, ZHU Shao-Lan, LIU Hong-Jun, LING Wei-Jun, CHEN Guo-Fu
Chin. Phys. Lett. 2006, 23 (8):
2098-2100
.
A compact femtosecond Ti:sapphire amplifier system is reported using single-stage multipass configuration with high beam quality. A high dispersion glass stretcher and a pair of double prisms for compression are introduced based on broadband femtosecond seed pulses. The non-grating-based pulse stretcher and compressor are advantageous to increase high beam quality and to reduce the high-order dispersion. A Gaussian filter is used to reduce the gain narrowing effect in amplification. The compact femtosecond Ti:sapphire nine-pass amplifier delivers pulses with a duration of 26fs and an energy of 800μJ at 7mJ pumping pulses energy at 1kHz. The 1-kHz femtosecond amplifier with high beam quality and high stability is very suitable for ultrafast physics research applications, such as attosecond science, ultra-precision micromachining, and THz wave generation.
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A Low-Pump-Threshold High-Repetition-Rate Intracavity Optical Parametric Generator Based on Periodically Poled Lithium Niobate
JI Feng, , ZHANG Bai-Gang, , LI En-Bang, ZHOU Rui, ZHANG Tie-Li, LU Yang, ZHAO Pu, WANG Peng, YAO Jian-Quan,
Chin. Phys. Lett. 2006, 23 (8):
2113-2116
.
A low-pump-threshold high-repetition-rate intracavity optical parametric generator (IOPG) by using a periodically poled lithium niobate (PPLN) is reported. The PPLN, which is 18.7mm long and has a grating period of 28.93μm at room temperature, is inserted in a diode-end-pumped Nd:YVO4 laser with an acousto-optic Q switch. The parametric generation threshold is 1.3W (diode laser power) at a Q-switch repetition rate of 19kHz. At an incident diode pump power of 5W, an average signal output power of 280mW has been achieved. The signal pulse duration is approximately 85ns. By changing the crystal temperature from 120°C to 250°C, the signal wavelength can be tuned from 1.493μm to 1.538μm.
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Spatially Inhomogeneous Gain Modification in Photonic Crystals
LI Fei, HUANG Yi-Dong, ZHANG Wei, PENG Jiang-De
Chin. Phys. Lett. 2006, 23 (8):
2117-2120
.
The electric and magnetic energy distributions in photonic crystals (PC) are calculated by using the plane wave expansion (PWE) method. Even though the total electric and magnetic energy in each unit cell of photonic crystals are equal to each other, the ratio of electric and magnetic energy densities varies depending on the local position. Based on Fermi’s golden rule, the optical gain is analysed in the full quantum framework that takes the nonuniform energy density ratio into account. This nonuniform energy density ratio in photonic crystals, defined in an equal form as gain modification factor, leads to spatially inhomogeneous modification of optical gain. Results reported in the paper provide a new perspective for analysing gain characteristics, as well as the lasing properties, in photonic crystals.
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Mode Exciting Properties of Photonic Crystal Fibres with the Optical Field Incident from a Single Mode Fibre
LIU Jian-Guo, XUE Li-Fang, KAI Gui-Yun, LIU Yan-Ge, ZHANG Wei-Gang, LI Yan, WANG Zhi, ZHANG Chun-Shu, DONG Xiao-Yi
Chin. Phys. Lett. 2006, 23 (8):
2125-2128
.
We numerically investigate the mode exciting properties of photonic crystal fibres by using the beam propagation method when the optical field is input from a traditional single mode fibre. The results show that both the excited mode spectrum and the coupling-efficiency of each excited mode depend on the normalized pitch Λ/λ and the normalized hole-size Λ/λ. Furthermore, we obtain the boundary profile of the optimizing coupling-efficiency for the excited fundamental mode: the boundary (Λ/λ)* is linear to the boundary (d\λ)*. All of these will pave the way for smoothing applications of photonic-crystal fibres, such as splicing and designing photonic-crystal-fibre functional devices.
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Investigation of Impurity Ion Transport with Laser Blow-off in HL-2A Tokamak
CUI Zheng-Ying, HUANG Yuan, SUN Ping, ZHENG Yong-Zhen, SHI Pei-Lan, LU Jie, FU Bing-Zhong, ZHANG Peng, PAN Yu-Dong, DONG Yun-Bo, DENG Wei, YANG Qing-Wei, DING Xuan-Tong
Chin. Phys. Lett. 2006, 23 (8):
2143-2146
.
Non-recycling impurities are injected into ohmic HL-2A plasma for the first time. The impurities of titanium and aluminium are injected in the discharges with varying plasma density and current. The convection and diffusion process of the injected impurity ions during the inward phase are qualitatively investigated. The results show that the transport of impurities is much slower in the central region of the plasma than outside of it and that it is greatly enhanced during sawtooth crashes.
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Ab Initio Study of Structural and Electronic Properties of Hexagonal BC2N
LUO Xiao-Guang, LIU Zhong-Yuan, GUO Xiao-Ju, HE Ju-Long, YU Dong-Li, TIAN Yong-Jun, SUN Jian, WANG Hui-Tian
Chin. Phys. Lett. 2006, 23 (8):
2175-2178
.
We investigate hexagonal BC2N in graphite unit cells using the first-principles method and calculate the total energies, lattice parameters, and electronic band structures after full relaxation. It is shown that stable hexagonal BC2N should be stacked sequentially with one graphite layer and one h-BN layer. The density of states indicates that this structure should have metallicity.
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Growth and Annealing Study of Mg-Doped AlGaN and GaN/AlGaN Superlattices
WANG Bao-Zhu, WANG Xiao-Liang, HU Guo-Xin, RAN Jun-Xue, WANG Xin-Hua, GUO Lun-Chun, XIAO Hong-Ling, LI Jian-Ping, ZENG Yi-Ping, LI Jin-Min, WANG Zhan-Guo
Chin. Phys. Lett. 2006, 23 (8):
2187-2189
.
Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition (MOCVD). Rapid thermal annealing (RTA) treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AlGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4×103Ωcm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7×1017cm-3 and a resistivity of 5.6Ωcm. The piezoelectric field in the GaN/AlGaN superlattices improves the activation efficiency of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.
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Relation of Structure and Superconductivity in Self-Compensating Y1-xCaxBa2-xLaxCu3Oy
SUN Xue-Feng, YU Jing, WANG Fa, ZHANG Han
Chin. Phys. Lett. 2006, 23 (8):
2221-2224
.
The self-compensating compound of Y1-xCaxBa2-xLaxCu3Oyis synthesized through a solid-state reaction method with x from 0.25 to 0.55. Structural and superconducting properties have been
investigated by x-ray diffraction, Rietveld refinement, and dc magnetization measurement, respectively. The impure peaks appear when x is more than 0.5 in the diffraction pattern. Orthorhombic--tetragonal transition occurs at x=0.45. Some local structural parameters, such as Cu(1)--O(4), Cu(2)--O(4) bond lengths, change randomly in a narrow range. The relationship between the character of (Ba/La)--O plane and Tc is rather interesting. We attribute the behaviour of superconductivity to the joint effects of these local structural parameters. The results give the evidence that the influence of the structural change on superconductivity is essential and independent of carrier concentration.
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Magnetic Properties of Melted ThMn12-Type Carbides and Their Nitrides
LIU Shun-Quan, HAN Jing-Zhi, DU Hong-Lin, WANG Chang-Sheng, YANG Ying-Chang
Chin. Phys. Lett. 2006, 23 (8):
2229-2231
.
The carbides of NdDy0.2Fe12-yMoyC0.6 (y=1.5, 2) crystallized in the ThMn12-type structure have been successfully synthesized by arc melting method, followed by a heat treatment. The magnetic properties are strongly enhanced with the addition of carbon. Upon the carbonation the saturation magnetization Ms is increased by about 20emu/g and the Curie temperature Tc is enhanced by 40--70K. The spin reorientation (SR) temperature decreases from 125 K for NdDy0.2Fe10Mo2 to 55 K for NdDy0.2Fe10Mo2C0.6 indicating the change of magnetocrystalline anisotropy in the Nd sublattice. It is found that the intrinsic magnetic properties of the carbides can be improved by further nitrogenation. The composite carbon--nitrogen compounds show a Tc~560K, Ms~105emu/g and Ha (anisotropy field) ~86kOe for NdDy0.2Fe10Mo2C0.6Nz and a Tc~628K, Mx~119emu/g and Ha~115kOe for NdDy0.2Fe10.5Mo1.5C0.6Nz. These magnetic properties are even better than those of simple nitrides, suggesting that these compounds can be considered as a good candidate for permanent magnet applications.
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Luminescent Characteristics of Near Ultraviolet InGaN/GaN MQWs Grown on Grooved Sapphire Substrates Fabricated by Wet Chemical Etching
YU Nai-Sen, GUO Li-Wei, CHEN Hong, XING Zhi-Gang, WANG Jing, ZHU Xue-Liang, PENG Ming-Zeng, YAN Jian-Feng, JIA Hai-Qiang, ZHOU Jun-Ming
Chin. Phys. Lett. 2006, 23 (8):
2243-2246
.
InGaN/GaN multiple quantum wells (MQWs) are grown on planar and maskless periodically grooved sapphires by metal organic vapour phase epitaxy (MOCVD). High-resolution x-ray rocking curves and transmission electron microscopy (TEM) are adopted to characterize the film quality. Compared with the MQWs grown on planar sapphire, the sample grown on grooved sapphire shows better crystalline quality: a remarkable reduction of dislocation densities is achieved. Meanwhile, the MQWs grown on grooved sapphire show two times larger PL intensity at room temperature. Temperature-dependent PL measurements are adopted to investigate the luminescence properties. The luminescence thermal quenching based on a fit to the Arrhenius plot of the normalized integrated PL intensity over the measured temperature range suggests that the nonradiative recombination centres (NRCs) are greatly reduced for the sample grown on grooved sapphire. We assume that the reduction of dislocations which act as NRCs is the main reason for the sample grown on pattern sapphire having higher PL intensity.
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Preparation of Cu(In,Ga)Se2 Thin Film Solar Cells by Selenization of Metallic Precursors in an Ar Atmosphere
XU Chuan-Ming, SUN Yun, ZHOU Lin, LI Feng-Yan, ZHANG Li, XUE Yu-Ming, ZHOU Zhi-Qiang, HE Qing
Chin. Phys. Lett. 2006, 23 (8):
2259-2261
.
Cu(In,Ga)Se2 thin films are deposited on Mo-coated glass substrates by Se vapour selenization of sputtered metallic precursors in the atmosphere of Ar gas flow under a pressure of about 10Pa. The it in situ heat treatment of as-grown precursor leads to the formation of a better alloy. During selenization, the growth of CuInSe2 phase preferably proceeds through Se-poor phases as CuSe and InSe at relatively low substrate temperature of 250°C, due to the absence of In2Se3 at intermediate stage at low reactor pressure. Subsequently, the Cu(In,Ga)Se2 phase is produced by the reactive diffusion of CuInSe2 with a Se-poor GaSe phase at high temperature of up to 560°C. The final film exhibits smooth surface and large grain size. The absorber is used to fabricate a glass/Mo/Cu(In,Ga)Se2/CdS/ZnO cell with the total-area efficiency of about 7%. The low open-circuit voltage value of the cell fabricated should result from the nonuniform distribution of In and Ga in the absorber, due to the diffusion-controlled reaction during the phase formation. The films, as well as devices, are characterized.
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Behaviour of Self-Standing CVD Diamond Film with Different Dominant Crystalline Surfaces in Thermal-Iron Plate Polishing
CHEN Guang-Chao, ZHOU Zu-Yuan, LI Bin, ZHOU You-Liang, J. Askri, LI Cheng-Ming, TANG Wei-Zhong, TONG Yu-Mei, LU Fan-Xiu
Chin. Phys. Lett. 2006, 23 (8):
2266-2268
.
Self-standing CVD diamond films with different dominant crystalline surfaces are polished by the thermal-iron plate polishing method. The influence of the dominant crystalline surfaces on polishing efficiency is investigated by measuring the removal rate and final roughness. The smallest rms roughness of 0.14μm is measured with smallest removal rate in the films with the initial (220) dominant crystalline surface. Activation energy for the polishing is analysed by the Arrhenius relation. It is found that the values are 170kJ/mol, 222kJ/mol and 214kJ/mol for the film with three different dominant crystalline surfaces. Based on these values, the polishing cause is regarded as the graphitization-controlling process. In the xperiment, we find that transformation of the dominant crystalline surfaces from (111) to (220) always appears in the polishing process when we polish the (111) dominant surface.
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Effect of Incident Intensity on Films Growth in Pulsed Laser Deposition
GUAN Li, ZHANG Duan-Ming, LI Zhi-Hua, TAN Xin-Yu, LI Li, LIU Dan, FANG Ran-Ran, LIU Gao-Bin, HU De-Zhi
Chin. Phys. Lett. 2006, 23 (8):
2277-2280
.
Incident intensity, defined by the amount of particles deposited per pulse, is an important parameter in the film growth process of pulsed laser deposition (PLD). Different from previous models, we investigate the irreversible and reversible growth processes by using a kinetic Monte Carlo method and find that island density and film morphology strongly depend on pulse intensity. At higher pulse intensities, lots of adatoms instantaneously diffuse on the substrate surface, and then nucleation easily occurs between the moving adatoms resulting in more smaller-size islands. In contrast, at the lower pulse intensities, nucleation event occurs preferentially between the single adatom and existing islands rather than forming new islands, and therefore the average island size becomes larger in this case. Additionally, our results show that substrate temperature plays an important role in film growth. In particular, it can determine the films shape and weaken the effect of pulse intensity on film growth at the lower temperatures by controlling the mobility rate of atoms. Our results can match the related theoretical and experimental results.
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First-Principles Calculations for Structures and Melting Temperature of Si6 Clusters
BAI Yu-Lin, CHEN Xiang-Rong, ZHOU Xiao-Lin, CHENG Xiao-Hong, YANG Xiang-Dong,
Chin. Phys. Lett. 2006, 23 (8):
2281-2284
.
We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of the Si6 cluster is a square bipyramid, and the corresponding melting temperature is about 1923K. In the heating procedure, the structures of the Si6 cluster change from high symmetry structures containing 5--8 bonds, via prolate structures containing 3--4 bonds, to oblate structures containing 1--2 bonds.
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Synthesis of Cubic Boron Nitride by the Reaction of Li3N and B2O3
SU Zuo-Peng, DU Yong-Hui, JI Xiao-Rui, YANG Da-Peng, YANG Xu-Xin, GONG Xi-Liang, ZHANG Tie-Chen
Chin. Phys. Lett. 2006, 23 (8):
2285-2287
.
Cubic boron nitride is synthesized by the reaction of Li3N and B2O3 under high pressure and high temperature (4.0--5.0GPa, 1350--1500°C). The minimum pressure of cBN formation is 4.0GPa. The present condition of cBN formation is clearly lower than the eutectic temperature of Li3BN2 and BN in the Li3N-hBN system (5.5GPa, 1610°C). The content of $c$BN in the sample increases, while the content of hBN decreases with the temperature and pressure. The maximum conversion rate (5.0GPa, 1500°C) is about 34%, which is higher than that in the hBN-Li3N system. The cBN crystals are octahedral or tetrahedral in shape and approximately 20μm in diameter.
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Demonstration of Four Fundamental Operations of Liquid Droplets for Digital Microfluidic Systems Based on an
Electrowetting-on-Dielectric Actuator
YUE Rui-Feng, WU Jian-Gang, ZENG Xue-Feng, KANG Ming, LIU Li-Tian
Chin. Phys. Lett. 2006, 23 (8):
2303-2306
.
An electrowetting-on-dielectric actuator is developed, in which the liquid is sandwiched between top and bottom plates. For the bottom plate, silicon wafer is used as the substrate, the heavily phosphorus-doped polysilicon film is deposited by low pressure chemical vapour deposition as the microelectrode array, and thermally grown SiO2 film as the dielectric layer. The top plate is a glass plate covered with transparent and conductive indium tin oxide as the ground electrode. In addition, a TeflonR AF1600 film is spun on the surface of both the plates as the hydrophobic layer. The experimental results show that when the gap height between two plates is 133μm, a prototype of the device is capable of creating, transporting, merging and dividing droplets of deionized water in an
air environment with a 70V at 10Hz voltage pulse. This is also established by simulations using the computational fluidic software of CFD-ACE+.
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An Economical Magnetocardiogram System Based on High-Tc SQUIDs
LI Zhuo, ZHU Xue-Min, ZHANG Li-Hua, HUANG Xu-Guang, REN Yu-Feng, CHEN Geng-Hua, YANG Qian-Sheng, FENG Ji
Chin. Phys. Lett. 2006, 23 (8):
2319-2322
.
An economical magnetocardiogram (MCG) system is built in our laboratory. It mainly consists of a MCG data acquisition stage equipped with two high-Tc superconducting quantum interference device (SQUID) magnetometers, a data processing stage with digital filtering and a one-layer μ-metal magnetically shielded room in conjunction with a high-Tc SQUID based active compensation. Experimental results show that a noise level of pico-tesla in MCG profiles, which is necessary for clinical applications, may be achieved with the system. Moreover, stable and convenient operations of the system are demonstrated with simulating MCG measurements.
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First-Principles Study of Orthorhombic Perovskites MgSiO3 up to 120GPa and Its Geophysical Implications
DENG Li-Wei, ZHAO Ji-Jun, JI Guang-Fu, GONG Zi-Zheng, WEI Dong-Qing,
Chin. Phys. Lett. 2006, 23 (8):
2334-2337
.
High-pressure behaviour of orthorhombic MgSiO3 perovskite crystal is simulated by using the density functional theory and plane-wave pseudopotentials approach up to 120GPa pressure at zero temperature. The lattice constants and mass density of the MgSiO3 crystal as functions of pressure are computed, and the corresponding bulk modulus and bulk velocity are evaluated. Our theoretical results agree well with the high-pressure experimental data. A thermodynamic method is introduced to correct the temperature effect on the 0-K first-principles results of bulk wave velocity, bulk modulus and mass density in lower mantle P/T range. Taking into account the temperature corrections, the corrected mass density, bulk modulus and bulk wave velocity of MgSiO3-perovskite are estimated from the first-principles results to be 2%, 4%, and 1% lower than the preliminary reference Earth model (PREM) profile, respectively, supporting the possibility of a pure perovskite lower mantle model.
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105 articles
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