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Chin. Phys. B  
  Chin. Phys. B--2012, Vol.21, No.6
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GENERAL

Fractional backward Kolmogorov equations

Zhang Hong, Li Guo-Hua, Luo Mao-Kang
Chin. Phys. B, 2012, 21 (6): 060201 doi: 10.1088/1674-1056/21/6/060201
Full Text: [PDF 97 KB] (Downloads:882)
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This paper derives the fractional backward Kolmogorov equations in fractal space-time based on the construction of a model for dynamic trajectories. It shows that for the type of fractional backward Kolmogorov equation in the fractal time whose coefficient functions are independent of time, its solution is equal to the transfer probability density function of the subordinated process X(Sα(t)), the subordinator Sα(t) is termed as the inverse-time α-stable subordinator and the process X(τ) satisfies the corresponding time homogeneous Itô stochastic differential equation.

Estimation of key rate after setting dead time

Liu Dong, Yin Zhen-Qiang, Wang Shuang, Wang Fen-Mei, Chen Wei, Han Zheng-Fu
Chin. Phys. B, 2012, 21 (6): 060202 doi: 10.1088/1674-1056/21/6/060202
Full Text: [PDF 119 KB] (Downloads:1737)
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The estimation of key rate is an important aspect of the quantum key distribution process, especially in the use of dead time. In this paper, we demonstrate a numerical simulation to estimate the average detection probability and the key rate. Using our method, the estimated average detection probability is better than the previous result. Besides, we can easily find the best dead time, especially when considering the impact of after pulse.

Oscillatory and anti-oscillatory motifs in genetic regulatory networks

Ye Wei-Ming, Zhang Zhao-Yang, Lü Bin-Bin, Di Zeng-Ru, Hu Gang
Chin. Phys. B, 2012, 21 (6): 060203 doi: 10.1088/1674-1056/21/6/060203
Full Text: [PDF 261 KB] (Downloads:760)
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Recently, self-sustained oscillatory genetic regulatory networks (GRNs) have attracted significant attention in the biological field. Given a GRN, it is important to anticipate whether the network could generate oscillation with proper parameters, and what the key ingredients for the oscillation are. In this paper the ranges of some function-related parameters which are favorable to sustained oscillations are considered. In particular, some oscillatory motifs appearing with high-frequency in most of the oscillatory GRNs are observed. Moreover, there are some anti-oscillatory motifs which have a strong oscillation repressing effect. Some conclusions analyzing these motif effects and constructing oscillatory GRNs are provided.

A density functional theory study on parameters fitting of ultra long armchair (n, n) single walled boron nitride nanotubes

Wang Yan-Li, Zhang Jun-Ping, Su Ke-He, Wang Xin, Liu Yan, Sun Xu
Chin. Phys. B, 2012, 21 (6): 060301 doi: 10.1088/1674-1056/21/6/060301
Full Text: [PDF 279 KB] (Downloads:860)
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Armchair (n, n) single walled boron nitride nanotubes with n=2-17 are studied by the density functional theory at the B3LYP/3-21G(d) level combined with the periodic boundary conditions for simulating the ultra long model. The results show that the structure parameters and the formation energies bear a strong relationship to n. The fitted analytical equations are developed with correlation coefficients larger than 0.999. The energy gaps of (2, 2) and (3, 3) tubes are indirect gaps, and the larger tubes (n=4-17) have direct energy gaps. Results show that the armchair boron nitride nanotubes (n=2-17) are insulators with wide energy gaps of between 5.93 eV and 6.23 eV.

Quantum dynamic behaviour in a coupled cavities system

Peng Jun, Wu Yun-Wen, Li Xiao-Juan
Chin. Phys. B, 2012, 21 (6): 060302 doi: 10.1088/1674-1056/21/6/060302
Full Text: [PDF 435 KB] (Downloads:571)
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The dynamic behaviour of the two-site coupled cavities model which is doped with ta wo-level system is investigated. The exact dynamic solutions in the general condition are obtained via Laplace transform. The simple analytical solutions are obtained in several particular cases, which demonstrate the clear and simple physical picture for the quantum state transition of the system. In the large detuning or hoppling case, the quantum states transferring between qubits follow a slow periodic oscillation induced by the very weak excitation of the cavity mode. In the large coupling case, the system can be interpreted as two Jaynes-Cummings model subsystems which interact through photon hop between the two cavities. In the case of λΔ >> g, the quantum states transition of qubits is accompanied by the excitation of the cavity, and the cavity modes have the same dynamic behaviours and the amplitude of probability is equal to 0.25 which does not change with the variation of parameter.

Security proof of counterfactual quantum cryptography against general intercept-resend attacks and its vulnerability

Zhang Sheng, Wang Jian, Tang Chao-Jing
Chin. Phys. B, 2012, 21 (6): 060303 doi: 10.1088/1674-1056/21/6/060303
Full Text: [PDF 173 KB] (Downloads:587)
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Counterfactual quantum cryptography, recently proposed by Noh, is featured with no transmission of signal particles. This exhibits evident security advantages, such as its immunity to the well-known photon-number-splitting attack. In this paper, the theoretical security of counterfactual quantum cryptography protocol against the general intercept-resend attacks is proved by bounding the information of an eavesdropper Eve more tightly than in Yin's proposal [Phys. Rev. A 82 042335 (2010)]. It is also shown that practical counterfactual quantum cryptography implementations may be vulnerable when equipped with imperfect apparatuses, by proving that a negative key rate can be achieved when Eve launches a time-shift attack based on imperfect detector efficiency.

Interactions between bright solitons in different species of Bose–Einstein condensates

Jia-Ren Yan, Jie Zhou
Chin. Phys. B, 2012, 21 (6): 060304 doi: 10.1088/1674-1056/21/6/060304
Full Text: [PDF 106 KB] (Downloads:572)
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The dynamics of a bright-bright vector soliton in a cigar-shaped Bose-Einstein condensate trapping in a harmonic potential is studied. The interaction between bright solitons in different species with small separation is derived. Unlike the interaction between solitons of the same species, it is independent of the phase difference between solitons. It may be of attraction or repulsion. In the former case, each soliton will oscillate about and pass through each other around the mass-center of the system, which will also oscillate harmonically due to the harmonic trapping potential.

Quantum phases of Bose gases on a lattice with pair-tunneling

Wang Yue-Ming, Liang Jiu-Qing
Chin. Phys. B, 2012, 21 (6): 060305 doi: 10.1088/1674-1056/21/6/060305
Full Text: [PDF 230 KB] (Downloads:512)
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We investigate the strongly interacting lattice Bose gases on a lattice with two-body interaction of nearest neighbors characterized by pair tunneling. The excitation spectrum and the depletion of the condensate of lattice Bose gases are investigated using the Bogoliubov transformation method and the results show that there is a pair condensate as well as a single particle condensate. The various possible quantum phases, such as the Mott-insulator phase (MI), the superfluid phase (SF) of an individual atom, the charge density wave phase (CDW), the supersolid phase (SS), the pair-superfluid (PSF) phase, and the pair-supersolid phase (PSS) are discussed in different parametric regions within our extended Bose-Hubbard model using perturbation theory.

Gravitational collapse with standard and dark energy in the teleparallel equivalent of general relativity

Gamal G. L. Nashed
Chin. Phys. B, 2012, 21 (6): 060401 doi: 10.1088/1674-1056/21/6/060401
Full Text: [PDF 286 KB] (Downloads:427)
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A perfect fluid with self-similarity of the second kind is studied within the framework of the teleparallel equivalent of general relativity (TEGR). A spacetime which is not asymptotically flat is derived. The energy conditions of this spacetime are studied. It is shown that after some time the strong energy condition is not enough to satisfy showing a transition from standard matter to dark energy. The singularities of this solution are discussed.

Gravitational waves from the axial perturbations of hyperon stars

Wen De-Hua, Yan Jing, Liu Xue-Mei
Chin. Phys. B, 2012, 21 (6): 060402 doi: 10.1088/1674-1056/21/6/060402
Full Text: [PDF 280 KB] (Downloads:613)
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The eigen-frequencies of the axial w-mode oscillations of hyperon stars are examined. It is shown that as the appearance of hyperons softens the equation of state of the super-density matter, the frequency of gravitational waves from the axial w-mode of hyperon star becomes smaller than that of a traditional neutron star at the same stellar mass. Moreover, the eigenfrequencies of hyperon stars also have scaling universality. It is shown that the EURO third-generation gravitational-wave detector has the potential to detect the gravitational-wave signal emitted from the axial w-mode oscillations of a hyperon star.

The stability of a non-extensive relativistic Fermi system

Wang Hai-Tang, Men Fu-Dian, He Xiao-Gang, Wei Qun-Mei
Chin. Phys. B, 2012, 21 (6): 060501 doi: 10.1088/1674-1056/21/6/060501
Full Text: [PDF 142 KB] (Downloads:522)
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Based on the statistical theory of non-extensive relativity, and using theoretical analysis and numerical simulation, the non-extensive mechanical stability of ultra-relativistic free Fermi gas is investigated. The expressions of the stability conditions under high and low temperatures are given, and the mechanisms of the influences of temperature, ultra-relativistic effect, and non-extensive parameter q on stability are analysed. Our results show that at high temperature and under the condition of q<1, the stability of a non-extensive system is weaker than that of an extensive system, and the relativistic effect reduces system stability as compared with a non-relativistic system. However, under the condition of q>1, the stability of the non-extensive system is stronger than that of the extensive system, and the relativistic effect strengthens the system stability as compared with the non-relativistic system. In addition, under the condition of low temperature, the variation of the stability of the non-extensive system with temperature has a turning point.

Cryptanalysis on an image block encryption algorithm based on spatiotemporal chaos

Wang Xing-Yuan, He Guo-Xiang
Chin. Phys. B, 2012, 21 (6): 060502 doi: 10.1088/1674-1056/21/6/060502
Full Text: [PDF 244 KB] (Downloads:821)
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An image block encryption scheme based on spatiotemporal chaos has been proposed recently. In this paper, we analyse the security weakness of the proposal. The main problem of the original scheme is that the generated keystream remains unchanged for encrypting every image. Based on the flaws, we demonstrate a chosen plaintext attack for revealing the equivalent keys with only 6 pairs of plaintext/ciphertext used. Finally, experimental results show the validity of our attack.

One-way hash function construction based on the spatiotemporal chaotic system

Luo Yu-Ling, Du Ming-Hui
Chin. Phys. B, 2012, 21 (6): 060503 doi: 10.1088/1674-1056/21/6/060503
Full Text: [PDF 1441 KB] (Downloads:812)
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Based on the spatiotemporal chaotic system, a novel algorithm for constructing a one-way hash function is proposed and analysed. The message is divided into fixed length blocks. Each message block is processed by the hash compression function in parallel. The hash compression is constructed based on the spatiotemporal chaos. In each message block, the ASCII code and its position in the whole message block chain constitute the initial conditions and the key of the hash compression function. The final hash value is generated by further compressing the mixed result of all the hash compression values. Theoretic analyses and numerical simulations show that the proposed algorithm presents high sensitivity to the message and key, good statistical properties, and strong collision resistance.

Arbitrary full-state hybrid projective synchronization for chaotic discrete-time systems via a scalar signal

Giuseppe Grassi
Chin. Phys. B, 2012, 21 (6): 060504 doi: 10.1088/1674-1056/21/6/060504
Full Text: [PDF 189 KB] (Downloads:573)
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In this paper we present a new projective synchronization scheme, where two chaotic (hyperchaotic) discrete-time systems synchronize for any arbitrary scaling matrix. Specifically, each drive system state synchronizes with a linear combination of response system states. The proposed observer-based approach presents some useful features: i) it enables {exact} synchronization to be achieved in finite time (i.e., {dead-beat} synchronization); ii) it exploits a {scalar} synchronizing signal; iii) it can be applied to a {wide} class of discrete-time chaotic (hyperchaotic) systems; iv) it includes, as a particular case, most of the synchronization types defined so far. An example is reported, which shows in detail that exact synchronization is effectively achieved in finite time, using a scalar synchronizing signal only, for any arbitrary scaling matrix.

Bursting oscillation in CO oxidation with small excitation and the enveloping slow-fast analysis method

Li Xiang-Hong, Bi Qin-Sheng
Chin. Phys. B, 2012, 21 (6): 060505 doi: 10.1088/1674-1056/21/6/060505
Full Text: [PDF 983 KB] (Downloads:487)
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Based on the traditional scheme for a nonlinear system with multiple time scales, the enveloping slow-fast analysis method is developed in the paper, which can be employed to investigate the dynamics of nonlinear fields with multiple time scales with periodic excitation. Upon using the method, the behaviors of the kinetic model of CO oxidation on the platinum group metals have been explored in detail. Two typical bursting phenomena such as Fold/Fold/Hopf bursting and Fold/Fold bursting, are presented, the bifurcation mechanisms of which have been obtained. Furthermore, the dynamic difference between the two cases corresponding to relatively large and small perturbation frequencies, respectively, has been presented, which can be used to describe the influence of the frequencies involving in the evolution on the bursting behaviors in the system.

Nonsingular terminal sliding mode approach applied to synchronize chaotic systems with unknown parameters and nonlinear inputs

Mohammad Pourmahmood Aghababa, Hassan Feizi
Chin. Phys. B, 2012, 21 (6): 060506 doi: 10.1088/1674-1056/21/6/060506
Full Text: [PDF 318 KB] (Downloads:1004)
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This paper deals with the design of a novel nonsingular terminal sliding mode controller for finite-time synchronization of two different chaotic systems with fully unknown parameters and nonlinear inputs. We propose a novel nonsingular terminal sliding surface and prove its finite-time convergence to zero. We assume that both the master's and the slave's system parameters are unknown in advance. Proper adaptation laws are derived to tackle the unknown parameters. An adaptive sliding mode control law is designed to ensure the existence of the sliding mode in finite time. We prove that both reaching and sliding mode phases are stable in finite time. An estimation of convergence time is given. Two illustrative examples show the effectiveness and usefulness of the proposed technique. It is worthwhile noticing that the introduced nonsingular terminal sliding mode can be applied to a wide variety of nonlinear control problems.

Adaptive H synchronization of chaotic systems via linear and nonlinear feedback control

Fu Shi-Hui, Lu Qi-Shao, Du Ying
Chin. Phys. B, 2012, 21 (6): 060507 doi: 10.1088/1674-1056/21/6/060507
Full Text: [PDF 1433 KB] (Downloads:649)
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Adaptive H synchronization of chaotic systems via linear and nonlinear feedback control is investigated. The chaotic systems are redesigned by using the generalized Hamiltonian systems and observer approach. Based on Lyapunov's stability theory, linear and nonlinear feedback control of adaptive H synchronization is established in order to not only guarantee stable synchronization of both master and slave systems but also reduce the effect of external disturbance on an H-norm constraint. Adaptive H synchronization of chaotic systems via three kinds of control is investigated with applications to Lorenz and Chen systems. Numerical simulations are also given to identify the effectiveness of the theoretical analysis.

Predictions of pressure-induced structural transition, mechanical and thermodynamic properties of α-and β-Si3N4 ceramics: ab initio and quasi-harmonic Debye modeling

Yu Ben-Hai, Chen Dong
Chin. Phys. B, 2012, 21 (6): 060508 doi: 10.1088/1674-1056/21/6/060508
Full Text: [PDF 282 KB] (Downloads:531)
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The plane-wave pseudo-potential method within the framework of ab initio technique is used to investigate the structural and elastic properties of α- and β-Si3N4. The ground-state parameters accord quite well with the experimental data. Our calculation reveals that α-Si3N4 can retain its stability to at least 40 GPa when compressed at 300 K. The α → βphase transformation would not occur in a pressure range of 0–40 GPa and a temperature range of 0–300 K. Actually, the α → βtransition occurs at 1600 K and 7.98 GPa. For α- and β-Si3N4, the c axes are slightly more incompressible than the a axes. We conclude that β-Si3N4 is a hard material and ductile in nature. On the other hand, α-Si3N4 is also found to be an ionic material and can retain its mechanical stability in a pressure range of 0–10 GPa. Besides, the thermodynamic properties such as entropy, heat capacity, and Debye temperature of α- and β-Si3N4 are determined at various temperatures and pressures. Significant features in these properties are observed at high temperature. The calculated results are in good agreement with available experimental data and previous theoretical values. Many fundamental solid-state properties are reported at high pressure and high temperature. Therefore, our results may provide useful information for theoretical and experimental investigations of the Si3N4 polymorphs.
ATOMIC AND MOLECULAR PHYSICS

One-range addition theorems for generalized integer and noninteger μ Coulomb, and exponential type correlated interaction potentials with hyperbolic cosine in position, momentum, and four-dimensional spaces

I. I. Guseinov
Chin. Phys. B, 2012, 21 (6): 063101 doi: 10.1088/1674-1056/21/6/063101
Full Text: [PDF 86 KB] (Downloads:402)
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The formulae are established in position, momentum, and four-dimensional spaces for the one-range addition theorems of generalized integer and noninteger μ Coulomb, and exponential type correlated interaction potentials with hyperbolic cosine (GCTCP and GETCP HC). These formulae are expressed in terms of one-range addition theorems of complete orthonormal sets of Ψα -exponential type orbitals (Ψα -ETO), φα -momentum space orbitals (φα -MSO), and zα -hyperspherical harmonics (zα-HSH) introduced. The one-range addition theorems obtained can be useful in the electronic structure calculations of atoms and molecules when the GCTCP and GETCP HC in position, momentum, and four-dimensional spaces are employed.

Transition probabilities and lifetimes of the low-lying levels of Fe XIV

Fan Jian-Zhong, Wang Qing-Min, Chang Zhi-Wei, Dong Chen-Zhong
Chin. Phys. B, 2012, 21 (6): 063102 doi: 10.1088/1674-1056/21/6/063102
Full Text: [PDF 118 KB] (Downloads:576)
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The multi-configuration Dirac-Fock method is employed to calculate the transition energies, probabilities, and oscillator strengths for electric dipole allowed (E1) and forbidden (M1, E2, M2) lines for the 3s23p, 3s3p2, 3s23d, 3p3, and 3s3p3d configurations of Fe XIV. The lifetimes of all 40 levels of these low-lying configurations are also derived. The valence-valence and core-valence correlation effects are accounted for in a systematic way. Breit interactions and quantum electrodynamics (QED) effects are estimated in subsequent relativistic configuration interaction (CI) calculations. The present results are in good agreement with other available theoretical and experimental values, and therefore can be used for the further astrophysical investigations.

Linear ion trap imperfection and the compensation of excess micromotion

Xie Yi, Wan Wei, Zhou Fei, Chen Liang, Li Chao-Hong, Feng Mang
Chin. Phys. B, 2012, 21 (6): 063201 doi: 10.1088/1674-1056/21/6/063201
Full Text: [PDF 976 KB] (Downloads:641)
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Quantum computing requires ultracold ions in a ground vibrational state, which is achieved by sideband cooling. We report our recent efforts towards the Lamb-Dicke regime which is a prerequisite of sideband cooling. We first analyse the possible imperfection in our linear ion trap setup and then demonstrate how to suppress the imperfection by compensating the excess micromotion of the ions. The ions, after the micromotion compensation, are estimated to be very close to the Doppler-cooling limit.

Nonradiative charge transfer in collisions of protons with rubidium atoms

Yan Ling-Ling, Qu Yi-Zhi, Liu Chun-Hua, Zhang Yu, Wang Jian-Guo, Buenker Robert J
Chin. Phys. B, 2012, 21 (6): 063401 doi: 10.1088/1674-1056/21/6/063401
Full Text: [PDF 267 KB] (Downloads:514)
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The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-3 keV-10 keV. The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region. The importance of rotational coupling for chargetransfer process is stressed. Compared with the radiative charge-transfer process, nonradiative charge transfer is a dominant mechanism at energies above 15 eV. The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail. The radiative and nonradiative charge-transfer rate coefficients from low to high temperature are presented.

Total cross sections for electron scattering from fluoromethanes: A revised additivity rule method

Tan Xiao-Ming, Zhao Gang
Chin. Phys. B, 2012, 21 (6): 063402 doi: 10.1088/1674-1056/21/6/063402
Full Text: [PDF 146 KB] (Downloads:541)
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The additivity rule for electron-molecule scattering is revised by considering the difference between the free atom and the bound atom in the molecule. The total cross sections for electron scattering from fluoromethanes (CF4, CF3H, CF2H2, and CFH3) are calculated in an energy range from 100 eV to 1500 eV by the revised additivity rule. The present calculations are compared with the original additivity rule results and the available experimental data. Better agreement with each other is obtained.

A grooved planar ion trap design for scalable quantum information processing

Ji Wei-Bang, Wan Jin-Yin, Cheng Hua-Dong, Liu Liang
Chin. Phys. B, 2012, 21 (6): 063701 doi: 10.1088/1674-1056/21/6/063701
Full Text: [PDF 184 KB] (Downloads:522)
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We describe a new electrode design for a grooved surface-electrode ion trap, which is fabricated in printed-circuit-board technology with segmented electrodes. This design allows a laser beam to get through the central groove to avoid optical access blocking and laser scattering from the ion trap surface. The confining potentials are modeled both analytically and numerically. We optimize the radio frequency (rf) electrodes and dc electrodes to achieve the maximum trap depth for a given ion height above the trap electrodes. We also compare our design with the reality ion chip MI I for practical considerations. Comparison results show that our design is superior to MI I. This ion trap design may form the basis for large scale quantum computers or parallel quadrupole mass spectrometers.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

Shrinking device realized by using layered structures of homogeneous isotropic materials

Guo Ya-Nan, Liu Shao-Bin, Zhao Xin, Wang Shen-Yun, Chen Chen
Chin. Phys. B, 2012, 21 (6): 064101 doi: 10.1088/1674-1056/21/6/064101
Full Text: [PDF 221 KB] (Downloads:444)
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We propose the practical realization of a shrinking device by using layered structures of homogeneous isotropic materials. By mimicking the shrinking device with concentric alternating thin layers of isotropic dielectrics, the permittivity and the permeability in each isotropic layer can be properly determined from the effective medium theory in order to achieve the shrinking effect. The device realized by multilayer coating with dielectrics is validated by TE wave simulation, and good shrinking performance is demonstrated with only a few layers of homogeneous isotropic materials.

The research of optical windows used in aircraft sensor systems

Zhou Feng, Li Yan, Tang Tian-Jin
Chin. Phys. B, 2012, 21 (6): 064201 doi: 10.1088/1674-1056/21/6/064201
Full Text: [PDF 364 KB] (Downloads:1012)
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The optical windows used in aircrafts protect their imaging sensors from environmental effects. Considering the imaging performance, flat surfaces are traditionally used in the design of optical windows. For aircrafts operating at high speeds, the optical windows should be relatively aerodynamic, but a flat optical window may introduce unacceptably high drag to the airframes. The linear scanning infrared sensors used in aircrafts with, respectively, a flat window, a spherical window and a toric window in front of the aircraft sensors are designed and compared. Simulation results show that the optical design using a toric surface has the integrated advantages of field of regard, aerodynamic drag, narcissus effect, and imaging performance, so the optical window with a toric surface is demonstrated to be suited for this application.

Near-field properties of diffraction through a circular subwavelength-size aperture

Wang Zheng-Ling, Zhou Ming, Gao Chuan-Yu, Zhang Wei
Chin. Phys. B, 2012, 21 (6): 064202 doi: 10.1088/1674-1056/21/6/064202
Full Text: [PDF 525 KB] (Downloads:851)
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Analytical nonparaxial vectorial electric field expressions for both Gaussian beams and plane waves diffracted through a circular aperture are derived by using the vector plane angular spectrum method for the first time, which is suitable for the subwavelength aperture and the near-field region. The transverse properties of intensity distributions and their evolutions with the propagating distance, and the power transmission functions for diffracted fields containing the whole field, the evanescent field and the propagating field are investigated in detail, which is helpful for understanding the relationship between evanescent and propagating components in the near-field region and can be applied to apertured near-field scanning optical microscopy.

Optical transfer function analysis of circular-pupil wavefront coding systems with separable phase masks

Zhao Ting-Yu, Liu Qin-Xiao, Yu Fei-Hong
Chin. Phys. B, 2012, 21 (6): 064203 doi: 10.1088/1674-1056/21/6/064203
Full Text: [PDF 502 KB] (Downloads:1064)
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This paper proposes a simple method to achieve the optical transfer function of a circular pupil wavefront coding system with a separable phase mask in Cartesian coordinates. Based on the stationary phase method, the optical transfer function of the circular pupil system can be easily obtained from the optical transfer function of the rectangular pupil system by modifying the cut-off frequency and the on-axial modulation transfer function. Finally, a system with a cubic phase mask is used as an example to illustrate the way to achieve the optical transfer function of the circular pupil system from the rectangular pupil system.

A generalized Weyl–Wigner quantization scheme unifying PQ and QP ordering and Weyl ordering of operators

Wang Ji-Suo, Fan Hong-Yi, Meng Xiang-Guo
Chin. Phys. B, 2012, 21 (6): 064204 doi: 10.1088/1674-1056/21/6/064204
Full Text: [PDF 113 KB] (Downloads:613)
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By extending the usual Wigner operator to the s-parameterized one as (1/4π2)∫-∞ dyduexp≤[iu≤(q-Q) + iy≤(p-P) + i(s/2)yu] with s being a real parameter, we propose a generalized Weyl quantization scheme which accompanies a new generalized s-parameterized ordering rule. This rule recovers P-Q ordering, Q-P ordering, and Weyl ordering of operators in s=1,-1,0 respectively. Hence it differs from the Cahill-Glaubers' ordering rule which unifies normal ordering, anti-normal ordering, and Weyl ordering. We also show that in this scheme the s-parameter plays the role of correlation between two quadratures Q and P. The formula that can rearrange a given operator into its new s-parameterized ordering is presented.

Three-qubit quantum-gate operation with an SQUID in a cavity

Shi Hui-Min, Yu Ya-Fei, Zhang Zhi-Ming
Chin. Phys. B, 2012, 21 (6): 064205 doi: 10.1088/1674-1056/21/6/064205
Full Text: [PDF 93 KB] (Downloads:528)
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We propose a method of realizing a three-qubit quantum gate with a superconducting quantum interference device (SQUID) in a cavity. In this proposal, the gate operation involves the SQUID ground-states and the Fock states of cavity modes b and ĉ. The two field-modes act as the controlling qubits, and the two SQUID states form the target qubit. Since only the metastable lower levels are involved in the gate operation, the gate is not affected by the SQUID decay rates.

Observation of linewidth narrowing due to a spontaneously generated coherence effect

Tian Si-Cong, Wang Chun-Liang, Kang Zhi-Hui, Yang Xiu-Bin, Wan Ren-Gang, Zhang Xiao-Jun, Zhang Hang, Jiang Yun, Cui Hai-Ning, Gao Jin-Yue
Chin. Phys. B, 2012, 21 (6): 064206 doi: 10.1088/1674-1056/21/6/064206
Full Text: [PDF 482 KB] (Downloads:594)
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We investigate the resonance fluorescence spectrum of an atomic three-level ladder system driven by two laser fields. We show that such a system emulates to a large degree a V-type atom with parallel dipole moments-the latter being a system that exhibits spontaneously generated coherence and can display ultrasharp spectral lines. We find a suitable energy scheme in a 85Rb atom and experimentally observe the narrowing of the central peak in a rubidium atomic beam. The corresponding spectrum can convincingly demonstrate the existence of spontaneously generated coherence.

Photon-number distribution of two-mode squeezed thermal states by entangled state representation

Hu Li-Yun, Wang Shuai, Zhang Zhi-Ming
Chin. Phys. B, 2012, 21 (6): 064207 doi: 10.1088/1674-1056/21/6/064207
Full Text: [PDF 91 KB] (Downloads:1739)
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Using the entangled state representation, we convert a two-mode squeezed number state to a Hermite polynomial excited squeezed vacuum state. We first analytically derive the photon number distribution of the two-mode squeezed thermal states. It is found that it is a Jacobi polynomial; a remarkable result. This result can be directly applied to obtaining the photon number distribution of non-Gaussian states generated by subtracting from (adding to) two-mode squeezed thermal states.

Modulation of atomic exit and injection rates on the phase-dependent gain without inversion in a Doppler broadened open four-level system

Liu Zhong-Bo, Jia Ke-Ning, Liang Ying, Tong Dian-Min, Fan Xi-Jun
Chin. Phys. B, 2012, 21 (6): 064208 doi: 10.1088/1674-1056/21/6/064208
Full Text: [PDF 468 KB] (Downloads:546)
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It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence (SGC), the gain without inversion (GWI) is very sensitive to the variation of the relative phase between the probe field and the driving field; the atomic exit rate (R0 ) and the ratio (S) of the atomic injection rates have a considerable modulation effect on the phase-dependent GWI. GWI first increases and then decreases with R0 increasing; in a certain value range of S, GWI increases monotonically with S increasing; by adjusting the values of R0 and S, in an open system a much larger GWI can be obtained than in the corresponding closed system [2011 Phys. Rev. A 83 043805]. The modulation effects of R0 and S on the phase-dependent GWI in the case with the counter-propagating probe and driving fields are stronger than those in the co-propagating case, GWI in the co-propagating case is much larger than that in the counter-propagating case.

Activation of silicon quantum dots and coupling between the active centre and the defect state of the photonic crystal in a nanolaser

Huang Wei-Qi, Chen Hang-Qiong, Shu Qin, Liu Shi-Rong, Qin Chao-Jian
Chin. Phys. B, 2012, 21 (6): 064209 doi: 10.1088/1674-1056/21/6/064209
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A new nanolaser concept using silicon quantum dots (QDs) is proposed. The conduction band opened by the quantum confinement effect gives the pumping levels. Localized states in the gap due to some surface bonds on Si QDs can be formed for the activation of emission. An inversion of population can be generated between the localized states and the valence band in a QD fabricated by using a nanosecond pulse laser. Coupling between the active centres formed by localized states and the defect states of the two-dimensional (2D) photonic crystal can be used to select the model in the nanolaser.

Study on a W-band modified V-shaped microstrip meander-line traveling-wave tube

Shen Fei, Wei Yan-Yu, Xu Xiong, Yin Hai-Rong, Gong Yu-Bin, Wang Wen-Xiang
Chin. Phys. B, 2012, 21 (6): 064210 doi: 10.1088/1674-1056/21/6/064210
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The study on a miniaturized, low-voltage, wide-bandwidth, high-efficiency modified V-shaped microstrip meander-line slow-wave structure is presented. This structure is evolved from the original U-shaped microstrip meander-line slow-wave structure, combining the advantages of a traditional microstrip and a rectangular helix. In this paper, simulations of the electromagnetic characteristics and the beam-wave interaction of this structure are carried out. Our study shows that when the design voltage and the current of a sheet electron beam are set to be 4700 V and 100 mA, respectively, this miniature millimeter-wave power amplifier is capable of delivering 160-W output power with a corresponding gain of 37.3 dB and a maximum interaction efficiency of 34% at 97 GHz.

Passively mode-locked 2-μm Tm:YAP laser with a double-wall carbon nanotube absorber

Qu Zun-Shi, Wang Yong-Gang, Liu Jie, Zheng Li-He, Su Liang-Bi, Xu Jun
Chin. Phys. B, 2012, 21 (6): 064211 doi: 10.1088/1674-1056/21/6/064211
Full Text: [PDF 358 KB] (Downloads:707)
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We report on a diode-pumped passively continuous wave (cw) mode-locked Tm:YAP laser with a double-wall carbon nanotube (DWCNT) absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.

Study of modulation property to incident laser by surface micro-defects on KH2PO4 crystal

Chen Ming-Jun, Cheng Jian, Li Ming-Quan, Xiao Yong
Chin. Phys. B, 2012, 21 (6): 064212 doi: 10.1088/1674-1056/21/6/064212
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KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement of the laser induced damage threshold. The modulation of an incident laser by using different kinds of surface defects are simulated by employing the three-dimensional finite-difference time-domain method. The results indicate that after the modulation of surface defects, the light intensity distribution inside the crystal is badly distorted, with the light intensity enhanced symmetrically. The relations between modulation properties and defect geometries (e.g., width, morphology, and depth of defects) are quite different for different defects. The modulation action is most obvious when the width of surface defects reaches 1.064 μ. For defects with smooth morphology, such as spherical pits, the degree of modulation is the smallest and the light intensity distribution seems relatively uniform. The degree of modulation increases rapidly with the increase of the depth of surface defects and becomes stable when the depth reaches a critical value. The critical depth is 1.064 μ for cuboid pits and radial cracks, while for ellipsoidal pits the value depends on both the width and the length of the defects.

Application of a characterized difference-frequency laser source to carbon monoxide trace detection

Alireza Khorsandi, Zahra Shabani, Monireh Ranjbar, S. Ali Hoseinzadeh Salati
Chin. Phys. B, 2012, 21 (6): 064213 doi: 10.1088/1674-1056/21/6/064213
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A tunable continuous wave (cw) mid-infrared (MIR) laser based on difference-frequency generation (DFG) in a 1.5-cm long AgGaS2 nonlinear crystal for trace gas detection is reported. Two visible and near-infrared diode lasers were used as pump and signal sources. The MIR-DFG laser was tunable in a wavelength range of 4.75 μm-4.88 μm. The phase-matching (PM) condition was non-critically achieved by adjusting the temperature of the crystal for fixed pairs of input pump and signal wavelengths. The required PM temperatures of the generated MIR-DFG wavelengths have been calculated by using three sets of recent Sellmeier equations and the temperature-dispersion equations of AgGaS2 given by Willer U, et al. (Willer U, Blanke T and Schade W 2001 Appl. Opt. 40 5439). Then the calculated PM temperatures are compared with the experimental values. The performance of the MIR-DFG laser is shown by the trace detection of the P(16) carbon monoxide (12C16O) absorption line in a laboratory-fabricated absorption cell. The enhanced sensitivity of about 0.6 × 10-4 was obtained through the long path absorption provided by consecutive reflections between coated cylindrical mirrors of a constructed cell.

The effect of a magnetic field on a 2D problem of fibre-reinforced thermoelasticity rotation under three theories

Kh. Lotfy
Chin. Phys. B, 2012, 21 (6): 064214 doi: 10.1088/1674-1056/21/6/064214
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In the present paper, we introduce the coupled theory (CD), Lord-Schulman (LS) theory, and Green-Lindsay (GL) theory to study the influences of a magnetic field and rotation on a two-dimensional problem of fibre-reinforced thermoelasticity. The material is a homogeneous isotropic elastic half-space. The method applied here is to use normal mode analysis to solve a thermal shock problem. Some particular cases are also discussed in the context of the problem. Deformation of a body depends on the nature of the force applied as well as the type of boundary conditions. Numerical results for the temperature, displacement, and thermal stress components are given and illustrated graphically in the absence and the presence of the magnetic field and rotation.

Measurement of the argon-gas-induced broadening and line shifting of the barium Rydberg level 6s24d 1D2 by two-photon resonant nondegenerate four-wave mixing

Sun Jiang, Xiong Zhi-Qiang, Sun Juan, Wang Ying, Su Hong-Xin
Chin. Phys. B, 2012, 21 (6): 064215 doi: 10.1088/1674-1056/21/6/064215
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We apply two-photon resonant nondegenerate four-wave mixing with a resonant intermediate state to the observation of the broadening and shifting of the barium Rydberg level 6s24d 1D2 by collision with argon. The collision broadening and shifting cross sections are measured. This technique is purely optical, and can investigate the pressure dependence of the transverse relaxation rate Γ21 between the Rydberg state and an intermediate state, as well as the transverse relaxation rate Γ20 between the Rydberg state and the ground state.

High-order harmonic generation in sub-one-cycle regime

Xiang Yang, Niu Yue-Ping, Qi Yi-Hong, Gong Shang-Qing
Chin. Phys. B, 2012, 21 (6): 064216 doi: 10.1088/1674-1056/21/6/064216
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We theoretically investigate the high-order harmonic generation from the hydrogen atom driven by the laser pulses with the durations less than the optical cycle. It is found that the switching term of the laser field may have an obvious influence on the cutoff, intensity or plateau structure of the high-order harmonic spectrum. Generally speaking, the switching term can shorten the cutoff of the high-order harmonic spectrum for a relatively longer pulse and extend the cutoff for a relatively shorter pulse.

The signal synchronization transmission of a spatiotemporal chaos network constituted by a laser phase-conjugate wave

Li Wen-Lin, Li Shu-Feng, Li Gang
Chin. Phys. B, 2012, 21 (6): 064217 doi: 10.1088/1674-1056/21/6/064217
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The signal synchronization transmission of a spatiotemporal chaos network is investigated. The structure of the coupling function between connected nodes of the complex network and the value range of the linear term coefficient of the separated configuration in state equation of the node are obtained through constructing an appropriate Lyapunov function. Each node of the complex network is a laser spatiotemporal chaos model in which the phase-conjugate wave and the unilateral coupled map lattice are taken as a local function and a spatially extended system, respectively. The simulation results show the effectiveness of the signal synchronization transmission principle of the network.

Elegant Ince–Gaussian breathers in strongly nonlocal nonlinear media

Bai Zhi-Yong, Deng Dong-Mei, Guo Qi
Chin. Phys. B, 2012, 21 (6): 064218 doi: 10.1088/1674-1056/21/6/064218
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A novel class of optical breathers, called elegant Ince-Gaussian breathers, are presented in this paper. They are exact analytical solutions to Snyder and Mitchell's mode in an elliptic coordinate system, and their transverse structures are described by Ince-polynomials with complex arguments and a Gaussian function. We provide convincing evidence for the correctness of the solutions and the existence of the breathers via comparing the analytical solutions with numerical simulation of the nonlocal nonlinear Schrödinger equation.

Two localized CO2 laser treatment methods for mitigation of UV damage growth in fused silica

Jiang Yong, Xiang Xia, Liu Chun-Ming, Luo Cheng-Si, Wang Hai-Jun, Yuan Xiao-Dong, He Shao-Bo, Ren Wei, Lü Hai-Bing, Zheng Wan-Guo, Zu Xiao-Tao
Chin. Phys. B, 2012, 21 (6): 064219 doi: 10.1088/1674-1056/21/6/064219
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Two methods: high-power, short-time, single-shot irradiation (Method A) and low-power, long-time, multi-shot irradiation (Method B) are investigated to mitigate the UV damage growth in fused silica by using a 10.6-μm CO2 laser. To verify the mitigation effect of the two methods, the laser induced damage thresholds (LIDTs) of the mitigated sites are tested with a 355-nm, 6.4-ns Nd:YAG laser, and the light modulation of the mitigation sites are tested with a 351-nm continuous Nd:YLF laser. The mitigated damaged sites treated with the two methods have almost the same LIDTs, which can recover to the level of pristine material. Compared with Method A, Method B produces mitigated sites with low crater depth and weak light modulation. In addition, there is no raised rim or re-deposited debris formed around the crater edge for Method B. Theoretical calculation is utilized to evaluate the central temperature of the CO2 laser beam irradiated zone and the radius of the crater. It is indicated that the calculated results are consistent with the experimental results.

A novel optical beam splitter based on photonic crystal with hybrid lattices

Zhu Qing-Yi, Fu Yong-Qi, Hu De-Qing, Zhang Zhi-Min
Chin. Phys. B, 2012, 21 (6): 064220 doi: 10.1088/1674-1056/21/6/064220
Full Text: [PDF 180 KB] (Downloads:718)
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A novel optical beam splitter constructed on the basis of photonic crystal (PC) with hybrid lattices is proposed in this paper. The band gap of square-lattice PC is so designed that the incident light is divided into several branch beams. Triangular-lattice graded-index PCs are combined for focusing each branch. Computational calculations are carried out on the basis of finite-different time-domain algorithm to prove the feasibility of our design. The waveguide is unnecessary in the design. Thus the device has functions of both splitting and focusing beams. Size of the divided beam at site of full-width at half-maximum is of the order of λ/2. The designed splitter has the advantages that it has a small volume and can be integrated by conventional semiconductor manufacturing process.

Experimental investigation of pre-irradiation effect on radiation sensitivity of temperature sensing fiber Bragg gratings

Jin Jing, Lin Song, Song Ning-Fang
Chin. Phys. B, 2012, 21 (6): 064221 doi: 10.1088/1674-1056/21/6/064221
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The effect of pre-irradiation on radiation sensitivity of fiber Bragg gratings (FBGs) is verified experimentally. FBGs are fabricated in photosensitive optical fibers and single mode fibers with Ge-concentration in a range from 3 mol% to 23.37 mol% in the core. In experiments, the FBGs are subjected to twice γ-radiation exposures to a Co60 source at a dose-rate of 0.1 Gy/s up to a total dose of 50 kGy. Pre-irradiation treatment can reduce the temperature sensitivity variation of FBGs by 18.12%-35.91%, as well as Bragg wavelength shift (BWS) by 8%-27.08 %. Our research demonstrates that pre-irradiation treatment is a feasible method to improve the radiation tolerance of FBGs.

Optimization of regenerator based on semiconductor optical amplifier for degraded differential phase shift keying signal

Ma Yong-Xin, Xi Li-Xia, Chen Guang, Zhang Xiao-Guang
Chin. Phys. B, 2012, 21 (6): 064222 doi: 10.1088/1674-1056/21/6/064222
Full Text: [PDF 305 KB] (Downloads:603)
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Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in recent years. In this paper, for this type of regenerator, its optimal working condition is found by solving the dynamic equations which describe the variance of the optical field and carrier density in the semiconductor optical amplifier by the finite difference method. The results show that the optimal improvement of signal Q factor can reach more than 2.2 dB.

Point defect states of a hollow cylinder in two-dimensional phononic crystal

Gao Xiao-Wei, Chen Shi-Bo, Chen Jian-Bing, Zheng Qin-Hong, Yang Hai
Chin. Phys. B, 2012, 21 (6): 064301 doi: 10.1088/1674-1056/21/6/064301
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Point defect states in two-dimensional phononic crystal of a hollow mercury cylinder in a water host are studied. An improved plane expansion method combined with the supercell technique is used to calculate the band gaps and the pressure distribution at the defect position. The sonic pressure of defect modes shows that the waves are localized at or near the defect. As the filing fraction increases, more defect modes appear in the band gaps.

High temperature thermal behaviour modeling of large-scale fused silica optics for laser facility

Yu Jing-Xia, He Shao-Bo, Xiang Xia, Yuan Xiao-Dong, Zheng Wan-Guo, Lü Hai-Bing, Zu Xiao-Tao
Chin. Phys. B, 2012, 21 (6): 064401 doi: 10.1088/1674-1056/21/6/064401
Full Text: [PDF 258 KB] (Downloads:951)
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High temperature annealing is often used for the stress control of optical materials. However, weight and viscosity at high temperature may destroy the surface morphology, especially for the large-scale, thin and heavy optics used for large laser facilities. It is necessary to understand the thermal behaviour and design proper support systems for large-scale optics at high temperature. In this work, three support systems for fused silica optics are designed and simulated with the finite element method. After the analysis of the thermal behaviours of different support systems, some advantages and disadvantages can be revealed. The results show that the support with the optical surface vertical is optimal because both pollution and deformation of optics could be well controlled during annealing at high temperature. Annealing process of the optics irradiated by CO2 laser is also simulated. It can be concluded that high temperature annealing can effectively reduce the residual stress. However, the effects of annealing on surface morphology of the optics are complex. Annealing creep is closely related to the residual stress and strain distribution. In the region with large residual stress, the creep is too large and probably increases the deformation gradient which may affect the laser beam propagation.

Symmetry of Lagrangians of a holonomic variable mass system

Wu Hui-Bin, Mei Feng-Xiang
Chin. Phys. B, 2012, 21 (6): 064501 doi: 10.1088/1674-1056/21/6/064501
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The symmetry of Lagrangians of a holonomic variable mass system is studied. Firstly, the differential equations of motion of the system are established. Secondly, the definition and the criterion of the symmetry of the system are presented. Thirdly, the conditions under which there exists a conserved quantity deduced by the symmetry are obtained. The form of the conserved quantity is the same as that of the constant mass Lagrange system. Finally, an example is shown to illustrate the application of the result.

Nonlinearity and periodic solution of a standard-beam balance oscillation system

Li Shi-Song, Lan Jiang, Han Bing, Tan Hong, Li Zheng-Kun
Chin. Phys. B, 2012, 21 (6): 064601 doi: 10.1088/1674-1056/21/6/064601
Full Text: [PDF 207 KB] (Downloads:797)
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We present the motion equation of the standard-beam balance oscillation system, whose beam and suspensions, compared with the compound pendulum, are connected flexibly and vertically. The nonlinearity and the periodic solution of the equation are discussed by the phase-plane analysis. We find that this kind of oscillation can be equivalent to a standard-beam compound pendulum without suspensions; however, the equivalent mass centre of the standard beam is extended. The derived periodic solution shows that the oscillation period is tightly related to the initial pivot energy and several systemic parameters: beam length, masses of the beam, and suspensions, and the beam mass centre. A numerical example is calculated.

Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods

Gao Qiong, Yi Shi-He, Jiang Zong-Fu, Zhao Yu-Xin, Xie Wen-Ke
Chin. Phys. B, 2012, 21 (6): 064701 doi: 10.1088/1674-1056/21/6/064701
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The nano-particle-based planar laser scattering (NPLS) technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference (OPL), which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is analysed using wavelet methods. The coherent structures of the OPL are extracted using three methods, including the methods of thresholding the coefficients of the orthogonal wavelet transform and the wavelet packet transform, and preserving a number of wavelet packet coefficients with the largest amplitudes determined by the entropy dimension. Their performances are compared, and the method using the wavelet packet is the best. Based on the viewpoint of multifractals, we study the OPL by the wavelet transform maxima method (WTMM), and the result indicates that its scaling behaviour is evident.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Study on the electromagnetic propertiesof a coated radar absorbent

Zhang Shuan-Qin
Chin. Phys. B, 2012, 21 (6): 065101 doi: 10.1088/1674-1056/21/6/065101
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The sol-gel method is used to fabricate Fe crystalline powders coated with SiO2. By controlling the molar ratio R of diluted water to tetraethoxysilane (TEOS), Fe powders coated with SiO2 with different morphological characteristics are fabricated. The influence of the core diameter on electromagnetic parameters is investigated. The effect of the amount of the coating material SiO2 on electromagnetic parameters is given. Radar wave absorbing properties of Fe coated with SiO2 and TiO2 respectively are compared.

The effects of substrate temperature on ZnO-based resistive random access memory devices

Zhao Jian-Wei, Liu Feng-Juan, Huang Hai-Qin, Hu Zuo-Fu, Zhang Xi-Qing
Chin. Phys. B, 2012, 21 (6): 065201 doi: 10.1088/1674-1056/21/6/065201
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Ag/ZnO/Zn/Pt structure resistive switching devices are prepared by radio frequency magnetron sputtering. The ZnO thin films are grown at room temperature and 400 ℃ substrate temperature, respectively. By comparing the data, we find that the latter device displayed better stability in the repetitive switching cycle test, and the resistance ratio between a high resistance state and a low resistance state is correspondingly increased. After 104-s storage time measurement, this device exhibits a good retention property. Moreover, the operation voltages are very low: -0.3 V/-0.7 V (OFF state) and 0.3 V (ON state). A high-voltage forming process in the initial state is not required, and a multistep reset process is demonstrated.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Evolution of the structural and optical properties of silver oxide films with different stoichiometries deposited by direct-current magnetron reactive sputtering

Zhao Meng-Ke, Liang Yan, Gao Xiao-Yong, Chen Chao, Chen Xian-Mei, Zhao Xian-Wei
Chin. Phys. B, 2012, 21 (6): 066101 doi: 10.1088/1674-1056/21/6/066101
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Nitrogen doping of silver oxide (AgxO) film is necessary for its application in transparent conductive film and diodes because intrinsic AgxO film is a p-type semiconductor with poor conductivity. In this work, a series of AgxO films is deposited on glass substrates by direct-current magnetron reactive sputtering at different flow ratios (FRs) of nitrogen to O2. Evolutions of the structure, the reflectivity, and the transmissivity of the film are studied by X-ray diffractometry and sphectrophotometry, respectively. The specular transmissivity and the specular reflectivity of the film decreasing with FR increasing can be attributed to the evolution of the phase structure of the film. The nitrogen does not play the role of an acceptor dopant in the film deposition.

The crystal structures and physical properties of the solid solution compound Ba5Y8-xMn4O21-1.5x (x=0, 1) Hot!

Gao Qing-Qing, Li Jing-Bo, Song Shi-Jia, Luo Jun, Rao Guang-Hui, Liang Jing-Kui
Chin. Phys. B, 2012, 21 (6): 066102 doi: 10.1088/1674-1056/21/6/066102
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New oxometallides with the formula Ba5Y8-xMn4O21-1.5x (x=0, 1) are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 (Y8) and 5/7/4 (Y7) are obtained. The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction, magnetization, conductivity, and dielectricity measurements. The Ba5Y8-xMn4O21-1.5x compound is demonstrated to be a Y-deficient solid solution. The solid solution compound Ba5Y8-xMn4O21-1.5x crystallizes into tetragonal symmetry with the space group I4/m. Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y(2) site. Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds, and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples, respectively. Strong frequency dependences of the dielectric constant are observed above ~ 175 K for the two compounds.

Density functional study of the pressure tensor for inhomogeneous Lennard–Jones fluids

Sun Zong-Li, Kang Yan-Shuang, Kang Yan-Mei, Liu Zhi-Cheng, Ma Heng-Xin
Chin. Phys. B, 2012, 21 (6): 066103 doi: 10.1088/1674-1056/21/6/066103
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Based on classical density functional theory, an expression of the pressure tensor for inhomogeneous fluids is presented. This takes into account greater correlation between particles, especially for systems that are geometrically confined or involve an interface. The density and pressure components of Lennard-Jones fluids confined in hard and softened nano-cavities are calculated. A comparison between the results of this work and IK expression suggests that the agreement depends on temperature. The interfacial tension for hard sphere fluids agrees well with the Monte Carlo result when the bulk density is not too large. The results of the solid-fluid interfacial tension for Lennard-Jones fluids demonstrate that different types of external potentials modulate the interfacial tension in different manners.

Azimuthal anchoring of a nematic liquid crystal on a grooved interface with anisotropic polar anchoring Hot!

Zhou Xuan, Zhang Zhi-Dong, Ye Wen-Jiang, Xuan Li
Chin. Phys. B, 2012, 21 (6): 066104 doi: 10.1088/1674-1056/21/6/066104
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Zhang Y J et al. [Zhang Y J, Zhang Z D, Zhu L Z and Xuan L 2011 Liquid Cryst. 38 355] investigated the effects of finite polar anchoring on the azimuthal anchoring energy at a grooved interface, in which polar anchoring was isotropic in the local tangent plane of the surface. In this paper, we investigate the effects of both isotropic and anisotropic polar anchoring on the surface anchoring energy in the frame of Fukuda et al.'s theory. The results show that anisotropic polar anchoring strengthens the azimuthal anchoring of grooved surfaces. In the one-elastic-constant approximation (K11 = K22 = K33 = K), the surface-groove-induced azimuthal anchoring energy is entirely consistent with the result of Faetti, and it reduces to the original result of Berreman with an increase in polar anchoring. Moreover, the contribution of the surface-like elastic term to the Rapini-Papoular anchoring energy is zero.

Investigation of the inhibiting outdiffusion of erbium atoms to a silicon-on-insulator surface after annealing at high temperature

Qin Xi-Feng, Li Hong-Zhen, Li Shuang, Ji Zi-Wu, Wang Hui-Ning, Wang Feng-Xiang, Fu Gang
Chin. Phys. B, 2012, 21 (6): 066105 doi: 10.1088/1674-1056/21/6/066105
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The annealing behaviour of 400 keV Er ions at a fluence of 2 × 1015 cm-2 implanted into silicon-on-insulator (SOI) samples is investigated by Rutherford backscattering spectrometry of 2.1 MeV He2+ ions with a multiple scattering model. It is found that the damage close to the SOI surface is almost removed after being annealed in O2 and N2 atmospheres, successively, at 900 ℃, and that only a small number of the Er atoms segregated to the surface of the SOI sample, whereas a large number of Er atoms diffused to a deeper position because of the affinity of Er for oxygen. For the SOI sample co-implanted with Er and O ions, there is no evident outdiffusion of Er atoms to the SOI surface after being annealed in N2 atmosphere at 900 ℃.

Growth characteristics of amorphous-layer-free nanocrystalline silicon films fabricated by very high frequency PECVD at 250 ℃

Guo Yan-Qing, Huang Rui, Song Jie, Wang Xiang, Song Chao, Zhang Yi-Xiong
Chin. Phys. B, 2012, 21 (6): 066106 doi: 10.1088/1674-1056/21/6/066106
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Amorphous-layer-free nanocrystalline silicon films were prepared by a very high frequency plasma enhanced chemical vapor deposition (PECVD) technique using hydrogen-diluted SiH4 at 250 ℃. The dependence of the crystallinity of the film on the hydrogen dilution ratio and the film thickness was investigated. Raman spectra show that the thickness of the initial amorphous incubation layer on silicon oxide gradually decreases with increasing hydrogen dilution ratio. High-resolution transmission electron microscopy reveals that the initial amorphous incubation layer can be completely eliminated at a hydrogen dilution ratio of 98%, which is lower than that needed for the growth of amorphous-layer-free nanocrystalline silicon using an excitation frequency of 13.56 MHz. More studies on the microstructure evolution of the initial amorphous incubation layer with hydrogen dilution ratios were performed using Fourier-transform infrared spectroscopy. It is suggested that the high hydrogen dilution, as well as the higher plasma excitation frequency, plays an important role in the formation of amorphous-layer-free nanocrystalline silicon films.

The influence of cation additives on the NIR luminescence intensity of Er3+-doped borate glasses

Zhou Yong-Liang, Zhang Xiao-Song, Xu Jian-Ping, Zhang Zhong-Peng, Zhang Gao-Feng, Wei Feng-Wei, Li Lan
Chin. Phys. B, 2012, 21 (6): 066301 doi: 10.1088/1674-1056/21/6/066301
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Er3+-doped 25BaO-(25-x)SiO2-xAl2O3-25B2O3 transparent glasses are prepared with x=0, 12.5 and 25 by a solid-state reaction. The Er-related NIR luminescence intensity, which corresponds to the transition of 4I15/2-4I13/2, is obviously altered with different silicon/aluminum ratios. The Judd-Ofelt parameters of the Er3+ ions are adopted to explain the intensity change in the NIR fluorescence, and the Raman scattering intensity versus the amount of Al and/or Si components are discussed. The spectra of the three samples are quite similar in the peak positions, but different in intensity. The maximal phonon density of state for the samples is calculated from the Raman spectra and is correlated to the NIR luminescence efficiency.

The effect of intragranular microstress in Al2O3–SiC nanocomposites

Wang Zhi-Yuan, Wu Yu-Gong, Tong Shuai, Wu Si-Qi
Chin. Phys. B, 2012, 21 (6): 066501 doi: 10.1088/1674-1056/21/6/066501
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A theoretical model is established to investigate the intragranular particle residual stress in Al2O3-SiC nanocomposites. Using this model, we calculate the average compressive stress on the Al2O3 grain boundary (GB) and the average tensile stress within Al2O3 grains caused by SiC nanoparticles. The normal compressive stress strengthens the GB, and the average tensile stress weakens the grains. The model gives a reasonable interpretation of the strength changes of Al2O3-SiC nanocomposites with the number of SiC particles.

The effect of interfacial energy anisotropy on planar interface instability in a succinonitrile alloy under a small temperature gradient

Wang Li-Lin, Wang Zhi-Jun, Lin Xin, Wang Meng, Huang Wei-Dong
Chin. Phys. B, 2012, 21 (6): 066801 doi: 10.1088/1674-1056/21/6/066801
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The morphological stability of a planar interface with different crystallographic orientations is studied under a small positive temperature gradient using a transparent model alloy of succinonitrile. Novel experimental apparatus is constructed to provide a temperature gradient of about 0.37 K/mm. Under this small temperature gradient, the planar interface instability depends largely on the crystallographic orientation. It is shown experimentally that the effect of interfacial energy anisotropy on planar interface stability cannot be neglected even in a small temperature gradient system. Higher interfacial energy anisotropy leads the planar interface to become more unstable, which is different from the stabilizing effect of the interfacial energy on the planar interface. The experimental results are in agreement with previous theoretical calculations and phase field simulations.

The properties of transparent conducting molybdenum-doped ZnO films grown by radio frequency magnetron sputtering

Xiu Xian-Wu, Zhao Wen-Jing
Chin. Phys. B, 2012, 21 (6): 066802 doi: 10.1088/1674-1056/21/6/066802
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Transparent conducting molybdenum-doped zinc oxide films are prepared by radio frequency (RF) magnetron sputtering at ambient temperature. The MoO3 content in the target varies from 0 to 5 wt%, and each film is polycrystalline with a hexagonal structure and a preferred orientation along the c axis. The resistivity first decreases and then increases with the increase in MoO3 content. The lowest resistivity achieved is 9.2 × 10-4 Ω·cm, with a high Hall mobility of 30 cm2·V-1·s-1 and a carrier concentration of 2.3 × 1020 cm-3 at an MoO3 content of 2 wt%. The average transmittance in the visible range is reduced from 91% to 80% with the increase in the MoO3 content in the target.

Molecular dynamics study of temperature-dependent ripples in monolayer and bilayer graphene on 6H–SiC surfaces

Tang Chao, Wei Xiao-Lin, Tan Xin, Peng Xiang-Yang, Sun Li-Zhong, Zhong Jian-Xin
Chin. Phys. B, 2012, 21 (6): 066803 doi: 10.1088/1674-1056/21/6/066803
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Using classical molecular dynamics and a simulated annealing technique, we show that microscopic corrugations occur in monolayer and bilayer graphene on 6H-SiC substrates. From an analysis of the atomic configurations, two types of microscopic corrugations are identified, namely periodic ripples at room temperature and random ripples at high temperature. Two different kinds of ripple morphologies, each with a periodic structure, occur in the monolayer graphene due to the existence of a coincidence lattice between graphene and the SiC terminated surface (Si- or C-terminated surface). The effect of temperature on microscopic ripple morphology is shown through analysing the roughness of the graphene. A temperature-dependent multiple bonding conjugation is also shown by the broad distribution of the carbon-carbon bond length and the bond angle in the rippled graphene on the SiC surface. These results provide atomic-level information about the rippled graphene layers on the two polar faces of the 6H-SiC substrate, which is useful not only for a better understanding of the stability and structural properties of graphene, but also for the study of the electronic properties of graphene-based devices.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Theoretical investigation on the electronic structure, elastic properties, and intrinsic hardness of Si2N2O

Ding Ying-Chun, Chen Min, Gao Xiu-Ying, Jiang Meng-Heng
Chin. Phys. B, 2012, 21 (6): 067101 doi: 10.1088/1674-1056/21/6/067101
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According to the density functional theory we systematically study the electronic structure, the mechanical properties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli (bulk modulus, Young's modulus, and shear modulus) are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.

Effects of N-doping concentration on the electronic structure and optical properties of N-doped β-Ga2O3

Zhang Li-Ying, Yan Jin-Liang, Zhang Yi-Jun, Li Ting
Chin. Phys. B, 2012, 21 (6): 067102 doi: 10.1088/1674-1056/21/6/067102
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The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method. We find that the N substituting O(1) atom is the most stable structure for the smallest formation energy. After N-doping, the charge density distribution significantly changes, and the acceptor impurity level is introduced above the valence band and intersects with the Fermi level. The impurity absorption edges appear to shift toward longer wavelengths with an increase in N-doping concentration. The complex refractive index shows metallic characteristics in the N-doped β-Ga2O3.

Comparative study of adsorption characteristics of Cs on the GaN (0001) and GaN (0001) surfaces

Du Yu-Jie, Chang Ben-Kang, Wang Hong-Gang, Zhang Jun-Ju, Wang Mei-Shan
Chin. Phys. B, 2012, 21 (6): 067103 doi: 10.1088/1674-1056/21/6/067103
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The adsorption characteristics of Cs on GaN (0001) and GaN (0001) surfaces with a coverage from 1/4 to 1 monolayer have been investigated using the density functional theory with a plane-wave ultrasoft pseudopotential method based on first-principles calculations. The results show that the most stable position of the Cs adatom on the GaN (0001) surface is at the N-bridge site for 1/4 monolayer coverage. As the coverage of Cs atoms at the N-bridge site is increased, the adsorption energy reduces. As the Cs atoms achieve saturation, the adsorption is no longer stable when the coverage is 3/4 monolayer. The work function achieves its minimum value when the Cs adatom coverage is 2/4 monolayer, and then rises with Cs atomic coverage. The most stable position of Cs adatoms on the GaN (0001) surface is at H3 site for 1/4 monolayer coverage. As the Cs atomic coverage at H3 site is increased, the adsorption energy reduces, and the adsorption is still stable when the Cs adatom coverage is 1 monolayer. The work function reduces persistently, and does not rise with the increase of Cs coverage.

Influence of a two-dimensional electron gas on current–voltage characteristics of Al0.3Ga0.7 N/GaN high electron mobility transistors

Ji Dong, Liu Bing, Lü Yan-Wu, Zou Miao, Fan Bo-Ling
Chin. Phys. B, 2012, 21 (6): 067201 doi: 10.1088/1674-1056/21/6/067201
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The J-V characteristics of AltGa1-tN/GaN high electron mobility transistors (HEMTs) are investigated and simulated using the self-consistent solution of the Schrödinger and Poisson equations for a two-dimensional electron gas (2DEG) in a triangular potential well with the Al mole fraction t=0.3 as an example. Using a simple analytical model, the electronic drift velocity in a 2DEG channel is obtained. It is found that the current density through the 2DEG channel is on the order of 1013 A/m2 within a very narrow region (about 5 nm). For a current density of 7 ? 1013 A/m2 passing through the 2DEG channel with a 2DEG density of above 1.2 ? 1017 m-2 under a drain voltage Vds=1.5 V at room temperature, the barrier thickness Lb should be more than 10 nm and the gate bias must be higher than 2 V.

Improved performance of organic light-emitting diodes with dual electron transporting layers

Jiao Zhi-Qiang, Wu Xiao-Ming, Hua Yu-Lin, Mu Xue, Bi Wen-Tao, Bai Juan-Juan, Yin Shou-Gen
Chin. Phys. B, 2012, 21 (6): 067202 doi: 10.1088/1674-1056/21/6/067202
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In this study the performance of organic light-emitting diodes (OLEDs) are enhanced significantly, which is based on dual electron transporting layers (Bphen/CuPc). By adjusting the thicknesses of Bphen and CuPc, the maximal luminescence, the maximal current efficiency, and the maximal power efficiency of the device reach 17570 cd/m2 at 11 V, and 5.39 cd/A and 3.39 lm/W at 3.37 mA/cm2 respectively, which are enhanced approximately by 33.4%, 39.3%, and 68.9%, respectively, compared with those of the device using Bphen only for an electron transporting layer. These results may provide some valuable references for improving the electron injection and the transportation of OLED.

A comparative investigation of an AB- and AA-stacked bilayer graphene sheet under an applied electric field: A density functional theory study

Wang Tao, Guo Qing, Liu Yan, Sheng Kuang
Chin. Phys. B, 2012, 21 (6): 067301 doi: 10.1088/1674-1056/21/6/067301
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An AB- and AA-stacked bilayer graphene sheet (BLG) under an electric field is investigated by ab initio calculation. The interlayer distance between the two layers, band structures, and atomic charges of the system are investigated in the presence of different electric fields normal to the BLG. The AB-stacked BLG is able to tune the bandgap into 0.234 eV with the increase of the external electronic field to 1 V/nm, however, the AA-stacked BLG is not sensitive to the external electric field. In both the cases, the spacing between the BLG slightly change in terms of the electric field. The charges in the AB-stacked BLG are increased with the increase of the electric field, which is considered to be the reason that causes the bandgap opening in the AB-stacked BLG.

A density functional theory study on the adsorption of CO and O2 on Cu-terminated Cu2O (111) surface

Li Min, Zhang Jun-Ying, Zhang Yue, Wang Tian-Min
Chin. Phys. B, 2012, 21 (6): 067302 doi: 10.1088/1674-1056/21/6/067302
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The adsorptions of CO and O2 molecules individually on the stoichiometric Cu-terminated Cu2O (111) surface are investigated by first-principles calculations on the basis of the density functional theory. The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of -1.69 eV, whereas the O2 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cu1 site, and has an adsorption energy of -1.97 eV. From the analysis of density of states, it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate. The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption, and overlaps substantially with bands of the adsorbed CO molecule. There is a broadening of the 2π orbital of the O2 molecule because of its overlapping with the Cu 3d orbital, indicating that strong 3d-2π interactions are involved in the chemisorption of the O2 molecule on the surface.

A GaAs planar Schottky varactor diode for left-handed nonlinear transmission line applications

Dong Jun-Rong, Yang Hao, Tian Chao, Huang Jie, Zhang Hai-Ying
Chin. Phys. B, 2012, 21 (6): 067303 doi: 10.1088/1674-1056/21/6/067303
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The left-handed nonlinear transmission line (LH-NLTL) based on monolithic microwave integrated circuit (MMIC) technology possesses significant advantages such as wide frequency band, high operating frequency, high conversion efficiency, and applications in millimeter and submillimeter wave frequency multiplier. The planar Schottky varactor diode (PSVD) is a major limitation to the performance of the LH-NLTL frequency multiplier as a nonlinear component. The design and the fabrication of the diode for such an application are presented. An accurate large-signal model of the diode is proposed. A 16 GHz-39.6 GHz LH-NLTL frequency doubler using our large-signal model is reported for the first time. The measured maximum output powers of the 2nd harmonic are up to 8 dBm at 26.4 GHz, and above 0 dBm from 16 GHz to 39.6 GHz when the input power is 20 dBm. The application of the LH-NLTL frequency doubler furthermore validates the accuracy of the large-signal model of the PSVD.

Far-infrared electroluminescence characteristics of an Si-based photodiode under a forward DC bias current

Xiao Wen-Bo, He Xing-Dao, Zhang Zhi-Min, Gao Yi-Qing, Liu Jiang-Tao
Chin. Phys. B, 2012, 21 (6): 067304 doi: 10.1088/1674-1056/21/6/067304
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At room temperature, the bias dependence of a far-infrared electroluminescence image of a photodiode is investigated in the dark condition. The results show that the electroluminescence image can be used to detect defects in the photodiode. Additionally, it is found that the electroluminescence intensity has a power law dependence on the dc bias current. The photodiode ideality factor could be obtained by a fitting a relationship between the electroluminescence intensity and the bias current. The device defect levels will be easily determined according to the infrared image and the extracted ideality factor value. This work is of guiding significance for current solar cell testing and research.

Performance of La2O3/InAlN/GaN metal–oxide–semiconductor high electron mobility transistors

Feng Qian, Li Qian, Xing Tao, Wang Qiang, Zhang Jin-Cheng, Hao Yue
Chin. Phys. B, 2012, 21 (6): 067305 doi: 10.1088/1674-1056/21/6/067305
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We report on the performance of La2O3/InAlN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) and InAlN/GaN high electron mobility transistors (HEMTs). The MOSHEMT presents a maximum drain current of 961 mA/mm at Vgs=4 V and a maximum transconductance of 130 mS/mm compared with 710 mA/mm at Vgs=1 V and 131 mS/mm for the HEMT device, while the gate leakage current in the reverse direction could be reduced by four orders of magnitude. Compared with the HEMT device of a similar geometry, MOSHEMT presents a large gate voltage swing and negligible current collapse.

Modulation of electrical and optical properties of gallium-doped ZnO films by radio frequency magnetron sputtering

Liang Shuang, Mei Zeng-Xia, Du Xiao-Long
Chin. Phys. B, 2012, 21 (6): 067306 doi: 10.1088/1674-1056/21/6/067306
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Ga-doped ZnO (GZO) films are prepared on amorphous glass substrates at room temperature by radio frequency magnetron sputtering. The results reveal that the gallium doping efficiency, which will have an important influence on the electrical and optical properties of the film, can be governed greatly by the deposition pressure and film thickness. The position shifts of the ZnO (002) peaks in X-ray diffraction (XRD) measurements and the varied Hall mobility and carrier concentration confirms this result. The low Hall mobility is attributed to the grain boundary barrier scattering. The estimated height of barrier decreases with the increase of carrier concentration, and the trapping state density is nearly constant. According to defect formation energies and relevant chemical reactions, the photoluminescence (PL) peaks at 2.46 eV and 3.07 eV are attributed to oxygen vacancies and zinc vacancies, respectively. The substitution of more Ga atoms for Zn vacancies with the increase in film thickness is also confirmed by the PL spectrum. The obvious blueshift of the optical bandgap with an increase of carrier concentration is explained well by the Burstein-Moss (BM) effect. The bandgap difference between 3.18 eV and 3.37 eV, about 0.2 eV, is attributed to the metal-semiconductor transition.

The mixed-spins 1/2 and 3/2 Blume–Capel model with a random crystal field

Erhan Albayrak
Chin. Phys. B, 2012, 21 (6): 067501 doi: 10.1088/1674-1056/21/6/067501
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The random crystal field (RCF) effects are investigated on the phase diagrams of the mixed-spins 1/2 and 3/2 Blume-Capel (BC) model on the Bethe lattice. The bimodal random crystal field is assumed and the recursion relations are employed for the solution of the model. The system gives only the second-order phase transitions for all values of the crystal fields in the non-random bimodal distribution for given probability. The randomness does not change the order of the phase transitions for higher crystal field values, i.e., it is always second-order, but it may introduce first-order phase transitions at lower negative crystal field values for the probability in the range about 0.20 and 0.45, which is only the second-order for the non-random case in this range. Thus our work claims that randomness may be used to induce first-order phase transitions at lower negative crystal field values at lower probabilities.

Texture and self-biased property of an oriented M-type barium ferrite thick film by tape casting

Chen Da-Ming, Liu Ying-Li, Li Yuan-Xun, Yang Kai, Zhang Huai-Wu
Chin. Phys. B, 2012, 21 (6): 067502 doi: 10.1088/1674-1056/21/6/067502
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In this paper, the oriented M-type barium ferrite (BaM) thick films with different thicknesses are prepared by tape casting. It is found that the crystallographic alignment degree (f), the pore and the squareness ratio (Mr/Ms) are not affected by the thickness of the film. XRD and SEM results show that the thick film has hexagonal morphology with a crystal texture of c-axis grains perpendicular to film plane. The hysteresis curve indicates that the BaM thick film exhibits a self-biased property with a remanent magnetization of 3.30 T, a squareness ratio (Mr/Ms) of 0.81, and a coercivity of 0.40 T. The results show that the BaM thick film has potential for use in self-biasing microwave devices, and also proves that the tape casting technique is capable of fabricating high-quality barium ferrite films, thus providing a unique opportunity to realize the large area production of thick film.

Defects mediated ferromagnetism in a V-doped 6H–SiC single crystal

Zhuo Shi-Yi, Liu Xue-Chao, Xiong Ze, Yan Wen-Sheng, Xin Jun, Yang Jian-Hua, Shi Er-Wei
Chin. Phys. B, 2012, 21 (6): 067503 doi: 10.1088/1674-1056/21/6/067503
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Undoped and V-doped 6H-SiC single crystals have been grown by the physical vapor transport method. The V concentration is determined to be 3.76 × 1017 at/cm3 and 6.14 × 1017 at/cm3 by secondary ion mass spectrometry for low V-doped and high V-doped SiC samples, respectively. The undoped 6H-SiC shows diamagnetism, while the V-doped 6H-SiC exhibits weak ferromagnetism. The lower V-doped sample shows stronger ferromagnetism compared to that of the higher V-doped sample. However, the structural characterization indicates that the lower V-doped SiC has a relative poor crystalline quality. It is found that both V dopants and defects are essential for introducing ferromagnetic exchange in V-doped SiC single crystals.

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Liang Wei-Zheng, Ji Yan-Da, Nan Tian-Xiang, Huang Jiang, Zeng Hui-Zhong, Du Hui, Chen Chong-Lin, Lin Yuan
Chin. Phys. B, 2012, 21 (6): 067701 doi: 10.1088/1674-1056/21/6/067701
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Barium titanate (BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition (PAD) technique. The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion. Crystal structures, surface morphologies, and dielectric performance were examined and compared for BTO thin films annealed under different temperatures. Correlations between the fabrication conditions, microstructures, and dielectric properties were discussed. BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr ~ 400 and tanδ <0.025 at 100 kHz. The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

Fabrication and optical properties of InGaN/GaN multiple quantum well light emitting diodes with amorphous BaTiO3 ferroelectric film

Peng Jing, Wu Chuan-Ju, Sun Tang-You, Zhao Wen-Ning, Wu Xiao-Feng, Liu Wen, Wang Shuang-Bao, Jie Quan-Lin, Xu Zhi-Mou
Chin. Phys. B, 2012, 21 (6): 067702 doi: 10.1088/1674-1056/21/6/067702
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BaTiO3 (BTO) ferroelectric thin films are prepared by the sol-gel method. The fabrication and the optical properties of an InGaN/GaN multiple quantum well light emitting diode (LED) with amorphous BTO ferroelectric thin film are studied. The photoluminescence (PL) of the BTO ferroelectric film is attributed to the structure. The ferroelectric film which annealed at 673 K for 8 h has the better PL property. The peak width is about 30 nm from 580 nm to 610 nm, towards the yellow region. The mixed electroluminescence (EL) spectrum of InGaN/GaN multiple quantum well LED with 150-nm thick amorphous BTO ferroelectric thin film displays the blue-white light. The Commission Internationale De L'Eclairage (CIE) coordinate of EL is (0.2139, 0.1627). EL wavelength and intensity depends on the composition, microstructure and thickness of the ferroelectric thin film. The transmittance of amorphous BTO thin film is about 93% at a wavelength of 450 nm-470 nm. This means the amorphous ferroelectric thin films can output more blue-ray and emission lights. In addition, the amorphous ferroelectric thin films can be directly fabricated without a binder and used at higher temperatures (200 ℃-400 ℃). It is very favourable to simplify the preparation process and reduce the heat dissipation requirements of an LED. This provides a new way to study LEDs.

Determination of elastic, piezoelectric, and dielectric constants of an R:BaTiO3 single crystal by Brillouin scattering

He Xiao-Kang, Zeng Li-Bo, Wu Qiong-Shui, Zhang Li-Yan, Zhu Ke, Liu Yu-Long
Chin. Phys. B, 2012, 21 (6): 067801 doi: 10.1088/1674-1056/21/6/067801
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From the sound velocity measured using the Brillouin scattering technique, the elastic, piezoelectric, and dielectric constants of a high-quality monodomain tetragonal Rh:BaTiO3 single crystal are determined at room temperature. The elastic constants are in fairly good agreement with those of the BaTiO3 single crystal, measured previously by Brillouin scattering and the low-frequency equivalent circuit methods. However, their electromechanical properties are significantly different. Based on the sound propagation equations and these results, the directional dependence of the compressional modulus and the shear modulus of Rh:BaTiO3 in the (010) plane is investigated. Some properties of sound propagation and electromechanical coupling in the crystal are discussed.

Numerical simulation of four-wave mixing efficiency and its induced relative intensity noise

Chen Wei, Meng Zhou, Zhou Hui-Juan, Luo Hong
Chin. Phys. B, 2012, 21 (6): 067802 doi: 10.1088/1674-1056/21/6/067802
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Four-wave mixing, as well as its induced intensity noise, is harmful to wavelength division multiplexing systems. The efficiency and the relative intensity noise of four-wave mixing are numerically simulated for the two-wave and the three-wave fiber transmissions. It is found that the efficiency decreases with the increase of both the frequency spacing and the fiber length, which can be explained using the quasi-phase-matching condition. Furthermore, the relative intensity noise decreases with the increase of frequency spacing, while it increases with the increase of fiber length, which is due to the considerable power loss of the pump light. This investigation presents a good reference for the practical application of wavelength division multiplexing systems.

Luminescence of a GaN grain with a nonpolar and semipolar plane in relation to microstructural characterization

Zhou Xiao-Wei, Xu Sheng-Rui, Zhang Jin-Cheng, Dang Ji-Yuan, Lü Ling, Hao Yue, Guo Li-Xin
Chin. Phys. B, 2012, 21 (6): 067803 doi: 10.1088/1674-1056/21/6/067803
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We report on the growth of the high-quality GaN grain on a r-plane sapphire substrate by using a self-organized SiN interlayer as a selective growth mask. Transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy are used to reveal the effect of SiN on the overgrown a-plane GaN growth. The SiN layer effectively terminates the propagation of the threading dislocation and basal plane stacking faults during a-plane GaN regrowth through the interlayer, resulting in the window region shrinking from a rectangle to a “black hole”. Furthermore, strong yellow luminescence (YL) in the nonpolar plane and very weak YL in the semipolar plane on the GaN grain is revealed by cathodoluminescence, suggesting that C-involved defects are responsible for the YL.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

ZnO nanorod arrays with tunable size and field emission properties on an ITO substrate achieved by an electrodeposition method

Gong Jiang-Feng, Dou Zhao-Ming, Wang Zhi-Qiang, Zhang Bo, Zhu Wei-Hua, Zhang Kai-Xiao, Liu Ming-Yi, Zhu Hao, Zhou Jian-Feng
Chin. Phys. B, 2012, 21 (6): 068101 doi: 10.1088/1674-1056/21/6/068101
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In the present work, vertically aligned ZnO nanorod arrays with tunable size are successfully synthesized on nonseeded ITO glass substrates by a simple electrodeposition method. The effect of growth conditions on the phase, morphology, and orientation of the products are studied in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It is observed that the as-prepared nanostructures exhibit a preferred orientation along c axis, and the size and density of the ZnO nanorod can be controlled by changing the concentration of ZnCl2. Field emission properties of the as-synthesized samples with different diameters are also studied, and the results show that the nanorod arrays with a smaller diameter and appropriate rod density exhibit better emission properties. The ZnO nanorod arrays show a potential application in field emitters.

Kinetic evolutionary behavior of catalysis-select migration

Wu Yuan-Gang, Lin Zhen-Quan, Ke Jian-Hong
Chin. Phys. B, 2012, 21 (6): 068201 doi: 10.1088/1674-1056/21/6/068201
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We propose a catalysis-select migration driven evolution model of two-species (A- and B-species) aggregates, where one unit of species A migrates to species B under the catalysts of species C, while under the catalysts of species D the reaction will become one unit of species B migrating to species A. Meanwhile the catalyst aggregates of species C perform self-coagulation, as do the species D aggregates. We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j)=Kkij and D species catalysis-select migration rate kernel J(k;i,j)=Jkij. The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration, in which the competition is between JD0 and KC0 (D0 and C0 are the initial numbers of the monomers of species D and C, respectively). When JD0-KC0>0, the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form. And in the case of JD0-KC0<0, species A and B exchange their aggregate size distributions as in the above JD0-KC0>0 case.

Photonic generation of arbitrary waveforms based on incoherent wavelength-to-time mapping

Dong Jian-Ji, Luo Bo-Wen, Yu Yuan, Zhang Xin-Liang
Chin. Phys. B, 2012, 21 (6): 068401 doi: 10.1088/1674-1056/21/6/068401
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We demonstrate experimentally a radio frequency arbitrary waveform generator using the incoherent wavelength-to-time mapping technique. The system is implemented by amplitude modulation of a broadband optical resource whose spectrum is reshaped by a programmable optical pulse shaper and transmitted over a single mode fiber link. The shape of the generated waveform is controlled by the optical pulse shaper, and the fiber link introduces a certain group velocity delay to implement wavelength-to-time mapping. Assisted by the flexible optical pulse shaper, we obtain different shapes of optical waveforms, such as rectangle, triangle, and sawtooth waveforms. Furthermore, we also demonstrate ultra-wideband generation, such as Gaussian monocycle, doublet, and triplet waveforms, using the incoherent technique.

Research of sine waveguide slow-wave structure for a 220-GHz backward wave oscillator

Xu Xiong, Wei Yan-Yu, Shen Fei, Huang Min-Zhi, Tang Tao, Duan Zhao-Yun, Gong Yu-Bin
Chin. Phys. B, 2012, 21 (6): 068402 doi: 10.1088/1674-1056/21/6/068402
Full Text: [PDF 624 KB] (Downloads:948)
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A watt-class backward wave oscillator is proposed, using the concise sine waveguide slow-wave structure combined with a pencil electron beam to operate at 220 GHz. Firstly, the dispersion curve of the sine waveguide is calculated, then, the oscillation frequency and operating voltage of the device are predicted and the circuit transmission loss is calculated. Finally, the particle-in-cell simulation method is used to forecast its radiation performance. The results show that this novel backward wave oscillator can produce over 1-W continuous wave power output in a frequency range from 210 GHz to 230 GHz. Therefore, it will be considered as a very promising high-power millimeter-wave to terahertz-wave radiation source.

A staggered double vane circuit for a W-band traveling-wave tube amplifier

Lai Jian-Qiang, Wei Yan-Yu, Liu Yang, Huang Min-Zhi, Tang Tao, Wang Wen-Xiang, Gong Yu-Bin
Chin. Phys. B, 2012, 21 (6): 068403 doi: 10.1088/1674-1056/21/6/068403
Full Text: [PDF 371 KB] (Downloads:812)
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Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell (PIC) simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules (MPM) and for other portable applications.

Temperature dependence of birefringence in olarization-maintaining photonic crystal fibres Hot!

Zhao Hong, Chen Meng, Li Gang
Chin. Phys. B, 2012, 21 (6): 068404 doi: 10.1088/1674-1056/21/6/068404
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In this paper, the temperature dependence of birefringence in polarization maintaining photonic crystal fibres (PM-PCFs) is investigated theoretically and experimentally. Utilizing the structural parameters of the PM-PCF samples in the experiment, two effects leading to the birefringence variation under different temperatures are analysed, which are the thermal expansion of silica material and the refractive index variation due to the temperature variation. The actual birefringence variation of the PM-PCF is the combination of the two effects, which is in the order of 10-9 K-1 for both fibre samples. Calculation results also show that the influence of refractive index variation is the dominant contribution, which determines the tendency of the fibre birefringence variation with varying temperature. Then, the birefringence beat lengths of the two fibre samples are measured under the temperature, which varies from -40 ℃ to 80 ℃. A traditional PANDA-type polarization maintaining fibre (PMF) is also measured in the same way for comparison. The experimental results indicate that the birefringence variation of the PM-PCF due to temperature variation is far smaller than that of the traditional PMF, which agrees with the theoretical analysis. The ultra-low temperature dependence of the birefringence in the PM-PCF has great potential applications in temperature-insensitive fibre interferometers, fibre sensors, and fibre gyroscopes.

A low on-resistance triple RESURF SOI LDMOS with planar and trench gate integration

Luo Xiao-Rong, Yao Guo-Liang, Zhang Zheng-Yuan, Jiang Yong-Heng, Zhou Kun, Wang Pei, Wang Yuan-Gang, Lei Tian-Fei, Zhang Yun-Xuan, Wei Jie
Chin. Phys. B, 2012, 21 (6): 068501 doi: 10.1088/1674-1056/21/6/068501
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A low on-resistance (Ron,sp) integrable silicon-on-insulator (SOI) n-channel lateral double-diffused metal-oxide-semiconductor (LDMOS) is proposed and its mechanism is investigated by simulation. The LDMOS has two features: the integration of a planar gate and an extended trench gate (double gates (DGs)); and a buried P-layer in the N-drift region, which forms a triple reduced surface field (RESURF) (TR) structure. The triple RESURF not only modulates the electric field distribution, but also increases N-drift doping, resulting in a reduced specific on-resistance (Ron,sp) and an improved breakdown voltage (BV) in the off-state. The DGs form dual conduction channels and, moreover, the extended trench gate widens the vertical conduction area, both of which further reduce the Ron,sp. The BV and Ron,sp are 328 V and 8.8 mΩ·cm2, respectively, for a DG TR metal-oxide-semiconductor field-effect transistor (MOSFET) by simulation. Compared with a conventional SOI LDMOS, a DG TR MOSFET with the same dimensional device parameters as those of the DG TR MOSFET reduces Ron,sp by 59% and increases BV by 6%. The extended trench gate synchronously acts as an isolation trench between the high-voltage device and low-voltage circuitry in a high-voltage integrated circuit, thereby saving the chip area and simplifying the fabrication processes.

Abnormal oxidation in nickel silicide and nickel germanosilicide in sub-micro CMOS

Wang Tao, Guo Qing, Liu Yan, Yun Janggn
Chin. Phys. B, 2012, 21 (6): 068502 doi: 10.1088/1674-1056/21/6/068502
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After post-silicidation annealing at various temperatures for 30 min, abnormal oxidation and agglomeration in nickel silicide and nickel germanosilicide are investigated under different conditions of NiSi, with As-, In-, and Sb-doped Si substrates of nickel germanosilicide without any dopants. The NiSi thickness, dopant species, doping concentration, and silicide process conditions are dominant factors for abnormal oxidation and NiSi agglomeration. Larger dopants than Si, thinner NiSi thickness and SiGe substrates, and higher dopant concentrations promote abnormal oxidation and agglomeration.

A novel power UMOSFET with a variable K dielectric layer

Wang Ying, Lan Hao, Cao Fei, Liu Yun-Tao, Liu Yun-Tao
Chin. Phys. B, 2012, 21 (6): 068503 doi: 10.1088/1674-1056/21/6/068503
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A novel split-gate power UMOSFET with a variable K dielectric layer is proposed. This device shows a 36.2% reduction in the specific on-state resistance at a breakdown voltage of 115 V, as compared with the SGE-UMOS device. Numerical simulation results indicate that the proposed device features high performance with an improved figure of merit of Qg ? RON and BV2/RON, as compared with the previous power UMOSFET.

A novel high-voltage light punch-through carrier stored trench bipolar transistor with buried p-layer

Zhang Jin-Ping, Li Ze-Hong, Zhang Bo, Li Zhao-Ji
Chin. Phys. B, 2012, 21 (6): 068504 doi: 10.1088/1674-1056/21/6/068504
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A novel high-voltage light punch-through (LPT) carrier stored trench bipolar transistor (CSTBT) with buried p-layer (BP) is proposed in this paper. Since the negative charges in the BP layer modulate the bulk electric field distribution, the electric field peaks both at the junction of the p base/n-type carrier stored (N-CS) layer and the corners of the trench gates are reduced, and new electric field peaks appear at the junction of the BP layer/N- drift region. As a result, the overall electric field in the N- drift region is enhanced and the proposed structure improves the breakdown voltage (BV) significantly compared with the LPT CSTBT. Furthermore, the proposed structure breaks the limitation of the doping concentration of the N-CS layer (NN -CS) to the BV, and hence a higher NN-CS can be used for the proposed LPT BP-CSTBT structure and a lower on-state voltage drop (Vce(sat)) can be obtained with almost constant BV. The results show that with a BP layer doping concentration of NBP=7 × 1015 cm-3, a thickness of LBP=2.5 μm, and a width of WBP=5 μm, the BV of the proposed LPT BP-CSTBT increases from 1859 V to 1862 V, with NN-CS increasing from 5 × 1015 cm-3 to 2.5 × 1016 cm-3. However, with the same N--drift region thickness of 150 μm and NN-CS, the BV of the CSTBT decreases from 1598 V to 247 V. Meanwhile, the Vce(sat) of the proposed LPT BP-CSTBT structure decreases from 1.78 V to 1.45 V with NN-CS increasing from 5 × 1015 cm-3 to 2.5 × 1016 cm-3.

The influence of AlGaN/GaN superlattices as electron blocking layers on the performance of blue InGaN light-emitting diodes

Gong Chang-Chun, Fan Guang-Han, Zhang Yun-Yan, Xu Yi-Qin, Liu Xiao-Ping, Zheng Shu-Wen, Yao Guang-Rui, Zhou De-Tao
Chin. Phys. B, 2012, 21 (6): 068505 doi: 10.1088/1674-1056/21/6/068505
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P-AlGaN/P-GaN superlattices are investigated in blue InGaN light-emitting diodes as electron blocking layers. The simulation results show that efficiency droop is markedly improved due to two reasons: (i) enhanced hole concentration and hole carrier transport efficiency in AlGaN/GaN superlattices, and (ii) enhanced blocking of electron overflow between multiple quantum-wells and AlGaN/GaN superlattices.

Simulation study of blue InGaN multiple quantum well light-emitting diodes with different hole injection layers

Wu Le-Juan, Li Shu-Ti, Liu Chao, Wang Hai-Long, Lu Tai-Ping, Zhang Kang, Xiao Guo-Wei, Zhou Yu-Gang, Zheng Shu-Wen, Yin Yi-An, Yang Xiao-Dong
Chin. Phys. B, 2012, 21 (6): 068506 doi: 10.1088/1674-1056/21/6/068506
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InGaN-based light-emitting diodes with p-GaN and p-AlGaN hole injection layers are numerically studied using the APSYS simulation software. The simulation results indicate that light-emitting diodes with p-AlGaN hole injection layers show superior optical and electrical performance, such as an increase in light output power, a reduction in current leakage and alleviation of efficiency droop. These improvements can be attributed to the p-AlGaN serving as hole injection layers, which can alleviate the band bending induced by the polarization field, thereby improving both the hole injection efficiency and the electron blocking efficiency.

Multiple helical scans and the reconstruction of over FOV-sized objects in cone-beam CT

Han Yu, Yan Bin, Li Lei, Yu Chao-Qun, Li Jian-Xin, Bao Shang-Lian
Chin. Phys. B, 2012, 21 (6): 068701 doi: 10.1088/1674-1056/21/6/068701
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In cone-beam computed tomography (CBCT), there are often cases where the size of the specimen is larger than the field of view (FOV) (referred to as over FOV-sized (OFS)). To acquire the complete projection data for OFS objects, some scan modes have been developed for long objects and short but over-wide objects. However, these modes still cannot meet the requirements for both longitudinally long and transversely wide objects. In this paper, we propose a multiple helical scan mode and a corresponding reconstruction algorithm for both longitudinally long and transversely wide objects. The simulation results show that our model can deal with the problem and that the results are acceptable, while the OFS object is twice as long compared with the FOV in the same latitude.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

A genetic resampling particle filter for freeway traffic-state estimation

Bi Jun, Guan Wei, Qi Long-Tao
Chin. Phys. B, 2012, 21 (6): 068901 doi: 10.1088/1674-1056/21/6/068901
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On-line estimation of the state of traffic based on data sampled by electronic detectors is important for intelligent traffic management and control. Because a nonlinear feature exists in the traffic state, and because particle filters have good characteristics when it comes to solving the nonlinear problem, a genetic resampling particle filter is proposed to estimate the state of freeway traffic. In this paper, a freeway section of the northern third ring road in the city of Beijing in China is considered as the experimental object. By analysing the traffic-state characteristics of the freeway, the traffic is modeled based on the second-order validated macroscopic traffic flow model. In order to solve the particle degeneration issue in the performance of the particle filter, a genetic mechanism is introduced into the resampling process. The realization of a genetic particle filter for freeway traffic-state estimation is discussed in detail, and the filter estimation performance is validated and evaluated by the achieved experimental data.

The co-phasing detection method for sparse optical synthetic aperture systems

Liu Zheng, Wang Sheng-Qian, Rao Chang-Hui
Chin. Phys. B, 2012, 21 (6): 069501 doi: 10.1088/1674-1056/21/6/069501
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Co-phasing between different sub-apertures is important for sparse optical synthetic aperture telescope systems to achieve high-resolution imaging. For co-phasing detection in such a system, a new aspect of the system's far-field interferometry is analysed and used to construct a novel method to detect piston errors. An optical setup is built to demonstrate the efficacy of this method. Experimental results show that the relative differences between measurements by this method and the criterion are less than 4%, and their residual detecting errors are about 0.01 λ for different piston errors, which makes the use of co-phasing detection within such a system promising.

Jet precession in neutrino-cooled disks for gamma-ray bursts: The effects of the mass and spin of a black hole

Liu Tong, Xue Li
Chin. Phys. B, 2012, 21 (6): 069801 doi: 10.1088/1674-1056/21/6/069801
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We present a model of jet precession driven by a neutrino-cooled disk around a spinning black hole to explain the quasi-periodic features observed in some gamma-ray burst light curves. The different orientations of the rotational axes between the outer part of a neutrino-cooled disk and a black hole result in precessions of the central black hole and the inner part of the disk. Hence, the jet arising from the neutrino annihilation above the inner disk is driven to precession. We find that the period of precession is positively correlated with the mass as well as the spin of a black hole.
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