bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of pressure and impurity hydrogen on the elastic property of metal lithium
Authors: Chen Chang-Bo  , Liu Zhi_Ming  , Ma Yan_Ming  , Cui Tian  , Liu Bing-Bing  , Zou Guang_Tian  ,   吉林大学超硬材料国家重点实验室，长春 130012
Published: December 2020

The pressure effects on the elastic properties of lithium doped by hydrogen are studied using first-principles methods based on density functional theory. A supercell including 16 Li atoms in hcp lattice is constructed with a hydrogen atom interstitially doped in. The supercell is fully relaxed at 0K. The elastic properties of the stable lattice are studied. The result shows that the bulk modulus increases after hydrogen atom is added. The elastic constants C11, C33, C66 and C12 are larger than those of pure Li，while the shear modulus C44 is smaller. The elastic constants increase with external pressure, with C11, C33 and C66 larger than those of pure Li while C12 being smaller. C13 is abnormally lower than that of pure Li within the pressure range from 2GPa to 4GPa, while C44 and C13 are greater at higher pressure area. The discrepancy of shear modulus between the doped and the pure system is enhanced by external pressure. The analysis of anisotropy ΔW shows that the doped system maintains isotropic under external pressure as does pure Li.
Optimized design of active layers in organic donor-acceptor solar cells
Authors: Ren Ju  , Zheng Jian-Bang  , Zhao Jian-Lin  ,   西北工业大学理学院光信息技术实验室,西安 710072
Published: December 2020

With the optical interference and exciton diffusion principle, the mechanism and process in a typical organic donor-acceptor solar cell are analyzed and simulated in virtue of a model established by MATLAB software. The effect of the organic film's thickness on the characteristics of organic solar cell is analyzed quantitatively, photo-absorptivity and exciton diffusivity are optimized by confining the thickness of organic active layers. The reliability of optimized model is validated by experiment.
Investigation of the impact of band offset perturbations on the performance of abrupt HBT with heavily doped base
Authors: Zhou Shou-Li  , Huang Hui  , Huang Yong-Qing  , Ren Xiao-Min  ,   (1)北京邮电大学电信工程学院, 北京 100876; (2)浙江工业大学信息学院,杭州 310014
Published: December 2020

Heavy impurity doping leads to bandgap narrowing (BGN) and this causes perturbations to the value of the band offsets at the hetero-interface. As a result, the form and height of energy barriers in abrupt HBT is disturbed, which changes the value of the current flowing through its interfaces. The analysis is based on the thermionic field-diffusion model which combines the drift-diffusion transport in the bulk of the transistor with the thermionic emission and tunneling at the base-emitter interface. The calculations reveal a more important role to the transport of carriers played by the modification of the built-in potential than that of the range of barrier energies available for tunneling because the impact of the built-in potential on the current is exponential. Therefore, it is important for a better description of the currents to use an accurate dopant-dependent BGN distribution model between bands.
Optical property of organic quantum well structures
Authors: Song Shu-Fang  , Zhao De-Wei  , Xu Zheng  , Xu Xu-Rong  ,   北京交通大学光电子技术研究所，发光与光信息技术教育部重点实验室,北京 100044
Published: December 2020

Single layer Alq3, double layer PBD/Alq3 and quantum well PBD/Alq3/PBD structures have been grown by organic molecular beam deposition. Energy levels and optical property of these samples are determined by cyclic voltammetry, optical absorption and photoluminescence (PL). Cyclic voltammetry and optical absorption results indicate that PBD/Alq3/PBD structures can be classified as type I quantum well. The PL experimental results indicate that PL peak, of single layer Alq3 structures do not shift to higher energy with decreasing layer thickness. However, for double layer PBD/Alq3 and quantum well PBD/Alq3/PBD structures, PL peaks shift to higher energy with decreasing layer thickness. The reason for blue shift of PL in organic quantum well structures is discussed in light of the theoretical and experimental results published in the literature.
Steady-state and nanosecond time-resolved photoluminescence spectroscopies of aqueous CdTe quantum dots
Authors: Wu Wen-Zhi  , Yan Yu-Xi  , Zheng Zhi-Ren  , Jin Qin-Han  , Liu Wei-Long  , Zhang Jian-Ping  , Yang Yan-Qiang  , Su Wen-Hui  ,   (1)哈尔滨工业大学凝聚态科学与技术研究中心，哈尔滨 150001; (2)哈尔滨工业大学凝聚态科学与技术研究中心，哈尔滨 150001；中国人民大学化学系，北京 100872; (3)吉林大学化学学院微分析仪器研究所，长春 130021
Published: December 2020

We have used femtosecond laser pulse to investigate the steady-state and nanosecond time-resolved photoluminescence of aqueous CdTe quantum dots (QDs). Up-conversion luminescences of the CdTe QDs induced by two-photon excitation were observed. Compared with 400nm excitation, the peak wavelength of photoluminescence induced by 1208nm excitation was red-shifted about 28nm (88meV). The decay kinetics showed a fast and a slow decay component which can be assigned to band-edge excitonic state (3—5ns) and surface trapping state (30—50ns), respectively. Luminescence and up-conversion luminescence at room temperature showed similar decay kinetics. The relative change of photoluminescence intensity between excitonic and trapping state is responsible for the red shift of emission peak. It was found that the proportion of excitonic emission in whole luminescence at 400nm excitation is bigger than that of excitonic emission at 800nm excitation, so with increasing the wavelength of laser excitation steady state spectra have the red shift of emission peaks.
Structure and spectroscopic properties of Tm3+ doped langasite (La3Ga5SiO14) crystal
Authors: Niu Yi  , Wang Zeng-Mei  , Liu Ying-Cai  , Yin Yan-Sheng  , Yuan Duo-Rong  ,   (1)山东大学晶体材料国家重点实验室，济南 250100; (2)中国海洋大学材料科学与工程研究院，青岛 266100
Published: December 2020

The structure of Tm3+-doped langasite(La3Ga5SiO14，abbreviated as LGS) crystal has been measured by XRD. The crystal lattice parameters were calculated with DICVOL91 program. The absorption spectra and emission spectra (excitated under 470nm) of Tm：LGS single crystal was measured at room temperature. And the optical parameters, such as transition-line intensity, oscillator strength and absorption section were calculated by using Judd-Ofelt theory. The three intensity parameters Ωt(t=2，4，6) were fitted to be 2.694×10-20cm2，1.842×10-20cm2，0.030×10-20cm2，respectively. The lifetime, branching ratio and integrated stimulated-emission cross section were obtained and the results were discussed.
Carrier injection process of polymer light-emitting diodes
Authors: Huang Wen-Bo  , Peng Jun-Biao  ,   (1)华南理工大学高分子光电材料及器件研究所，广州 510640; (2)华南理工大学高分子光电材料及器件研究所，广州 510640；华南理工大学特种功能材料及其制备新技术教育部重点实验室，广州 510640
Published: December 2020

The carrier injection process of polymer light-emitting diodes (PLEDs) with MEH-PPV(poly［2-methoxy，5-(2-ethylhexoxy)-1，4-phenylene vinylene］) as the light-emitting layer, was investigated using impedance spectroscopy, capacitance-voltage (C-V) and capacitance-frequency (C-F) techniques. The diodes have the configuration of ITO/PEDOT/MEH-PPV/Ba/Al. The experiments showed that there is an ohmic contact between electrodes and MEH-PPV, and holes and electrons injected from the cathodes are unbalanced. Charged traps in the MEH-PPV result in space-charge under positive bias, and the trap concentration was estimated at about 3.75×1016cm-3.
Magnetic field effects on organic electroluminescence
Authors: Wang Zhen  , He Zheng-Hong  , Tan Xing-Wen  , Tao Min-Long  , Li Guo-Qing  , Xiong Zu-Hong  ,   西南大学物理科学与技术学院，重庆 400715
Published: December 2020

A conventional organic light emitting diode, which has a structure of ITO/NPD/Alq3/LiF/Al, was fabricated and the magnetic field effects(MFEs) on its electroluminescence(EL) were measured. We found that the MFEs of the organic EL is strongly dependent on the applied bias on the device while the photoluminescence from the Alq3 film within the device is independent of the magnetic field. At low bias, the MFEs first rapidly increase with the magnetic field and then saturate at about 40kA/m, however at high bias the MFEs will decrease after this saturation, and the larger the bias, the stronger the decrease. The mutual annihilation of triplet-triplet pairs producing excited singlet excitons and the interaction between triplet excitons and excess carriers of Alq3 anion or cation are the physical mechanisms of the phenomena observed in this study.
Electronic structure of MnS studied by resonant inelastic soft X-ray scattering
Authors: Zhou Ke-Jin  , Yasuhisa Tezuka  , Cui Ming-Qi  , Ma Chen-Yan  , Zhao Yi-Dong  , Wu Zi-Yu  , Akira Yagishita  ,   (1)Department of Advanced Physics,Faculty of Science and Technology,Hirosaki University,Aomori 036-8561,Japan; (2)Photon Factory,Institute of Materials Structure Science,High Energy Accelerator Research Organization,Oho 1-1,Tsukuba 305-0801,Japan; (3)中国科学院高能物理研究所，北京 100049
Published: December 2020

The electronic structure of MnS was studied using resonant inelastic soft X-ray scattering (RIXS) from 2p63d5→2p53d6→2p63d5 channel. The d-d excitation and charge-transfer (CT) excitation were obtained which were resonant at excitation energies corresponding to L absorption edge and the satellites, respectively. RIXS and XAS spectra were simulated by Hartree-Fock method under atomic SO3 and cubic Oh symmetries. The crystal field 10Dq value was evaluated to 0.80eV—0.85eV. The stronger CT excitation of MnS than that of MnO originates from its narrower bandwidth.
Theoretical calculation of quantum yield for exponential-doping GaAs photocathodes
Authors: Zou Ji-Jun  , Chang Ben-Kang  , Yang Zhi  ,   (1)南京理工大学电子工程与光电技术学院，南京 210094; (2)南京理工大学电子工程与光电技术学院，南京 210094；东华理工学院电子工程系，抚州 344000
Published: December 2020

Exponential-doping photocathodes, in which from the GaAs bulk to the surface the doping concentration is distributed exponentially from high to low, can form a stable built-in electric field in the active layer, and the electric field facilitates the excited photoelectron emission. The quantum yield formulas of both reflection-mode and transmission-mode of exponential-doped photocathodes have been solved from the 1-diemnsion continuity equations, in which the build-in electric field is considered. According to these formulas, we calculate the theoretical quantum yield of the exponential-doped photocathodes. The calculated results show that the exponential-doping structure can increase the quantum yield of photocathodes significantly. To compare with the uniformly-doped photocathodes, the integral sensitivity of the reflection-mode exponential-doped photocathodes increases by nearly 20%, and for transmission-mode photocathodes the increase is more than 30%. The performance improvements of exponential-doping photocathodes are mainly attributed to the built-in electric field, the photoelectrons driven by the field move towards the cathode surface by way of diffusion and drift, accordingly, decrease the influence of the back-interface recombination velocity on photoemission and increase the equivalent electron diffusion length of cathodes.
Study on FN-DLC thin films: (Ⅳ) effect of nitrogen doping on structural properties of films
Authors: Xiao Jian-Rong  , Xu Hui  , Wang Huan-You  , Deng Chao-Sheng  , Li Ming-Jun  ,   (1)中南大学材料科学与工程学院，长沙 410083; (2)中南大学物理科学与技术学院，长沙 410083; (3)中南大学物理科学与技术学院，长沙 410083；中南大学材料科学与工程学院，长沙 410083
Published: December 2020

Nitrogen doped fluorinated diamond-like carbon (FN-DLC) films were deposited on p-type silicon wafers under different deposition conditions. Fourier transform infrared absorption spectrometry (FTIR) shows that the number of C—H bonds decreases with increasing r(r=N2/［N2+CF4+CH4］), but those of C=N, C≡N bonds increase gradually. Gaussian fit results of C1s and N1s in X-ray photoelectron spectra (XPS) show that the β-C3N4 and a-CNx(x=1,2,3) structures have formed in the films. The G band widening and the peak shift to the low wave-number in Raman spectra show that doping of N2 increases the fraction of sp2. Atomic force microscopy (AFM) reveals that the surface morphology of the films becomes smooth due to doping of nitrogen.
A new empirical model for retrieving sea surface salinity in L band
Authors: Li Zhi  , Wei En-Bo  , Tian Ji-Wei  ,   (1)中国海洋大学物理海洋实验室，青岛 266003; (2)中国科学院海洋研究所，青岛 266071
Published: December 2020

Sea surface salinity is a key physical parameter in ocean science. It is important in the ocean remote sensing to retrieve sea surface salinity by the microwave probe technology. Based on the in situ measurement data and remote sensing data of the Yellow Sea, we have built a new empirical model in this paper, which can be used to retrieve sea surface salinity of the Yellow Sea by means of the brightness temperature of the sea water at L-band. In this model, the influence of the roughness of the sea surface is considered, and the retrieved result is in good agreement with the in situ measurement data, where the mean absolute　error of the retrieved sea surface salinity is about 0.288 psu. This result shows that our model has greater retrieval precision compared with similar models.
Asymptotic solutions of perturbed N-component nonlinear Schr?dinger equations
Authors: Cheng Xue-Ping  , Lin Ji  , Wang Zhi-Ping  ,   浙江师范大学非线性物理研究所，金华  321004
Published: December 2020

We apply the direct perturbation method to an integrable nonlinear Schrdinger equation with a correction term to obtain its asymptotic solutions. It is shown that there is a good qualitative agreement between the asymptotic and the exact solutions when ε is small enough. Then the direct perturbation method is applied to the perturbed N-component nonlinear Schrdinger equations and their asymptotical solutions are obtained.
Interference of Bose-condensed gas in a 1D optical lattice
Authors: Xu Zhi-Jun  , Wang Dong-Mei  , Li Zhen  ,   浙江工业大学应用物理系，杭州  320032
Published: December 2020

For the Bose-condensed gas in a combined potential consisting of an axially-symmetric harmonic magnetic trap and one-dimensional (1D) optical lattice, using the mean-field Gross-Pitaevskii (G-P) equation and the propagator method, we study the formation of matter-wave interference upon releasing the condensate from the combined potential. The analytical result of the wave function for matter wave interference at any time t is given, and the relation between the interference fringe period and the optical lattice period is obtained. The interference pattern of Bose-condensed gas in the optical lattices is analogous to the multiple slit interference pattern in optics, and coincides with the results of experiment performed by Andrews et al. and Peil et al. and the numerical solution of the G-P equation by Sadhan K. Adhikari.
The Hawking radiation as tunneling from a Reissner-Nordstr?m-anti-de Sitter black hole
Authors: Jiang Qing-Quan  , Wu Shuang-Qing  , Cai  Xu  ,   华中师范大学物理科学与技术学院，武汉  430079
Published: December 2020

By taking into account the particle's self-gravitation interaction, Hawking radiation of the uncharged and charged particles as tunneling from a Reissner-Nordstrm-anti-de Sitter black hole has been studied firstly by using the Parikh-Wilczek's semi-classical tunneling approach. Next, we generalize the complex path method to reexamine the same question. Results obtained from both methods support the viewpoint of Parikh and Wilczek's, that is, the tunneling rate is related to the change of Bekenstein-Hawking entropy, and the actual emission spectrum is not exactly thermal.
Evolvement between bright and dark soliton of condensates
Authors: He Zhang-Ming  , Wang Deng-Long  ,   (1)湘潭大学物理系和低维材料及其应用技术教育部重点实验室，湘潭  411105; (2)湘潭大学物理系和低维材料及其应用技术教育部重点实验室，湘潭  411105; 南京航空航天大学理学院，南京  210016
Published: December 2020

By using Darboux transformation method, we study analytically the nonlinear dynamics properties of Bose-Einstein condensates trapped in an stable external poten tial. It is shown that the strength of inter-atomic interaction condensate has an important effect on its nonlinear dynamics properties. When atom-atom repulsive interaction of condensate is strong enough, there only exhibits bright soliton. While the inter-atomic repulsive interaction is less than a critical value, the alternative evolvement phenomenon between bright and dark soliton appears.
A chaos-based self-embedding secure watermarking algorithm
Authors: He Hong-Jie  , Zhang Jia-Shu  ,   西南交通大学信号与信息处理四川省重点实验室，成都  610031
Published: December 2020

This paper presents a novel chaos-based self-embedding secure watermarking algorithm based on the chaotic pseudorandom ness and sensitivity to initial value of chaotic map. In the proposed approach, the real-valued chaotic sequence, which is generated by the given initial value as secret key, is used to produce the ordered indices as the watermark embedding positions. The proposed algorithm has a larger key space than the existing self-embedding watermarking algorithms due to its watermark embedding positions being randomly selected by the secret key. Furthermore, the problem, how to locate the tampered image block in the self-embedding watermarking algorithm has been solved successfully. Theoretical analysis and simulation results show that our scheme not only improves the abilities of tamper localization, but also has better security against many attacks, including the vector quantization and synchronous counterfeiting attacks.
Lag synchronization for a class of chaotic systems with unknown parameters
Authors: Jia Fei-Lei  , Xu Wei  ,   西北工业大学理学院应用数学系,西安  710072
Published: December 2020

In this paper, the problem of lag synchronization for a class of chaotic systems with unknown parameters is proposed. Based on Lyapunov stability theory, lag controller and update law of parameters are obtained. This method is simple and systemic. A new chaotic system is taken as an example to illustrate the effectiveness of this proposed method. Numerical simulation illustrates the feasibility of this technique. To demonstrate the robustness against the effective of bounded noise of the proposed control strategy, it is applied to the new system and perfect simulation results are obtained.
A class of switchable 3D chaotic systems
Authors: Liu Yang-Zheng  , Jiang Chang-Sheng  , Lin  Chang-Sheng  , Xiong Xing  , Shi Lei  ,   (1)南京工程学院非线性物理研究所,南京  211167; (2)南京工程学院非线性物理研究所,南京  211167; 南京航空航天大学自动化学院,南京  210016; (3)南京航空航天大学自动化学院,南京  210016
Published: December 2020

A class of switchable three-dimensional chaotic systems is built. These systems have seven terms on the right-hand side, three of which are quadratic nonlinear. Some of its basic dynamical properties are studied detailedly, such as the feature of equilibrium, the chaos attractor, Lyapunov exponent and fractal dimension. A practical circuit is designed to realize these systems.
Linear feedback control of Hopf bifurcation in Langford system
Authors: Liu Su-Hua  , Tang Jia-Shi  ,   (1)湖南大学力学与航空航天学院,长沙 410082; (2)湖南大学力学与航空航天学院,长沙 410082; 安阳工学院，安阳 455000
Published: December 2020

The Hopf bifurcation characteristic in Langford system is analyzed and the control of Hopf bifurcation in this system is investigated by means of the method of linear state feedback control. The condition in which Hopf bifurcation occurs in the controlled system is arrived at in analysis and the analytical expressions of the limit cycles are obtained. Hopf bifurcation points are transformed and the stability of the limit cycles is controlled. The analytical results on controlling Hopf bifurcation points via the controllers agree well with the numerical results.
Research on the correlation between the mutual information and Lempel-Ziv complexity of nonlinear time series
Authors: Zhang Dian-Zhong  ,   中南大学数学科学与计算技术学院，长沙 410083
Published: December 2020

To explore the correlation between the mutual information and complexity of nonlinear dynamic system, the nonlinear time series of Logistic map， Lorenz model and cardiac RR intervals were used as the experimental data. The multi-segmented time-delayed mutual information， multi-segmented Lempel-Ziv complexity and their correlation coefficients were calculated. The results show that the mutual information of these series are strongly negatively correlated with the complexity. For the 201 series generated by Logistic equation, the absolute value of all correlation coefficients between the mutual information and the complexity of various segments are 0.9126 plus and the maximum reach to 0.9923， and for the 94 series of cardiac RR intervals， they are 0.8555 plus and the maximum reach to 0.9860. The investigations also indicate that the mutual information is more sensitive than the complexity in characterizing a nonlinear dynamic system.
Analysis of the property of train flow in the fixed autoblock systems
Authors: Li Feng  , Gao Zi-You  , Li Ke-Ping  ,   北京交通大学轨道交通控制与安全国家重点实验室，北京 100044
Published: December 2020

Based on the NS traffic model, we propose a cellular automaton traffic model for four-aspect fixed autoblock systems. We simulate the traffic phenomenon of train delay. We also investigate the effects of main factors including train interval, proportion of freight train, dwell time of the train in the station and unmber of platforms. Simulation results show that: (i) the freight train can restrain the running velocity of the passenger train following it; (ii) the delay may be relaxed by adjustment of the train's dwell time in the station; (iii) the increase in number of platforms in the station may improve the traffic density, however, the using frequency of the platform may be reduced when the train interval is large.
Research on the amplitude frequency characteristics compensation based on wavelet neural network for vibration velocity transducer
Authors: Yu A-Long  ,   淮阴师范学院物理与电子学系，淮安 223001
Published: December 2020

A method of amplitude frequency characteristics compensation is presented to realize ultra-low frequency vibration measurement based on wavelet neural network(WNN) for vibration velocity transducer. In this method, a dynamic compensation network can be set up according to measurement data of dynamic response of vibration velocity transducer. The compensation principle is introduced and the geometrical structure of the network is analyzed and the algorithms for the training and initialization of network parameters are given. The weights of network, scale factor and displacement factor are trained by the steepest descent method and the network parameters initialization is integrated with the wavelet type, time-frequency parameters of wavelet and the training samples. The results show that the proposed wavelet neural network has good robustness, on-line correction ability, and higher precision and faster training speed than the BP neural network when used in the amplitude frequency characteristics compensation of vibration velocity transducer, and has practical value in measurement field.
Upconversion luminescence mechanisms of Er3+-doped barium gallogermanate glasses
Authors: Xiao Kai  , Yang Zhong-Min  , Feng Zhou-Ming  ,   特种功能材料及其制备新技术教育部重点实验室,广州 510641; 华南理工大学光通信材料研究所,广州 510641
Published: December 2020

The absorption, Raman and upconversion luminescence spectra of Er3+-doped barium gallogermanate glasses have been measured and the upconversion mechanisms of Er3+-doped barium gallogermanate glasses have been analyzed. The absorption and Raman spectra show that barium gallogermanate glasses have the ultraviolet absorption edge of 275nm and the maximum vibrational energy of 828cm-1, respectively. Intense green and red emissions, excited by 800nm and 980nm laser diode, were observed at room temperature. With increasing Er3+ ion concentration, the green emission increases initially and then decreases, while the red emissions increases monotonicly. Under the excitation of 800nm laser diode, the green emission is mainly attributed to the excited state absorption from the 4I13/2 level and the red emission to the energy transfer between the 4I13/2 level and the 4I11/2 level. Under the 980nm laser diode excitation, the green emission mainly originates from the energy transfer between the 4I11/2 levels and the red emission from the energy transfer between the 4I13/2 and 4I11/2 levels as well as the excited state absorption of the 4I13/2 level. The calculation results of quantum efficiency for different pumping wavelengths show that the upconversion efficiency of the green emission in barium gallogermanate glass with 1mol% Er3+ ions reaches a maximum value under the excitation of 800nm laser diode.
Quantum description of interference effect with two holes
Authors: Yao Zhi-Xin  , Zhong Jian-Wei  , Mao Bang-Ning  , Chen Gang  , Pan Bai-Liang  ,   浙江大学物理学系，杭州 310027
Published: December 2020

By using one-dimensional photon state-vector function obtained previously, a general analytic expression is deduced for the optical two-hole interference experiment, which not only greatly enlarges the range of the observable, but also completely represents the probability distribution for a photon in the whole space. On the basis of the basic rules of quantum optics, we quantitatively analyze and discuss the domain of definition of the experiment, and the quantum behavior of the interference item on the average of space.
Model potential calculations of oscillator strength spectra of lithium atoms in parallel electric and magnetic fields
Authors: Meng Hui-Yan  , Kang Shuai  , Shi Ting-Yun  , Zhan Ming-Sheng  ,   (1)中国科学院武汉物理与数学研究所波谱与原子分子物理国家重点实验室，武汉 430071; (2)中国科学院武汉物理与数学研究所波谱与原子分子物理国家重点实验室，武汉 430071; 中国科学技术大学近代物理系，合肥 230026; 中国科学院研究生院，北京 100080; (3)中国科学院武汉物理与数学研究所波谱与原子分子物理国家重点实验室，武汉 430071; 中国科学院研究生院，北京 100080
Published: December 2020

We present oscillator strength spectra of Rydberg lithium atoms in parallel electric and magnetic fields obtained via the B-spline basis set method combined with model potential. Both the radial and angular wavefunctions are expanded in terms of B-spline functions. The results are in good agreement with previous high-precision experiments. By analyzing the components of partial-wave, we give an explanation to the oscillator strength of part of the spectrum. The method of this paper is simple and effective. It is suggested that the present method can be applied to deal with the problem of Rydberg atom in crossed magnetic and electric field.
Density functional theory study on the structure and properties of CoBen(n=1—12) clusters
Authors: Wang Qing-Lin  , Ge Gui-Xian  , Zhao Wen-Jie  , Lei　Xue-Ling  , Yan Yu-Li  , Yang Zhi  , Luo You-Hua  ,   (1)河南大学物理与电子学院，开封 475004; (2)河南大学物理与电子学院，开封 475004; 华东理工大学理学院，上海 200237
Published: December 2020

Geometric structures of CoBen(n=1—12) clusters are optimized using the generalized gradient approximation (GGA) density functional theory. The energy, vibrational frequency and magnetism are calculated. The results indicate that the spin multiplicities of the ground-state clusters are 2 and 4. Furthermore, the investigated magnetic moments confirm that the Co atomic magnetic moments of CoBen(n=1—12) clusters display an odd-even oscillation feature. In addition, the Co atomic magnetic moments of CoBe6 is the smallest of all clusters due to the strong hybridization between the 4s, 3d state of Co and 2s, 2p state of Be and short Co-Be average bond distance and low symmetry. By analyzing the properties of electrons, it is concluded that doping of impurity increases the stability and the chemical activity of Be cluster. It is found that CoBe5 and CoBe10 clusters are more stable than the neighboring ones.
Determination of thermal focal length of diode laser end-pumped solid-state amplifier
Authors: He Wan-Jun  , Yao Bao-Quan  , Wang Yue-Zhu  , Ju You-Lun  ,   哈尔滨工业大学可调谐激光国家重点实验室，哈尔滨 150001
Published: December 2020

Thermal focal length of amplifier is investigated by analyzing the variation of beam radius after thermal lens. According to the theory of laser beam propagation, the expressions of the thermal focal length are obtained. Also, the preconditions and the deviations of the expressions are analyzed. Based on the theoretical analysis, the thermal focal length of the laser diode (LD) end-pumped Tm,Ho∶GdVO4 amplifier is measured.
Analysis of the evolvement of hot-image in case of thick nonlinear medium
Authors: Peng Tao  , Zhao Jian-Lin  , Xie Liang-Ping  , Ye Zhi-Jun  , Li Qiang  , Su Jing-Qin  ,   (1)西北工业大学理学院光信息技术研究所，陕西省光信息技术重点实验室，西安 710072; (2)中国工程物理研究院激光聚变研究中心，绵阳 621900
Published: December 2020

Based on the split-step-Fourier-transform and the diffraction theory of hot-image model we made the simulation of the evolvement of hot-image in case of thick nonlinear medium. The changes of some parameters influencing the intensity and location of hot-image, such as the modulation coefficient (including amplitude modulation and phase modulation), the distance between scatterer and the front surface of nonlinear medium, the size of the scatterer, the intensity of incident beams and so on, were detailedly analysed respectively. Numerical results were found to be in agreement with analytical theory for the changes in modulation coefficient and the intensity of incident beams, but not in agreement with analytical theory for the changes in the size of the scatterer. Moreover, when the distance between scatterer and the front surface of nonlinear medium is zero, hot-image will also be found on the back surface of nonlinear medium.
Generating femtosecond double pulses using Dammann reflection gratings
Authors: Liu Wen-Jun  , Bai Bing  , Zhou Chang-He  , Qu Shi-Liang  , Dai En-Wen  , Li Guo-Wei  ,   (1)哈尔滨工业大学光电科学系(威海),威海 264209; (2)哈尔滨工业大学光电科学系(威海),威海 264209；中国科学院上海光学精密机械研究所,上海 201800; (3)中国科学院上海光学精密机械研究所,上海 201800
Published: December 2020

A novel device for generating femtosecond double pulses is constructed, which mainly consists of three Dammann reflection gratings. Being free from transmission elements, pulse distortion is avoided. Measuring the generated double pulses with a home-made second-harmonic generation frequency-resolved optical gating, experimental results demonstrated that this device can generate double pulses exactly equal in pulse intensity and pulse width with arbitrary delay time. This method should be highly interesting for double pulses generation and its practical applications.
Analysis of the fully destructive interference of overlapping-images in MMI couplers
Authors: Sun Yi-Ling  , Pan Jian-Xia  ,   (1)杭州电子科技大学电子信息学院,杭州 310027; (2)深圳大学工程技术学院,深圳 518060
Published: December 2020

Based on self-imaging effect and overlapping-imaging properties of multimode interference couplers, the phenomenon of fully destructive interference of overlapping-images in MMI couplers is revealed, for the first time. The condition for overlapping-image fully destructive interference is derived. From the point of view of overlapping-image fully destructive interference, we explain the paired interference and the symmetric interference. The expressions of the positions and number of output images for two especial overlapping-images are also given. We prove that this kind of phenomena exists not only in the paired interference and the symmetric interference by way of an example. The influence of the positional number on the fully destructive interference images is also analyzed. And the guided-mode propagation analysis method is used to confirm the analytical results.
State equation of phonon gas and conservation equations for phonon gas motion
Authors: Guo Zeng-Yuan  , Cao Bing-Yang  , Zhu Hong-Ye  , Zhang Qing-Guang  ,   清华大学工程力学系，北京 100084
Published: December 2020

Based on the mass-energy relation of Einstein's relativity theory, the mass of solid lattices is divided into two parts: the rest mass of solid atoms and the equivalent mass of thermal vibration energy of lattices. The latter is exactly the equivalent mass of the phonon gas in a solid. The vibration energy of the solid lattices includes the thermal energies consisting of the rest mass of the solid lattices and the equivalent mass of the phonon gas. The state equations for the lattice rest mass and the phonon gas are deduced based on the state equation of solids. The heat conduction is just the motion of the phonon gas in a solid. The conservation equations for the phonon gas motion are established. It is found that the conservation equation of phonon gas momentum degenerates to the Fourier's conduction law when the inertial force of the phonon gas can be ignored. The physical nature of the Fourier's law is the balance between the driving force and the resistance for the motion of the phonon gas. Under ultrahigh heat flux conditions where the inertial force is too high to be ignored, the Fourier's law is no longer valid even under the steady condition.
Study of high frequency characteristics of the rectangular waveguide grating slow-wave structure with arbitrary grooves
Authors: Lu Zhi-Gang  , Wei Yan-Yu  , Gong Yu-Bin  , Wu Zhou-Miao  , Wang Wen-Xiang  ,   电子科技大学物理电子学院，成都 610054
Published: December 2020

The rectangular waveguide grating slow-wave structure (SWS) is a new type of RF system of millimeter traveling wave tube (TWT). However, it has narrow pass band. For the purpose of broadening the bandwidth of this circuit, it is necessary to study the influence of groove shapes on the characteristics. In this paper, the dispersion equation of a rectangular waveguide grating SWS with arbitrary grooves is derived by means of an approximate field-theory analysis, in which the continuous profile of the groove is approximately replaced by a series of steps, and the field continuity at the interface of two neighboring steps and the matching conditions at the interface between the groove region and the interaction region are ensured. The cold test on dispersion characteristics of a rectangular groove SWS shows that the theoretical results are in good agreement with the experimental results. We have calculated the dispersion characteristics and the coupling impedance of the slow-wave structures with some special groove shapes. It shows that the dispersion characteristics of the triangle-groove structure is the weakest and the coupling impedance of it is the lowest, while the dispersion characteristics of the inverted-trapezoid-groove structure is the strongest and the coupling impedance of it is the highest.
Strain in AlInGaN thin films caused by different contents of Al and In studied by Rutherford backscattering/channeling and high resolution X-ray diffraction
Authors: Wang Huan  , Yao Shu-De  , Pan Yao-Bo  , Zhang Guo-Yi  ,   (1)北京大学物理学院技术物理系,北京 100871; (2)北京大学物理学院人工微结构与介观物理国家重点实验室,北京 100871
Published: December 2020

A series of AlInGaN films with different contents of Al and In were grown by metal-organic chemical vapor deposition on sapphire with GaN (>2μm) intermediate layer. Rutherford backscattering/channeling was used to measure the compositions and the crystal quality of the AlInGaN films. Combining with the high resolution x-ray diffraction, the lattice constants and the strain in perpendicular andthe parallel directions of the AlInGaN epilayer can be determined accurately bytheθ-2θ scan of (0002) and (1015) reflections and the reciprocal-space x-ray mapping. We find that different contents of In and Al can effect the strain in the quaternary AlInGaN films obviously, and with the help of Vegard's law we give an explanation for this phenomenon.
Optimization of GaAs (110) quantum well material growth technology by reflection high energy electron diffraction
Authors: Liu Lin-Sheng  , Liu Su  , Wang Wen-Xin  , Zhao Hong-Ming  , Liu Bao-Li  , Jiang Zhong-Wei  , Gao Han-Chao  , Wang Jia  , Huang Qing-An  , Chen Hong  , Zhou Jun-Ming  ,   (1)兰州大学物理科学与技术学院，兰州 730000; (2)兰州大学物理科学与技术学院，兰州 730000；东南大学MEMS教育部重点实验室，南京 210096; (3)兰州大学物理科学与技术学院，兰州 730000；中国科学院物理研究所凝聚态国家实验室，北京 100080；东南大学MEMS教育部重点实验室，南京 210096; (4)中国科学院物理研究所凝聚态国家实验室，北京 100080
Published: December 2020

Recently, there is an increasing interest in the molecular beam epitaxy growth of various high quality heterostructures on the nonpolar GaAs(110) surface for the unique properties which arise from this unconventional orientation. Considering that the Ga and As atoms are coplanar in GaAs(110) surface, the range of bestgrowth temperature is small. It is difficult to find the best growth condition by observing the change of reflection high energy electron diffraction (RHEED) pattern because this kind of (1×1) RHEED pattern is insensitive to growth temperature and V/III beam equivalent pressure ratio. In the process of the GaAs(110) quantum well growth, we observed the single and double period variation of oscillation of RHEED intensity. This implies that there are two growth modes (monolayer-by-monolayer and bilayer-by-bilayer) of GaAs quantum wells growing on the GaAs (110) substrate under different growth conditions. The measurements of transmission electron microscopy and photoluminescence at room temperature showed that the quantum wells have very bad optical property under the bilayer_by_bilayer growth mode, while the quantum wells grown under the monolayer-by-monolayer growthmode have much better optical property with rough interfaces. By means of RHEEDoscillations, high quality quantum wells have been grown on GaAs (110) substrate under optimized growth conditions.
Numerical simulation of the dynamic interactions between dislocation and solute atoms
Authors: Jiang Hui-Feng  , Zhang Qing-Chuan  , Chen Xue-Dong  , Fan Zhi-Chao  , Chen Zhong-Jia  , Wu Xiao-Ping  ,   (1)合肥通用机械研究院,国家压力容器与管道安全工程技术研究中心,合肥 230031; (2)合肥通用机械研究院,国家压力容器与管道安全工程技术研究中心,合肥 230031；中国科技大学,中科院材料力学行为和设计重点实验室,合肥 230027; (3)中国科技大学,中科院材料力学行为和设计重点实验室,合肥 230027
Published: December 2020

Using the Cottrell-Bilby kinetics model for solute atoms, evolution of the solute concentration around dislocation line has been investigated with respect to the strain rate. Three types of interactions between dislocation and solutes were obtained: At low strain rates, the dislocation is effectively pinned by its condensed solute cloud and the solute concentration remains almost at its saturation value. At high strain rates, the npinning effect predominates and dislocation moves at high velocity with little solute disturbance. While at the intermediate strain rates, the aging and unpinning effects take place alternately and dynamic strain ageing operates. Morevover, the N-shaped relationship between the rate-dependent flow stress and strain rate has also been naturally deduced from the model equations without additional assumptions.
The effect of radiation induced strain relaxation on electric performance of AlmGa1－mN/GaN HEMT
Authors: Fan Long  , Hao Yue  ,   (1)北京时代民芯科技有限公司,北京 100076; (2)宽禁带半导体材料与器件教育部重点实验室,西安电子科技大学,西安 710071
Published: December 2020

A complete model for studying the effect of radiation induced strain relaxation on electric performance of AlGaN/GaN HEMT was built utilizing the degree of strain relaxation related to radiation dose and energy as a basic variable. The effects of radiation induced strain relaxation on carrier density, threshold voltage and I-V characteristic were systematically investigated. The calculation results indicated that decrease in polarization induced charges as a result of strain relaxation causes decrease in carrier density, increase in threshold volgate and degradation in saturation drain current according to a linear rule. All results showed that the effect of radiation induced strain relaxation on HEMTs with high Al content appears more prominent. The calculation results also imply that strain relaxation is one of the important radiation damage mechanisms, the sensitivity of Al content to radiation induced strain relaxation degree need to be considered when improving the figure of merit of HEMTs by virtue of enhancement in Al content.
A 1/f noise based research of radiation induced interface trap buildup process
Authors: Li Rui-Min  , Du Lei  , Zhuang Yi-Qi  , Bao Jun-Lin  ,   西安电子科技大学技术物理学院,西安 710071
Published: December 2020

Based on the two-step interface trap buildup model and the statistical thermodynamics mechanism of point defects in solids, a relation between the radiation induced increase of oxide hole-traps and the buildup of interface traps in MOSFET is proposed. Then, based on the correlation between pre-irradiation 1/f noise power spectral density and post-irradiation oxide-trap charge, a sim-empirical expression of pre-irradiation 1/f noise and post-irradiation interface traps buildup is established which agrees well with the experimental results. This model shows that the process of interface trap buildup was influenced by the increasing of oxide hole-traps that could dissociated hydrogen into proton under irradiation. So, the magnitude of pre-irradiation 1/f noise is directly proportional to post-irradiation interface-trap charge and sub-threshold slope. Our results not only proves that the 1/f noise can play a important role in MOSFET irradiation effects, but also proves a new nondestructive method to estimate MOSFET radiation response.
Phase transformation in process of deposition of cubic boron nitride thin films
Authors: Chen Hao  , Deng Jin-Xiang  , Liu Jun-Kai  , Zhou Tao  , Zhang Yan  , Chen Guang-Hua  ,   (1)北京工业大学材料学院,北京 100022; (2)北京工业大学应用数理学院,北京 100022
Published: December 2020

Phase transitions between the polytypes of boron nitride and the influence of defect and impurity on preparation of c-BN thin film are studied from energy and structure aspects. A pathway from h-BN to c-BN is analysed, namely: h-BN→r-BN→c-BN. The transformation from h-BN to c-BN is more difficult than that from r-BN to c-BN. The energy barrier is very high in direct transformation from h-BN to c-BN, but it is very low from r-BN to c-BN. In fact, defects and impurities in c-BN thin films may favorably drive the transformation from h-BN to c-BN. Defects and impurities can reduce the energy barrier for the transformation sufficiently enough for it to proceed under conditions obtainable in common laboratories. Based on the theoreticd model, we developed a new method to prepare c-BN thin film (three-step method). The effect of time and substrate bias voltage on the first step of preparation of c-BN thin film is investigated. The study proves that 5 min and -180V is very favorable. The c-BN thin film that content with cubic phase exceeding 80% can be repeatedly prepared using the three-step method. Results of experiments accord with the theoreticat model very well.
Study of the stress in doped CVD diamond films
Authors: Li Rong-Bin  ,   上海电机学院材料成型系,上海 200245
Published: December 2020

Sulphur-doped and boron-sulphur co-doped diamond thin films were prepared using chemical vapour deposition (CVD) on Si substrates under different conditions. The influence of doping on stress in CVD diamond films were investigated with X-ray diffraction and Raman spectra. The results show that the sp2-carbon content, the concentration of defects and the residual compressive stress in CVD diamond films increase with increasing of sulphur content. Compared with sulphur doping of diamond films, the boron-sulphur co-doping with few boron atoms facilitates sulphur atom incorporation into diamond crystal. The boron-sulphur complexes in diamond can reduce crystal lattice distortion and crystal imperfection. As a result, sp2-carbon content and residual compressive stress in boron-sulphur co-doped diamond are reduced, and diamond crystal prefection is improved.
Effect of N2 partial pressure on the defect properties and mechanical behaviors of nanoscale ZrN/WN multilayers
Authors: Wang Li-Qun  , Wang Ming-Xia  , Li De-Jun  , Yang Jin  , Yu Da-Shu  , Su Jie  ,   天津师范大学物理与电子信息学院，天津 300387
Published: December 2020

ZrN/WN nanoscale multilayer coatings were synthesized with different N2 partial pressure by radio frequency magnetron sputtering. The vacancy-defect properties were measured by slow positron annihilation, and mechanical behaviors were studied using nanoindentation. The results indicate that the multilayer coating with N2 partial pressure of 0.4 Pa has the lowest concentration of vacancy-defects, and the average S-parameters of the central and the combination layers are 0.4402 and 0.4641, respectively. Lower or higher N2 partial pressure results in an increase in vacancy-defect concentration. With vacancy-defect concentration decreasing, the hardness and critical load of multilayer coatings increase. The multilayer coating with lowest concentration of vacancy-defects also exhibits maximum hardness and critical load (34.8 GPa and 100 mN). The decrease of vacancy-defect concentration is helpful to improve the mechanical properfies of multilayer coatings.
Investigation on micro-modification mechanism on surface of microfluidic glass chip
Authors: Li Bao-Xing  , Ye Mei-Ying  , Chu Qiao-Yan  , Yu Jian  ,   杭州师范学院物理系、化学系、杭州师范学院有机硅化学及材料技术教育部重点实验室和微流控芯片研究所，杭州 310036
Published: December 2020

The surface of the glass channel of microfluidic chip is treated with dichlorodimethylsilan. After the treatment, the silicon hydroxyl on the surface of the glass channel is silylated, which results in the reduction or even the elimination of the electroosmotic flow. Furthermore, full-potential linear-muffin-tin-orbital molecular dynamics method is used to investigate the micro -mechanism of surface reaction theoretically. The calculation results indicate that the hydrogen atom in silicon hydroxyl binds with the chlorine atom in dichlorodimethylsilan to form a stable HCl molecule and goes off, thereby the surface of the channel is covered with silylane.
Curie-temperature modulation by polarization-induced built-in electric fields in Mn δ-doped GaN/AlGaN quantum wells
Authors: Shen Ye  , Xing Huai-Zhong  , Yu Jian-Guo  , Lü Bin  , Mao Hui-Bing  , Wang Ji-Qing  ,   (1)东华大学物理系，上海 200051; (2)上海华东师范大学信息学院电子系，上海 200062
Published: December 2020

Transfer matrix method has been used to analyze Curie-temperature (TC) modulation by polarization-induced built-in electric fields in Mn δ-doped GaN/AlGaN quantum wells. Schrdinger equation is employed to calculate the quantum-confined subband energies and the distribution of their corresponding envelope fuctions. Based on these，we investigate the dependence of TC on the built-in electric fields in different structures of quantum well. By changing the asymmetry of double quantum wells (DQW)，TC can be raised up to 3 times.
First-principle calculations of phase transitions and equation of state at T=0K for gold
Authors: Hou Yong  , Yuan Jian-Min  ,   国防科学技术大学理学院物理系，长沙 410073
Published: December 2020

In the framework of density functional theory, the static-lattice equation of state and structural phase stability of gold have been calculated to 2 TPa by using the augmented plane wave plus local orbital method with two distinct exchange-correlation energies; corresponding to the generalized gradient approximation (GGA) and the local density approximation (LDA), respectively. The fcc structure is predicted to be the most stable phase at zero pressure, transforming to the hcp structure at 380GPa (GGA) or 490GPa (LDA), and the hcp structure transforming to the bcc structure at 1250GPa (GGA) or 790GPa (LDA), which then remains stable to up 2 TPa. The possible reasons of the phase-transition are analyzed from the electronic density of state at the different phases and volumes. The equation of state at T=0K is also given based on the calculated structural result.
Difference in electric conduction of monocrystal and polycrystal graphite
Authors: Wang Zhi-Ming  , Xu Qing-Yu  , Zhang Shi-Yuan  , Xing Ding-Yu  , Du You-Wei  ,   (1)德国莱比锡大学物理系，莱比锡 D-04103，德国; (2)南京大学固体微结构国家重点实验室，南京 210093; (3)南京理工大学机械工程学院，南京 210094；南京大学固体微结构国家重点实验室，南京 210093
Published: December 2020

In this paper, we report the difference in electric conduction of monocrystal and polycrystal graphite. Under a magnetic field of 8.15T, the positive magnetoresistance ratio of monocrystal and polycrystal graphite samples are found to be 69400%, 170% respectively at 4.5K. The polycrystal graphite presents accordingly the insulator-like character in a wide interval of temperature under 0 and 8T applied magnetic field, but the magnetic-field-correlated semimetal-insulator-like Transition has been reported for the monocrystal graphite (highly oriented pyrolitic graphite, HOPG). On analysis, it is revealed that large difference in electric conduction originates predominantly from the Coulomb interaction in HOPG graphite layers in contrast with the crystal interface scattering in the polycrystal graphite.