bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical properties of surface plasmons induced by the plan of a periodically arranged dielectric spheres on the metal slab
Authors: Zheng Jun-Juan  , Sun Gang  ,   中国科学院物理研究所，北京  100080
Published: December 2020

Optical properties of a system composed of a metal slab with two planes of periodically arranged dielectric spheres on the metal surface have been investigated.The results obtained from multiple scattering method show that the periodic dielectric spheres on the upper surface of the metal could induce surface plasmons on the metal-dielectric interface.For a very thick metal slab,the existence of the surface plasmons can be observed by corresponding peaks in absorption spectrum.The position of the absorption peak is mainly determined by the periodicity ofdielectric spheres,and is consistent with the analytic theory very well.For the limited thickness of metal slab,there exist two surface plasmon modes,corresponding to symmetric and antisymmetric modes,respectively,and the absorption peak that occurs in the thick metal slab splits into a double-peak strurcture.For a symmetric or antisymmetric surface plasmon,the magnitudes of the electric and magnetic fields are the same on both sides of the metal slab,thus these surface plasmons can results in a strong transmittance.The plane of periodically arranged dielectric spheres beneath the metal slab can lead the surface field out of the metal,and form a transmission plane wave.The results obtained from multiple scattering method show that the transmittance is fairly high when surface plasmons exist.The fundamental physical mechanism is studied in detail,and the occurrence of the surface plasmons,and hence the position of the peak of absorbance or transmittance,can be controlled by adjusting corresponding parameters in the system.
Theoretical and experimental research on the second harmonic of focused ultrasound in layered biological media
Authors: Xue Hong-Hui  , Liu Xiao-Zhou  , Gong Xiu-Fen  , Zhang Dong  ,   近代声学国家重点实验室,南京大学声学研究所,南京  210093
Published: December 2020

Based on the Khokhlov-Zabolotkaya-Kuznetsov (KZK) equation in frequency-domain, a theoretical model of focused ultrasonic waves in the layered biological medium with consideration of the sound absorption, nonlinearity, boundary of the media and the diffraction of the source is presented. The propagation of focused ultrasonic waves for fundamental and second harmonic in the multi-layered biological media are numerically studied and compared with the experimental results. Good agreement of the theory with the measurement shows that this approach can effectively describe the second harmonic sound field in multi-layered biological media.
Structure and magnetic properties of Er3(Fe, Co, M)29 compounds (M=Cr, V, Ti, Mn, Ga, Nb)
Authors: Luo Hong-Zhi  , Jia Lin  , Li Yang-Xian  , Meng Fan-Bin  , Shen Jiang  , Chen Nan-Xian  , Wu Guang-Heng  , Yang Fu-Ming  ,   (1)北京科技大学应用物理研究所,北京  100083; (2)河北工业大学材料学院,天津  300130; (3)中国科学院物理研究所北京凝聚态物理国家实验室,北京  100080; (4)中国科学院物理研究所北京凝聚态物理国家实验室,北京  100080;北京科技大学应用物理研究所,北京  100083; (5)中国科学院物理研究所北京凝聚态物理国家实验室,北京  100080;河北工业大学材料学院,天津  300130
Published: December 2020

A series of Er３(Fe, Co, M)２９ (M=Cr, V, Ti, Mn, Ga, Nb) compounds has been synthesized and their structure and magnetic properties have been investigates by means of x-ray diffraction and magnetic measurements. It is found that the Fe-based Er３(Fe,M)２９ compounds crystallize in the Th2Ni17-type structure with disordered substitution of the dumbbell Fe-Fe, instead of Nd3(Fe,Ti)２９-type structure, so its chemical formula can also be expressed as Er2－n(Fe,M)17+2n (n=0.2). Substitution of M for Fe in the Er３Fe29 compound leads to an increase in the Curie temperature. With the substitution of Co for Fe in the Er３(Fe,M)２９ (M=Cr, V) compounds, a new phase was found which crystallizes in monoclinic symmetry. The anisotropy of the Er３Fe19.5Co6V3.5 compound at room temperature is of easy-axis type and a spin reorientation transition from the easy-axis type to the easy-plane type anisotropy occurs when temperature decreases to 162K. A first order magnetization process (FOMP) was observed in the HMD magnetization curve of Er３Fe19.5Co6V3.5 at 5K, the critical field of the FOMP was derived to be 3.8T.
Preparation, structural characterization and nitrogen adsorption properties of a self-supported nanostructured gold film
Authors: Fu Xiao-Nan  , Li Xin-Jian  ,   (1)郑州大学物理工程学院，材料物理教育部重点实验室(郑州大学),郑州  450052; (2)郑州大学物理工程学院，材料物理教育部重点实验室(郑州大学),郑州  450052;河南工业大学数理系,郑州  450052
Published: December 2020

Employing silicon nanoporous pillar array (Si-NPA), a novel silicon micron/nanometer complex systems as reducing substrate, a self-supported, nanostructured gold film was prepared by immersion technique. The microstructure and surface morphology of the film were characterized. Our experiments disclosed that the preparation of the film is a self-stop process. With the exhaustion of Si-NPA, the chemical reducing reaction related with the Au3+ ions occurring in the immersing solution would stop automatically, and the deposited nanostructured gold film would disengage from the substrate to form a self-supported thin film. The formation mechanism of the film is due to the high surface reactivity and strong chemical reducibility of Si-NPA. The elemental composition analysis by energy dispersive x-ray spectroscopy showed that the prepared gold film exhibits strong capability in nitrogen adsorption and storage, which may find potential applications in the technical fields of gas sensors, air separation, nitrogen purification and membrane synthesis of various nitrides.
Study of structure optimization of carbon nanotubes using hybrid genetic algorithm based on clonal selection principle
Authors: Bao Wen-Xing  , Zhu Chang-Chun  , Cui Wan-Zhao  ,   (1)西安交通大学电子与信息工程学院,西安  710049; (2)西安交通大学电子与信息工程学院,西安  710049;西北第二民族学院计算机系,银川  750021
Published: December 2020

Focusing on the problem of carbon nanotube structure optimization by molecule dynamics simulation, a novel algorithm is proposed which combines the genetic algorithm with simulated annealing and the clone select algorithm.Test results of five typical functions show that this algorithm has high stability and gives good global optimization. Applied to structure optimization of carbon nanotubes, it can accelerate the process of energy optimization and improve the quality of structure optimization.The simulation results show that the optimizing time increases linearly with the number of atoms.The time of structure optimization is reduced one order of maguitucle compared with the conjugate gradient methods.
Density functional theory investigation on structural properties of MgS crystal
Authors: Chen Zhong-Jun  , Xiao Hai-Yan  , Zu Xiao-Tao  ,   (1)电子科技大学应用物理系,成都  610054; (2)电子科技大学应用物理系,成都  610054;中国科学院国际材料物理中心,沈阳  110016
Published: December 2020

We have systematically studied the structural and electronic properties of MgS crystal by means of accurate first principle calculations. Our results show that this crystal has indirect band gap in the B1 structure and direct band gap in the B2,B3 and the B4 structures. Energy band width of the B2 structure is the smallest. When the pressure is below 200.3GPa, the B1 structure of MgS crystal is most stable. Above 200.3GPa this compound would undergo a structural phase transition from the relatively loose NaCl structure to the more dense CsCl atomic arrangement.
A first-principle study of electronic and geometrical structures of semiconducting β-FeSi2 with doping
Authors: Pan Zhi-Jun  , Zhang Lan-Ting  , Wu Jian-Sheng  ,   上海交通大学材料科学与工程学院教育部高温材料及测试开放实验室，上海  200030，中国
Published: December 2020

Firstly,the electronic structure of β-FeSi2 and the density of states (DOS) of subshells of Fe and Si were calculated. The calculations were carried out using the self-consistent full-potential linearized augmented plane wave method within the density functional theory. The general gradient approximation was used to treat the exchange and correlation potential. The DOS of β-FeSi2 is mainly composed of d-shell electrons of Fe and p-shell electrons of Si. Secondly,the stable atomic substitution positions of doping atoms were determined by calculating the total energies for Fe1-xCoxSi2 and Fe(Si1-xAlx)2. The Fe atom at the FeⅡ position and the Si atom at the SiⅠ position were preferentially substituted by Co and Al,respectively. This preferential substitution is in good agreement with results of the existing publications. Finally,the elctronic structures of Fe1-xCoxSi2 and Fe(Si1-xAlx)2 were calculated and analyzed as well. The intrinsic relations between electronic structures of Fe1-xCoxSi2 and Fe(Si1-xAlx)2 and their respective thermoelectric properties including Seebeck coefficient,electric conductivity and thermal conductivity were discussed in detail.
Inversed polarization of the single excited state of polaron
Authors: Gao Kun  , Liu Xiao-Jing  , Liu De-Sheng  , Xie Shi-Jie  ,   山东大学物理与微电子学院；晶体材料国家重点实验室，济南  250100
Published: December 2020

The single excited state of a polaron in polymers has been studied. It was found that its polarization is negative under an external electric field. The single excited state of a polaron has a similar behavior with that of a biexciton. The inversed polarization will disappear under a strong electric field and the single excited state of a polaron will dissociate into a polaron and a bipolaron.
Effect of Ni, Fe-doping on the structure and properties of Ge-Sb-Se thin films
Authors: Zhang Hai-Fang  , Du Pi-Yi  , Weng Wen-Jian  , Han Gao-Rong  ,   浙江大学材料系，硅材料国家重点实验室，杭州  310027
Published: December 2020

Fe, Ni doped Ge-Sb-Se thin films are grown by electron-beam evaporation with targets sintered at low temperature, and show p-typed in conducting status. Investigated by AFM,UV-VIS,Hall and Impedance Analyzer, we observed that thin films have a more perfect network and less defects if the doped ion has a higher activity and smaller electronegative difference with the system elements, or the films are annealed. Fe and Ni doped in Ge-Sb-Se system not only take part in binding and affect the network perfection but also introduced defects near Fermi energy. Thin films doped with Ni have a more perfect network, lower neutron-hanging binding concentration and less polarons produced under AC electric field compared with Fe doped thin films, thus have smaller roughness, larger optical band gap, higher carrier mobility, lower carrier concentration and smaller dielectric loss.
Study of the helical wave-guide
Authors: Wang E-Feng  , Li Hong-Fu  , Li Hao  , Yu Sheng  , Niu Xin-Jian  , Liu Ying-Hui  ,   成都电子科技大学高能电子研究所，成都  610054
Published: December 2020

According to the coupled-wave equations, the irregular properties at boundaries of the wave-guide with helical corrugation is analyzed using the method of impedonce perturbation. The general coupled equation of the helical wave-guide and the formuale for coupled coefficient are obtained. Based on rules of mode coupling in helical wave-guide, the dispersion equation is obtained and the dispersion characteristics are discussed.
Structural stability and electronic structures of Nb atomic chains
Authors: Shen Han-Xin  , Cai Na-Li  , Wen Yu-Hua  , Zhu Zi-Zhong  ,   (1)厦门大学物理系，厦门  361005; (2)厦门大学物理系，厦门  361005;福建省龙岩学院计算机系，龙岩  364000
Published: December 2020

The structural stabilities and electronic structures of Nb atomic chains are studied by employing first-principles plane wave pseudopotential method based on the density functional theory. The calculations show that niobium can form planarchains in linear-, zigzag-, dimer- and ladder-form one-dimensional structures. The most stable one among the studied structures are the zigzag-form linear chain, and all the other structures are metastable. The relative structural stabilit y, the electronic energy bands, the density of states and the charge densities a re discussed based on the ab initio calculations and the Jahn-Teller effects.
Time-resolved photoluminescence of sub-monolayer InGaAs/GaAs quantum-dot-quantum-well heterostructures
Authors: Xu Zhang-Cheng  , Jia Guo-Zhi  , Sun Liang  , Yao Jiang-Hong  , Xu Jing-Jun  , J. M. Hvam  , Wang Zhan-Guo  ,   (1)丹麦技术大学通讯、光学和材料研究中心，Lyngby,DK-2800,丹麦; (2)弱光非线形光子学材料先进技术及制备教育部重点实验室，南开大学物理科学学院和泰 达应用物理学院,天津  300457; (3)弱光非线形光子学材料先进技术及制备教育部重点实验室，南开大学物理科学学院和泰 达应用物理学院,天津  300457;丹麦技术大学通讯、光学和材料研究中心，Lyngby,DK-2800,丹麦; (4)弱光非线形光子学材料先进技术及制备教育部重点实验室，南开大学物理科学学院和泰 达应用物理学院,天津  300457;中国科学院半导体研究所半导体材料科学重点实验室，北京
Published: December 2020

Time-resolved photoluminescence (PL) of sub-monolayer (SML) InGaAs/GaAs quantum-dot-quantum-well heterostructures was measured at 5 K for the first time. The radiative lifetime of SML quantum dots (QDs) increases from 500 ps to 800 ps with the increase of the size of QDs, which is related to the small confinement energy of the excitons inside SML QDs and the exciton transfer from smaller QDs to l arger ones through tunneling. The rise time of quantum-dot state PL signal stron gly depends on the excitation power density. At low excitation power density, th e rise time is about 35 ps, the mechanism of carrier capture is dominated by the emission of longitudinal-optical phonons. At high excitation power density, the rise time decreases as the excitation density increases, and Auger process pla ys an important role in the carrier capture. These results are very useful for u nderstanding the working properties of sub-monolayer quantum-dot devices.
Preparation and phase formation of sol-gel derived PST thin film doped with Mg
Authors: Du Pi-Yi  , Sui Shuai  , Weng Wen-Jian  , Han Gao-Rong  , Wang Jian-Xun  ,   浙江大学硅材料国家重点实验室，杭州  310027
Published: December 2020

PST thin film doped with Mg was successfully prepared using sol-gel process. The phase structure of the thin film was measured by XRD and the morphology of microstructure of the thin film was observed by SEM. Results showed that the cubic perovskite phase is formed in Mg-doped Pb0.4Sr0.6MgxTi1-xO3-x thin film prepared by sol gel process. The clustered crystallites are distributed and embedded in the base matrix of thin f ilm. However, the contents of the perovskite phase was controlled by both Mg dop ing and heat treatment condition due to formation of intrinsic oxygen vacancy in the perovskite phase. The charge balance between the positive from the intrinsi c oxygen vacancy and the negative from Mg substitution for Ti occurs when small amount of Mg is doped in the perovskite phase. The stable perovskite phase forms easily, and the crystallization of the perovskite phase is hence increased with increasing Mg doping up to x=0.01. The distortion of the perovskite phase struc ture would increase with farther increase of Mg doping in the crystallites above about x=0.01 due to the generation of a lot of oxygen vacancies. Henceforth uns table perovskite phase is formed and the crystallization of the film decreases w ith increasing Mg. Thus highest content of the perovskite phase is reached and t he charge balance between positive and negative occurs in the film when Mg dopin g is x=0.01. Furthermore, the formed crystalline phase may decompose with increa sing Mg content and time of heat treatment. So in the case of high Mg doping the higher the content of Mg and the longer the time of heat treatment, the lower t he content of perovskite phase is contained in the film.
Unified quantum field theory of Raman scattering of light in piezoelectric crystals
Authors: Cheng Ze  ,   华中科技大学物理系，武汉  430074
Published: December 2020

Although the classical and quantum theories of Raman scattering of light by optical phonons have been well established, the papers genarally emphasized on some particular aspects of the scattering. For this reason, we need to develop a gene ral quantum theory of Raman scattering, taking account of both nonpolar and pola r modes. In our quantum theory, Raman scattering of light by longitudinal and tr ansverse polar modes can be described within a unified theoretical framework.
Absorption and photoluminescence properties Er/Yb co-doped soda-silicate glasses
Authors: Li Shan-Feng  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室，大连  116024
Published: December 2020

Er/Yb co-doped soda-silicate glasses with 0.5 at.% Er and various concentrations Yb were fabricated. The absorption and the photoluminescence (PL) spectra were measured and analyzed. The PL intensity of the Er/Yb co-doped soda-silicate glasses is enhanced 4 times approximately, and the optimum Yb concentration for the PL intensity at 1536 nm is 3.0 at.%. The PL spectrum becomes broader with the in crease of Yb concentration, up to a FWHM of 80 nm at 6.0 at.% Yb. The relation b etween absorption and PL spectra, together with the mechanism of PL broadening, has been addressed.
Research on the effects of thickness of cobalt layers on the orbital and spin moments of Co atoms using x-ray magnetic circular dichroism in absorption
Authors: Wang Jie  , Li Hong-Hong  , Li Rui-Peng  , Guo Yu-Xian  , Wang Ya-Xin  ,   (1)南京大学物理系，南京  210093; (2)中国科学技术大学国家同步辐射实验室，合肥  230029
Published: December 2020

Orbital and spin moments of Co atoms in films of different thickness deposited by magnetron-sputtering on silicon wafers have been investigated by use of soft x -ray magnetic circular dichroism in absorption. Layers with thickness 2nm, 10nm and 30nm are covered by 0.8—1nm of protection overlayer. Orbital and spin momen ts of 0.249—0.195μB and 1.230—1.734μB are found from X MCD sum rules. Increase in orbital moments and decrease in spin moments are obse rved with reducing cobalt film thickness. There is a ratio variation from 0.101 to 0.168 of orbital moment to total moment, that is, contribution of orbital mom ent of cobalt atoms to total moment in 2nm film is 83% greater than that in the 30nm film.
Momentum-dependent symmetries and non-Noether conserved quantities for mechanico-electrical systems
Authors: Zheng Shi-Wang  , Fu Jing-Li  , Li Xian-Hui  ,   (1)青岛大学物理系，青岛  266071; (2)商丘师范学院物理系，商丘  476000; (3)商丘师范学院物理系，商丘  476000;浙江理工大学物理系，杭州  310018;青岛大学物理系，青岛  266071
Published: December 2020

The Hamiltonian canonical equation of the systems, the definition, criterion, structure equation and conserved quantities of momentum-dependent symmetries for Lagrange-Maxwell mechanico-electrical systems were presented. This work shows that the function ψ in the structure equation is only an invariant on the symmetry group. A new method to deduce conserved quantities of mechanico-electrical systems is obtained. An example is designed to illustrate these results.
Basic differential equation of self-similar motion of one-dimensional nonsteady flow of ideal gas
Authors: Bian Bao-Min  , He An-Zhi  , Li Zhen-Hua  , Yang Ling  , Zhang Ping  , Shen Zhong-Hua  , Ni Xiao-Wu  ,   南京理工大学信息物理与工程系，南京  210094
Published: December 2020

Self-similar function of one-dimensional nonsteady flow is extended to a general form. With total energy kept constant, basic differential equation of self-similar motion of one-dimensional nonsteady flow of ideal gas is derived using dimension theory in combination with the basic motion equations of hydromechanics. When a non-dimensional natural parameter L, which is the ratio of velocity of fluid (u) and self-similar surface (r·), serves as the independent variable, the theoretical model reveals that self-similar law of non-dimensional nonsteady flow of ideal gas has the simplest mathematical form. The model overcomes the difficulty of divergence at the origin of self-similar function of Taylor and thus has significant importance.
A novel quantum key distribution scheme with unextendible product basis and exact entanglement basis
Authors: Yang Yu-Guang  , Wen Qiao-Yan  , Zhu Fu-Chen  ,   (1)北京邮电大学理学院，北京  100876; (2)现代通信国家级重点实验室，成都  610041
Published: December 2020

A novel quantum key distribution scheme with unextendible product basis and exact entanglement basis in the 33 Hilbert space is proposed. The probability of successful eavesdropping by the eavesdropper is also analysed. This scheme has many distinct features such as great capacity, high efficiency.
Keyed Hash function based on composite nonlinear autoregressive filter
Authors: Wang Xiao-Min  , Zhang Jia-Shu  , Zhang Wen-Fang  ,   (1)西南交通大学计算机安全与通信保密研究所，成都  610031; (2)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

In recent years, chaotic dynamic systems are widely applied in information security because of its characteristic that the trajectory is sensitive to initial conditions and seems to be random though it is really a determinate process. The nonlinear autoregressive digital filters satisfying the Kelber conditions can also produce chaotic sequences just like chaotic maps do. The composite filter system consists of several above-mentioned filters, and the filter used for iteration is completely decided by a predetermined sequence called composite sequence. Consequently, the trajectory of the composite filter system is not only sensitive to its initial conditions, but also related with the composite sequence, which determines the choice of iterated sub-filter system in the iterating process. o the trajectory is more complex than that of general chaotic systems or single filter system. After analyzing some properties of composite filter systems such as N-dimensional uniform distribution and invariant distribution density function,a new keyed Hash algorithm based on composite system is presented. The approach selects the sub-filter system with the composite sequence obtained from message to be hashed, uses the initial iteration value of composite system as the secret key, and the coarse-grained trajectory as Hash value. Because of the sensitivity to initial value and randomicity of the iteration process, there is a very complex nonlinear relation between Hash value and the corresponding message and secret key, and then every bit of the Hash value derived from the message M is related with every bit of M. Furthermore, the filter-based algorithm is simple enough without complex operations, so it can be realized easily.
A stochastic digital oscillating system induced by the truncation error
Authors: Sheng Li-Yuan  , Jia Wei-Yao  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

It is generally believed that chaotic systems will collapse due to computer truncation error. In this paper we introduce a contrary example, in which a simple system is induced to complication or chaos completely by computer truncation. The system is defined as a cross-focus system in elliptical reflecting cavity map system. The theoretical solution is a limiting sequence and the computer solution is a stochastic digital oscillating system induced from the theoretical solution by truncation error. There is only a turn-round mechanism in the system theoretically. On the other hand, round-off induces the nonhyperbolic fixed points in the system to produce a new escape mechanism of intermittent chaos.
Tracking control and synchronization of the R?ssler's chaotic system
Authors: Wang Xing-Yuan  , Shi Qi-Jiang  ,   大连理工大学电子与信息工程学院，大连  116024
Published: December 2020

This paper presents a strategy of the Rssler's chaotic system tracking control based on the theory of stability of the linear system. This strategy can track all kinds of reference signals. It is also proved that the strategy can make the system approach to any desired smooth orbit at an exponential rate. Numerical simulations have shown the proposed strategy can not only trace the given reference signals, but also synchronize structures, including self structures and diverse ones.
Structure and potential energy function of the ground state (X2Π) of OH
Authors: Fan Xiao-Wei  , Geng Zhen-Duo  , Zhang Yan-Song  ,   河南师范大学物理系，新乡  453007
Published: December 2020

The equilibrium structure, harmonic frequency and dissociation energy of the ground state of OH are calculated using density functional theory (B3LYP) method and quadratic CI method including single, double and triple substitutions (QCISD(T)). Based on the theory of atomic and molecular statics, the reasonable dissociation limit for the ground state (X2Π) of OH is derived. The potential energy curve and relevant optical constants of this state are obtained by least square fitting to the Murrell-Sorbie function. All calculation results are in good agreement with the experimental data.
Propagation of matter waves through the joint between two atomic waveguides
Authors: Duan Zheng-Lu  , Zhang Wei-Ping  , Li Shi-Qun  , Zhou Zhao-Ying  , Feng Yan-Ying  , Zhu Rong  ,   (1)华东师范大学物理系,光谱学与波谱学教育部重点实验室,上海  200062; (2)清华大学精密仪器系,北京  100084; (3)清华大学物理系,北京  100084
Published: December 2020

In this paper, the propagation properties of matter waves through the joint between two atomic waveguides are investigated. A multimode coupling model is developed to describe the excitation of the matter waves through the waveguides. We analyze the dependence of the reflection and excitation on the parameters of the atomic waveguides. The condition to minimize the excitation of the atomic waves is given.
Influence of upconversion effect on Er3+, Yb3+co-doped phosphate glass lasers
Authors: Wu Zhao-Hui  , Song Feng  , Liu Shu-Jing  , Qin Bin  , Su Jing  , Tian Jian-Guo  , Zhang Guang-Yin  ,   南开大学光子学中心,天津  300071
Published: December 2020

An analytical model of cw longitudinally diode-pumped Er３＋,Yb３＋ co-doped phosphate glass lasers that includes the influence of cooperative upconversion and cumulative energy transfer effects has been developed. The results of general output modeling were applied to a laser with Gaussian beams, and numerical calculation has been made to study the influence of cooperative upconversion and cumulative energy transfer effects, where the dependence of laser output on the influence of cooperative upconversion and cumulative energy transfer effects was investigated in particular. Especially, we find that the influence of cooperative upconversion on the threshold can be up to 22%. The model is in good agreement with measurements of the laser in a plane-plane cavity. Further numerical analysis will be developed.Our results are useful for optimizing the parameters of this kind of lasers.
The far-field properties of ultrashort pulsed beams with constant waist width in free space
Authors: Zou Qi-Hui  , Lü Bai-Da  ,   四川大学激光物理与化学研究所,成都  610064
Published: December 2020

By using the angular spectrum and complex analytic signal representations, the analytic propagation expression and its Fourier spectrum for ultrashort Gaussian pulsed beams with constant waist width in the far field are derived. The far-field properties of few- and single-cycle ultrashort Gaussian pulsed beams with constant waist width are studied, and compared with those of ultrashort Gaussian pulsed beams with constant diffraction length. The properties of pulse broadening, spectrum narrowing, off-axis spectrum redshift and on-axis spectrum blueshift are found for ultrashort Gaussian pulsed beams with constant waist width in the far field.
Experimental and theoretical study of heat generation in Ti:sapphire end-pumped Nd:YAG ceramic lasers
Authors: Zhu Hong-Tao  , Lou Qi-Hong  , Qi Yun-Feng  , Ma Hai-Xia  , Dong Jing-Xing  , Wei Yun-Rong  ,   中国科学院上海光学精密机械研究所,上海  201800
Published: December 2020

The heat generation in Nd:YAG ceramic lasers under the conditions of laser extraction was investigated through the heat generation coefficient, which was defined as the ratio of heat generation power to laser output power. The heat generation coefficient of the 1.0% neodymium-doped YAG ceramic laser was calculated to be 0.63. The main factors which influences the heat generation coefficient were discussed in this paper, and the results showed that the heat generation coefficient was very sensitive to the changes in quantum emission efficiency, overlap efficiency and laser extraction efficiency. This work provides a reference for further research of thermal effect of Nd:YAG ceramic lasers.
Absorbing boundary conditions for two-dimensional photonic crystal waveguides
Authors: Zhang Bo  ,   北京交通大学电子信息工程学院，国家电工电子教学基地，北京  100044
Published: December 2020

We designed a distributed Bragg reflector waveguide for terminating the square lattice dielectric cylinder photonic crystal waveguide and evaluated the reflection of their interface numerically. The reflection coefficient was reduced to below 1% in a large part of the frequency range of the guided mode.
Simulation study of effects of cooling rate on microstructure of liquid metal Na during solidification processes
Authors: Hou Zhao-Yang  , Liu Rang-Su  , Li Chen-Shan  , Zhou Qun-Yi  , Zheng Cai-Xing  ,   湖南大学应用物理系，长沙  410082
Published: December 2020

A tracing simulation study has been performed for the solidification process of liquid metal Ni with four different cooling rates by means of molecular dynamics method. The pair distribution function g(r) curves, the bond-type index method of Honeycutt-Andersen (HA) and the cluster-type index method have been used to analyze the variations of microstructures during the solidification processes. The results show that the cooling rate plays a critical role in the transitions of microstructures. When the cooling rates are 1.0×1014 K/s and 1.0×1013 K/s, the amorphous structures are formed mainly with the 1551 and 1541 bond-types or polyhedron basic cluster (13 １ 10 2) and icosahedron cluster (12 0 12 0) in the system. When the cooling rates are 1.0×1012 K/s and 1.0×1011 K/s, the crystal structures are formed mainly with 1441 and 1661 bond-types or the bcc basic cluster (14 6 0 8) in the system. At the same time, it has been found that the effects of different cooing rates on the microstructures of metal Na are very small in liquid and supercooled states, however, they are very remarkable in solid (amorphous and crystal) states, and can be fully displayed only near the liquid-solid transition points,i.e., the glass transition temperature Tg and the crystallization temperature Tc, respectively. Accordingly,it possibly provides a new method to determine the Tg and Tc of liquid metals.The cluster-type index method would be more favorable than the bond-type index method for investigating the concrete structural characteristics of the disordering liquid, the amorphous and some crystallized systems.
The laser ablated deposition of Si nanocrystalline film with narrow photoluminescence peak
Authors: Wang Ying-Long  , Lu Li-Fang  , Yan Chang-Yu  , Chu Li-Zhi  , Zhou Yang  , Fu Guang-Sheng  , Peng Ying-Cai  ,   (1)河北大学电子信息工程学院，保定  071002; (2)河北大学物理科学与技术学院，保定  071002
Published: December 2020

The single crystalline Si target with high resistivity was ablated by a XeCl excimer laser (laser fluence 4J/cm2, repetition rate 1Hz), and at the ambient pressure of 10Pa of pure Ar gas, the nanocrystalline silicon film was deposited on a glass or single crystalline (111) Si substrate located at a distance of 3cm from the Si target in 30 and 10min, respectively. The Raman and x-ray diffraction spectra of the film deposited on the glass substrate indicate the film is nanocrystalline, which means that it is composed of Si nanoparticles. Scanning electron microscopy of the film on the Si substrate shows that the film has the mosaic structure of Si nano-crystallites of uniform size. The photoluminescence peak wavelength is 599nm with full width at half maximum of 56nm, which is blue-shifted and narrower than that obtained in He gas.
Theory and experiment of surface thermal lens technique used in absorption measurement of thin films
Authors: Fan Shu-Hai  , He Hong-Bo  , Fan Zheng-Xiu  , Shao Jian-Da  , Zhao Yuan-An  ,   (1)中国科学院上海光学精密机械研究所，上海  201800; (2)中国科学院上海光学精密机械研究所，上海  201800;中国科学院研究生院，北京  100039
Published: December 2020

The expression of surface thermal lens(STL) signal is deduced from photothermal deformation theory of thin film surface and STL diffraction theory. The linearity of STL signal to absorption of thin film can be seen from the expression. A measurement apparatus for thin film absorption based on STL technique is constructed. The measuring results prove that the sensitivity and accuracy of this instrument reach 10-6 magnitude.
Study on the influence of substitutional impurity on the stability of noble metal (111) surfaces by molecular dynamics simulation
Authors: Zhang Chao  , Tang Xin  , Wang Yong-Liang  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室,大连  116024
Published: December 2020

The stability of noble metal(111) surfaces doped with substitutional impurities were studied by molecular dynamics simulation. The atomic interaction potentials with the embedded atom method were applied in the simulation. The change of surface energy and the formation energy of surface vacancy induced by substitutional impurity were calculated. We found that the main factors effecting the surface energy of noble metal(111) surfaces are the cohesive energy and atomic radius of the substitutional impurity. The heat of solution of the binary alloy also has an important role in the influence of substitutional impurity on the formation energy of surface vacancy, along with the cohesive energy and atomic radius of substitutional impurity. Furthermore, the change of surface energy induced by substitutional impurity was used to predict the segregation of the binary alloy in the surface theoretically, yielding good agreement with the experimental results obtained by others.
Pulsed laser deposition of epitaxial CeO2 thin films on biaxially textured Ni substrate
Authors: Liu Zhen  , Wang Shu-Fang  , Zhao Song-Qing  , Zhou Yue-Liang  ,   (1)河北大学物理科学与技术学院，保定  071002; (2)中国科学院物理研究所，北京  100080
Published: December 2020

High-quality epitaxial CeO2 thin films were fabricated on the biaxially textured Ni substrates by pulsed laser deposition using a gas mixture of 4%H2 and 96%Ar. X-ray diffraction θ—２θ scan and ω-scan indicate the CeO2 thin films are c-axis textured, and φ-scan and pole figure of the films reveal the presence of good in-plane texture. The biaxially textured CeO2 films provide a good template for the fabrication of YBCO conductors.
Magnetism of 3d transition metal monolayers on Pd(001) surface: density functional theory study
Authors: Zhao Xin-Xin  , Tao Xiang-Ming  , Chen Wen-Bin  , Cai Jian-Qiu  , Tan Ming-Qiu  ,   浙江大学物理系，杭州  310027
Published: December 2020

In this article we present a report on the total energy calculations for the series of 3d transition metals as monolayers on Pd(001) surface using the density functional theory simulation. Analysis of total energy and magnetic moment shows that the first four atoms, i.e., Sc, Ti, V and Cr, favor p(1×1) ferro-magnetic configuration. Manganese prefers c(2×2) anti-ferromagnetic configuration on this surface. For the next three 3d transition metals, iron, cobalt and nickel, both p(1×1) (ferro-magnetic) and c(2×2) (antiferro-magnetic) configurations exist with a little difference in total energy. Copper and zinc monolayers do not show any magnetic ordering on the Pd(001) surface. Magnetic moment of vanadium in p(1×1) configuration is 2.41μＢ per atom, which is in contrast to the previously reported 0.51μＢ using full-potential linearized augmented-plane-wave method. For the rest 3d atoms, the present results are very close to the available research results both quantitatively and qualitatively.
Generation mechanism of stress induced leakage current in flash memory cell
Authors: Liu Hong-Xia  , Zheng Xue-Feng  , Hao Yue  ,   西安电子科技大学微电子学院，宽禁带半导体材料与器件教育部重点实验室, 西安  710071
Published: December 2020

The generation mechanism of stress induced leakage current (SILC) in flash memory cell is studied by experiments. The result shows that the reliability problem under low electronic field stress is mainly caused by carriers charging and discharging inside the oxide, while under high electronic field, the trap-assisted tunneling and positive charge assisted tunneling induced charge variation of floating-gate is the major cause of flash memory cell failure. For both high and low electronic field stresses, the transient current and the steady-state current in SILC are calculated, respectively.
Modeling of resistance changes based on the free volume in VLSI interconnection electromigration
Authors: Zong Zhao-Xiang  , Du Lei  , Zhuang Yi-Qi  , He Liang  , Wu Yong  ,   (1)西安电子科技大学技术物理学院，西安  710071; (2)西安电子科技大学微电子研究所，西安  710071
Published: December 2020

A well-known model for the rate of heterogeneous nucleation and growth of a second-phase precipitate in a solid matrix has successfully been applied to analyze the electromigration process in Al thin-film interconnects. The change of resistance is considered resulting mainly from the scattering of electrons by atoms around the vacancies or voids at grain boundaries. Free volume is introduced to describe the behavior of these atoms and to simplify the complicated scattering process by means of the effective scattering cross section of the free volume. The quantitative relation between the scattering cross section and the resistance change is established, and from which the resistance revolution can be characterized during different electromigration stages. Comparison of our simulation results with experimental data shows good agreement and our model can explain the previously unexplained abrupt resistance change phenomena.
Magnetic properties and magnetocaloric effects of Mn5Ge2.7M0.3 (M=Ga, Al, Sn) compounds
Authors: Liu Xi-Bin  , Shen Bao-Gen  ,   (1)中国科学院物理研究所磁学国家重点实验室,北京  100080; (2)中国科学院物理研究所磁学国家重点实验室,北京  100080;中国人民武装警察部队学院基础部, 廊坊  065000
Published: December 2020

The magnetic properties and magnetocaloric effects of Mn5Ge2.7M0.3(M=Ga, Al, Sn) compounds have been studied. All samples crystallize in the hexagonal Mn5Si3-type structure with space group P63/mcm. The average Mn magnetic moment decreases and the Curie temperature remains almost unchanged by the substitution of M for Ge. The magnetic entropy changes in these compounds are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation. The substitution of M for Ge reduces the magnitude of the magnetic entropy change owing to the decrease of the magnetic moment but broadens the magnetic entropy change peak. The maximum magnetic entropy changes for a field changes of 4.0×106A·m-1 are 6.1, 6.3, and 5.3J·kg-1K-1 for M=Ga, Al, and Sn, respectively. In addition, anomalies are found in the Arrott curves of Mn5Ge2.7M0.3(M=Ga Al, Sn) compounds under a critical field Hc when the temperature is higher than the Curie temperature TC, which indicates that the paramagnetic susceptibilities of these compounds change sharply. The value of Hc increases almost linearly with increasing temperature. This phenomenon is probably due to the change of Fermi energy by the applied magnetic field, which reduces the number of the effective charges.
Magnetization behavior and magnetic viscosity in nanocomposite Pr9Fe74Co12B5Snx(x=0, 0.5) ribbons
Authors: Chen Yun-Zhong  , He Shu-Li  , Zhang Hong-Wei  , Chen Ren-Jie  , Rong Chuan-Bing  , Sun Ji-Rong  , Shen Bao-Gen  ,   (1)首都师范大学物理系，北京  100037; (2)中国科学院物理研究所磁学国家重点实验室，北京  100080; (3)中国科学院物理研究所磁学国家重点实验室，北京  100080;首都师范大学物理系，北京  100037
Published: December 2020

Nanocomposite Pr9Fe74Co12B5 and Pr9Fe74Co12B5Sn0.5 ribbons were directly prepared by melt-spinning. Measurements of reversible and irreversible magnetization and magnetic viscosity were performed on the ribbons. It is found that the demagnetization curves of the both samples show a single hard phase behavior at room temperature, while a two-phase behavior at low temperature. The sample with Sn addition, because of its more homogeneous microstructure, shows a more obvious two-phase behavior than the Sn free one at low temperature. Furthermore, the increase of the volume fraction and grain sizes of the soft phase, in the Sn-doped ribbons, increases the portions of reversible magnetization and decreases the nucleation field Hn. The investigation of the magnetic viscosity shows that the activation volume is related to the grain sizes of the soft phase.
Optimization of photoelectrode introduced to dye-sensitized solar cells by anodic oxidative hydrolysis
Authors: Xu Wei-Wei  , Dai Song-Yuan  , Fang Xia-Qin  , Hu Lin-Hua  , Kong Fan-Tai  , Pan Xu  , Wang Kong-Jia  ,   中国科学院等离子体物理研究所，合肥  230031
Published: December 2020

The influence of three different modification methods on the photoelectrode introduced to dye-sensitized solar cells by anodic oxidative hydrolysis of acidic aqueous TiCl3 solutions was investigated. X-ray diffraction analysis shows that the nanocrystalline TiO2 prepared by sol-gel and electrodeposition is anatase. The average nanocrystalline size of TiO2 prepared by electrodeposition is 19nm and that by sol-gel method is 23.7nm. The surface structure of the nanoporous TiO2 films and TCO glass are observed by field-emission scanning electron microscopy before and after electrodeposition. It is found that the short-current density and the photoelectric conversion efficiency of dye-sensitized solar cells are improved a lot through these different methods.
Optical characteristics of DBR with inhomogeneous graded interfaces
Authors: Wang Xiao-Dong  , Wu Xu-Ming  , Wang Qing  , Cao Yu-Lian  , He Guo-Rong  , Tan Man-Qing  ,   中国科学院半导体研究所，北京  100083
Published: December 2020

Optical properties of Al0.9Ga0.1As/AlyGa1-yAs/GaAs/AlxGa1-xAs DBR with inhomogeneous graded interfaces has been investigated by using characteristic matrix method. The refractive index model and the analytic characteristic matrix of graded interfaces are obtained. The reflectance spectrum and the reflective phase shift are calculated for GaAs/Al0.9Ga0.1As DBR and graded interfaces DBR by using characteristic matrix method. The effect of graded interfaces on the optical properties of DBR is discussed. The result shows an extra graded phase matching layer must be added in front of the graded interfaces DBR to fulfil the conditions of phase matching at central wavelength. The accurate thickness of phase matching layer is calculated by optical thickness approximation method.
Hojman method for solving differential equations
Authors: Wu Hui-Bin  , Zhang Yong-Fa  , Mei Feng-Xiang  ,   北京理工大学理学院，北京  100081
Published: December 2020

First, the method presented by Hojman for finding the conserved quantity of the system of second order differential equations is generalized and applied to the system of first order differential equations, particularly to the odd-dimensional system for finding the integral in this paper. Next, it is proved that the Hojman theorem is a special case of the theorem given in this paper. Finally, an example is given to illustrate the application of the result.
New exact solutions and complex wave excitations in (2+1)-dimensional generalized Nozhnik-Novikov-Veselov system
Authors: Zhu Hai-Ping  , Zheng Chun-Long  ,   (1)浙江丽水学院物理系，丽水  323000; (2)浙江丽水学院物理系，丽水  323000;上海大学应用数学和力学研究所，上海  200072
Published: December 2020

Starting from an extended mapping approach and a linear variable separation method, new families of exact solutions with arbitrary functions for (2+1)-dimensional Generalized Nozhnik-Nivikov-Veselov system(GNNV) are derived. We found that some new and interesting complex wave excitations are derived from a periodic wave solution.
Effect of the longitudinal and transverse stacking period of InAs/GaAs quantum dots on the distribution of strain field
Authors: Liu Yu-Min  , Yu Zhong-Yuan  , Yang Hong-Bo  , Huang Yong-Zhen  ,   (1)北京邮电大学理学院,北京  100876;北京邮电大学光通信与光波技术教育部重点实验室，北京  100876; (2)中国科学院半导体研究所集成光电子学国家重点实验室，北京  100083
Published: December 2020

A systematic investigation is made on the influence of the longitudinal and transverse period distributions of quantum dots on the elastic strain field. The results showed that the effects of the longitudinal period and transverse period on the strain field are just opposite along the direction of center-axis of the quantum dots, and under proper conditions, both effects can be eliminated. The results demonstrate that in calculating the effect of the strain field on the electronic structure, one must take into account the quantum dots period distribution, and it is inadequate to use the isolated quantum dot model in simulating the strain field.
A nonlinear hybrid method for detecting the frequency of unknown weak composite periodic signal
Authors: Zhang Zheng-Wei  , Fan Yang-Yu  , Zeng Li  ,   西北工业大学电子信息学院，西安  710072
Published: December 2020

The odd multiple frequency phenomenon emerging in the stochastic resonance was studied, and some new theoretical conclusions was drawn. Based on these conclusions we found the reference frequency which must be set in the chaotic detector. Using the frequency selectivity of chaotic detector, the false frequency existing in the odd multiple frequency was filtered out.
Effects of deposition conditions on infrared spectroscopic ellipsometry of CVD diamond films
Authors: Su Qing-Feng  , Liu Jian-Min  , Wang Lin-Jun  , Shi Wei-Min  , Xia Yi-Ben  ,   上海大学材料科学与工程学院，电子信息材料系，上海  200072
Published: December 2020

Diamond films deposited by hot filament chemical vapor deposition (HFCVD) under different deposition conditions are characterized using spectroscopic ellipsometric measurements in infrared region of 2.5—12.5 μm. Effects of deposition conditions on infrared spectroscopic ellipsometry of diamond films are investigated. The optical properties of diamond films depend strongls on its quality. The refractive index increases and the extinction coefficient decreases monotonicly with increasing sp3 C content. High quality optical diamond films are obtained under reactor pressure of 4.0 kPa when substrate temperature and carbon concentration are 750℃ and 0.9%, respectively. Refractive index and extinction coefficient of diamond film of high transparency are 2.385 and of the order of 10-4, respectively.
Study of space charge field based on sheath helix model of TWTS
Authors: Xiao Liu  , Su Xiao-Bao  , Liu Pu-Kun  ,   (1)中国科学院电子学研究所，北京  100080; (2)中国科学院电子学研究所，北京  100080;中国科学院研究生院，北京  100039
Published: December 2020

The electromagnetic field of helix TWTs in the sheath model is analyzed. The dispersion and coupling impedance equations are derived and the one-dimensional space charge reduction factor is discussed in detail. The study shows that the difference of the space charge reduction factor between the sheath model and the perfect conducting tube is small at high frequency. The difference can be interpreted as the effect of the sheath helix. The higher frequency electromagnetic field has greater ability to affect the e-beam. Therefore, the space charge reduction factor equation based on the sheath helix model is inappropriate at high frequency.
Experimental and theoretical studies on auxiliary violet light increasing the diffraction efficiency of holographic gratings in bacteriorhodopsin film
Authors: Wang Ying-Li  , Yao Bao-Li  , Menke Neimule  , Ren Zhi-Wei  , Lei Ming  , Ren Li-Yong  ,   中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安  710068
Published: December 2020

Due to the saturation absorption characteristic of bacteriorhodopsin film, in holography, when the intensity of the recording light is higher than the saturation intensity, the distribution of the transmission of the holographic gratings deviates from the cosine shape. As a result, the steady level of diffraction efficiency is very low. Using the mutual suppression property of bacteriorhodopsin films between the violet light and the red light, the saturation intensity of the film at 633nm can be increased by adding an auxiliary irradiation of 405nm violet light, which results in the holographic recording being changed from the nonlinear region to linear region. Consequently the distribution of the transmission of the holographic gratings retrieves to the cosine shape, and the diffraction efficiency is improved to a high value. Base on this principle, a three-beam holography system is set up. The diffraction efficiency and the quality of the diffraction image are shown to be greatly improved by the auxiliary violet light.