bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on thermal contact conductance between crystal rod and heat sink in LD end-pumped solid-state laser
Authors: Liu Hai-Qiang  , Guo Zhen  , Wang Shi-Yu  , Lin Lin  , Guo Long-Cheng  , Li Bing-Bin  , Cai De-Fang  ,   School of Technical Physics, Xidian University, Xi'an 710071, China
Published: December 2020

In LD end-pumped solid-state laser, the crystal rod is held and cooled by the metal heat sink. The force applied to the side surface of the crystal is non-axisymmetric. Under such circumstances, three kinds of thermal contact conductance (TCC) models are established, including not using thermal interface material, using thermal interface material with its thickness equal to the average thickness of the gaps and using thermal interface material with its thickness much greater than the thickness of the gaps. Regarding to the first two models, the influences of the assembly force and the equivalent root-mean-square (RMS) roughness on thermal contact conductance are discussed based on the Truncated-Gaussian model and the plastic-deformation model. The contact heat dissipation model of the crystal rod and the heat sink is established. For the Gaussian heat consumption, the spatial distributions of temperature inside the crystal with and without thermal interface material are obtained by the finite element method. The results show that without thermal interface material, the thermal contact conductance between the crystal rod and the heat sink changes significantly in the circumferential direction, which reaches a maximum on the bottom of the heat sink groove and a minimum on the contact area of the heat sink couple. With the assembly force increasing and the equivalent root-mean-square roughness decreasing, the thermal contact conductance gets larger and more nonuniform, and the temperature of the whole crystal rod reduces. When the indium foil is used as thermal interface material, the thermal contact conductance gets larger and more uniform, the temperature of the whole crystal rod reduces as well and its distribution is axisymmetric.
Theoretical analysis on gain characteristics of siliconRaman amplifiers
Authors: Liu Zu-Xue  , Feng Ming  , Guo Qing-Hua  , Qiao Li  , Lü Ke-Cheng  ,   The Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, School of Physics,Nankai University, Tianjin 300071, China
Published: December 2020

We report the new theoretical analysis method to obtain net gain in silicon waveguide by stimulated Raman scattering, and the key parameters of the free carrier lifetime and the pump light intensity are analyzed. The free carrier lifetime threshold and pump light intensity threshold are deduced. The gain characteristics of silicon Raman amplifiers with different pumping schemes are investigated, and the results show that the gain can be significantly enhanced in the bidirectional pump scheme.
The defect mode and the quantum effect of light wave in cylindrical anisotropic photonic crystal
Authors: Liu Qi-Neng  ,   Computer Science and Information Engineering College of Chongqing Technology and Business University, Chongqing 400067, China
Published: December 2020

The quantum effect of light wave mode is studied under restriction condition of light wave in 1-D cylindrical anisotropic doped photonic crystal. The defect mode character of TE wave and TM wave are calculated by characteristic matrix method . New defect mode structure of 1-D cylindrical anisotropic doping photonic crystal was obtained. The defect mode frequency and transmission angle increases with increasing quantum number. The defect mode frequency of the same pattern decreases with increasing cylinder radius.
Design and fabrication of sub-wavelength metal wire-grid and its application to experimental study of polarimetric imaging
Authors: Kang Guo-Guo  , Tan Qiao-Feng  , Chen Wei-Li  , Li Qun-Qing  , Jin Wei-Qi  , Jin Guo-Fan  ,   (1)School of Optoelectronic, Beijing Institute of Technology University, Beijing 100081, China; (2)State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100084, China; (3)Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
Published: December 2020

Metal wire-grid whose period is far less than the illuminating wavelength exhibits strong polarization selectivity within a large field of view over a wide wave length range. Thus it could be used as the polarization-controller in the polarimetric imaging system. For infrared polarimetric imaging system, an aluminum wire-grid on the CaF substrate with period of 200nm and depth of 100nm was designed based on effective medium theory. The calculation results demonstrate that the designed wire-grid has the extinction ratio larger than 35 dB within a field of view ±20° over both middle wave infrared (MWIR) (3—5 μm) and long wave infrared (LWIR) (8—12 μm). The aluminum wire-grid was fabricated by electron beam lithography, reactive ion etching and plasma stripping. A clear-cut polarimetric image was obtained when wire-grid was placed in front of a MWIR thermal infrared imager.
Measurement of the group refractive index of bulk material using white-light spectral interferometry
Authors: Zhang Shu-Na  , Luo Zhen-Yue  , Shen Wei-Dong  , Liu Xu  , Zhang Yue-Guang  ,   State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

It is a radical but pressing problem to measure the group refractive index of dispersive material both accurately and rapidly in optical engineering field. In this paper, a white-light spectral interferometric system employing a fiber-optic spectrometer is developed for solving this problem. The system takes advantage of the characteristic of fiber-optic spectrometer which can get all the interferometric information by a single shot image without any mechanical scanning. Compared with the traditional windowed Fourier transform, a wavelet transform algorithm is used to directly extract the group delay rather than the phase from the interferogram. Therefore, the new method can provide a simple and fast solution, while still maintaining high accuracy. Based on this white-light Michelson interferometric system, fused silica and BK7 glass samples are measured respectively and the results agree well with the theoretical values over a broad spectral range. At the end of this paper, different mirror positions are used to verify the repeatability of our method.
The dynamical analysis of energy decay in one-dimensionalcomposite granular chain
Authors: Xia Ji-Hong  , Liu Hui  , Yan Long  , Liu Chang-Song  , Wang Ping-Jian  ,   (1)Institute of Solid State Physics, Chinese Academy Sciences, Hefei 230031, China; (2)School of Information & Electronics Engineering,Shandong Institute Of Business and Technology,Yantai 264005,China
Published: December 2020

The structure transition from compression state to dilation state in both heavy-particle sections gives rise to the crossover of the energy decay in one-dimensional composite granular chain. And the structure transition closely relates to the change in state of motion of heavy grain at both interfaces. The analysis demonstrates that the change in state of motion gives rise to the great difference of reflectivity in both branches, which induces different rates of energy decay of light-particle section in both branches.
Time-frequency spectral analysis of gas-liquid two-phase flow’s fluctuations
Authors: Sun Bin  , Wang Er-Peng  , Zheng Yong-Jun  ,   College of Metrological Technology and Engineering, China Jiliang University, Hangzhou 310018, China
Published: December 2020

In order to study different flow patterns’ dynamic characteristics of gas-liquid two-phase flow, three time-frequency analysis methods are introduced to process the dynamic differential pressure signal of gas-liquid two-phase flow, such as the wavelet transform, Hilbert-Huang transform and adaptive optimal-kernel method. The results show that the main part of energy is transferred from frequency band 15—35 Hz to 0—8 Hz when the flow pattern changes from bubbly flow to slug flow and plug flow, and two spectrum peaks are observed at slug flow. The experimental results show that the time-frequency resolution of Hilbert-Huang transform and adaptive optimal-kernel is higher than that of wavelet transform. The extractions of ridge information based on adaptive optimal-kernel overcome the influence of fuzzy plane windowing effect, and enhance the readability of time-frequency plane information. The time-frequency analysis clearly shows the dynamic characteristics of different flow patterns, and describes the variation rules with time. It is helpful to further study the mechanism of gas-liquid two-phase flow.
Study on the mechanism of shock ignition in laser fusion
Authors: Yuan Qiang  , Hu Dong-Xia  , Zhang Xin  , Zhao Jun-Pu  , Hu Si-De  , Huang Wen-Hui  , Wei Xiao-Feng  ,   (1)Department of Engineering Physics, Tsinghua University, Beijing 100084, China; (2)Department of Engineering Physics, Tsinghua University, Beijing 100084, China;Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China; (3)Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

As a novel method to assemble and ignite thermonuclear fuel, shock ignition offers several significant advantages, including low ignition threshold, high gain, and good hydrodynamic stability. In this paper, the mechanism of shock ignition is analyzed theoretically and simulated numerically. First, using one-dimensional planer model, the principles of shock collision in shock ignition are analyzed. Then simulations are performed to study the mechanism of the shock ignition scheme. The simulation results are compared with the theoretically analysis, and the robustness of the ignition scheme in terms of shock launching time is studied.
Study on K-shell X-ray production of double-shellneon gas puff Z-pinch
Authors: Wu Gang  , Qiu Ai-Ci  , Wang Liang-Ping  , Lü Min  , Qiu Meng-Tong  , Cong Pei-Tian  ,   (1)Department of Engineering Physics, Tsinghua University,Beijing 100084, China; (2)Department of Engineering Physics, Tsinghua University,Beijing 100084, China;Northwest Institute of Nuclear Technology, Xi'an 710024, China; (3)Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

The main results of investigation on K-shell X-ray production of double-shell neon gas puff Z-pinch, driven by Qiangguang-I facility (1.6 MA, 70 ns), are reported. The exit radii of the outer and inner shells are 1.5—1.4 cm and 0.75—0.6 cm, respectively. Both shells have a throat width of 0.32 mm, while the ratio of the throat radii is 2.8 ∶1, to which the mass ratio would be approximately equal for identical plenum pressures. K-shell yield and peak power up to 7 kJ and 0.28 TW, respectively, for a 20 ns full width at half maximum pulse have been obtained with about 120 ns implosions, the load mass per unit length of which are estimated to be 60—70 μg/cm. Time-resolved X-ray images show that RT instability during the implosion stage has been well suppressed, resulting in a final pinch diameter compressed to less than 2.5 mm. The final implosion velocity exceeds 25 cm/μs. K-shell yields and peak powers are largely reduced with longer implosion time. For shots with lower mass, i.e. 28—63 μg/cm, the electron temperature inferred from time-gated K-shell spectra should be greater than 500 eV, implying an overheated plasma column being formed in the stagnation stage. While for shots with load mass of 72—80 μg/cm, time resolved electron temperatures are in the range of 300—400 eV. The inferred ion densities of the K-shell emitting region are in the range of (3—9)×1019 cm-3, which have been used to calculate the mass fractions that contribute to K-shell radiation. Those shots with near 7 kJ yields also have maximum K-shell emitting load mass (about 46 μg/cm).
Analysis on the ionization of high power pulsed unbalanced magnetron sputtering powered by direct current
Authors: Mu Zong-Xin  , Mu Xiao-Dong  , Wang Chun  , Jia Li  , Dong Chuang  ,   Key Laboratory of M7aterials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, School of Physics and Optoelectronic technology, Dalian University of Technology, Dalian 116024,China
Published: December 2020

High Power impulse Unbalanced Magnetron Sputtering has been coupled to a direct current source (dc-HPPUMS or dc-HiPUMS). A coaxial coil and an attached hollow cathode were applied to control discharge properties and improve pulsed power density. A large extent breakdown was induced for avalanche discharge mechanism. The magnetic trap on sputtering target traps the secondary electrons excited by the avalanche and forms a drift current in magnetic trap. The peak pulse current density is higher than 100 A/cm2 with a pulse frequency less than 40 Hz. The space charge limited condition controls the discharge for plasma far away from equilibrium. The discharge theory was taken to describe the high ionization mechanism in dc-HPPUMS discharge. The parameters deduced from Child law agree with the experimental results.
Small angle X-ray scattering study of the microstructure and interface characteristics of single crystal superalloys during creep process
Authors: Wu Zhong-Hua  , Sun Guang-Ai  , Liu Yi  , Chen Bo  , Yan Guan-Yun  , Wang Jie  , Huang Chao-Qiang  , Wu Er-Dong  , Li Wu-Hui  ,   (1)Insitute of High Energy Physics, CAS, Beijings 100049, China; (2)Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900, China; (3)Institute of Shanghai Apply Physics, CAS, Shanghai 201800, China; (4)National Laboratory for Materials Science, IMR CAS, Sehnyang 110016, China
Published: December 2020

The two-dimensional scattering patterns for micro-structural changes during creep observed by SAXS are different from that obtained by SANS technique. The changes in morphology and size characteristics of different regions of the secondary γ' precipitates have been demonstrated by the variation of SAXS scattering intensity. The results show that the secondary γ' precipitates have two types of feature sizes, which have similar trends of change during the creep process characterized by decreasing in the first and second stage and increasing in the final stage. As comparison shows, the larger γ' precipitates have more noticeable changes. The elements of the secondary γ' precipitates diffuse seriously in the second stage with the character of creep 15 h, the surfaces of γ' phase are blurred, and interfaces of two-phase become clear again in the final stage. Due to the increasing size or the reducing number of the secondary γ' phase, the total ares of interfaces between the secondary γ' precipitates and matrix phase then decreases.
Atomic structure of Zr48Cu45Al7 bulk metallic glass
Authors: Guo Gu-Qing  , Yang Liang  , Zhang Guo-Qing  ,   (1)College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 , China; (2)Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Zhejiang Sci-Tech University, Ministry of Education, Hangzhou 310018, China
Published: December 2020

Atomic structures of Zr48Cu45Al7 ternary and Zr50Cu50 binary metallic glasses were investigated by performing reverse Monte Carlo (RMC) simulation upon synchrotron radiation based X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) data. Bond shortening in Zr-Al and Cu-Al atomic pairs was detected in Zr48Cu45Al7, which is attributed to strong interactions between Al atoms and its neighbors. Subsequently, their atomic structure was further analyzed by Voronoi tessellation method, it was found that all kinds of Voronoi clusters have smaller volume in Zr48Cu45Al7 than their counterparts in Zr50Cu50. Accordingly it is suggested that atoms may be more densely packed in atomic structure of Zr48Cu45Al7 ternary than in corresponding Zr50Cu50 binary MG at cluster scale, which may be the structural origin of high glass-forming ability of CuZr-based bulk metallic glass prepared by Al addition.
The bistable state of a nematic liquid crystal cell with surface order-electricity polarization and flexoelectric polarization at saturation point
Authors: Guan Rong-Hua  ,   School of Sciences, North China Electric Power University, Baoding 071003, China
Published: December 2020

Using both numerical simulations and an analytical theory we study the influence of the surface order-electricity polarization and flexoelectric polarization on the bistable state of a non-xymmetric weak anchoring nematic liquid crystal cell at saturation point.The equilibrium equation and boundary condition of the director have been obtained when surface order-electricity polarization and flexoelectric polarization coexistence. By adopting a new state parameter, the physical effects caused by the two polarizations have been discussed from the energy point of view. The results show that the bistable state can be induced under certain condition and by changing the anchoring energy at saturation point. The condition for the bistable state existence is deduced and it accord well with the numerical results.
Molecular dynamics simulation on carbon nanotube bundles sandwitched between Si surfaces
Authors: Li Rui  , Hu Yuan-Zhong  , Wang Hui  ,   (1)School of Mechanical Engineering, University of Science & Technology Beijing 100083, China; (2)State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
Published: December 2020

Distortion and friction of bundle of SWCNT(10,10) sandwiched between two hydrogen-terminated Si(1,1,0) surfaces are investigated by molecular dynamics simulation. After reaching the equilibrium state, a compressive force is applied to the carbon nanotubes until structural destruction appears on carbon nanotubes or substrates. Friction of the system is then investigated when the upper substrate slides along X direction under no load and high load conditions. Distortion of carbon nanotubes can be observed during loading process and no structural destruction occurs even under the pressure as high as 3.8GPa because of their flexibility. Bundles of SWCNT (10,10) roll randomly and slightly under no pressure condition, but exhibit slide-and-roll combined motion under 3.8GPa pressure. The results also show relatively low lateral forces in both cases. The low friction is attributed to the relatively weak Lennard-Jones interaction between substrate and carbon nanotubes with no hanging bond. Excellent performance is therefore expected when carbon nanotubes without defects are used as lubricant or addictives.
Molecular dynamics investigation of shock front in nanocrystalline aluminum: grain boundary effects
Authors: Ma Wen  , Zhu Wen-Jun  , Chen Kai-Guo  , Jing Fu-Qian  ,   (1)National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, Mianyang 621900, China; (2)National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, Mianyang 621900, China;Department of Physics, National University of Defense Technology, Changsha 410073, China
Published: December 2020

The shock front structure and the plastic deformation of nanocrystalline aluminum under shock loading are investigated by using molecular dynamics simulations. The simulation results show that: after the elastic wave was generated, the grain boundary sliding and deformation dominated the early plastic deformation mechanisms, then the partial dislocations were nucleated at the deformed grain boundaries and spread within the grains, finally the process of stacking faults, deformation twins and full dislocation formation in the grain dominated the latter stage of the plastic deformation. The structural characteristics after the shock front swept over is that the stacking faults and the deformation twins are left in grains, and the majority of the full dislocations are annihilated at the opposite grain boundaries. It is reported for the first time that the shock front structure reflects the time sequence of two different plastic deformation mechanisms in nanocrystalline aluminum.
Optimized growth of p-type AlGaN electron blocking layer in the GaN-based LED
Authors: Wang Bing  , Li Zhi-Cong  , Yao Ran  , Liang Meng  , Yan Fa-Wang  , Wang Guo-Hong  ,   Lighting R & D Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

In the High-power InGaN/GaN-based LED structures, p-AlGaN layer plays a role as electron blocking layer. In this paper, GaN/InGaN-based LED have been grown on sapphire by metal organic chemical vapor deposition (MOCVD), and the p-type doping mechanism and structural optimization of AlGaN layer were studied. The ways to change AlGaN components have been discussed. We found that the growth temperature, growth pressure and flow TMAl (mole ratio) have strong effect on the Al components through different mechanisms. In the AlGaN electron blocking layer, the Al composition is between 10%—30% and the electron could be well limited to the quantum well region, maintaining a high quality crystal material. The p-type doping efficiency of AlGaN layer is low, and there is a magnesium droop problem due to lack of hole injection. A new growth method is suggestece to solve the problem. Grown under optimal conditions, the p-type AlGaN inserted in a LED structure greatly improves the output optical power of LED device.
Anisotropy analysis of surface energy and prediction of surface segregation for fcc metals
Authors: Wang Bo  , Zhang Jian-Min  , Yin Bao-Xiang  , Lu Yan-Dong  , Gan Xiu-Ying  , Xu Ke-Wei  ,   (1)College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China; (2)College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China;Key Laboratory of Ecophysics, Shihezi University, Shihezi 832003, China; (3)Headmaster's office, Shihezi University, Shihezi 832003, China; (4)Key Laboratory of Ecophysics, Shihezi University, Shihezi 832003, China; (5)State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University,
Published: December 2020

In the atomic scale, the surface energy anisotropy analysis of 38 surface planes of 10 fcc metals Cu, Ag, Au, Ni, Pd, Pt, Rh, Al, Ir and Pb have been simulated by using the elemental variables φ* and nWS and modified analytical embedded-atom method (MAEAM). The results show that the close-packed surface (111) of fcc metals which have the lowest surface energies will grow preferentially, the surface energies for all the other surface planes increase linearly with cosθ(hkl), where cosθ(hkl) are the angles between the surface planes (hkl) and (111), which is consistent with the experimental and the linear-muffin-tin-orbital atomic-sphere approximation (LMTO－ASA) results. A graphical approach which correctly explains the relation of the surface segregation energy and surface energy is employed. We conclude that the surface segregation takes place or not is mainly determined by the rule that an impurity (solute) with lower surface energy will segregate to the surface of the host (solution) with higher surface energy.
Electronic and optical properties of zigzag graphene nanoribbon with Stone-Wales defect
Authors: Wang Zhi-Yong  , Hu Hui-Fang  , Gu Lin  , Wang Wei  , Jia Jin-Feng  ,   (1)College of Physics and Microelectronics Science,Hunan University,Changsha 410082,China; (2)College of Physics and Microelectronics Science,Hunan University,Changsha 410082,China;College of Science, Guilin University of Technology, Guilin 541004, China
Published: December 2020

Using the first principle based on the density-functional theory, we have studied the electronic structures and optical properties of zigzag graphene nanoribbon with different Stone-Wales defects. We take two kinds of models, namely that with and without spin polarization, into consideration. The results suggest that graphene nanoribbon with symmetrical Stone-Wales defect has the concavo-convex geometry structure in the defective region without considering spin polarization, both kinds of Stone-Wales defects give rise to the charge redistribution. The spin density of graphene nanoribbon with Stone-Wales defects is obviously affected by considering spin polarization, which leads to the changes of density of states for different kinds of spin. We have further investigated the optical properties of the graphenen nanoribbons; it was found that the peaks of absorption and reflectance have significent changes in the graphene nanoribbon with the presence of Stone-Wales defects, and red shift is observed when compared with the perfect graphene nanoribbon.
Thickness dependence of the interfacial interaction for the Fe/ZnO (0001) system studied by photoemission
Authors: Zhang Wang  , Xu Fa-Qiang  , Wang Guo-Dong  , Zhang Wen-Hua  , Li Zong-Mu  , Wang Li-Wu  , Chen Tie-Xin  ,   National Synchrotron Radiation Laboratory, College of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230029, China
Published: December 2020

Synchrotron radiation photoemission spectroscopy (SRPES) and conventional X-ray photoelectron spectroscopy (XPS) were used to study the Fe/ZnO(0001 ) interface formation at room temperature. The interaction extent of Fe overlayer during the ZnO substrate was carefully monitored during the increase of Fe coverage, the results showed obvious Fe2+ formation at the initial stage of Fe deposition. Based on the photoemission spectra (PES) changes observed during the deposition of Fe on ZnO up to 3 nm, three meaningful and critical thicknesses have been observed which may be related to the surface charge transport, chemical reaction, and magnetic property, respectively. The new finding may be helpful to the design of related devices based on Fe/ZnO interface.
Theoretical studies on vibronic Jahn-Teller systems using group theory
Authors: Feng Sheng-Qi  , Fang Hai  , Qiu Qing-Chun  ,   (1)Department of physics and electronic engineering, Hanshan Normal University, Chaozhou 521041, China; (2)Department of physics and informatics, Medical College, Shantou University, Shantou 515041, China
Published: December 2020

A general form of Hamiltonian for vibronic Jahn-Teller systems is derived on the basis of adiabatic approximation and group theory. The electronic operators and active Jahn-Teller modes appearing in a vibronic system are also discussed. Further calculations of excited states in minima are carried out using unitary transformation method and energy minimization procedure. The results of energy splitting for an electronic triplet Jahn-Teller system are analyzed and compared with particular reference to tetrahedral and its related crystal systems. It is shown that the lift of electronic degeneracy can be quantitatively described by the decomposition of irreducible representations of related group and subgroups.
Model of electron mobility in inversion layer of strained Si/Si1-xGex n type metal-oxide-semiconductor field-effect transistors
Authors: Li Bin  , Liu Hong-Xia  , Yuan Bo  , Li Jin  , Lu Feng-Ming  ,   Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

In order to describe the electron mobility enhancement in inversion layer in strained-Si on Si1-xGex n type metal-oxide-semiconductor field-effect transistors (nMOSFETs), a new physically-based electron mobility model is presented in the paper. This model can not only show the dependence of acoustic phonon-limited mobility and surface roughness-limited mobility on transverse electrical field normal to the semiconductor-insulator interface, but also explains the electron mobility enhancement mechanism due to scattering suppression caused by germanium (Ge) content. The expression of the new model is simple and can simulate the mobility for any Ge content. Numerical analysis results show that this model fits the reported experimental data very well. In addition, this model can be easily included in the device simulator ISE and gives good agreement with simulated results of device simulator with built-in model.
A supercontinuum in the plateau generated by asymmetric molecular gases exposed to a two-color field
Authors: Li Qian-Guang  , Yi Xu-Nong  , Zhang Xiu  , Lü Hao  , Ding Yao-Ming  ,   School of Physics and Electronic-information Engineering, Xiaogan College, Xiaogan 432000,Chian
Published: December 2020

The high order harmonic generation (HHG) from asymmetric molecular gas in two-color field has been investigated and a method for broadband supercontinuum generation in the plateau by asymmetric molecular gas exposed to multicycle laser pulse is proposed. The numerical simulation shows that the harmonics at the end of the plateau become continuous and form a supercontinuum with a bandwidth of about 80 eV, from which a 50 as pulse in the transform limited case can be generated, when asymmetric molecules are exposed to a multicycle two-color field, which is synthesized by a 10 fs/800 nm fundamental pulse and a 15 fs/1200 nm control pulse. After propagation through the molecular gas, most of the modulations in the supercontinuum are eliminated, and the supercontinuum becomes smoother, from which a 90 as isolated pulse can be produced.
Collector junction depletion-layer width model of SiGeheterojunction bipolar transistor with intrinsic SiGe layer
Authors: Hu Hui-Yong  , Shu Yu  , Zhang He-Ming  , Song Jian-Jun  , Xuan Rong-Xi  , Qing Shan-Shan  , Qu Jiang-Tao  ,   Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071,China
Published: December 2020

By solving Poisson equation, models of voltage and electric field distribution are build respectively in collector junction depletion layer of SiGe HBT (heterojunction bipolar transistor) with intrinsic SiGe layer. On this basis, models of the collector junction depletion layer width and delay time are obtained. Applying MATLAB, the impact of physical and electrical parameters on SiGe HBT collector junction depletion layer width and depletion delay time are quantitatively analyzed. When base doping concentration and collector junction reverse bias are large, the depletion delay time is quite long. But, when base doping external diffusion depth and collector region doping are large, the depletion delay time is quite short.
The two-band Ginzburg-Landau theory analysis of the surface critical field of the two-band superconductor Lu2Fe3Si5
Authors: Liu Min-Xia  ,   Department of Electronic Engineering, Dongguan University Technology, Dongguan 523808, China
Published: December 2020

Two-band Ginzburg-Landau (GL) theory is adopted to analyze the surface critical field Hc3 of Lu2Fe3Si5 . When the surface of a superconductor coincides with any of crystallographic planes and is parallel to the external magnetic field H, the ratio Hc3/Hc2 (where Hc2 is the upper critical field of Lu2Fe3Si5) is strongly dependent on temperature. When the surface of a superconductor coincides with the bc plane and is parallel to H, the ratio depends not only on temperature, but also on the angle between the c axis and H. However, the ratio is constant for single-band superconductors.
Preparation and characterization of magnetic nanoparticles of Fe3O4 coated with mesoporous SiO2
Authors: Lei Jie-Mei  , Lü Liu  , Liu Ling  , Xu Xiao-Liang  ,   Department Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

We prepared the magnetic nanoparticles of Fe3O4from thermal decomposition of the Fe oleates precursors synthesized by iron chlorides and sodium oleate,and the SiO2-coated Fe3O4nanoparticles by combining the reverse microemulsion and organic template methods. FTIR was adopted to investigate the surface of Fe oleate under different treatments,and the growth of Fe3O4 nanoparticles with different reactant concentrations of oleic acid and heating rates. The results indicated that the superficial oleic acid of the waxy solid Fe oleates after extraction from ethanol and acetone was partially removed,which impairs the formation of monodispersion Fe3O4 naoparticles. The effect of heating rate on the growth of nanoparticles was weak compared with that of the concentration of Fe oleates. When the concentration of oleic acid is 0.09 mol/L, a characteristic peak of Fe3O4 at 576 cm-1(assignable to the bending vibrations of Fe-O) is enhanced significantly. The XRD (X-ray diffraction) spectra,TEM (transmission electron microscopy) images and SQUID (superconducting quantum interference device) confirmed that the Fe3O4 nanoparticles are spinel cubic crystal and have a good monodispersity and super-paramagnetism. Whats more,the TEM of SiO2-coated Fe3O4 nanoparticles also confirmed that the Fe3O4 nanoparticles were well coated by mesoporous SiO2.
Investigation on annealed Fe43Co43Hf7B6Cu1 amorphous alloy by positron annihilation spectroscopy
Authors: Chao Yue-Sheng  , Guo Hong  , Gao Xiang-Yu  , Luo Li-Ping  , Zhu Han-Xian  ,   College of Science, Northeastern University, Shenyang 110004, China
Published: December 2020

Amorphous Fe43Co43Hf7B6Cu1 alloy prepared by melt-spun technique were annealed at temperature 200 ℃, 300 ℃, 400 ℃ and 500 ℃ for 30 min. The structure and structural defects in annealed specimens were investigated by positron annihilation lifetime spectra, X-ray diffraction (XRD) and Mssbauer spectroscopy (MS), etc. . The results show that in the as-quenched amorphous alloy, more than 85% of the positrons are localized at vacancy-sized free volumes in the amorphous based phase, annihilation lifetime τ1=158.4 ps, and the other 11.9% of positrons are trapped by microvoids, with lifetime τ2=397 ps. After annealing at temperature 200 ℃, 300 ℃ and 400 ℃ for 30 min, the atomic short range diffusion will give rise to the migration and annihilation of vacancy-like defects. The major component τ1 will be reduced continuously. The value of τ1 will decrease to 149 ps at 400 ℃, their relative intensities I1 decreases and reaches 80.8%. Meanwhile the annihilation lifetime of positrons in the microvoids τ2 will change from 353 ps to 364 ps, their relative intensities I2 are increased to 18.0%. When annealed at temperature 500 ℃ for 30 min, new trapping centers of positrons are produced owing to the crystallization of amorphous phase, I2 increases drastically to 26.7%.
Dielectric relaxation of (Pb(1-3x/2)Lax)(Zr0.5Sn0.3Ti0.2)O3 antiferroelectric ceramics induced by lanthanum doping
Authors: Liu Peng  , Zhang Dan  ,   College of Physics and Information Technology, Shanxi Normal University, Xi'an 710062, China
Published: December 2020

The (Pb(1-3x/2)Lax)(Zr0.5Sn0.3Ti0.2)O3(PLZST, 0.00≤x≤0.18)antiferroelectric ceramics were prepared by traditional ceramic process. The effect of La modification on phase structures, phase transition, and electrical properties of PLZST ceramics were investigated by X-ray diffraction, P-E hysteresis loop and dielectric spectroscopy. With the increase of La content x,the samples at room temperature are rhombohedral ferroelectric phase (x≤0.0.04),tetragonal antiferroelectric phase(AFEt, 0.06x≤0.0.08, and cubic phase (PE' cx≥0.1), respectively. The dielectric spectroscopy shows that with the increase of La content x, AFE-PE phase transformation temperature decreases, and for samples with La content x exceeding 0.12, strong dielectric frequency dispersion is observed around dielectric ε' and tanδ peaks. The peak temperatures Tm corresponding to the maxim dielectric constant shifts to higher temperatures with the increase of frequency, indicating that PLZST antiferroelectric transform to typical relaxors. The curves of dielectrics as functions of temperatures in the PLZST systems are fitted by a modified Curie–Weiss law proposed by Santos.
Comprehensive Survey for the Frontier Disciplines
Authors: Zheng Xiao-Hu  , Huang An-Ping  , Yang Zhi-Chao  , Xiao Zhi-Song  , Wang Mei  , Cheng Guo-An  ,   (1)Department of Physics, Beihang University, Beijing 100191, China; (2)Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, Beijing 100875, China
Published: December 2020

As the scaling of MOSFETs continues towards 45 nm technology node, it is inevitable that Hf-based high-k materials replace the traditional SiO2 as the gate dielectrics of MOSFETs. But there are still many issues to be settled. Rare earth doping can increase the k value of dielectrics, decrease the defect densities of dielectrics and modulate the threshold voltage shift of MOSFETs. This paper reviews recent progress, the challenge of Hf-based high-k materials, the influence of rare earth doping on Hf-based high-k materials and its future trend.
Spatiotemporal dynamics of photogenerated carriers in GaAs/AlGaAs multiple quantum wells
Authors: Hu Chang-Cheng  , Ye Hui-Qi  , Wang Gang  , Liu Bao-Li  ,   (1)Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China; (2)College of Physics,Jilin University,Changchun 130021,China;Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China
Published: December 2020

The ambipolar diffusion coefficient of (110) GaAs/AlGaAs multiple quantum wells was measured by the transient spin grating technique.The ambipolar diffusion coefficient and carrier life time,which are Da=13.0 cm2/s and τR=1.9 ns,were obtained directly by this technique under carrier concentration nex=3.4×1010/cm2 at room temperature.The measured Da keeps almost a constant value when the photoexcited carrier concentration is increased up to 1.2×1011/cm2.
Correlation measurement of quantum cascade photons in single InAs quantum dot
Authors: Li Yuan  , Dou Xiu-Ming  , Chang Xiu-Ying  , Ni Hai-Qiao  , Niu Zhi-Chuan  , Sun Bao-Quan  ,   State Key Laboratory for Superlattices and Microstructure, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083, China
Published: December 2020

Single InAs quantum dot (QD) sample was grown by molecular-beam epitaxy (MBE). The Photoluminescences (PL) of the exciton and biexciton in a single QD were measured at 5 K. The PL intensity as a function of the laser excitation power, the fine structure splittings of the exciton and biexciton, and the corresponding linearly polarized emissions were analyzed. By means of Hanbury-Brown and Twiss (HBT) setup, the photon correlation between the PL of exciton and biexciton were measured, which is gave an evidence of the quantum cascade emissions between biexciton and exciton PL.
Study on photonic crystal grating slow-wave circuits for millimeter-wave ribbon-beam traveling wave tubes
Authors: Xu Jie  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

A kind of photonic crystal grating slow-wave circuit, namely the cross-section distributing two-dimensional photonic crystal slow-wave circuit (CD2DPhSWC), was proposed. And the way of designing CD2DPhSWC was put forward. To simply the design, the process was realized in two steps, firstly the calculation of the photonic band gap (PBG) for the TE polarization, and then the dispersion of the equivalent rectangular waveguide grating. The numerical results show that the bandwidth of the traveling wave tubes (TWTs) based on CS2DPhSWC is wider, and the operating voltage is lower, than that of the rectangular waveguide grating. Correspondingly, the cost of the TWTs is reduced.
Study on power characteristics of deep sub-micron SOI RF LDMOS
Authors: Bi Jin-Shun  , Hai Chao-He  , Han Zheng-Sheng  ,   Institute of Microelectronics of Chinese Science Academy, Beijing 100029, China
Published: December 2020

A large signal equivalent circuit model of SOI LDMOS is proposed. Power gain and power-added efficiency of n-type LDMOS are modeled. Deep sub-micron SOI LDMOS was fabricated and measured. We investigated the dependence of SOI LDMOS power characteristics on channel length, single gate finger width, supply voltage and working frequency. Power gain and power-added efficiency are increased by 44％ and 9％, respectively, with channel length reduction from 0.5 μm to 0.35 μm. When single gate finger width is increased from 20 μm to 40 μm, power gain and power-added efficiency of 600 μm /0.5 μm device are decreased by 23％ and 9.3％, respectively. Power-gain and power-added efficiency are increased by 13％ and 5.5％, respectively, with supply voltage increased from 3 V to 5 V. When the working frequency is increased from 2.5 GHz to 3.0 GHz, power gain and power added efficiency of LDMOS are decreased by 15％ and 4.5％, respectively.
Theoretical study of GaN interval layers and quantum well barrier layers of different doping types in dual-wavelength LED
Authors: Zhang Yun-Yan  , Fan Guan-Han  ,   Institute of Opto-Electronic Materials and Technology, South China Normal University, Guangzhou 510631, China
Published: December 2020

A 2D simulation of electrical and optical characteristics of dual-wavelength LED with GaN interval layers and quantum well barrier layers of different doping types was conducted with APSYS software. It showed that with the use of p-type doped GaN interval layer and quantum well barrier layers, we can greatly improve the hole concentration in QWs and reduce the electron overflow of the chip. We can also increase the luminous intensity and dramatically improve the dropping of internal quantum efficiency of the LED when the current increases.
Relations of classical-quantum correspondencein Dicke model
Authors: Wang Yu-Bo  , Song Li-Jun  , Yan Dong  , Gai Yong-Jie  ,   (1)School of Science, Changchun University of Science and Technology, Changchun 130022, China; (2)School of Science, Changchun University, Changchun 130022, China
Published: December 2020

Dicke model displays quantum chaotic dynamic properties in the non-rotating wave approximation. On the basis of properties of the classical phase space of Dicke model, we employ the one-to-many notion, namely, evolution from one point on the classical phase space to two initial coherent states. Then we obtain a good quantum phase space, which corresponds to the classical one, by using the method of averaging the statistical entangled values of two initial states in the evolution. The numerical computation shows that classical chaos can promote the origination of bipartite entanglement, and simultaneously, the average entanglement can be regarded as the signature of quantum chaos. A good classica-quantum correspondence can be obtained by using the average entanglement.
The single solitary wave with double peaks of the coupled KdV equation and its stability
Authors: Shi Yu-Ren  , Zhang Juan  , Yang Hong-Juan  , Duan Wen-Shan  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070,China
Published: December 2020

We obtained six classes of exact solutions for the coupled KdV equation by the extended hyperbola function expansion Method.One of the solutions is a solitary wave solution, which has two peaks.This solution is reduced to the kink or bell-like soliton solution of the coupled KdV equation under different limitations. We also investigated the stability of the single solitary wave solution with double peaks numerically.The results indicate that the solution is stable when the amplitude of the disturbance, which has long wave length, and is very small.
Abrupt change of synchronization of ring coupled Duffing oscillator
Authors: Wu Yong-Feng  , Zhang Shi-Ping  , Sun Jin-Wei  , Peter Rolfe  ,   School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The ring coupled Duffing oscillator was investigated, a phenomenon was observed when analyzing the synchronization evolution between coupled oscillators, which shows that if all oscillators are driven by the same periodic driving force,the motion trajectory between weakly coupled oscillators will generate two abrupt changes from synchronization to non-synchronization and then to synchronization in the phase transition of period-doubling bifurcation, chaotic state and large-scale periodic state. Any synchronous abrupt change can be used to rapidly identify system phase transition, and thus a weak periodic signal detection method was proposed based on the phase transition of period-doubling bifurcation and chaotic state.
Preparation and photoluminescence study of patterned substrate quantum wires
Authors: Wang Xiu-Ping  , Yang Xiao-Hong  , Han Qin  , Ju Yan-Ling  , Du Yun  , Zhu Bin  , Wang Jie  , Ni Hai-Qiao  , He Ji-Fang  , Wang Guo-Wei  , Niu Zhi-Chuan  ,   (1)State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 China; (2)State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

GaAs/AlGaAs quantum wires grown by molecular beam epitaxy on a V-groove patterned substrate was described. The cross section of scan electron microscopy (SEM) image shows that crescent-type quantum wire were formed at the V groove bottom, which is a triangle of about 60nm in width and 14nm in height. Two peaks at 793.7nm and 799.5nm of photoluminescence spectrum at 87K verified the existence of quantum wires. Theoretical calculation gives 8meV blue shift, which is proved to be casued by lateral confinement compared with quantum well of the same width.
Renormalization of two neutral mixing-loop chain propagators in standard model and its e+e-→μ+μ- cross section
Authors: Chen Xue-Wen  , Fang Zhen-Yun  , Zhang Jia-Wei  , Zhong Tao  , Tu Wei-Xing  ,   Institute of Theoretical Physics, Chongqing University, Chongqing 400030, China
Published: December 2020

Adopting the electroweak standard model, We analyzd the framework forms of photon γ and neutral gauge boson Z0 mixing-loop chain propagators and the relevant renormalization. Based on this, We obtained the analytic results of renormalized γ and Z0 mixing-loop chain propagators composed of different physical loops that participate in electroweak interactions. In addition, We applied our result to an important type of lepton interaction in high energy physics: e+e-→μ+μ-, then obtained the analytic result of cross section via renormalized γ and Z0 mixing-loop chain propagators. Furthermore, we compared the result with a series of experimental results, and found that the result of this paper is in good agreement with the experimental results. This study would offer certain academic reference to the theoretical study and application of common complex propagators.
Composite electromagnetic scattering from two adjacent finite length cylinders
Authors: Zhang Yan-Min  , Guo Li-Xin  , Wang Yun-Hua  ,   (1)College of Information Science & Engineering, Ocean University of China, Qingdao 266100, China; (2)School of Science, Xidian University, Xi’an 710071, China
Published: December 2020

Based on the equivalence principle and the reciprocity theorem, the composite electromagnetic scattering from two adjacent finite length cylinders is considered and a solution that accounts for multiple scattering up to second-order is deduced. Numerical results obtained by our formulas are compared with the results obtained by the method of moments. Meanwhile, the dependence of the composite scattered field on the parameters, such as the distance between the cylinders, the length of the cylinders, polarization state and so on, is discussed.