bluuebunny/crossref_metadata_2025 huggingface dataset:
A spectroscopic ellipsometry study of the abnormal scaling behavior of high-rate-deposited microcrystalline silicon films by VHF-PECVD technique
Authors: Gu Jin-Hua  , Ding Yan-Li  , Yang Shi-E  , Gao Xiao-Yong  , Chen Yong-Sheng  , Lu Jing-Xiao  ,   郑州大学物理工程学院材料物理教育部重点实验室，郑州  450052
Published: December 2020

The scaling behaviour of surface roughness evolution of high rate deposited μc-Si:H by very high frequency plasma-enhanced chemical vapor deposition （VHF-PECVD） is investigated using spectroscopic ellipsometry （SE）. Films deposited at Pg=300 Pa with deposition rate of 5 ?/s, show abnormal scaling behavior with the exponent β of about 0.81, which is much larger than 0.5 of zero diffusion limit in the scaling theory. This implies that there are some roughening increasing mechanisms, and this roughening increasing mechanism is correlated with the shadowing effect.
The electronic structure and transport properties ofgraphene nanoribbons with divacancies defects
Authors: Ouyang Fang-Ping  , Xu Hui  , Lin Feng  ,   (1)清华大学物理系，北京  100084; (2)中南大学物理科学与技术学院，长沙  410083
Published: December 2020

Based on first-principles calculation of the electronic structure and transport properties, we study the electronic structure and transport properties of graphene nanoribbons （GNRs） with 585 divacancies defects. It is shown that because of the existence of 585 divacancies defects, there are defected band belts in the energy gap located at the defects for the zigzag graphene nanoribbon （ZGNRs） and their energy gaps will increase. The spatial orientations of the divacancies defects have effect on the electronic structure of the system. In addition, the influences of 585 divacancies defects on the transport properties of the ZGNRs with small energy gaps are great, while that on the transport properties of the ZGNRs with large energy gaps are small. And the spatial orientations of the defects have no obvious influence on the transport properties.
First-principles study of thermal decomposition of liquid nitromethane and its compressive effect
Authors: Xu Jing-Cheng  , Zhao Ji-Jun  ,   大连理工大学物理与光电工程学院&高科技研究院，大连  116024；北京理工大学爆炸科学与技术国家重点实验室，北京  100081
Published: December 2020

Based on the framework of density functional theory，we employed the first-principles molecular dynamics to simulate the thermal decomposition of liquid nitromethane and obtained the time-evolution for the population of decomposition productions. We discussed the three possible reactions at the initial stage of thermal decomposition: intramolecule proton transfer reacton, intermolecule proton transfer reaction, and C—N bond rupture. We also studied the dynamic behavior of thermal decomposition of liquid nitromethane under different density （pressure） conditions. We found that the thermal decomposition of liquid nitromethane sensitively depends on the liquid density of pressure. A possible explanation was given.
Propagation properties of a surface plasmonic waveguide with double elliptical metallic nanorods
Authors: Guo Ya-Nan  , Xue Wen-Rui  , Zhang Wen-Mei  ,   山西大学物理电子工程学院，太原  030006
Published: December 2020

We introduce a kind of surface plasmonic waveguide with double elliptical metallic nanorods. The dependence of the distribution of longitudinal energy flux density, the effective index and the propagation length of the fundamental mode with longer propagation length supported by this waveguide, on the geometrical parameters and the working wavelengths are analysed using the finite-difference frequency-domain （FDFD） method. Results show that the longitudinal energy flux density is distributed mainly in the middle area, which are formed by two elliptical metallic nanorods, and the longitudinal energy flux density is stronger closer to the arc sides of the metallic nanorods. The effective index and propagation length of the fundamental mode can be adjusted by the centric distance of two ellipses as well as the size of the two semiaxis. At a certain working wavelength, relative to the case of a=b, in the case of ab, the size of the contact area of field and metallic surface is large, the interaction of field and silver is weak, the effective index becomes small, so the propagation length becomes large. With certain geometric parameters, relative to the case of λ=7050 nm, in the case of larger λ, the area of field distribution is large, the size of the contact area of field and metallic surface is also large, the interaction of field and silver is weak, the effective index becomes small, so the propagation length becomes large. This kind of metallic surface plasmonic waveguide can be applied to the field of photonic device integration and sensors.
Transation of charged vortex structures in underdoped high-temperature superconductors
Authors: Zhao Hong-Wei  , Meng Hao  , Zhang Ling-Feng  , Zha Guo-Qiao  , Zhou Shi-Ping  ,   上海大学物理系，上海  200444
Published: December 2020

Vortex structures in high-temperature superconductors are studied by solving Bogoliubov-de Gennes equations based on a mean-field t-t′-U-V-Vc model. The results show that transition from checkerboard pattern to stripe structure for spin density wave, charge density wave, and d-wave orderings may occur by enhancing the strength of the on-site repulsion U. When a reasonable long-range Coulomb interaction is introduced into the model Hamiltonian, two-dimensional modulations or the checkerboard patterns may appear for the underdoped samples, which is consistent with the scanning-tunneling-microscopy experiments.
Study of the dipole rotation path of BaTiO3 single crystal based on dielectric properties in structure phase transition
Authors: Li Xiao-Bing  , Zhao Xiang-Yong  , Wang Yao-Jin  , Wang Fei-Fei  , Chen Chao  , Luo Hao-Su  ,   (1)中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室，上海  200050; (2)中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室，上海  200050；中国科学院研究生院，北京  100049
Published: December 2020

The temperature-dependence of dielectric-constant of BaTiO3 single crystals in 〈001〉 direction is measured under different voltages and frequencies. The crystal experiences rhombohedral-orthorhombic-tetragonal phase transition with the increase of temperature. Base on the assumption of dipoles rotation and the experimental results of dielectric constant, a model is proposed, which holds that the dipoles rotation path can be inferred by the dielectric properties of the adjacent structure phase of BaTiO3. The dipoles rotation paths of rhombohedral, orthorhombic and tetragonal phases are given. The influences of bias dc electric field on the dipoles rotation path are discussed.
Influence of Si crystallization evolution on 1.54 μm luminescence in Er-doped Si/Al2O3 multilayer
Authors: Wang Jun-Zhuan  , Shi Zhuo-Qiong  , Lou Hao-Nan  , Zhang Xin-Luan  , Zuo Ze-Wen  , Pu Lin  , Ma En  , Zhang Rong  , Zheng You-Liao  , Lu Fang  , Shi Yi  ,   (1)复旦大学物理系，上海  200433; (2)南京大学物理系，江苏省光电功能材料重点实验室，南京  210093; (3)中国科学院福建物质结构研究所，福州  350002
Published: December 2020

The crystallization evolution of the nanostructured Si （ns-Si） in the Er-doped Si/Al2O3 multilayer fabricated by using pulsed laser deposition technique and its effects on the Er3+ luminescence at 1.54 μm are investigated. Raman scattering and transmission electron microscopy measurements are used to characterize the microstructure evolution of the ns-Si during annealing treatment processes. The maximum photoluminescence intensity is obtained in the sample with ultrathin ns-Si sublayers annealed at 600—700 ℃, where the density, the size of Si nanocrystals, the interaction distance, and the optimized local environment for effectively activating the Er3+ are well controlled. From the analysis of the decay process of time-dependent luminescence, two decay channels are considered, the fast and slow decay channels. The bulk-like Si is responsible for the fast process and the Si nanocrystals are responsible for the slow decay process.
Efficient WCA algorithm for 65—90 nm processes
Authors: Wang Jun-Ping  , Hao Yue  ,   (1)西安电子科技大学通信工程学院，西安  710071; (2)西安电子科技大学微电子学院，西安  710071
Published: December 2020

For modern processes at 90 nm and 65 nm technology nodes, the random yield loss can contribute much to the total yield loss. Hence, it is essential to calculate the critical area to analyse the areas of design, and make changes to improve the random yield. This study provides a novel weighted critical area （WCA） of arbitrary defect outline, which takes into account the clustering effect in the metal and empty regions of the chip as well as the size distribution of random defects. Then, two fast and accurate algorithms related-WCA extraction and its sort of WCAs are implemented, which can sever as a cost function of layout optimization for the random yield improvement.
Structure and thermoelectric properties of p-type Ge-based Ba8Ga16CdxGe30-x type-Ⅰ clathrates doping by Cd
Authors: Deng Shu-Kang  , Tang Xin-Feng  , Yang Pei-Zhi  , Yan Yong-Gao  ,   (1)武汉理工大学材料复合新技术国家重点实验室，武汉  430070; (2)云南师范大学教育部可再生能源材料先进技术与制备重点实验室，太阳能研究所，昆明  650092; (3)云南师范大学教育部可再生能源材料先进技术与制备重点实验室，太阳能研究所，昆明  650092；武汉理工大学材料复合新技术国家重点实验室，武汉  430070
Published: December 2020

Cd-doping Ba8Ga16CdxGe30-x（x=0.95, 1.00, 1.05, 1.10） type-I clathrates with different Cd contents were synthesized by combining solid-state reaction with spark plasma sintering （SPS） method. The effects of Cd doping on the structure and thermoelectric properties were investigated. Rietveld refinement reveals that Ba8Ga16CdxGe30-x compounds prepared by this method are type-I clathrates with space group pm3n; Cd atoms mainly occupy the 6c and 16i sites in the framework, and the atom displacement parameter （ADP） of Cd is relatively higher than that of other atoms. All specimens show the characteristics of p-type conduction. The carrier scattering mechanism is mainly ionized impurity mechanism in the low temperature range, and gradually changes to acoustical mechanism with the increase of temperature. With the increase of Cd content, the electrical conductivity increases while the Seebeck coefficient decreases gradually. The lattice thermal conductivity of the Ba8Ga16CdxGe30-x compounds is relatively low due to the larger ADP of Cd, and it decreases by about 38% compared with that of Ba8Ga16Ge30 The maximum ZT value of 0.173 is obtained at 600 K for Ba8Ga16Cd100Ge2900 compound.
Study of cisplatin-induced DNA compaction using single molecule magnetic tweezers
Authors: Zhang Xing-Hua  , Xiao Bin  , Hou Xi-Miao  , Xu Chun-Hua  , Wang Peng-Ye  , Li Ming  ,   中国科学院物理研究所北京凝聚态物理国家实验室，北京  100190
Published: December 2020

We report a single molecule study on cisplatin-induced DNA compaction. It is found that, at a small external tension （<1 pN）, the DNA compaction time course is irregular with many continuous shortening processes and abrupt large size jumps. The time course becomes smooth and hyperbolic when the external tension increases to a moderate value, which is not large enough to inhibit the compaction. The time course depends on the external tension rather than the concentration of cisplatin; the latter only influences the compaction rate. The results are consistent with a looping-and-cross-linking compaction model. Namely, in aqueous solutions, cisplatin forms both monoadducts and diadducts with DNA. When cisplatin induces distant cross-links between DNA bases, micro-loops are formed, which make DNA compact. Further cross-linking between the micro-loops leads to complete compaction of DNA. In addition, the compacted DNA structure is quite stable.
The formation mechanism and evolution of the double piral arms in vortex
Authors: Tao Jian-Jun  , Li Chao-Kui  ,   湖南科技大学地球和空间信息研究所，湘潭  411201
Published: December 2020

We study the formation mechanism of the double piral arms in vortex with the eddy equation in column coordinates. Results show that growth of undulations is very quick when m=2（double spiral arms） in basic flow field,whereas the increment rate is limited over time. Undulations can evolve into double piral arms and expand toward outside. Mechanism of undulation development is the strong advection process in which vorticity is transfered from basic to undulation field.
Analysis of climate record breaking temperature events in China during the past 50 years
Authors: Zhang Da-Quan  , Yang Jie  , Wang Qi-Guang  , Feng Guo-Lin  ,   (1)国家气候中心中国气象局气候研究开放实验室，北京  100081; (2)兰州大学大气科学学院，兰州  730000；中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029; (3)兰州大学大气科学学院，兰州  730000；中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029；国家气候中心中国气象局气候研究开放实验室，北京  100081
Published: December 2020

The occurrence of record breaking temperature events （RBTE） became more and more frequent under the background of global warming. What is the probability that the current temperature record will be broken in the next five years? In this study, answers are provided by given a variety of simple statistical models for temperature, and the relationship between the probability of RBTE of China and the global warming is explored by comparative analysis of the probability of RBTE in the last 50 years. The results show that the frequency of RBTE is influenced by global warming and the autocorrelation. This study quantitatively estimates the relationship between the probability of RBTE and global warming, which can deepen our knowledge about the in-creasing frequency and amplitude of RBTE under the background of global warming.
Mechanism of heavy rainfall maintenance and increment in convergence excited by coupling forces between dynamic and thermodynamic fields
Authors: Chen Zhong-Ming  , Yang Kang-Quan  , Wu Hong-Yu  ,   (1)成都信息工程学院，成都  610225; (2)贵州山地环境气候研究所，贵阳  550002; (3)贵州省气象局，贵阳  550002；中国气象局成都高原气象研究所，成都  610072
Published: December 2020

According to the occurrence and maintenance of torrential rain relating closely to moisture convergence increment in low layer of troposphere, factors affecting the evolution of divergence is analysed to reveal the dynamic mechanism of heavy rainfall maintenance. Starting from the primitive equations, we obtain a new type of divergence equation including the coupling forces between Q vector and vertical shear of wind. Analysis on this equation brings to light the main factors to influence the evolution of divergence. They are separately the barotropic non-equilibrium force and the baroclinic coupling forces between Q vector and vertical shear of wind. Especially, the evolution of divergence is only controlled by the above-mentioned two factors on the layer with the maximum convergence . In addition, the definite integral for new type of divergence equation is formed from the earth’s surface to the un-divergent level. Results show that the self-exciting process of divergence fields lead to the decrease of convergence in the low layer of troposphere. Oppositely, the barotropic non-equilibrium force and the baroclinic coupling forces between Q vector and vertical shear of wind are the main factors that promote the increment of convergence in the air column, which we should pay more attention to in studying the mechanism of heavy rainfall maintenance.
(G′/G)-expansion method and new exact solutions for (2+1)-dimensional asymmetrical Nizhnik-Novikov-Veselov system
Authors: Li Bang-Qing  , Ma Yu-Lan  ,   (1)北京工商大学,北京  100048; (2)北京工商大学,北京  100048；中国矿业大学（北京）,北京  100081
Published: December 2020

By introducing and extending the （G′/G）-expansion method, the new exact general solutions are constructed for （2+1）-dimensional asymmetrical Nizhnik-Novikov-Veselov system. These solutions include general hyperbolic function solutions, general trigonometric function solutions and general rational function solutions. The solitary ware solutions are obtained when the constants involved in the general hyperbolic solutions are set at special values.
Quantum-resonance ratchet in a kicked Bose-Einstein condensate
Authors: Qu Chun-Lei  , Zhao Qing  ,   北京理工大学理学院物理系，北京  100081
Published: December 2020

The dynamical evolution of a periodically kicked Bose-Einstein condensate was investigated by simulation. Emphasis was placed on the influence of the nonlinear interaction between atoms on the quantum-resonance ratchet effect. It was found that weak nonlinear interaction reduces the ratchet effect while the strong nonlinear interaction causes the ratchet current to disappear or even reversed. The ratchet effect under high-order quantum resonance conditions was further studied. The ratchet effect is not obvious in this case and can be easily destroyed by the noise of the kicking potential period.
Analysis of the fast-slow Lorenz-Stenflo system
Authors: Han Xiu-Jing  , Jiang Bo  , Bi Qin-Sheng  ,   (1)江苏大学理学院，镇江  212013; (2)江苏大学理学院，镇江  212013；江苏技术师范学院数理学院，常州  213001
Published: December 2020

By rescaling the system，we obtain the Lorenz-Stenflo system with slow variation of the flow rotation. Based on Routh-Hurwitz criteria，the stabilities of the equilibria are analyzed and the bifurcation sets are sought to divide the parameter plane into different regions，corresponding to different types of the solutions. Different types of the solutions may bifurcate from the equilibria with the chang of the parameters. Furthermore，the symmetric bursting and the symmetric chaos are presented，and the mechanism of the symmetric bursting is explored by the method of slow-fast analysis.
Spreading dynamics on scale-free networks
Authors: Wang Yan  , Zheng Zhi-Gang  ,   北京师范大学物理系，北京  100875
Published: December 2020

The spreading dynamics on scale-free networks is considered. Based on the SIS （susceptible-infected-susceptible） model，we investigate the critical point at which the epidemic breaks out in a very general setting. Some previous results，each of which is analyzed，can be seen as the special cases of our result，and the modeling reliability in each case is also discussed.
Effect of leaf nodes on synchronizability of complex networks
Authors: Ma Xiao-Juan  , Wang Yan  , Zheng Zhi-Gang  ,   北京师范大学物理系，北京  100875
Published: December 2020

The synchronizability of the complex network has aroused much interest during the past years. But most studies pay little attention to the leaf nodes （whose degree equals 1），which do exist in the real networks. In this paper，we study the influence of leaf nodes on the synchronizability of the whole network systematically and find that as the proportion of the leaf nodes increases，the network becomes less synchronizable. Both numerical and theoretical results are given in the paper.
Bifurcation analysis of a compound oscillator with parametric and external excitation
Authors: Ji Ying  , Bi Qin-Sheng  ,   江苏大学理学院，镇江  212013
Published: December 2020

The dynamics of a compound oscillator with parametric and external excitation has been investigated. Local bifurcation analysis of the first order approximation shows that simple bifurcation as well as Hopf bifurcation may take place，as have been observed in the original system. The influence of several parameters on the dynamics has been explored，which reveals that different nonlinear behaviors can be obtained with the variation of the parameters. Furthermore，by employing global bifurcation theory，the necessary conditions for homoclinic and heteroclinic bifurcation has been presented，which agrees well with the numerical results.
Study on control power in Boost converter with parameter ramp resonance
Authors: Cheng Wei-Bin  , Guo Ying-Na  , Kang Si-Min  , Wang Yue-Long  , Huo Ai-Qing  , Tang Nan  ,   西安石油大学陕西省钻机控制技术重点实验室，西安  710065
Published: December 2020

The bifurcation and chaos should exist in Boost converter while the circuit stability conditions are not satisfied，and the stable state could not be gotten by its self control power. As a kind of OGY method without feedback，the parameter resonance can control the bifurcation and chaos in Boost converter. Based on current controlled Boost circuit，the regulating process and its control power are discussed with the reference value of inductor current as the resonant parameter，and the characteristic parameters in the stable state are also deduced in detail. The control power of parameter resonance with different resonant voltages and the stable characteristic parameters are analyzed for the bifurcation and chaos circuits，so as to realize the precise design of circuit parameters and ensure the Boost converter to work steadily and reliably.
First principle study of Mg，Si and Mn co-doped GaN
Authors: Xing Hai-Ying  , Fan Guang-Han  , Zhang Yong  , Zhao De-Gang  ,   (1)华南师范大学光电子材料与技术研究所，广州  510631; (2)中国科学院半导体研究所集成光电子学国家重点联合实验室，北京  100083
Published: December 2020

Calculations of electronic structures and optical properties of Mg (or Si) and Mn co-doped GaN were carried out by means of first-principle plane-wave pesudopotential (PWP) based on density functional theory. The spin polarized impurity bands of deep energy levels were found for both systems. They are half metallic and suitable for spin injectors. Compared with GaN：Mn，GaN：Mn-Mg exhibits a significant increase in TC，while the 1.3eV absorption peak in GaN：Mn disappears due to addition of Mg. In addition，a strong absorption peak due to 4T1(F)→4T2(F) transition of Mn4+ were observed near 1.1eV. Nevertheless，GaN：Mn-Si failed to show increase of TC，and the absorption peak was not observed at the low energy side.
Multiferroicity in single phase Bi0.9Ba0.1Fe0.85Mn0.15O3 ceramic
Authors: Luo Bing-Cheng  , Zhou Chao-Chao  , Chen Chang-Le  , Jin Ke-Xin  ,   西北工业大学凝聚态结构与性质陕西省重点实验室,西安  710072
Published: December 2020

The Bi0.9Ba0.1Fe0.85Mn0.15O3 ceramic sample was prepared by sol-gel process. XRD analysis showed that it was the single-phase rhombohedral perovskite structure. A weak ferromagnetic and ferroelectric were obtain from the hysteresis loops. The dielectric constant which increased with an increase in the magnetic field showed that the Ba-Mn codoped BFO has greater magnetocapacitance effects.
An FDTD combined with semi-analytical recursive convolution algorithm for the analysis of general dispersive media
Authors: Zhang Yu-Qiang  , Ge De-Biao  ,   (1)西安电子科技大学理学院物理系,西安   710071; (2)西安电子科技大学理学院物理系,西安   710071；延安大学物理与电子信息学院,延安   716000
Published: December 2020

A novel finite-difference time-domain （FDTD） method combined with the semi-analytical recursive convolution （SARC） algorithm in DSP techniques for the analysis of electromagnetic characteristics in dispersive media is presented. In this method, the flexibility of FDTD in dealing with complicated objects is retained, while the advantages of absolute stability, high accuracy, low storage and high effectiveness of SARC in treating the linear system problem is introduced. The proposed SARC FDTD approach can therefore be applied to the analysis of general dispersive media provided the poles and corresponding coefficients in the dispersive medium model of interest are given. Three typical kinds of dispersive model, i.e. Debye, Drude and Lorentz medium are tested to demonstrate the feasibility of the present scheme.
A novel approach of dual GPOF /DCIM for fast computation of the sommerfeld integrals and electromagnetic scattering from an object partially embedded in dielectric half-space
Authors: Ye Hong-Xia  , Jin Ya-Qiu  ,   复旦大学波散射与遥感信息教育部重点实验室，上海  200433
Published: December 2020

The mixed-potential integral equation （MPIE） has been usually employed in numerical approach of electromagnetic scattering of the object, such as the method of moment （MoM）, due to its low-level singularity of vector and scalar potential Green functions. When an object is embedded partially in dielectric half-space medium, the Green’s function contains the Sommerfeld-type integrals, which embody the effect of the dielectric interface on scattering fields. Using the discrete complex image method （DCIM） and the Sommerfeld identity, the Sommerfeld integrals can be evaluated as the summation of finite complex image functions without directly numerical integration which always consumes large CPU time. As the points of the field and source are co-located in the same side of the interface, the spectrum function g（kzp） is not related with the field or source positions, and the complex image parameters fitted with the general pencil of functions （GPOF） method are approximate for all positions. However, if the points of the field and source are located, separately, in different sides of the interface, the spectral function is now related to z and z′. Generally, the GPOF is repetitiously used to find the complex image parameters for every z and z′, which consumes large CPU time and memory. This paper presents a novel method of Dual GPOF combining with DCIM for fast computation of the Sommerfeld integral. Firstly, the factors related with the variable z are separated, and the GPOF is used to find the complex image parameters for finite discrete source points z′l. Secondly, GPOF is used again to fit the relationship of each complex image parameter with variable z′. Then, the complex image parameter of any z′ can be evaluated as the direct function summation, and there is no need to perform GPOF for all z′ points. Comparing numerical values of Dual GPOF, point-by-point GPOF, and direct numerical integration, the Dual GPOF method is proved effective and efficient. Finally, Dual GPOF is applied to computation of electromagnetic scattering from a P.E.C. sphere object partially embedded in dielectric half-space, and the scattering patterns are presented and analyzed.
A real space study on the conducting polymer with a ground-state nondegenerate structure
Authors: Shi Jing  , Gao Kun  , Lei Jie  , Xie Shi-Jie  ,   (1)山东大学物理学院，济南  250100; (2)山东大学物理学院，济南  250100；济南铁道职业技术学院，济南  250013
Published: December 2020

The ground and the excited states for the nondegenerate polymer such as cis-PA have been studied using the Kronig-Penney model with unequal potential barriers in the real space. The electronic states，the electron density distributions，and the lattice distortions in the system with different states are obtained. By comparing with those obtained in the Su-Schrieffer-Heeger (SSH) model，we find that our results of electron state densities and electron density distribution are more precise.
Research on reflectors in terahertz wireless communication systems
Authors: Zhang Rong  , Li Hua  , Cao Jun-Cheng  , Feng Song-Lin  ,   信息功能材料国家重点实验室，中国科学院上海微系统与信息技术研究所，上海  200050
Published: December 2020

Terahertz （THz） wireless communication system, which exhibits great potential in the future short-range wireless communications, is known to be a kind of ultra-broadband system with high data rates. THz sources, modulators and detectors are key elements in these systems, while in order to maintain high-quality connection, the THz reflectors are also very important. Here, a reflector which is a kind of one-dimensional photonic crystal made of polyvinylidene fluoride （PVDF）/polycarbonate （PC） is studied carefully. According to the refractive indices of materials in the THz range, the reflection coefficients for THz waves are obtained through transfer-matrix method and Fresnel formula calculation. We demonstrate that, in sub-THz waveband, this device shows high performance and wide reflection band. Furthermore, based on the calculation, the research and the design of THz reflectors are also discussed in this article.
The far-field divergence angle and the far-field radiant intensity distribution of Gaussian Schell-model array beams
Authors: Ji Xiao-Ling  , Li Xiao-Qing  ,   四川师范大学物理学院，成都  610068
Published: December 2020

The analytical expressions for the mean-squared beam width, the far-field divergence angle and the far-field radiant intensity of Gaussian Schell-model （GSM） array beams are derived, and the condition under which GSM array beams have the same far-field divergence angle as a single Gaussian beam. It is shown that GSM array beams and a Gaussian beam which have the same far-field divergence angle may have different far-field radiant intensity distribution, which is quite different from the behavior of GSM beams.
Long-pulse optical pumping THz laser based on optical amplification
Authors: Qi Chun-Chao  , Zuo Du-Luo  , Meng Fan-Qi  , Lu Yan-Zhao  , Jiu Zhi-Xian  , Cheng Zu-Hai  ,   武汉光电国家实验室，华中科技大学光电子科学与工程学院，武汉  430074
Published: December 2020

To obtain narrower linewidth and more intense THz radiation, long-pulse and high-peak power optical pumping source is attempted by performing a light amplification experiment in which a 6 W tunable continuous-wave CO2 seeding laser is amplified by a double-pass amplifier with TEA CO2 laser. The result of an amplification factor of 30 at 14 μs pulse duration （FWHM） is obtained experimentally. During the amplification, the output power of the amplified light increases with that of seeding light increasing, especially for the CO2 10P （20）line. Based on the optical pumping source of long pulse laser, a dynamic model for generating pulsed THz radiation is established, and the expression of saturation pumping intensity which yields THz radiation is given, thus the range of pumping intensity can be determined. In addition, by solving time-dependent equation of dynamic model, the expression of pumping energy absorbed by THz medium is deduced. Theoretical analysis shows further that the heavy molecules will be more appropriate for THz gain medium for long pulse pumping source, and no THz radiation can be generated due to the absence of population reversion below pumping intensity.
Localized electron state on porous silicon quantum dots
Authors: Huang Wei-Qi  , Wang Xiao-Yun  , Zhang Rong-Tao  , Yu Shi-Qiang  , Qin Chao-Jian  ,   (1)贵州省光电子技术与应用重点实验室,贵州大学，贵州  550025; (2)中国科学院地球化学研究所，贵阳  550003
Published: December 2020

Porous silicon can be fabricated by laser irradiation and annealing. The center wavelength of photoluminescence （PL） band is pinned in the region of 700—780 nm and its intensity increases obviously after oxidation of the sample. It was found that the PL intensity changes with time of laser irradiation and annealing. Calculation shows that some localized states appear in the band gap of the smaller nanocrystal when SiO bonds or Si—O—Si bonds are passivated on the surface. It was discovered that the number of SiO bonds or Si—O—Si bonds, which are related to irradiation and annealing time, obviously affects the generation of localized gap states.
Investigation on a four-beam serial laser combination for a non-collinear scheme based on Brillouin amplification
Authors: Wang Yu-Lei  , Lü Zhi-Wei  , Wang Shuang-Yi  , Zheng Zhen-Xing  , He Wei-Ming  ,   哈尔滨工业大学光电子技术研究所，哈尔滨  150080
Published: December 2020

A non-collinear laser beam combination based on Brillouin amplification was proposed. The influence of non-collinear Brillouin amplification on the combination efficiency was analyzed and discussed theoretically. It was shown that the efficiency of 80% can be achieved with the angle between the Stokes and the pump limited in the range of 90 mrad. According to the theoretical results, a four-beam non-collinear combination experiment was designed and carried out. The output energy of 189 mJ at 10 Hz was achieved with the energies of the four pumps being 70.4, 71.3 , 78.9 and 70.1 mJ， respectively. In order to simplify the scheme and reduce the optical loss, a construction of SBS cell for non-collinear combination of multiple beams was also designed.
Temperature and wavelength tuning of second harmonic generation in a nonlinear photonic quasi-crystal
Authors: Dou Jun-Hong  , Sheng Yan  , Zhang Dao-Zhong  ,   中国科学院物理研究所北京凝聚态物理国家重点实验室和中科院光物理重点实验室,北京  100190
Published: December 2020

In the LiNbO3 nonlinear photonic crystals with a two-dimensional octagonal quasilattice, the collinear quasi-phase-matched second harmonic generation processes at multiple wavelengths were observed. The maximum conversion efficiency was 36%. Meanwhile, for the fist time we measured the change of the second harmonic conversion efficiency with the temperature and incident wavelength. The results show that the second harmonic has broader temperature and wavelength tuning bandwidth in long waveband. It is believed the study might be significant for the application of quasi-periodic nonlinear photonic crystal in practice.
Group velocity matching in femtosecond optical parametric amplification of the KBe2BO3F2
Authors: Ma Jing  , Liu Ying  ,   天津大学理学院物理系,天津  300072
Published: December 2020

In this paper a method is presented for the first time, witch can match completely group velocities of three pulses in femtosecond optical parametric amplification （OPA） of the KBe2BO3F2 （KBBF） crystal. We combine noncollinear configuration with tilting pulse front of pump, and collinear configuration with tilting pulse front of pump and signal, in type-Ⅰ and type-Ⅱ　phase matching configurations respectively, to realize complete match of group velocities of three pulses in maximal parametric bandwidth of the femtosecond OPA, thus can obtain parametric pulses with higher gain and shorter duration.
Influence of dielectric substrates on surface wave bandgap of uniplanar electromagnetic band-gap structure
Authors: Wang Wei  , Cao Xiang-Yu  , Wang Shuai  , Wang Rui  , Zheng Qiu-Rong  ,   (1)安徽合力股份有限公司装载机事业部研究所,合肥  230601; (2)空军工程大学电讯工程学院,西安  710077; (3)西北大学信息科学与技术学院,西安  710127
Published: December 2020

The method of lines is used to analyze the influence of dielectric substrates on uniplanar EGB structure. The analysis process is introduced. According to periodic boundary conditions, one unit cell has been isolated as the calculation region, and the method of lines is used to get the propagation equation of potential function in different interfaces of medium layers. By combining the conversion relationship between field component and potential function on the continuity condition of the tangential field components in interfaces, eigen value equations are established, and the frequency band diagrams of eigen mode are obtained to describe the surface wave bandgap of EBG structure. The method is used to do a series of calculations on surface wave bandgap with dielectric substrates of different dielectric constants and different thicknesses. Through analysis of calculation results, six conclusions are obtained on the influence of dielectric substrates, which can provide some references for the design of uniplanar EGB structure.
Performance test and closed-loop correction experiment of a 20-element bimorph deformable mirror
Authors: Ning Yu  , Yu Hao  , Zhou Hong  , Rao Chang-Hui  , Jiang Wen-Han  ,   (1)中国科学院光电技术研究所,成都  610209; (2)中国科学院光电技术研究所,成都  610209；国防科学技术大学光电科学与工程学院,长沙  410073; (3)中国科学院光电技术研究所,成都  610209；中国科学院研究生院,北京  100049
Published: December 2020

Performances of a 20-element bimorph deformable mirror are measured and a closed-loop adaptive optics system, which consists of the bimorph mirror and a Shack-Hartmann wave-front sensor with 13×13 sub-aperture array, is established to test the mirror’s capability of correcting static aberrations. Experimental results show that, the mean displacement response to voltage of discrete actuators is 0.57 μm/100 V and that of defocus electrode is 1.09 μm/100 V. The hysteresis of actuator is limited to ten percents of the maximal displacement. With the ambient temperature increasing from 13℃ to 25℃, the P-V of defocus of the mirror surface is enlarged by 1.37 μm and the P-V of other distortions, such as astigmatism, coma and spherical aberration, is enlarged by 0.15 μm. The frequency response of the bimorph mirror is about 4 kHz. When the closed-loop control is on, intensity distributions at the image plane of distorted wave-fronts are effectively improved. The Strehl ratios increase from 0.02 to 0.95, and 0.03 to 0.54， respectively.
Photoacoustic angiography for mouse brain cortex using near-infrared light
Authors: Yang Si-Hua  , Yin Guang-Zhi  ,   华南师范大学激光生命科学研究所暨激光生命科学教育部重点实验室,广州  510631
Published: December 2020

Photoacoustic imaging is a novel noninvasive imaging technique of biological tissue that overcomes the overwhelming scattering of light in biological tissue by utilizing ultrasonic wave to translate the image signal. In this study, near-infrared light and indocyanine green as an optical contrast agent were used to achieve the cerebrovascular distribution by photoacoustic imaging. Near-infrared light penetrates deep into the brain tissues through the skin and skull, and the indocyanine green enhances the photoacoustic signals of the blood vessels. A photoacoustic angiography of vascular distribution in the mouse brain in vivo was acquired that matches the anatomical photograph well. The experimental result demonstrates the photoacoustic imaging with near-infrared light and optical contrast agent has the potential for functional and molecular biomedical imaging.
A novel method for heat exchanger analysis
Authors: Liu Xiong-Bin  , Guo Zeng-Yuan  ,   清华大学工程力学系，北京  100084
Published: December 2020

Since the heat transfer irreversibility of a heating or cooling process should be measured by the entransy dissipation rate, an equivalent thermal resistance for a heat exchanger was defined based on the entransy dissipation rate of the heat exchanger. The equivalent thermal resistance includes both the overall heat transfer resistance and the extra thermal resistance caused by the non-counter-flow arrangement and the non-equilibrium heat capacity rate ratio of a heat exchanger. The reciprocal of the equivalent thermal resistance was defined as the equivalent thermal conductance. The relationship is established between the heat transfer irreversibility and the effectiveness of a heat exchanger in terms of the equivalent thermal resistance. Finally, a formula describing the relation among the effectiveness, the equivalent thermal resistance and the heat capacity rate ratio is obtained which does not depend on the different flow arrangements. Therefore the effectiveness-thermal resistance （conductance） method is more suitable for the performance comparison of different heat exchangers.
Atomistic simulation of yield mechanism of single crystal copper nanowires
Authors: Xu Zhen-Hai  , Yuan Lin  , Shan De-Bin  , Guo Bin  ,   哈尔滨工业大学材料科学与工程学院，哈尔滨  150001
Published: December 2020

Molecular statics simulation was used to study the yielding mechanism of 〈100〉 oriented single crystal copper nanowires under tension. The results show that, the yield of nanowires is initially realised via {111}〈112〉 twinning from random activation of partials, and subsequently via slip of {111}〈112〉 partial dislocation; in addition, the partial dislocations on different planes successively slip and meet to form stair-rod dislocation at the initial stage of plastic deformation, while some partial dislocations are piled up near the rigid boundary at the later stage of plastic deformation, both of which hinder dislocation slip, resulting in strengthening of the single crystal copper nanowires.
Effects of cathodic voltage pulse duty cycle on characteristics of microarc oxidation coatings of titanium alloy
Authors: Tang Yuan-Guang  , Wu Han-Hua  , Chang Hong  , Chen Gen-Yu  , Sang Yong  , Bai Yi-Zhen  ,   (1)大连理工大学物理系，三束材料改性国家重点实验室，大连  116024; (2)吉林大学物理学院，长春  130021
Published: December 2020

Under the condition of keeping the bipolar pulse voltage constant, the effect of cathodic pulse voltage duty cycle （dc） on characteristics of microarc oxidation coatings of titanium alloy have been studied by using a multifunction microarc oxidation power supply. Experimental results show that the variations of cathodic and anodic currents with treatment time show obviously several stages, and the beginning and ending time of various stages are closely related to dc. The coating consists mainly of rutile and anatase phases, and there is a sudden change in the rutile phase content at dc=50%. The thickness, morphology and microhardness of the coating strongly depend on dc change. The microhardness valucs of the coatings prepared at dc=50% and dc=70% are the minimum （4.96 GPa） and the highest （6.1 GPa）, respectively. In general, the MAO coatings prepared in the range of 65%≤dc≤80% have higher growth rate and quality.
The vacancy defect clusters in polycrystalline pure aluminum induced by high-current pulsed electron beam
Authors: Guan Qing-Feng  , Cheng Du-Qing  , Qiu Dong-Hua  , Zhu Jian  , Wang Xue-Tao  , Cheng Xiu-Wei  ,   江苏大学材料科学与工程学院，镇江  212013
Published: December 2020

The specimens of polycrystalline pure aluminum were irradiated with high-current pulsed electron beam （HCPEB）. The microstructure of vacancy defect clusters has been investigated in detail by using transmission electron microscopy （TEM）. The results reveal that large numbers of vacancy cells including dislocation loop and even stacking fault tetrahedra （SFT） can be formed in the specimens of polycrystalline pure aluminum irradiated with HCPEB. For the specimen irradiated with one pulse, vacancy dislocation loops were formed in the vacancy cells. SFTs became the dominating structures after five pulses. For the specimen irradiated with ten pulses, dislocation loops were frequently present and SFTs were only formed in some local zones of vacancy cells. In the vicinity of SFT formation, dislocation-free or very low dislocation densities were observed. It is suggested that high stress and strain rate induced by rapid heating and cooling due to HCPEB irradiation could cause the shifting of whole atomic planes synchronously. This is the more probable mechanism of the formation of SFTs.
Relativistic mean field theory of electron and first, second-order Rashba effects
Authors: Xu Jian-Wei  , Wang Shun-Jin  ,   四川大学物理科学与技术学院理论物理中心,成都   610064
Published: December 2020

Within the framework of relativistic mean field theory- the Dirac equation of electrons in solid states, the electron spin dynamics and the related problems are discussed.Firstly, we discuss the high-order effects of electron spin dynamics by virtue of non-relativistic expansion of the Hamiltonian for large component of Dirac equation, the electron spin dynamics Hamiltonian including the first-order and second-order Rashba effects have been derived. In the case of two-dimension and perpendicular constant electric field, the corresponding eigenenergies and eigenfunctions of the spin dynamics Hamiltonian are obtained. Finally, the physical meaning and the magnitude of the correction of the second-order Rashba effect are discussed.
First-principles study of the electonic structure of nitrogen-doped silicon carbide nanotubes
Authors: Song Jiu-Xu  , Yang Yin-Tang  , Liu Hong-Xia  , Zhang Zhi-Yong  ,   (1)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试验室,西安  710071; (2)西北大学信息科学与技术学院，西安  710069
Published: December 2020

The electronic structures of the intrinsic and nitrogen-doped silicon carbide nanotubes （SiCNTs） have been calculated by first-principles approach based on the density functional theory. The intrinsic （8, 0） SiCNT is a direct band-gap semiconductor with a gap value of 0.94 eV. The band-gap of the SiCNT with the doping concentration of nitrogen being 1.56% and 3.12％ is narrowed to 0.83 eV and 0.74 eV， respectively. The narrowing of the band-gap is the result of the weakening of the Si-N bonds compared with the corresponding Si-C bonds, which can be seen by comparing the charge density difference of the intrinsic SiCNT with that of the nitrogen-doped nanotube.
Optical properties of PuO2 and α-Pu2O3 studied by empirical potentials simulation
Authors: Chu Ming-Fu  , Meng Da-Qiao  , Lai Xin-Chun  , Lü Xue-Chao  , Bai Bin  , Zhang Yong-Bin  ,   表面物理与化学国家重点实验室，绵阳  621907
Published: December 2020

The BMH empirical potentials of Pu-O bond in α-Pu2O3 are fitted by GULP program. The structure and optical properties of PuO2 and α-Pu2O3 crystal are calculated by molecular statics and molecular dynamics using BMH and shell potentials. The result shows that their simulated space groups, cell parameters, densities and entropies are approximately the samc as the data in published papers, with relative error less than 1.2%. Furthermore, their static （high frequency） dielectric constant tensor, IR dielectric function spectra and crystal lattice vibration peaks are all calculated. Part of the results are validated by experiment of spectroscopic ellipsometry, and the indirect energy bandgap of PuO2 is found to be 2.1 eV.
Influence of high-temperature AlN interlayer on the electrical properties of AlGaN/GaN heterostructure and HEMTs
Authors: Ni Jin-Yu  , Hao Yue  , Zhang Jin-Cheng  , Duan Huan-Tao  , Zhang Jin-Feng  ,   西安电子科技大学微电子学院,宽禁带半导体材料与器件重点实验室,西安  710071
Published: December 2020

GaN buffer with insertion of a 40-nm-thick high-temperature （HT） AlN interlayer is studied. The HT-AlN interlayer enhances the in-plane compressive strain of GaN film and thereby improves the electrical properties of AlGaN/GaN high electron mobility transistors （HEMTs）. Base on the precise measurement of Bragg angle, the strain states of GaN are calculated. It is found that the increased compressive stress enhances the piezoelectric polarization field in GaN, which consequently causes accumulation of more electrons at the AlGaN/GaN interface. On the other hand, the influence of AlGaN layer induced by the enhanced compressive stress on the two-dimensional electron gas （2DEG） sheet carrier density, both positive and negative, are proved to counteract each other. Meanwhile, the employment of the HT-AlN interlayer reduces the lattice mismatch between the GaN and AlGaN and smoothes the AlGaN/GaN interface, thus increases the 2DEG mobility by weakening the interface roughness scattering. The 1-μm gate-length HEMTs by using the GaN buffer layer with the HT-AlN interlayer are fabricated. The measurements show that the maximum drain current and transconductance are increased by 42% and 20% respectively compared with the conventional HEMTs without HT-AlN interlayer.
Photoluminescence study of quantum confined acceptors
Authors: Li Su-Mei  , Song Shu-Mei  , Lü Ying-Bo  , Wang Ai-Fang  , Wu Ai-Ling  , Zheng Wei-Min  ,   (1)山东大学威海分校空间科学与物理学院，威海  264209; (2)山东大学威海分校空间科学与物理学院，威海  264209；山东大学威海分校信息工程学院，威海  264209
Published: December 2020

Photoluminescence of shallow Be acceptors in both bulk GaAs and a series of δ-doped GaAs/AlAs multiple quantum well samples with well width range from 30 to 200　? were studied. A series of Be δ-doped GaAs/AlAs multiple quantum wells with the doping at the well center and a single epilayer of GaAs uniformly Be doped were grown by molecular beam epitaxy. The photoluminescence spectra were measured at 4.2 K. The two-hole transition of the acceptor-bound exciton from the ground state, 1s3/2（Γ6）, to the first-excited state, 2s3/2（Γ6）, have been clearly observed. A variational principle is used to obtain the 2s-1s transition energy of quantum confined Be acceptors as a function of the well width. It is found that the acceptor transition energy increases with decreasing quantum well width, and the experimental results are in good agreement with the theoretical calculation.
Photoinduced effect in Cu doping La0.67Sr0.33Cux Mn1-xO3 thin films
Authors: Jin Ke-Xin  , Zhao Sheng-Gui  , Chen Chang-Le  ,   西北工业大学凝聚态结构与性质陕西省重点实验室，西安  710072
Published: December 2020

The compounds and films of La0.67Sr0.33CuxMn1-xO3（x= 0.05, 0.10, and 0.15） were prepared using the sol-gel technique and an RF magnetron sputtering method, respectively. The effect of Cu doping on the photoinduced properties of La0.67Sr0.33CuxMn1-xO3 films was investigated. Experimental results indicate that the increasing Cu doping content leads to a decrese of the insulator-metal transition temperature and an increase of the resistance. The laser irradiation induces an increase of the resistance in the metallic state. The maximum values of the photoinduced relative change in the resistance increase with increasing x, and it reaches 58.3％ at x =0.15. The intriguing mechanism of the photoinduced effect on the resistance was discussed, which may be the photoinduced electrons being trapped at a localized state outside the CuO2 planes in combination with and the lattice effect.