bluuebunny/crossref_metadata_2025 huggingface dataset:
Band structures of three-dimensional photonic crystals consisting of dielectric spheres: a plane-wave approach
Authors: Dong Hui-Yuan  , Liu Mei  , Wu Zong-Han  , Wang Jing  , Wang Zhen-Lin  ,   (1)东南大学生物医学系，南京  210096; (2)东南大学物理系，南京  210096; (3)南京大学固体微结构物理国家重点实验室，南京  210093
Published: December 2020

Using the plane-wave method, we calculate the band structures and transmission characteristics of the three-dimensional fcc photonic crystals. For a SiO2 opa l photonic crystal, we calculate the energy spectrum and the transmission featu re of electromagnetic waves along the [111] direction using both the plane-wave method and the transfer-matrix method, the obtained results are consistent wit h each other. For a full band gap studies of the inverse-opal structure, the co nvergence effect in the plane-wave method on the calculation is discussed. For an fcc lattice of core-shell sphere, it is shown that the relative L-gap width of a suitable coating of dielectric spheres of a lower dielectric material can increase by 50% as compared with that of homogeneous high-dielectric spheres. We also find that the optimum radius ratio between interior and entire spheres is 0.69.
Spin dynamics of GaAs(100) by two-photon photoemission
Authors: Guo Li-Jun  , Wüstenberg Jan-Peter  , Oleksiy Andreyev  , Bauer Michael  , Aeschlimann Martin  ,   (1)凯泽斯劳腾大学物理系，凯泽斯劳腾D-67663，德国; (2)凯泽斯劳腾大学物理系，凯泽斯劳腾D-67663，德国;河南大学物理与信息光电子学院,开封  475001
Published: December 2020

On p-doped GaAs(100) surface, the band bending arising from Fermi-level pinning significantly affects the carrier and spin dynamics. In this paper, we report th e dynamics of spin polarization of p-doped GaAs(100) by using the time-resolve d and the energy-resolved two-photon photoemission techniques. By measuring the spin and energy relaxation of electrons emitted from the GaAs(100) surfaces, th e dynamics of spin polarization were observed and the mechanism of spin relaxati on was discussed as well. The experimental measurements together with the theore tical results indicate that the Bir-Aronov-Pikus (BAP) mechanism plays a dominan t role for spin polarization decay, especially in band bending region of GaAs(10 0).
Structure and tribology properties of diamond-like carbon films prepared by microwave electron cyclotron resonance plasma source ion implantation
Authors: Gao Peng  , Xu Jun  , Deng Xin-Lu  , Wang De-He  , Dong Chuang  ,   大连理工大学三束材料改性国家重点实验室，大连  116024
Published: December 2020

Diamond-like carbon(DLC) films were prepared on silicon (100) wafer by microwave electron cyclotron resonance(MW-ECR) plasma source ion implantation(PSII). Th e results showed that the films had typical properties of DLC. The films was den se and homogeneous, and the roughness and friction coefficient was low. The conn ection between the properties of the films and the flow ratio of hydrogen was cl osely. With the increase of the flow ratio of hydrogen to methane, the depositio n rate and the roughness of the films decreased. The sp3 bond obtaine d was mor e likely diamond like, which had low surface energy, consequently making the fri ction coefficient of the films decrease rapidly.
Influences of the period of repeating thickness on the stress of alternative high and low refractivity ZrO2/SiO2 multilayers
Authors: Shao Shu-Ying  , Fan Zheng-Xiu  , Shao Jian-Da  ,   (1)中科院上海光学精密机械研究所，光学薄膜技术研究与发展中心，上海  201800; (2)中科院上海光学精密机械研究所，光学薄膜技术研究与发展中心，上海  201800;中国科学院研究生院，北京  100864
Published: December 2020

The effect of period of repeating thickness on the stress is studied in ZrO 2/SiO2 multilayers deposited by electron beam evaporation on BK7 glass a nd fused silica substrates, separately. The results show that the residual stress in the multilayers is compressive, and with the increase of the period of repeating thickness the residual stress in multilayers decrease in both BK7 and fused silica substrates. At the same time, the residual stress in multilayers deposited on BK7 glass substrates is less than that in the samples deposited on fused silica substrates. The variation of the microstructure examined by the x-ray diffraction shows that the microscopic deformation does not correspond to the macroscopic stress, which may be due to the variation of the interface stress.
Low-temperature metal-induced unilateral crystallized polycrystalline silicon thin-film transistor and gate-modulated lightly-doped drain structure
Authors: Meng Zhi-Guo  , Wu Chun-Ya  , Li Juan  , Xiong  Shao-Zhen  , Kwok Hoi S.  , Man Wong  ,   (1)南开大学信息学院光电子器件与技术研究所，光电子薄膜器件与技术天津市重点实 验室，光电信息技术科学教育部重点实验室（南开大学，天津大学），天津  300071; (2)香港科技大学电机电子工程系，香港九龙清水弯
Published: December 2020

In this paper the low-temperature metal-induced unilaterally crystallized (MIUC ) polycrystalline silicon thin-film transistors (TFTs) have been developed and c haracterized. These TFTs have higher field-effect mobility, lower off-state curr ent and better spatial uniformity. A new structure of gate-modulated lightly dop ed drain of TFT was proposed. It is very effective to lower gate-induced drain-l eakage current of the TFTs when a higher source drain voltage is applied to it. This type MIUC TFT is suitable to fabricate active matrices for liquid crystal and organic light-emitting diode flat-panel displays on large area glass substr ates.
Studies on surface dry treatment for improving the performance of RF superconducting cavities
Authors: Hao Jian-Kui  , Jiao Fei  , Huang Sen-Lin  , Zhu Feng  , Zhao Kui  ,   北京大学重离子物理教育部重点实验室，重离子物理研究所，北京  100871
Published: December 2020

RF superconducting (SC) cavities are more frequently used in particle accelerators with excellent performance which cannot be substituted by normal conducting cavities. The surface status of superconducting cavities directly affects the properties of the cavity. In order to improve the accelerating performance of superconducting cavities, Peking University made researches and developments on a “dry treatment method” on the surface of SC cavities. It uses argon ion cleaning technique in ultra-high vacuum. Compared with the traditional wet methods (Chemical polishing and electrical polishing), dry method has special advantages. It might become a new surface treatment method to improve the performances of SC cavities. Further researches are in progress.
Theory of temporal aberrations for electron optical imaging systems by direct integral method
Authors: Zhou Li-Wei  , Li Yuan  , Zhang Zhi-Quan  , Monastyrski M. A.  , Schelev M. Y.  ,   (1)北京理工大学信息科学技术学院，北京  100081; (2)俄罗斯科学院普罗霍洛夫普通物理研究所，莫斯科  119991; (3)装甲兵工程学院，北京  100072
Published: December 2020

A new approach to calculate the temporal aberration coefficients of dynamic electron optical imaging systems is put forward in this paper. A new definition o f temporal aberration is given in which a certain initial energy of electron emi ssion along the axial direction εz1(0≤εz1≤ε0max) as a cr iterion is considered. The new method for calculating the temporal aberration c oefficients of dynamic electron optical imaging systems named “direct integral method" is presented which gives new expressions of the temporary aberration coe fficients expressed in integral form. The difference between “direct integral m ethod" and “τ-variation method" is that the “τ-variation method" n eeds to solve the differential equations for the three of temporal geometrical a berration coefficients of second order, while the “direct integral method" need s only to carry out the integral calculation of them, which is more convenient a nd suitable for computation in the practical design.
Modeling and canceling of the readout crosstalk in photochromic dual-wavelength storage
Authors: Jian Ji-Qi  , Ma Cheng  , Jia Hui-Bo  ,   清华大学精密仪器与机械学系,北京  100084
Published: December 2020

With the disk reflectivity optional and with the recording information distribut ion discretionary, this paper analyzes the readout and crosstalk in photochromic dual-wavelength storage, establishes the models for them, and presents a method to reduce the readout crosstalk. It shows that as the crosstalk of the readout of a laser corresponding to a certain material is canceled, the parameter of the method is determined only by the molar extinction coefficient of the other mate rial, and the parameter is irrelative to the disk reflectivity distribution and the recording information, even irrelative to the molar extinction coefficient of the former material. This point is validated in the readout crosstalk cancelin g experiments with the two kinds of diarylethene with different absorption spect ra.
Study on spontaneous magnetization in a double-junction π ring
Authors: Tan Zhong-Kui  , Mao Bo  , Wang Fu-Ren  , Li Zhuang-Zhi  , Nie Rui-Juan  , Dai Yuan-Dong  ,   北京大学人工微结构和介观物理国家重点实验室，物理系，北京  100871
Published: December 2020

We have discussed the conditions under which a double_junction π ring magnetize spontaneously and provided the theoretical derivation. The condition is not onl y related with the parameter of induction, but also related to the ratio of the critical currents of the two junctions. Analyzing the free energy illustrates th at the spontaneous magnetization results in a stable state.
Calibration of interferometric autocorrelation trace for femtosecond pulse in frequency domain and the real-time chirp diagnostic for Ti:sapphire oscillator
Authors: Xie Xu-Dong  , Wang Qing-Yue  , Chai Lu  ,   (1)天津大学精密仪器与光电子工程学院,光电信息技术科学教育部重点实验室,天津  3 00072; (2)天津大学精密仪器与光电子工程学院,光电信息技术科学教育部重点实验室,天津  3 00072;中国工程物理研究院激光聚变研究中心,绵阳  621900
Published: December 2020

The time delay of interferometric autocorrelation trace of femtosecond pulse was calibrated in frequency domain. By virtue of the calibrated interferometric aut ocorrelation trace, root-mean-square width and chirp parameter of the femtosecon d pulse to be measured were calculated. Based on these parameters, the Ti:sapphi re oscillator was optimized to generate 115fs pulse in full width at half ma ximum, which was very close to the width of the transform-limited pulse. The mea surement involved only an integration and a fast Fourier transform. Consequently , real-time chirp diagnostics for Ti:sapphire oscillator was feasible.
Study of ferromagnetic semiconductor films: Ti1－xCoxO2
Authors: Song Hong-Qiang  , Chen Yan-Xue  , Ren Miao-Juan  , Ji Gang  ,   山东大学物理与微电子学院晶体材料国家重点实验室，济南  250100
Published: December 2020

Co-doped TiO2 ferromagnetic semiconductor flms were prepared by rf co-sputteri ng method and then annealed in vacuum at 300℃ for 2 h. Superconducting quantum interference device (SQUID) measurements indicate that the samples are ferromagn etic and the Curie temperature is above 300K. The saturation magnetization, coer civity, and saturation field are 55emu/cm3, 400×80A/m and 1500×80A/m at room temperature, respectively. And the magnetic moment was observed to be 0679 μB/Co. No pure Co metal grains were found by x-ray diffraction and x-ray p hotoemission spectroscopy measurements.
Thin-film photonic crystal omnidirectional reflector used in visible region
Authors: Gu Pei-Fu  , Huang Bi-Qin  , Zheng Zhen-Rong  ,   浙江大学现代光学仪器国家重点实验室,杭州  310027
Published: December 2020

Thin_film one_dimensional photonic crystal omnidirectional reflector used in vis ible region can be achieved by using angle domain overlapping reflectance bands. By using this method, the relative band width of the omnidirectional reflector consisting of four TiO2/SiO2 thin_film photonic crystals i s up to 41 33%. By comparison, the relative band width of the omnidirectional reflector c onstructed under the same condition as the above is only 1426% by using the co nventional frequency domain overlapping. The basic principle of the angle domai n overlapping is described. A thin_film one_dimensional photonic crystal omnidir ectional reflector used in visible region is calculated and given. Meanwhile, th e omnidirectional reflector used in ultraviolet region can be constructed by usi ng this new method, which cannot be obtained by the conventional method.
Crystal structure and optical characterization of cerium-doped Lu2Si2O7
Authors: Yan Cheng-Feng  , Zhao Guang-Jun  , Hang Yin  , Zhang Lian-Han  , Xu Jun  ,   中国科学院上海光学精密机械研究所，上海  201800
Published: December 2020

Cerium_doped lutetium pyrosilicate（Ce:LPS）crystal was grown by Czochralski met hod. X_ray diffraction analysis showed that the structure of Ce:LPS crystal was monoclinic with space group of C2/m. Cleavage (110) of the crystal was obse rved by optical microscope. Optical absorption, excitation and emission spectra of Ce:LPS crystal were measured at room temperature. Results indicated that both absorption and excitation spectra of Ce:LPS showed two broad bands peaking at 3 02 and 349 nm, assigned to the Ce3+ 4f1→5d1 tr ansitions. The Gaussian fits to the emission spectra excited at 349 nm, showed band characteri stics with two peaks at 384 and 407 nm, in which the latter intensity was highe r than the former.
The partition function and correlation functions of the Ising model on a diamond fractal lattices
Authors: Sun Chun-Feng  ,   孝感学院物理系,孝感  432100
Published: December 2020

With a diamond fractal lattice, the Ising model was exactly solved by parameter_ transformation technique. The rigorous partition function, free energy and corre lation functions were obtained for zero as well as non_zero field. In particular , an equation of cumulant pair correlation function and its analytical asymptoti c expression was derived in the zero field. The result indicated that the corre lation behaviors of the Ising model on a diamond fractal lattices are similar to the two_dimensional transitionally invariant lattices.
A study on interfacial phase of Ti-Si-N composite films
Authors: Kong Ming  , Hu Xiao-Ping  , Dong Yun-Shan  , Li Ge-Yang  , Gu  Ming-Yuan  ,   (1)上海大学材料科学与工程学院，上海  200072; (2)上海交通大学金属基复合材料国家重点实验室，上海  200030
Published: December 2020

To reveal the interfacial phase structure and its effect on mechanical propertie s of Ti_Si_N composite films, x_ray diffractometry, high_resolution transmission electron microscopy, Auger electron spectroscopy, and microhardness tester were employed to investigate theinterfacial phase structure and mechanical pro perties of magnetron sputtered Ti_Si_N composite films. A series of TiN/Si3 N4 multilayered films in nanometer scale were also prepared and characte rized for comparison. The results indicated that Ti_Si_N composite films formed a structure of nanocrystalline TiN surrounded by Si3N4 int erfacial p hase. In the Ti_Si_N composite film with lower silicon content, the Si3 N4 interfacial phase with a thickness of less than 1 nm crystal lized and formed a coherent interface with TiN nanocrystals, leading to an enhancement in the hardness of the film. Whereas, in the composite film of larger silicon cont ent, Si3N4 phase existed as amorphous and resulted in a de crease in hardness. Our research indicated that the crystallization of Si3N4 i nterfacial phase was essential to obtain a high hardness in the Ti_Si_N composit e films, and the strengthening mechanism of the composite films appeared to be the same as TiN/Si3N4 multilayered films.
Influence of interface dipoles on the UV/solar rejection ratios of GaN/AlGaN/GaN photodetectors
Authors: Zhang Chun-Fu  , Hao Yue  , You Hai-Long  , Zhang Jin-Feng  , Zhou Xiao-Wei  ,   西安电子科技大学微电子学研究所，宽禁带材料与器件教育部重点实验室,西安  710071
Published: December 2020

In the inverted heterostructure photodiodes(IHPs), the strong polarization effect at the interface of the AlGaN/GaN heterostructure influences UV/Solar rejection ratios of this type of structure. In this paper, the total effect of polarization is divided into two parts: the polarization and dipole terms. Based on the model of GaN/AlGaN/GaN IHPs, the influence of dipoles on the UV/Solar rejection ratios is analyzed. The results show that when dipoles are considered, UV/Solar rejection ratios of photodetectors are about three orders of magnitude, which agree with the experiment of Tarsa. The influence of dipoles should be considered in the IHPs.
A theoretical method to calculate the surface free energies of crystals
Authors: Yu Zhi-Ming  , Yin Deng-Feng  ,   中南大学材料科学与工程学院，长沙  410083
Published: December 2020

An ideal density of dangling bonds and the surface free energy (SFE) of (1×1)-(hkl) surface of cubic crystals are calculated by using a broken-bond model. The results show that the SFE(γ) can be expressed as γ=f(hkl)·(Eb/d2 0) where f(hkl) is a periodically convergent function, Eb and d0 are respectively the bond energy and the bond length. The f(hkl) is rela ted to the crystal structure. The anisotropy of the SFE and the equilibrium form (EF) of the crystal can be readily determined by using the results. It is found that the EFs of the crystals of fcc and bcc are truncated octahedron and rhombi c dodecahedron, respectively, which are coincident with the corresponding crysta ls' three dimensional first Brillouin zones, respectively.
Microfabrication methods of magnetic tunnel junctions with high tunneling magnetoresistance
Authors: Li Fei-Fei  , Zhang Xie-Qun  , Du Guan-Xiang  , Wang Tian-Xing  , Zeng Zhong-Ming  , Wei Hong-Xiang  , Han Xiu-Feng  ,   中国科学院物理研究所磁学国家重点实验室，北京  100080
Published: December 2020

In this work, on the one hand, the contact-shadow-mask method and technique were used to micro-fabricate the magnetic tunnel junction (MTJ) and optimize the experimental conditions. The width of the gap for the long and narrow top or bottom magneto-electrode is 100 μm, which can be used to deposit MTJs and form a cross strip with the tunnel section of 100 μm×100 μm. The MTJs with tunneling magnetoresistance (TMR) ratio of 30%—48％ can be directly obtained for the structure of Ta(5 nm)/Cu(25 nm)/Ni79Fe21(5 nm)/Ir22Mn78(10 nm)/Co75Fe25(4 nm)/Al(08 nm)-O/Co75Fe25(4 nm)/Ni79Fe21(20 nm)/Ta(5 nm). On the other hand, t he MTJs with high TMR ratio and small active area from 20 μm×40 μm down to 4 μm×8 μm were fabricated using two optical lithography methods of milling contact hole and lift-off resist, combined with Ar ion-beam etching or CF4 reactive etching technique s. Then, the TMR ratio from 22% up to 50% can be achieved before and after annealing at around 300 ℃ for 1 h. Our investigation shows that the patterned MTJs, which were microfabricated using the two optical lithography methods stated above, can b e used as the fundamental element of magnetoresistive random access memory, magn etic read-heads in hard disk drives and the field sensitive sensor.
Magnetoelectric effect of the TbDyFe/PZT laminated composite
Authors: Wan Hong  , Xie Li-Qiang  , Wu Xue-Zhong  , Liu Xi-Cong  ,   (1)国防科学技术大学航天与材料工程学院，长沙   410073; (2)国防科学技术大学机电工程与自动化学院，长沙   410073
Published: December 2020

The great magnetoelectric(ME) effect is a product property of the composite consisting of individual piezoelectric and magnetostrictive phases. The TbDyFe/PZT laminate composites were prepared by magnetron sputtering, and the ME coefficients αE were examined experimentally and calculated by using a finite e lement analysis software. Results showed that the experimental data were in agreement with the calculated results and the value of αE reached the maxim um at the resonance frequency, and αE increased with the increase of the magnetostricive thickness.
Synthesis of carbon nanotube/polyaniline composite nanotube and its microwave permittivity
Authors: Zhao Dong-Lin  , Zeng Xian-Wei  , Shen Zeng-Min  ,   北京化工大学可控化学反应科学与技术基础教育部重点实验室，碳纤维及复合材料研究所 ，北京  100029
Published: December 2020

A carbon nanotube/polyaniline composite nanotube with a diameter of 50—80 nm has been prepared. The carbon nanotubes encapsulated by polyaniline (PANI) with a thickness of 20—30 nm have been synthesized by in-situ emulsion polymerization. The microwave permittivity of the carbon nanotube/polyaniline composite nanotubes has been investigated in the frequency range of 2—18 GHz. The real part (ε′) and imaginary part (ε″) of the complex permittivity of carbon nanotube/polyaniline composite nanotube change little, as compared with those of carbon nanotubes at frequencies 2—18 GHz. The ε′ and ε″ of the carbon nanotube/polyaniline composite nanotube are small at low frequencies, which make it easy to match the impedance of free-space in the design of microwave absorbing materials. The dissipation factor tanδ(ε″/ε′) of carbon nanotube/polyaniline composite nanotube is high. So the carbon nanotube/polyaniline composite nanotube is a good microwave absorbent.
Design of wide-angle and broad-band two-dimensional photonic crystal polarization splitter by the automatic shaping mechanism
Authors: Li Yi-Yu  , Gu Pei-Fu  , Li Ming-Yu  ,   浙江大学现代光学仪器国家重点实验室,杭州  310027
Published: December 2020

Based on the mechanism of automatic shaping, the corrugated multilayer films of two_dimensional (2D) phtonic crystal is designed.This structure realizes omnidirectional polarization splitting with TM mode passing window between λ＝148 and 152μm, which is the complete band gap of TE mode. The variable rang es of the slope angle of the layers and the width of a-Si single layer are 38° —49° and 014—015μm, respectively. Band structure has been used to expl ain the omnidirectional polarization effect. An arrow-end_like 2D photonic cryst al which is the deformation of the corrugated multilayer films is introduced for comparison. It can only work as a wide-angle polarization splitter not as an o mnidirectional one for wavelength from 128 to 131μm. The comparison of th e band structures of these two different 2D photonic crystals leads to the metho d of extending the incident angle of polarization splitter.
Investigation about the Lorenz model and logistic equation based on the complexity
Authors: Hou Wei  , Feng Guo-Lin  , Dong Wen-Jie  ,   (1)国家气候中心气候研究开放实验室，北京  100081; (2)国家气候中心气候研究开放实验室，北京  100081;中国科学院大气物理研究所，北京  100029; (3)扬州大学物理科学与技术学院，扬州   225009
Published: December 2020

The complexity series of the logistic equation and the Lorenz model were respectively calculated using a dynamical nonlinear analysis method for time series— —Lemper-Ziv complexity algorithm, and the physical implication of Lemper-Ziv co mplexity is also discussed. Results show that for the logistic equation, the com plexity is obviously different when the complicated degree of the time series i s variational; and for Lorenz model, i.e. its x-, y-, and z-portions, th eir complexities are all chaotic and are all composed of many cycles whose swings are almost the same and the lengths are different. The result reflects the in ternal quasi-periodicity. Further investigations indicate that when different wi ndow lengths are selected, the characters of the complexity series for a given t ime series are basically the same, and there exists a coherency between the jump s of the complexity series and the jumps of the time series. Thus one can judge the characteristic of a time series by calculating its complexity. This may be u seful to predict the kinetic behavior of a time series.
Higher-order differential equations of motion of a holonomic mechanical system
Authors: Zhang Xiang-Wu  ,   陇东学院物理系，庆阳  745000
Published: December 2020

Starting from Newtonian kinetic equations of a particle system, the energy of higher order-velocity of the system is introduced; higher-order Lagrange equations, higher-order Nielsen equations and higher-order Appell equations of a holonomic mechanical system are derived, from which we prove that the three kinds of higher-order differential equations of motion of the holonomic system are equivalent to each other. The result indicates that the higher-order differential equations of motion of the holonomic system reveal the relationship between the chan ges of the system's motion state and the rate of change of force at every order, which cannot be obtained by using Newtonian kinetic equations and the tradition al analytical mechanical equations. Therefore, the higher-order differential equ ations of motion of the holonomic system are a complement to the second-order di fferential equations of motion, including Newtonian kinetic equations and the tr aditional Lagrange equations, Nielsen equations and Appell equations.
One way Hash function construction based on spatiotemporal chaos
Authors: Zhang Han  , Wang Xiu-Feng  , Li Zhao-Hui  , Liu Da-Hai  ,   南开大学信息技术科学学院，天津  300071
Published: December 2020

A Hash function construction method based on spatiotemporal chaos is proposed. We take the rumor after linearly transformed as a group of initial values and utilize the one-way coupled map lattice of spatiotemporal chaos to iterate the grou p of initial values concurrently.Then in spatiotemporal chaos convergence the pr oper items of the chaos convergence produced in the last space are linearly tran sformed into Hash value of 128 bits.The result obtained shows that the Hash func tion based on spatiotemporal chaos have advantages of irreversibility,weak colli sion and sensitivity to initial values.The method has a stronger secret performa nce than the Hash function based on low-dimensional chaos maps, and it is simple to be realized.
Studies on the density profiles of square-well chain fluid confined in a slit pore by density functional theory
Authors: Ye Zhen-Cheng  , Cai Jun  , Zhang Shu-Ling  , Liu Hong-Lai  , Hu Ying  ,   华东理工大学化学系，结构可控先进功能材料教育部重点实验室和化学工程国家重点实验室，上海  200237
Published: December 2020

The density profiles of square-well chain fluid confined in two planar walls are calculated using density-functional theory based on the weighted-density appro ximation of Yethiraj. The free energy functional of the system consists of an id eal part and excess part. We obtain the excess part by the equation of state of corresponding uniform system combined with the weighted-density approximation. We adopted respectively the equations of state based on cavity correlation fun ction and the statistically associating fluid theory. The calculated density pro files are compared with the corresponding Monte Carlo simulation data at differe nt chain lengths, temperatures, volume fractions and different attractions of t he wall. For a square-well chain fluid confined in two hard planar walls, result s from both equations of state are in good agreement with that of the Monte Car lo simulations at high temperature and high volume fraction. Both results devia te from the Monte Carlo result at low temperature and low volume fraction. The density profile in hard wall slit pore calculated from the equation of state of SAFT-VR is in better agreement with the available simulation data than that fro m the equation of state developed by Liu et al. We find that the equation of st ate has significant influence on theoretical prediction. For the walls with attr active forces, predictions from both equations of state deviate from the simula tion data. This deviation results from the increasing non-uniformity of the flu ids. Therefore, more suitable weighted-density function is needed to improve the density-functional theory.
Energy spectra of high-power ion beams measured with a pile of thin films on FLASH Ⅱ
Authors: Yang Hai-Liang  , Qiu Ai-Ci  , Li Jing-Ya  , Sun Jian-Feng  , He Xiao-Ping  , Tang Jun-Ping  , Wang Hai-Yang  , Huang Jian-Jun  , Ren Shu-Qing  , Zou Li-Li  , Yang Li  ,   西北核技术研究所，西安  710024
Published: December 2020

The preliminary experimental results obtained for the energy spectra of high-power ion beam(HPIB) with a pile of thin films on FLASH Ⅱ accelerator are reported. Code was developed to calculate the theoretical energy-loss of proton and C ion beams transmited through the Mylar films with different thickness. T he apertures of Faraday Cups are covered with Mylar films of different thicknes s, and then the signal attenuations can be recorded with oscilloscope. The energ y spectra of HPIB and the diode voltage are obtained according to the signal al lenuations. The diode voltage measured with a pile of thin films agrees with the voltage measured with a differential ring. And the ion number versus time curv e was given. In addition, the ion energy of HPIB is also measured with Thomson spectrometer and time of flight method and the results agree with those measured with a pile of thin films.
A new microscopy for THz radiation
Authors: Yang Yu-Ping  , Shi Yu-Lei  , Yan Wei  , Xu Xin-Long  , Ma Shi-Hua  , Wang Li  ,   中国科学院物理研究所和凝聚态物理中心，光物理实验室，北京  100080
Published: December 2020

Because the central wavelength of terahertz (THz) pulse is long, the spatial resolution of the THz detection is limited to sub-millimeter due to the diffraction effect. We report a new THz microscopy by attaching an electro-optical crystal directly to a thin generation crystal. By focusing tightly the optical pump beam, the detected spatial resolution can reach several microns. In additior this mechanism cacan avoid the loss of intensity and spectrum components. In this letter, the configuration and characteristics of this device are described in details.
Photonic band gap of two-dimensional photonic crystal based on silicon in mid-infrared
Authors: Zhou Mei  , Chen Xiao-Shuang  , Xu Jing  , Zeng Yong  , Wu Yan-Rui  , Lu Wei  , Wang Lian-Wei  , Chen Yu  ,   (1)华东师范大学电子科学与工程系，上海  200062; (2)中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083
Published: December 2020

Two_dimensional macroporous photonic crystal with mid_infrared band gap was fabr icated by electrochemical etching method in this work. The sample structure is o f square lattice with structure parameters: lattice constant a=4μm and the length of the square lattice structure l=2μm. The reflection spectrum of th e sample was measured using the microscopic infrared spectrometer and showed the photonie crystal characteristics.
First principles study on structure and stability of small GanPm clusters
Authors: Li En-Ling  , Yang Cheng-Jun  , Chen Gui-Can  , Wang Xue-Wen  , Ma De-Ming  ,   (1)西安交通大学微电子研究所，西安  710049; (2)西安交通大学微电子研究所，西安  710049;西安理工大学理学院，西安  710048; (3)西安理工大学理学院，西安  710048; (4)西北大学电子系，西安  710068; (5)咸阳师范学院物理系，咸阳  712000
Published: December 2020

Geometric structures, electronic states and energies of GanP and GanP2 (n= 1—7) clusters have been studied using the density functional theory. Structural optimization and frequency analysis were carried out at the B3LYP/6-31G* level.All ground states of GanP and GanP2 (n=1—7) clusters have been obtained.Our calculations reveal that there exists a transition from planar to spacial structures at n=5 with increasing cluster size. The strong P-P bond is favored over P-Ga in GanP2 (n=1—7) clusters. Among different GanP and GanP2 (n=1—7) clusters, Ga3P,Ga4P, GaP2, Ga2P2 and Ga4P2 are more stable. Their stability tends to reduce with the increase of the number of total atoms.
Magnetic and dielectric properties of ferroelectromagent Pb(Fe1/2 Nb1/2)O3
Authors: Yang Ying  , Li Qi-Chang  , Liu Jun-Ming  , Liu Zhi-Guo  ,   (1)南京大学固体微结构物理实验室，南京  210093; (2)南京大学固体微结构物理实验室，南京  210093;南京航空航天大学材料科学与技术学院，南京  210016
Published: December 2020

The magnetic and dielectric properties of the ferroelectromagnet(FEM) Pb(Fe1／2Nb1／2)O3 (PFN) single crystals have be en investigated.Anoma lies i n the dielectric constant as a function of temperature have been observed near i ts Neltemperature of　～143K，which are indicative of the so-called magnet oelectric coupling between the ferroelectric and antiferromagnetic orders in thi s compound.It is demonstrated that a weak magnetic transition appeared at the te mperature a little below the Nel temperature，which confirms the earlier predi ction from the Monte Carlo simulation in a qualitative sense.The magnetic hyster esis measurement proves that there does exists a weak magnetic order in PFN crys tal below its Nel temperature.
Optical properties of Er3+ in TeO2-based oxyhalide glasses pumped by 977nm
Authors: Lui Yue-Hui  , Chen Dong-Dan  , Hou Zhi-Yuan  , Chen He  , Zhang Qin-Yuan  , Deng Zai-De  , Jiang Zhong-Hong  ,   (1)华南理工大学光通信材料研究所，广州  510640; (2)华南理工大学光通信材料研究所，广州  510640；中国科学院上海光学精密机械研究所，上海  201800
Published: December 2020

We report on fluorescence and upconversion emissions of Er3+-doped TeO2-ZnO-PbCl2 tellurite-based oxyhalide glasses under 977nm laser diode excitation. A strong 153μm emission from 4I13/2→4I15/2 transition with a full width at half maximum of ～69 nm, and three intense infrared -to-visible upconversion emissions at 524, 546 and 668 nm, corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F11/2→4I15/2 transitions of Er3+ ions, respectivel y, have been observed under 977 nm excitation and the mechanisms involved have b een explained. The intensity parameters Ωt (t=2,4,6) of Er3+-doped TeO2-ZnO-PbCl2 oxyhalide glasses have been calculated according to the Judd- Ofelt theory, and the results are Ω2=59×10-20cm2，Ω4=2 1×10-20cm2，and Ω6=12×10-20cm2，respectively. The e mission cross_section has also been calculated from the absorption cross-section and the emission spectrum by using the McCumber theory. The maximum emission cr oss_section is 875×10-21cm2 at 153μm. Our results indicate that Te O2_ZnO_PbCl2 oxyhalide glasses are promising candidates for optical amplifie rs and upconversion lasers in comparison with the glasses such as silicate, phos phate, and fluoride glasses.
The dispersion characteristics of the coaxial arbitrary-shaped-groove periodic slow-wave structure
Authors: Yue Ling-Na  , Wang Wen-Xiang  , Wei Yan-Yu  , Gong Yu-Bin  ,   电子科技大学物理电子学院，成都  610054
Published: December 2020

The dispersion equation of a coaxial arbitrary-shaped-groove slow-wave structure is derived by means of an approximate field-theory analysis，in which the continuous profile of the groove is approximately replaced by a series of recta ngular steps，and the field continuity at the interface of two neighboring step s and the matching conditions at the interface between the groove region and central region are employed.The simulation results by CST MWS are in good agreement with the numerical calculation results of the dispersion equation.We have calculated the dispersion characteristics and the coupling impedance of the slo w-wave structures with some special groove shape.It shows that the dispersion c haracteristic of the triangle-groove structure is the weakest and the coupling i mpedance of it is the least, while the dispersion characteristic of the inverted -trapezoid-groove structure is the strongest and the coupling impedance of it is the largest.
Fabrication of graphite nano-structures
Authors: Liu Shou-Peng  , Zhou Feng  , Jin Ai-Zi  , Yang Hai-Fang  , Ma Yong-Jun  , Li Hui  , Gu Chang-Zhi  , Lü Li  , Jiang Bo  , Zheng Quan-Shui  , Wang Sheng  , Peng Lian-Mao  ,   (1)北京大学电子学系，北京  100871; (2)清华大学力学工程系，北京  100084; (3)中国科学院物理研究所，北京  100080
Published: December 2020

Nano-sized graphite patterns were obtained by tailoring graphite sheets using different methods. With focused ion beam etching we are able to produce grooves of minimum width ～ 30 nm. However, at the edges of the grooves there deposit with Ga-C compound which prevents the easy cleavage of the graphite sheets. With electron beam lithography and reactive ion etching techniques we are able to produce graphite patterns of sizes down to 50 nm. Three different types of masks are tested, and the results are compared and discussed.
Molecular dynamics simulations of various metastable structures on Si(001) at different temperatures
Authors: Wang Chang-Qing  , Jia Yu  , Ma Bing-Xian  , Wang Song-You  , Qin Zhen  , Wang Fei  , Wu Le-Ke  , Li Xin-Jian  ,   (1)复旦大学光科学与工程系，先进光子学材料和器件国家重点实验室，上海  200433; (2)郑州大学物理工程学院，郑州大学材料物理教育部重点实验室，郑州  450052
Published: December 2020

By using Stillinger-Weber potential, we have carried out the constant temperature molecular dynamics simulations of surface structures on Si(001) at different temperatures. Our results show that the dimers rearranged into p(2×1) cell are the primary structure on Si(001) surface. Besides this, trimers and c(2×2) metastable structures as well as two-dangling-bond single atoms are observed on the surface at different temperatures. Up to the surface melting temperature, these metastable structures disappear and the simple p(2×1) structure remains on the surface.
Competition of two terms in exchange Hamiltonian for magnetic substances
Authors: Wang Yong-Zhong  ,   中国科学院金属研究所，沈阳  110016
Published: December 2020

The unjustifiable or mistake in the previous magnetism theories has been pointed out in this paper. For a N-electron system with Heisenberg exchange integral A 1+A2 （A1>0, A2ex=-2A1ii ·sj-2A2ii·sj，not H ex=-2Aii·s j as in the previous magnetism theories, where A=A1+A 2. The role of the mi nor term in the exchange Hamilton was considered. Based on the principle of supe rposition of state, the eigenstate of the system with Heisenberg exchange integr al A=A1+A2 （A1>0, A2 21+A22(A11〉+A2‖2 〉), and t he energy (relative to exchange interaction) eigenvalue E =-Nz（A1-A2）-2NzA 22A1+A2=-Nz（A2-A1）-2NzA21A1+A2,were attained，wh ere z is t he number of the nearest neighbours electrons, 1〉 means the state of the syste m when the spins of all electrons in the system arrange parallelly (the parallel spins state, for simply)，2〉 means the state when the spins of all electrons o r the nearest neighbor electrons in the system arrange antiparallelly (the antip arallel spins state, for simply). When A1 =A2≠0 ，X〉=12( 1〉+2〉)， and E=- NzA1, the system is in the spin glass（SG）state，the probabilities o f paralle l and antiparallel arrange for every pair of spins of electron of nearest neighb ours in the system are equal. When A1≠A２，the probabilit ies are not equal, and there coexist the parallel spins state and SG or the antiparallel spins sta te and SG， X〉=1A21+A22［(A1-A2)1〉+A2(1〉+2〉)］,orX〉=1A21+A22［(A2-A1 )2〉+A1(1〉+2〉)］. When the parallel spins st ate and SG or the antiparallel spins state and SG coexist, the energy of the sys tem is lower than that when only FM or AFM exists as in previous theory. Weiss f erromagnetic state or Neel anti ferromagnetic state is just a special state when A1=0 or A2=0.
Dependence of magnetoelectric properties of La0.8Ba0.2MnO3 on Mn valence of oxide precursors
Authors: Jiang Kuo  , Li He-Fei  , Ma Wen  , Gong Sheng-Kai  ,   北京航空航天大学材料学院，北京  100083
Published: December 2020

The influence of temperature (in the range of 2—390K) on the magnetic moment,and magnetoresistance has been investigated in this paper. It is found that the magnetoelectric properties, particularly the Curie temperature TC, th e metal-insulator transition temperature, Tmi, and the maximum m agnetoresistance TMR, of La0.8Ba0.2MnO 3 are closely related to the valence of Mn in the oxides. La0.８Ba０.2M nO3 synthesize d with 2+ Mn oxides exhibited the lower resistivity, and a Curie temp erature c loser to room temperature (290K) compared with that synthesized with 3+ Mn ox ides. It can be concluded that the magnetoelectric properties of La0.8Ba 0.2MnO3 are dependent on the Mn valence of oxides. This cou ld be attribut ed to the influence of oxygen vacancy concentration variation on the Mn4+ /M n3+ ratio in the resultant compounds during solid sintering react ion, which results from the valence difference of oxide precursors.
Influence of pressure expanding treatment on electret properties of positively corona charged cellular PP films
Authors: Wang Fei-Peng  , Xia Zhong-Fu  , Qiu Xiao-Min  , Lü Hang  , Qiu Xun-Lin  , Shen Jun  ,   同济大学波耳固体物理研究所，200092  上海
Published: December 2020

Pressure expanding treatment is an effective method for improving the piezoelect ric activity of cellular PP films. In this work, the character of trap-level dis tribution for positively corona charged cellular PP films and the influence of t he pressure expanding treatment on its charge stability and charge transportatio n have been studied by means of thermal pulse technique, surface potential decay measurements, SEM and TSD spectrum analyses, etc. The results point out that th ere are three kinds of traps with different energy values in the range of middl e energy level for the cellular PP films, i.e. most of the deep traps and the shallow traps in the bulk, and most of the traps with middle energy values near the free surface. The pressure expanding treatment changes the state of traps a nd also, to a certain extent, reduces the charge storage stability of the cellul ar PP films, but has not impact on its charge transportation rule, in which the slow retrapping effect is dominant.
Laser properties of rotating prism Q-switched Cr3+, Yb3+, Er3+: phosphate glasses
Authors: Liu Zhu-Ping  , Tang Jing-Ping  , Hu Li-Li  , Jiang Zhong-Hong  ,   中国科学院上海光学精密机械研究所,上海  201800
Published: December 2020

The laser properties of Q-switched Cr3+,Yb3+,Er3+:phosphate gl asses have been studied in this work.Rotating prism Q-switched laser at 1.53μm was obtained at room temperature in this erbium glass pumped by flash lamp.The b est laser properties are realized in the glass with 0.5wt% Er2O3 concentrati on.The properties include 14.5mJ threshold energy,9.6mJ maximum laser output and 0.55% slope efficiency.The laser properties of Cr14 was compared with QE-7S pro duced by Kigre under the same experimental condition.It is deduced from experime ntal results that the former has a higher threshold energy,maximum laser output and slope efficiency.
A study of Raman and optical emission spectroscopy on microcrystalline silicon films deposited by VHF-PECVD
Authors: Zhang Xiao-Dan  , Zhao Ying  , Zhu Feng  , Wei Chang-Chun  , Wu Chun-Ya  , Gao Yan-Tao  , Hou Guo-Fu  , Sun Jian  , Geng Xin-Hua  , Xiong Shao-Zhen  ,   南开大学光电子所，天津  300071
Published: December 2020

Structural properties of microcrystalline silicon films deposited by very high f requency plasma_enhanced chemical vapor deposition(VHF_PECVD) and on-line monit or were studied using Raman and optical emission spectroscopy. The results obta ined showed that the discharge power has a modulation function on crystalline volume fraction (χc) of materials. A larger silane concentration means a stronger modulation function. The intensity of SiH* peak can characterize the deposition rate in a certain range, however the higher power indicates the lower deposition rate, and the ratio of intensity Hα* to SiH* peak value reflects the extent of crystallinity which is consistent with the result obtained from Raman measurement. In addition, the ratio of I［Hβ *］／ I［Hα*］ indicates the decrease of electronic temperatur e in hydrogen plasma with the increase of discharge power.
On Mei symmetry of Lagrangian system and Hamiltonian system
Authors: Fang Jian-Hui  , Peng Yong  , Liao Yong-Pan  ,   (1)河西学院物理系，张掖  734000; (2)石油大学(华东)物理科学与技术学院，东营  257061
Published: December 2020

In this paper, the symmetries of Lagrange system and Hamilton system have been studied. It is indicated that two kinds of description of Mei symmetry are equiva lent for Lagrange system ,so only one kind of Mei symmetry can be given; however , they are not equivalent for Hamilton system, so two kinds of Mei symmetry can be given.
Solution of time-dependent harmonic oscillator system using explicit Euler method and discussion of the cyclic initial states
Authors: Zheng Yi  , Yang Xin-E  ,   (1)天津大学理学院，天津  300072; (2)天津大学理学院，天津  300072;南开大学天津大学刘徽应用数学中心，天津  300072
Published: December 2020

The Schrdinger equation of forced timedependent harmonic oscillator is solved by using the explicit Euler method. The result of evolution of the initial state is given, the feasibility and applicability of explicit Euler method are discussed. Using coherent state, the nonadiabatic berry phase and the cyclic initial states of the system are discussed.
Determination of signal-to-background ratio of single molecular photon source based on photon counting statistics
Authors: Wang Xiao-Bo  , Huang Tao  , Shao Jun-Hu  , Jiang Yu-Qiang  , Xiao Lian-Tuan  , Jia Suo-Tang  ,   山西大学物理电子工程学院,量子光学与光量子器件国家重点实验室,太原  030006
Published: December 2020

The real triggered single molecule source is recognized as an ideal single photon source with a Poissonian statistics background. By considering the effect of the triplet state in single molecule energy level, an explicit function is given for the signaltobackgound ratio(SBR) by use of photoncounting statistics. When PRS(1)2PRS(2)-3PRS(2), we present an effici ent method to determine the SBR of the triggered single photons source, which s hows SBR=P2RS(1)/2PRS(2).In addition, the expression of Q, as a function of signaltobackgound ratio, has been obtained. It turns o ut that this method is simpler and gives a greater accuracy than previous proce dures.
Optically stimulated luminescence in SrSO4: Eu phosphors
Authors: Tang Qiang  , Zhang Chun-Xiang  , Leung P. L.  , Mike Li  , Luo Da-Ling  ,   (1)香港城市大学物理及材料科学系; (2)中山大学物理系,广州  510275
Published: December 2020

The optically stimulated luminescence (OSL) of SrSO4:Eu (01mol%) powder samples was studied. The continuous wave OSL and linearly modulated OSL curves measured after irradiation by beta rays of 90Sr in the dose range of 0116—116kGy, illustrate that there are four components in OSL signal and the OSL dose response is linear-sublinear. Thermal stability of OSL signal was also measured, and the results showed that OSL from SrSO4:Eu is quite stable a t temperatures up to ～200℃. Meanwhile, the intensity of OSL signal is stronges t when the read temperature is about 180℃. The thermal luminescence(TL) three-d imensional spectra were measured after gamma rays irradiation (absorbed dose is 100Gy) of 60Co source. The emission wavelength at about 375nm indicate s that the luminescence comes from the transitions between energy levels of Eu 2+.
Fractional Fourier transform of beams in the use of the Wigner distribution function method
Authors: Wu Ping  , Lü Bai-Da  , Chen Tian-Lu  ,   (1)四川大学激光物理与化学研究所,成都  610064; (2)西南交通大学应用物理系,成都  610031
Published: December 2020

By using the Wigner distribution function(WDF)method,the fractional Fourier transform (FRFT) of beams is studied.HermiteGaussian (HG) beams are taken as an example; closedform expressions for the intensity distribution and beam widths of HG beams at the FRFT's plane are derived and changes in the intensity dist ribution of HG beams with the order of the FRFT are illustrated with numerical examples.It is shown that a symmetrical intensity distribution with equal beam width in the x and y directions can be achieved by a suitable choice of the transform order p.
Experimental verification of the characteristic of one-dimensional metamaterials by use of lumped-elements L-C
Authors: Zhang Dong-Ke  , Zhang Ye-Wen  , He Li  , Li Hong-Qiang  , Chen Hong  ,   (1)同济大学波耳固体物理研究所，上海  200092; (2)同济大学波耳固体物理研究所，上海  200092;同济大学电子与信息工程学院，上海  200092; (3)同济大学电子与信息工程学院，上海  200092
Published: December 2020

The metamaterials by use of L_C lumped_elements in the transmission line have the preternatural characteristic,which is different from the conventional dielectrics.We report the experimental results in the left_handed range with anti_parallel phase and group velocities in the metamaterials,with the negative refractive index, and we find the bandgap corresponding to zero averaged refractive index.The configuration offers some significant advantages:it is more compact in si ze,the material parameters can be tuned,and the method of fabrication is easy to carried out.
The colour centre model related to lead vacancy in PbWO4 crystal
Authors: Liu Ting-Yu  , Zhang Qi-Ren  , Zhuang Song-Lin  ,   (1)上海理工大学光学与电子信息工程学院，上海  200093; (2)上海理工大学理学院，上海  200093
Published: December 2020

The local structure geometry around a lead vacancy V2-Pb in PbWO 4 is optimized using a planewave pseudopotential formulation within the fr amework of local density approximation (LDA), with generalized gradient correcti on in the form of Perdew_Wang_91 The results of the lattice relaxation decreas e the electrical negativity on V2-Pb site and increase the elect rical positivity on O2- site near by the V2-Pb. All of the electronic structures around V2-Pb in PWO crystal are studied i n the molecular_cluster model with the framework of the fully relativistic self_ consistent Direc_Slater theory by using a numerically discrete variational (DV_X α) method. By analyzing the electronic structures, we can reasonably believe th at once V2-Pb is formed in PWO crystal, O2- turns to be pr ior to trap holes to compensate the electrical negativity of V2-Pb . Pb2+ may never be the holetrapper compensating V2-Pb , and Pb3+ and Pb4+ in PWO crystal may not actually exist. The possi ble defect micromodel caused by V2-Pb in the asgrown PWO cry stal is that each V2-Pb creates a V＋KV-F aggr egate color center.