The interconnection of polarization and phase in electromagnetic scattering process has attracted both fundamental and practical interest.Here we propose the principle and experimental demonstration of a scatteringcon...The interconnection of polarization and phase in electromagnetic scattering process has attracted both fundamental and practical interest.Here we propose the principle and experimental demonstration of a scatteringcontrol mechanism based on the simultaneous control of polarization and phase via a continuously shaped planar metasurface.Under circularly polarized illumination,the scattering is redirected to off-specular direction,leading to significant reduction of the scattering cross section.Theoretical investigation shows that the underlying physical mechanism is the spin-dependent phase modulation in the anisotropic scattering process.Our approach would provide valuable guidance for the full control of electromagnetic wave for diverse applications.展开更多
Seismic safety of underground structures is one of the main concerns in underground space exploitation.As the first step for dynamic seismic response analysis,the free vibration of long large cross-section underground...Seismic safety of underground structures is one of the main concerns in underground space exploitation.As the first step for dynamic seismic response analysis,the free vibration of long large cross-section underground structures is studied in the present paper.The general free transverse vibration motion equation of long large cross-section underground structure is derived with the comprehensive consideration of internal and external damping,effects of shear,cross-sectional rotational inertia and axial force,and a two-parameter soil model.In this way,Timoshenko's beam theory is extended.Two limit cases of free transverse vibration of underground structures are discussed.Parameter study shows that in general wave propagation velocities in structures increase with soil elastic parameters.However the influence of Winkler's parameter k-is significant while the effect of the second soil elastic parameter g-P is insignificant.The free vibration frequency of underground structures increases with relative wave number and soil elastic parameters.Unlike the influence of soil elastic parameters on wave propagation velocities,the influence of soil elastic parameters k-and g-P on the vibration frequency of underground structures have the same order;therefore the influence of the second soil parameter g-P on the free vibration of underground structures should not be neglected in dynamic seismic analysis of underground展开更多
Zn1-xMgxO films are grown on A-sapphire substrates by molecular beam epitaxy, and Mg content in the Zn1-xMgxO films is measured by electron probe microanalysis （EPMA） when the acceleration voltage, the emission curr...Zn1-xMgxO films are grown on A-sapphire substrates by molecular beam epitaxy, and Mg content in the Zn1-xMgxO films is measured by electron probe microanalysis （EPMA） when the acceleration voltage, the emission current, and the magnification are set to be 1 k V, 30 μA and 1000, respectively. The dead time is controlled within 17%-20% during the measurement with the receive angle of characteristic x-ray of 45°. The Mg content of the ZnMgO film is calculated by the low energy calibration and the ZAF calibration. By comparing the measurement result with the theoretical analysis and the EPMA result with the inductively coupled plasma （ICP）, one can obtain that the measured value of Mg content of the samples is in good agreement with the theoretical analysis no matter whether the phase separation exists or not, and the correctness of ICP and EPMA is valid when Mg content in the samples is less than 0.5.展开更多
The transition among multiple charging states of a semiconductor＇s localized intrinsic/impurity defects is considered as phase transitions, and the concept of transition Gibbs free energy level （TGFEL） is proposed....The transition among multiple charging states of a semiconductor＇s localized intrinsic/impurity defects is considered as phase transitions, and the concept of transition Gibbs free energy level （TGFEL） is proposed. Dependence of the cross section of TGFEL on its charge state is discussed. Introduction of TGFEL to replace acti- vation energy has fundamentally important consequences for semiconductor physics and devices. TGFEL involves entropy. What is to be included and not included in the entropy term consistently for all defect levels is an unre- solved open question, related to correct interpretation of various experimental data associated with various defect levels. This work is a first step towards resolving this question.展开更多
The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model ...The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.展开更多
Recently discovered magnetic van der Waals(vdW)materials provide an ideal platform to explore low-dimensional magnetism and spin transport.Its vdW interaction nature opens up unprecedented opportunities to build verti...Recently discovered magnetic van der Waals(vdW)materials provide an ideal platform to explore low-dimensional magnetism and spin transport.Its vdW interaction nature opens up unprecedented opportunities to build vertically stacked heterostructures with novel properties and functionalities.By engineering the planar structure as an alternative degree of freedom,herein we demonstrate an antisymmetric magnetoresistance(MR)in a vdW Fe_(3)GeTe_(2)flake with a step terrace that breaks the planar symmetry.This antisymmetric MR originates from a sign change of the anomalous Hall effect and the continuity of the current transport near the boundary of magnetic domains at the step edge.A repeatable domain wall due to the unsynchronized magnetization switching is responsible for this sign change.Such interpretation is supported by the observation of field-dependent domain switching,and the step thickness,temperature,and magnetic field orientation dependent MR.This work opens up new opportunities to encode magnetic information by controlling the planar domain structures in vdW magnets.展开更多
The widely used deep level transient spectroscopy（DLTS） theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n–p junction. In this w...The widely used deep level transient spectroscopy（DLTS） theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n–p junction. In this work we introduce the concept of effective Fermi level of the steady state of semiconductor, by using which deep level transient spectroscopy depth profiling（DLTSDP） is proposed. Based on the relationship of its transition free energy level（TFEL） and the effective Fermi level, the rules of detectivity of the defect levels are listed. Computer simulation of DLTSDP is presented and compared with experimental data. The experimental DLTS data are compared with what the DLTSDP selection rules predicted. The agreement is satisfactory.展开更多
基金the China Triumph International Engineering Co. Ltd.(CTIEC),Shanghai,China,which offers generous financial support for this work
文摘The interconnection of polarization and phase in electromagnetic scattering process has attracted both fundamental and practical interest.Here we propose the principle and experimental demonstration of a scatteringcontrol mechanism based on the simultaneous control of polarization and phase via a continuously shaped planar metasurface.Under circularly polarized illumination,the scattering is redirected to off-specular direction,leading to significant reduction of the scattering cross section.Theoretical investigation shows that the underlying physical mechanism is the spin-dependent phase modulation in the anisotropic scattering process.Our approach would provide valuable guidance for the full control of electromagnetic wave for diverse applications.
基金Financial support from the Beijing Natural Science Foundation (No. KZ200810016007)the National 973 Key Program (No. 2010CB732003)the National Science Foundation of China(NSFC) (No. 50825403) is gratefully acknowledged
文摘Seismic safety of underground structures is one of the main concerns in underground space exploitation.As the first step for dynamic seismic response analysis,the free vibration of long large cross-section underground structures is studied in the present paper.The general free transverse vibration motion equation of long large cross-section underground structure is derived with the comprehensive consideration of internal and external damping,effects of shear,cross-sectional rotational inertia and axial force,and a two-parameter soil model.In this way,Timoshenko's beam theory is extended.Two limit cases of free transverse vibration of underground structures are discussed.Parameter study shows that in general wave propagation velocities in structures increase with soil elastic parameters.However the influence of Winkler's parameter k-is significant while the effect of the second soil elastic parameter g-P is insignificant.The free vibration frequency of underground structures increases with relative wave number and soil elastic parameters.Unlike the influence of soil elastic parameters on wave propagation velocities,the influence of soil elastic parameters k-and g-P on the vibration frequency of underground structures have the same order;therefore the influence of the second soil parameter g-P on the free vibration of underground structures should not be neglected in dynamic seismic analysis of underground
文摘Zn1-xMgxO films are grown on A-sapphire substrates by molecular beam epitaxy, and Mg content in the Zn1-xMgxO films is measured by electron probe microanalysis （EPMA） when the acceleration voltage, the emission current, and the magnification are set to be 1 k V, 30 μA and 1000, respectively. The dead time is controlled within 17%-20% during the measurement with the receive angle of characteristic x-ray of 45°. The Mg content of the ZnMgO film is calculated by the low energy calibration and the ZAF calibration. By comparing the measurement result with the theoretical analysis and the EPMA result with the inductively coupled plasma （ICP）, one can obtain that the measured value of Mg content of the samples is in good agreement with the theoretical analysis no matter whether the phase separation exists or not, and the correctness of ICP and EPMA is valid when Mg content in the samples is less than 0.5.
基金support from CNBM (China National Building Materials) Group for its partial financial support of the work
文摘The transition among multiple charging states of a semiconductor＇s localized intrinsic/impurity defects is considered as phase transitions, and the concept of transition Gibbs free energy level （TGFEL） is proposed. Dependence of the cross section of TGFEL on its charge state is discussed. Introduction of TGFEL to replace acti- vation energy has fundamentally important consequences for semiconductor physics and devices. TGFEL involves entropy. What is to be included and not included in the entropy term consistently for all defect levels is an unre- solved open question, related to correct interpretation of various experimental data associated with various defect levels. This work is a first step towards resolving this question.
文摘The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.
基金the National Key Research and Development Program of China(No.2017YFA0402902)the National Natural Science Foundation of China(No.1210041089)+1 种基金National Synchrotron Radiation Laboratory(No.KY2060000177),NJUPT-SF(No.NY220163)the US NSF(No.DMR-2005108).
文摘Recently discovered magnetic van der Waals(vdW)materials provide an ideal platform to explore low-dimensional magnetism and spin transport.Its vdW interaction nature opens up unprecedented opportunities to build vertically stacked heterostructures with novel properties and functionalities.By engineering the planar structure as an alternative degree of freedom,herein we demonstrate an antisymmetric magnetoresistance(MR)in a vdW Fe_(3)GeTe_(2)flake with a step terrace that breaks the planar symmetry.This antisymmetric MR originates from a sign change of the anomalous Hall effect and the continuity of the current transport near the boundary of magnetic domains at the step edge.A repeatable domain wall due to the unsynchronized magnetization switching is responsible for this sign change.Such interpretation is supported by the observation of field-dependent domain switching,and the step thickness,temperature,and magnetic field orientation dependent MR.This work opens up new opportunities to encode magnetic information by controlling the planar domain structures in vdW magnets.
基金the China Triumph International Engineering Company (CTIEC), Shanghai, China, which offered generous financial support for this work
文摘The widely used deep level transient spectroscopy（DLTS） theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n–p junction. In this work we introduce the concept of effective Fermi level of the steady state of semiconductor, by using which deep level transient spectroscopy depth profiling（DLTSDP） is proposed. Based on the relationship of its transition free energy level（TFEL） and the effective Fermi level, the rules of detectivity of the defect levels are listed. Computer simulation of DLTSDP is presented and compared with experimental data. The experimental DLTS data are compared with what the DLTSDP selection rules predicted. The agreement is satisfactory.
