多层纳米薄膜结构热物性重构

基于谐波探测技术测量材料导热系数和热扩散系数的基本原理,给出3ω法用于多层纳米薄膜结构热物性实验表征的方法.考虑了层间接触热阻的作用,在频域内定义了热阻抗的概念.理论分析了各层纳米薄膜的导热系数、热扩散系数等热参数对加热膜温度波动影响的敏感性.将敏感系数与实验数据处理相结合,利用三次谐波的实部和虚部分量测量了ZrO2/SiO2增透膜多层膜结构中各层的导热系数和热扩散系数.该方法可用来有效表征其他微纳米结构的热性能.     

电动效应作用下微通道内粒子运动的数值模拟

本文采用有限体积法数值模拟了轴向方波电场和直流电场作用下,具有不同电泳淌度粒子的运动情况.结果表明,在半个方波电场周期内,具有不同电泳淌度的粒子在相同的时间内达到各自的稳定速度,周期变化的方波电场使微粒子在微通道内做往复的运动;在直流电场作用下,两个不同电泳淌度的粒子会在轴向方向上产生位移差.定义从溶液中分离粒子的最短距离与微通道高度的比值为分离效率,数值模拟结果表明,分离效率随横向电场强度和粒子电泳淌度的增加而减小.     

Specific Heat of a Two-Layer Magnetic Superlattice

The specific heats of both a two-layer ferromagnetic superlattice and a two-layer ferrimagnetic one are studied. It is found that the spin quantum numbers, the interlayer and intralayer exchange couplings, the anisotropy, the applied magnetic field, and the temperature all affect the specific heat of these superlattices. For both the ferromagnetic and ferrimagnetic superlattices, the specific heat decreases with increasing the spin quantum number, the absolute value of interlayer exchange coupling, intralayer exchange coupling, and anisotropy, while it increases with increasing temperature at low temperatures. When an applied magnetic field is enhanced, the specific heat decreases in the twolayer ferromagnetic superlattice, while it is almost unchanged in the two-layer ferrimagnetic superlattice at low field range at low temperatures.     

Charge transfer of 1 ML C60/Ag（100）

We have measured the synchrotron radiation photoelectron spectra of monolayer C60on Ag（100）, By calculating the intensity ratios between the LUMO bands and the two deeper bands （HOMO and HOMO- 1）, we estimate the amount of the charges transferred from Ag（100） to C60 within the range of 1 e to 1.8 e. The results dismay the expectation of surface superconductivity and afford a good reference for further studies of the monolayer C60/Ag（100） system.     

Vortex Pinning due to Dynamic Spin-Vortex Interaction in aSuperconductor/Ferromagnet Multilayer

We investigate the mutual interaction between superconductivity and ferromagnetism in a Nb/Ni81 Ee19 multilayer by ac susceptibility measurements. Compared with a pure superconducting Nb film, the critical current density of the multilayer is apparently enhanced in a low magnetic field region but remains nearly the same in high magnetic fields, which indicates that a continuous ferromagnetic layer with in-plane magnetization can produce strong vortex pinning in a low field region. We interpret this unusual vortex-pinning phenomenon as a consequence of dynamic spin vortex interaction which induces a spin rotation following vortex movement. In addition, we propose that this dynamic interaction could be used for spin manipulation via a superconductor.     

Inter-Layer Energy Transfer through Wetting-Layer States in Bi-layer InGaAs/GaAs Quantum-Dot Structures with Thick Barriers

The inter-layer energy transfer in a bi-layer InGaAs/GaAs quantum dot structure with a thick GaAs barrier is studied using temperature-dependent photoluminescence. The abnormal enhancement of the photoluminescence of the QDs in the layer with a larger amount of coverage considering the resonant Forster energy transfer between the at 110K is observed, which can be explained by wetting layer states at elevated temperatures.     

Theoretical Study on Inner Shell Electron Impact Excitation of Lithium

Cross sections for electron impact excitation of lithium from the ground state 1s^22s to the excited states 1s2s^2, 1s2p^2, 1s2snp （n = 2-5）, 1s2sns （n = 3 5）, 1s2pns （n = 3-5）, and 1s2pnp （n = 3-5） are calculated by using a full relativistic distorted wave method. The latest experimental electron energy loss spectra for inner-shell electron excitations of lithium at a given incident electron energy of 2500 eV [Chin. Phys. Lett. 25 （2008）3649] have been reproduced by the present theoretical investigation excellently. At the same time, the structures of electron energy loss spectra of lithium at low incident electron energy are also predicted theoretically, it is found that the electron energy loss spectra in the energy region of 55-57eV show two-peak structures.     

聚合物基纳米复合材料性能及理论研究

对近些年来国内外聚合物／MMT纳米复合材料(polymer montmorillonite nanocomposites,PMN)的研究进行了归纳总结,详细讨论了该类材料结晶、流变和力学性能,阐述了合成过程中的热力学、动力学理论和平均场理论,最后对该类材料的制备方法提出展望。     

A SCREW DISLOCATION IN A THREE-PHASE COMPOSITE CYLINDER MODEL WITH INTERFACIAL RIGID LINES

The problem of the elastic interaction between a screw dislocation and a three-phase circular inclusion with interracial rigid lines （anti-cracks） is investigated. An efficient and concise method for the complex multiply connected region is developed, with which explicit series form solutions of the complex potentials in the matrix, and the interphase layer and inclusion regions are derived. Based on the complex potentials, the image force on the screw dislocation is then calculated by using the Peach-Koehler formula. The equilibrium position of the dislocation is discussed in detail for various rigid line geometries, interphase layer thicknesses and material property combinations. The main results show that the interracial rigid lines exert a significant perturbation effect on the motion of the screw dislocation near the circular inclusion surrounded by an interphase layer.     

一类非线性奇摄动问题的匹配解法

利用匹配渐近展开法,讨论了一类非线性奇摄动问题的解,得出了奇摄动边值问题的零次渐近展开式.