利用自制可加磁场样品台对链状位移型磁畴壁的原位洛伦兹电子显微术研究

利用自制的可加磁场样品台,结合离焦洛仑兹电子显微术,原位研究了坡莫合金中的一种链状位移型磁畴壁在磁化和反磁化过程中的变化,并据此提出了相应的样品薄膜面内的磁力线分布模型.     

中温退火对坡莫合金薄膜AMR的影响

制备了纳米级(Ni82Fe18)72．9Nb27．1(3．5nm)／Ni82Fe18(tnm)／Ta(3nm)坡莫合金系列膜，并进行了中温退火(200℃)，测量了退火前后样品的零场电阻率(ρ)，各向异性磁电阻(AMR)和微结构；从实验角度研究了中温退火对ρ和AMR随NiFe厚度(t)变化的影响，并探讨了该影响的微观机制。     

利用MFM研究薄膜厚度对Co60Fe20B20薄膜磁畴结构的影响

本文利用磁力显微镜(MFM)主要研究了由磁控溅射法制备的Co60Fe20B20软磁薄膜的厚度变化(2.5nm～400nm)对薄膜磁畴结构的影响.在室温下观察到垂直各向异性随薄膜厚度的增大而增大.从薄膜的表面形貌像观察到在溅射过程中薄膜温度随薄膜厚度增大而升高.当薄膜厚度小于20nm时,磁畴尺寸随薄膜厚度的增大而增大;当薄膜厚度大于20nm时,磁畴尺寸随薄膜厚度的增大而减小;厚度在20nm附近时,畴壁尺寸达到一个最小值.     

TEM study of the influence of antisite defects on magnetic domain structures in double perovskite Ba2FeMoO6

Magnetic domain structures and crystal structures of double perovskite Ba(2)FeMoO(6) were studied using Lorentz transmission electron microscopy (TEM), dark-field imaging and high-resolution TEM. Two types of magnetic domain structure were observed below the Curie temperature: an ordinary 180 degrees ferromagnetic domain structure and a typical maze-pattern structure. In regions where maze-pattern structures were observed, antiphase boundaries were found by dark-field imaging and high-resolution TEM and develop densely in Fe/Mo-ordering domains, suggesting that Fe/Mo antisite defects affect magnetic domain structures.     

Characterization of the microstructure of Co thin film on silicon substrate by TEM

The microstructure of as-deposited Co thin films on silicon (001) substrate was characterized by TEM using wedge-shaped planar-view samples. Selected area electron diffraction showed that the as deposited Co thin films were composed of Co (α) and that no interfacial reaction took place between Co thin films and the Si substrate. The microstructure of Co thin films annealed at 250°C for 30 min was also investigated by using conventional planar-view samples. The analysis of selected area electron diffraction indicates that Co thin films react entirely with the Si substrate, and a silicide layer forms at the Co/Si interface. Dark field images clearly indicate that the interfacial layer consists of Co₂Si in irregular stripes and CoSi as fine particles but no CoSi₂ forms.     

利用MFM研究薄膜厚度对Co60Fe20820薄膜磁畴结构的影响

本文利用磁力显微镜（MFM）主要研究了由磁控溅射法制备的Co60Fe20B20软磁薄膜的厚度变化（2．5nm-400nm）对薄膜磁畴结构的影响。在室温下观察到垂直各向异性随薄膜厚度的增大而增大。从薄膜的表面形貌像观察到在溅射过程中薄膜温度随薄膜厚度增大而升高。当薄膜厚度小于20nm时，磁畴尺寸随薄膜厚度的增大而增大；当薄膜厚度大于20nm时，磁畴尺寸随薄膜厚度的增大而减小；厚度在20nm附近时，畴壁尺寸达到一个最小值。     

重度污染天气下大气颗粒物PM_(1.0)物理化学特征的透射电子显微镜研究

大气颗粒物样品采自徐州市区2013年12月~2014年1月间重度污染天气。采样期间PM1.0主要由烟尘颗粒、复合酸冷凝颗粒、硫酸盐颗粒、矿物颗粒、金属及金属氧化物颗粒等组成。本文通过透射电子显微镜(TEM)及能谱仪(EDS)给出的大气颗粒物PM1.0高分辨结构信息、颗粒相尺寸及化学相尺寸信息、颗粒相中不同化学相嵌布特征信息等,对组成颗粒相的化学相连生关系进行了比较系统的分析研究。分析数据表明,大气颗粒物PM1.0的颗粒模态转变过程与颗粒物形成过程的相关性较强。异相凝结颗粒中化学相物质结构类型的判别是识别颗粒成因及形成过程的重要因素。     

对向列相液晶反转壁中+1缺陷处挠曲电效应的理论分析

基于Pramoda Kumar等人文章中关于向列相液晶反转壁中+1缺陷处挠曲电效应的实验现象,我们利用Landau-de Gennes理论给出相应的理论分析。当对弱锚定的平行排列向列相液晶盒施加垂直基板的直流电压,在反转壁中的±1缺陷会发生旋转。对于其中的+1缺陷,我们给出了外加电场作用下液晶分子的自由能表达式并通过模拟描述指向矢的方位角和极角的变化情况给出相应的缺陷处电场驱动的结构变化。模拟结果给出的挠曲电效应引起的方位角的变化角度与Pramoda Kumar等人的实验得到的在+1缺陷处消光刷的变化情况是一致的。     

Resonant enhancement of magnetic damping driven by coherent acoustic phonons in thin Co2FeAl film epitaxied on GaAs

The magnetic dynamics of a thin Co₂FeAl film epitaxially grown on GaAs substrate was investigated using the timeresolved magneto-optical Kerr measurement under an out-of-plane external field.The intrinsic magnetic damping constant,which should do not vary with the external magnetic field,exhibits an abnormal huge increase when the precession frequency is tuned to be resonant with that of the coherent longitudinal acoustic phonon in the Co₂FeAl/GaAs heterostructure.The experimental finding is suggested to result from the strong coherent energy transfer from spins to acoustic phonons via magnetoelastic effect under a resonant coupling condition,which leads to a huge energy dissipation of spins and a greatly enhanced magnetic damping in Co₂FeAl.Our experimental findings provide an experimental evidence of spin pumping-like effect driven by propagating acoustic phonons via magnetoelastic effect,suggesting an alternative approach to the possible long-range spin manipulation via coherent acoustic waves.     

热效应对三向侧面泵浦DPL中TEM00模输出功率的影响

以三向侧面泵浦时晶体内泵浦光强分布为基础 ,数值计算了三向侧面泵浦DPL中热效应引起的热致衍射损耗随泵浦功率、腔模束腰半径和泵浦光束腰半径的变化规律。进一步讨论了热效应存在时的泵浦功率、腔模束腰半径和泵浦光束腰半径对TEM0 0 模输出功率的影响。从计算结果看出 ,热致衍射损耗使输出功率明显降低。泵浦功率、腔膜束腰半径和泵浦光束腰半径对输出功率都有不同程度的影响。文中还用小孔光阑选TEM0 0 模 ,进行了输出功率随泵浦功率变化的实验 ,实验结果与数值计算结果非常接近。     

In situ nanoscale refinement by highly controllable etching of the(111) silicon crystal plane and its influence on the enhanced electrical property of a silicon nanowire

Nanoscale refinement on a(100) oriented silicon-on-insulator(SOI) wafer was introduced by using tetra-methyl-ammonium hydroxide(TMAH,25 wt%) anisotropic silicon etchant,with temperature kept at 50℃to achieve precise etching of the(111) crystal plane.Specifically for a silicon nanowire(SiNW) with oxide sidewall protection,the in situ TMAH process enabled effective size reduction in both lateral(2.3 nm/min) and vertical (1.7 nm/min) dimensions.A sub-50 nm SiNW with a length of microns with uniform triangular cross-section was achieved accordingly,yielding enhanced field effect transistor(FET) characteristics in comparison with its 100 nm-wide pre-refining counterpart,which demonstrated the feasibility of this highly controllable refinement process. Detailed examination revealed that the high surface quality ofthe(111) plane,as well as the bulk depletion property should be the causes of this electrical enhancement,which implies the great potential of the as-made cost-effective SiNW FET device in many fields.