【作者】 李锐鹏；

【导师】 潘国强；

【作者基本信息】 中国科学技术大学 ， 同步辐射及应用， 2008， 博士

【摘要】 X射线衍射是重要的结构表征手段。依托国家同步辐射实验室X射线衍射与散射实验站和康奈尔高能同步辐射光源（CHESS）的D-Line,发展了多种衍射和散射技术手段,包括掠入射衍射（GID）、非对称衍射、微束小角散射（μSAXS）和微束掠入射广角散射（μGIWAXS）,对ZnO、SiC半导体薄膜和PI-b-PEO/resol薄膜、P3HT微米线高分子材料进行了结构探测,得到一系列的结构信息。最后还对Fe、Co等铁磁薄膜的磁圆二色（MCD）效应进行了探讨。主要研究工作如下:1.国家同步辐射实验室X射线衍射与散射光束线站建设参与建设了国家同步辐射实验室X射线衍射与散射光束线站,介绍了合肥光源和XRDS光束线的参数、设备、设计指标和实际性能,对光束线上的主要器件聚焦镜和单色器做了详细说明,并发展了其在材料学上的主要应用,包括Si/C多层膜的X射线反射、Si标准样品的粉末衍射、弛豫铁电体的散射和聚合物单晶结构测定等。2.多种X射线衍射手段表征ZnO和SiC半导体薄膜。利用掠入射衍射和非对称衍射方法系统地研究了ZnO和SiC半导体薄膜。ZnO薄膜使用脉冲激光沉积（PLD）方法制备,掠入射衍射分析对比了在Si衬底上有无SiC缓冲层的ZnO薄膜的晶格驰豫和界面结构;对不同衬底温度和氧气氛浓度的一系列ZnO/Al₂O₃薄膜的界面品格结构做对比并得到了最优化的制备条件;非对称衍射分析对比ZnO/Al₂O₃薄膜和ZnO/SiC薄膜的晶体取向,计算得到了ZnO薄膜tilt和twist取向差之间的关系和不同薄膜体系的螺旋位错和线位错密度;还利用CCD面探测器进行掠入射衍射实验,分析在不同衬底温度上生长的ZnO/Si（111）薄膜的取向性和晶体质量。SiC薄膜使用分子束外延（MBE）方法制备,掠入射衍射研究了SiC同质外延膜的层间界面结构,得到了三层结构模型:研究了SiC/Si异质外延薄膜的的晶格驰豫和界面结构;利用非对称衍射分析SiC/Si薄膜的晶体取向信息,对比得到薄膜tilt和twist取向差之间的关系。3.微束X射线对高分子材料的散射研究。在CHESS、D-line,利用单次反射毛细管获得了高通量(约1×10¹⁰photons/s)、低发散度（小于2mrad）的微束光斑（约15μm）,分辨率可以达到50nm,并详细介绍了微束光斑的特性和调试方法。对于PI-b-PEO/resol薄膜样品,进行微束小角散射（μSAXS）实验,发现其含有两种结构不同尺寸不一的晶粒,得到了两种晶粒的尺寸、结构、取向和结晶度等结构信息。对于P3HT微米线样品进行了微束掠入射广角散射（μGIWAXS）实验,建立了微米线内部结构模型,分析得到了微米线中表面附近、介面附近和样品中心的P3HT取向,得到微米线宽度,并第一次观察到沿着表面分布的不同取向的P3HT排列。4.纳米铁磁薄膜中MCD效应的初步研究在同步辐射实验室软X射线磁圆二色实验站,我们得到了能量范围100～1000 eV的单色软X射线,分辨本领为1V,通量超过10⁸photons/s。可以有效的对导体半导体薄膜进行XMCD测量。我们研究了Fe/MgO和Co/Au两个纳米铁磁薄膜体系的MCD效应。对于Fe/MgO薄膜,利用XMCD实验技术得到铁原子的自旋磁矩和轨道磁矩分别是0.069μ_B和2.33μ_B。为考察铁膜沿膜的面内磁各向异性,在入射角为600的情况下选择[110]、[100]、[010]三个方向测量铁的XMCD吸收谱,发现双轴磁各向异性与单轴磁各向异性叠加在一起,使得轨道磁矩在不同晶向上具有不同的原子磁矩。磁晶各向异性能和单轴各向异性能基本相同。对于Co/Au薄膜,研究了Si衬底上沉积的不同厚度的Co膜的轨道磁矩和自旋磁矩。薄膜厚度分别是2nm、10nm和30nm的样品得到的轨道磁矩和自旋磁矩分别在0.249～0.195μB和1.230～1.734μB之间。随着膜厚的减小,Co原子的轨道磁矩增加,而自旋磁矩下降。轨道磁矩与总磁矩的比值由0.101上升至0.168。随着薄膜厚度减小,轨道磁矩对总磁矩的贡献显著增加。更多还原

【Abstract】 X-ray diffraction is one of the most important methods for structure analysis. Based on the X-Ray Diffraction and Scattering（XRDS） Station in National Synchrotron Laboratory（NSRL） in Hefei, China and D-line in Cornell High Energy Synchrotron Source（CHESS）, several techniques of diffraction were developed, including of Grazing Incidence Diffraction（GID）, Asymmetric Diffraction, Micro-beam Small Angle X-ray Scattering（μSAXS）, and Micro-beam Grazing3 Incidence Wide Angle X-ray Scattering（μGIWAXS）. And some thin films were investigated, including of ZnO, SiC thin films as semiconductor material and PI-b-PEO/resol complex, P3HT micron-wire as polymer material. At last, X-ray Magnetic Circular Dichroism （XMCD） was employed on Fe and Co nano ferromagnetic thin films. The main works are shown below.1. Building up of the beamline and station of XRDS in NSRLI was involved in the construction of the beamline and station, which were described here on the construction, facilities and performance. The focusing mirror and monochromter as the important facilities in the beamline were introduced detailed. Many new applications were developed in material science, including of the X-ray Reflectivity on the Si/C multilayer, the powder diffraction on the standard Si sample, the scattering from quasiperiodic structures in relaxor ferroelectrics, the structure of single crystal in insoluble coordination polymer and so on.2. Investigations of the ZnO and SiC thin films by multi diffractionsThe ZnO and SiC semiconductor thin films were investigated by GID and asymmetric diffraction. ZnO films, made in several series by Pulsed Laser Deposition （PLD）, were investigated by GID for the lattice relaxation and interface structure in different depth. One series are the ZnO/Si with and without the SiC buffer layer, the other series are the ZnO/Al₂O₃ made in different temperatures and oxygen concentrations to look for the film with the best quality. The asymmetric diffraction was used to show the difference of orientations and density of screw and edge dislocations between the ZnO/Al₂O₃ and ZnO/SiC films. The correlation between the tilt and twist mosaics were also shown. Besides, the CCD detector was join into the GID and the different orientation and crystal quality were shown in a series of ZnO/Si（111） films with different temperatures. For the SiC films made in Molecular Beam Epitaxy （MBE）, the GID was employed in the homoexpitaxy films to obtain the three layer structure model in the interface. Also, lattice relaxation and interface structure in different depth were shown in hereoepitaxy SiC/Si films. At last, the results from the asymmetric diffraction indicated the orientation of the SiC/Si film and the correlation between the tilt and twist mosaics.3. Investigations of the polymer material by the microbeamIn the D-line, CHESS, the single-bounced capillary was used to obtain the micron-sized beam （about 15μm） with the high flux (about 1×10¹⁰photons/s), low divergence （lower than 2 mrad） and 50nm resolution. The character of the microbeam was shown after the introduction of the line-up process. The PI-b-PEO/resol complex was characterized by the Microbeam Small Angle X-ray Scattering （μSAXS） and there are two kinds of grains with different size and structure. The details of the structure are obtained, including of the size, lattice, orientation and crystalline degree. For the P3HT microwire, the Microbeam Grazing Incidence Wide Angle X-ray Scattering （μGIWAXS） was employed to construct the structure model and distinguish the difference of orientations in the surface region, interface region and center region. The width of the microwire was shown from the beam scan and the orientation changing of the P3HT packing following with the round surface in the surface region was observed in the first time.4. XMCD effect in the nano-ferromagnetic thin filmsOn the X-ray Magnetic Circular Dichroism （XMCD） station in NSRL, the soft X-ray was obtained with the energy range of 100-1000eV, resolution of 1000 in 1000eV and high flux （more than 10⁸photons/s）, and used in the conductor and semiconductor thin films. We investigated the XMCD effect in the Fe/MgO and Co/Au nano-ferromagnetic thin films. For the Fe/MgO film, the spin and orbital magnetic moments of the iron atoms were 0.069μ_B and 2.33μ_B, respectively. Compared with the different orbital magnetic moments in three orientations, [110], [100] and [010], the magnetic anisotropy on the surface is shown as the two-axis and one-axis anisotropic energy roughly equally. The series of the Co/Au films with different thickness are shown with magnetic moments. With the decrease of the 30nm, 10nm and 2nm thickness, the orbital magnetic moments are increased in the range of 0.195--0.249μ_B as the spin magnetic moments decreased in the range of 1.734--1.230μ_B. It means the ratio of the orbital and total magnetic moments are increased remarkably from 0.101 to 0.168.更多还原