DEVELOPMENT OF A HIGH-PRECISION ELECTRON DENSITY MEASUREMENT TECHNIQUE FOR MULTILAYER FILMS

设计了一种具有晶体单色仪和分析仪的x射线反射仪，用于多层薄膜中电子密度分布的高精度测定。使用不对称通道切割硅单色仪，x射线束强度比传统设计高一个数量级。为了进行数据分析，我们利用基于畸变波玻恩近似的散射理论编写了一套计算机代码，使我们能够从包括全外反射区域在内的大散射角范围内收集的镜面和非镜面漫射散射数据中确定界面粗糙度及其在面内和面外方向上的相关性。该系统已应用于半导体SiGe/Si超晶格层厚度及其变化、界面粗糙度的测定，以及Gd、Co、Gd等磁性多层层和Al/C纳米层的测定。结果表明，表面台阶结构在相邻硅衬底上的复制很大程度上取决于硅层中Ge的合金成分。该系统用于同步加速器x射线共振磁散射实验中磁性多层材料的结构表征。它也被应用于从异常色散x射线反射数据中对Al/C薄膜中电子密度分布的模型独立测定。

An X-ray reflectometer with a crystal monochromator and analyzer has been designed for high-precision determination of electron of density profiles in multilayr films. Use of an asymmetric channel-cut silicon monochromator resulted in an X-ray beam intensity one order of magnetitue greater than in the conventional design. For data analysis a package of computer codes has been prepared using the scattering theory based on the distorted-wave Born approximation, which allows us to determine the interface roughness and its correlations in the in-plane and out-of-plane directions from specular and non-specular diffuse scattering data collected over a large range of scattering angle including the total-external reflection region. The system has bee applied to the determination of layr thicknesses and their variation, interface roughness in semiconductor SiGe/Si superlattices and magnetic multilayrs including Gd Co and Gd layrs, an Al/C nanolayrs. It was found that the replication of surfacestep structure on a vicinal siicon substrate strongly depends on the alloy composition of Ge in the SiGe layr. The system was proved useful in the structure characterization of magnetic multilayrs for X-ray resonant magnetic scattering experiments at synchrotron sources. It was also applied to a model-independent determination of electron density profiles in Al/C films from anomalous dispertion X-ray reflectometry data.