X-ray reflection study of layred structures in multilayrs for magnetic recording

我们设计了一台实用的X射线反射仪，测定了各种磁性多层膜的层结构和表面/界面结构。反射计使用双轴衍射仪和非对称硅沟道切割晶体作为单色器，并在双阳极X射线发生器处使用分析器。单色器中使用的非对称Si 111反射提供了比传统设计强三倍的CuK α光束。对于分析仪，可以根据分辨率要求使用机械狭缝和非对称通道切割晶体。软件校正将光子计数的线性范围扩展到5*10^5 cps。X射线源以恒定输出运行，以避免由于旋转阳极上X射线焦点的轻微位移而导致光学设置的偏移。反射计由日立UNIX工作站控制，该工作站允许rheta、2 rheta和rheta-2 rheta扫描探索倒易空间。镜面反射轮廓记录在一个通宵的测量和非镜面漫散射轮廓可以在合理的短时间内测量。开发的数据分析软件使用X射线散射的扭曲波玻恩近似，它允许通过镜面轮廓的最小二乘拟合来确定单个层的厚度和界面粗糙度。该软件还包括例程，以确定内部和界面间的粗糙度结构的相关性，和分形维数，从非镜面反射数据。

Designing a practical X-ray reflectometer, we have determined the layr structures and surface/interface structures in various magnetic multilayrs. The reflectometer uses a two-axis diffractometer and asymmetric silicon channel-cut crystals for the monochromator and analyzer at a rotating-anode X-ray generator. The asymmetric Si 111 reflection used in the monochromatorprovides a three times more intense CuK alpha beam than the conventional design. For the analyzer a mechanical slit and an asymmetric channel-cut crystal can be used depending on the resolution requirement. The software correction extended the linear range of photon counting to 5*10^5 cps. The X-ray source is run at a constant output to avoid the shift of the optics setting due to the slight displacement of the X-ray focus on the rotating anode. The reflectometer is controlled by a HITACHI UNIX workstation, which allows rheta, 2rheta and rheta-2rheta scans exploring reciprocal space. Specular reflection profiles are recorded in an overnight measurement and non-specular diffuse scattering profiles can be measured in reasonably short time. The data analysis software developed uses the distorted-wave Born approximation of X-ray scattering, which allows the thickness and interface roughness of individual layrs tp be determined by least-squares fit of specular profiles. The software also includes routines to determine the intra and inter-interface correlations of the roughness structures, and the fractal dimension, from nonspecular data.