Membrane structure characterization using variable-period x-ray standing waves.
Membrane structure characterization using variable-period x-ray standing waves.
复制标题
使用可变周期 X 射线驻波表征膜结构。
DOI：
10.1016/s0006-3495(98)77901-9
复制
发表时间：
1998
影响因子：
3.4
通讯作者：
Caffrey,M
中科院分区：
文献类型：
--
作者：
Zhang,R;Itri,R;Caffrey,M
变周期X射线驻波（XSW）技术正在成为研究膜结构的一个强有力的工具。然而，当该方法用于表征厚度dL <100 μ m的膜时，出现了两个显著的问题。首先，支撑反射镜的表面粗糙度σr与膜中的标记原子分布的固有半宽σin卷积，并且有助于在XSW实验中测量的表观半宽σ。在这里，我们展示了后两项是如何定量相关的[σin=（σ2−σr2）1/2]，使得粗糙的反射镜产生更大的标记原子分布宽度σ，以及如何在XSW测量中确定所需的量σ in。第二，当标记原子层的平均位置，λ z λ，接近膜的一个或两个边界时，其分布函数在边界处被截断。在这种情况下，我们说明了为什么标记原子分布应表示在其第一和第二时刻。我们还通过对实际样品的数值模拟证明了物理参数σr、σ、λ z和dL如何影响X射线反射率和荧光产额分布，以帮助解释它们。
The variable-period x-ray standing wave (XSW) technique is emerging as a powerful tool for studying membrane structure. However, two significant problems arise when the method is used to characterize membranes of thicknessdL<100Å. First, the surface roughness,σr, of the supporting reflecting mirror convolutes with the intrinsic half-width of the marker atom distribution in the membrane,σin, and contributes to an apparent half-width,σ, which is measured in the XSW experiment. Here we show how the latter terms are related quantitatively [σin=(σ2−σr2)1/2], such that rough mirrors give rise to larger marker atom distribution widths,σ, and how the required quantityσincan be determined in the XSW measurement. Second, when the mean position of the marker atom layer, 〈z〉, is close to one or both boundaries of the membrane, its distribution function is truncated at the boundary. In such cases, we show why marker atom distribution should be expressed in terms of its first and second moments. We also demonstrate by numerical simulations of realistic samples how the physical parameters,σr,σ, 〈z〉, anddL, affect x-ray reflectivity and fluorescence yield profiles as an aid in their interpretation.