High Resolution Electron Microscope Imaging and Quantification of Interface Structure in X-Ray Multilayers,

Abstract : We discuss the applications and limits of high resolution electron microscopy (HREM) to quantifying atomic-scale structure in X-Ray mirror multilayer (XMM) structures. It is shown how detailed processing of HREM images can yield quantitative measurements of interface planarity and diffuseness, which are critical parameters in determining the reflectivity of XMM structures. Application of HREM to the study of atomic-scale interface structure is established in a wide range of materials systems. For many classes of structures, including XMMs, absolutely abrupt, planar interfaces are desired. Deviations from ideality of such interfaces may be defined-in terms of the interface roughness, delta R and interface diffuseness, delta D. In Figure 1 we illustrate a simple model which defines interface structure in terms of these concepts, and which is amenable to measurement by HREM (2). The interface normal is along the z direction and lies between two materials A and B. The reference position of the interface is arbitrarily-defined as the limit of pure material A.