High-resolution electron microscopy study of x-ray multilayer structures

Multilayered structures containing thin (1--12 nm) layers of W or Mo, alternating with C or Si, have been prepared to produce thin cross-sectional specimens, and direct structural information on the atomic scale has been obtained using an ultrahigh resolution electron microscope. Layer thickness and flatness have been analyzed: the average layer thickness varies by up to 0.6 nm from the average value, and the flatness of the layers depends on the quality of the substrate surface. The degree of crystallinity and crystal orientation within the layers has also been examined. This information should enable more accurate theoretical models to be proposed for the multilayer materials and their x-ray optical properties. The results for the Mo/Si multilayers suggest a model for their growth when prepared by sputtering