Surface characterization of multilayer x-ray diffraction specimens

Multilayer specimens of high-Z/low-Z alternating layer stacking have utility as efficient elements for the diffraction and reflection of x rays and ultraviolet radiation. Bielement multilayers of W/C and W/Si, prepared commercially on ultrasmooth substrates, have been characterized by atomic force microscopy (AFM) and by scanning tunneling microscopy to assess the smoothness and nature of the diffraction surface and by transmission electron microscopy to evaluate the uniformity of layering. The diffraction properties of these multilayers have been evaluated by measurements using crystal spectrometers, and by calculations using coherent Bragg diffraction atomic scattering and classical multilayer reflection theory based on stacking uniformity. We have found that the x-ray diffraction performance of W/Si multilayers to be better than W/C multilayers. In addition, the surface of the W/Si specimens were determined by atomic force microscopy to be smoother than W/C and that agreement exists with a roughness factor determined by analytical diffraction theory. The evaluation of multilayers will enhance our understanding of nanostructures, leading to improved diffraction structures.