Optical constant determination of thin films is critical to the design of x-ray multilayers. In the x-ray region, surface roughness, interfacial roughness, interdiffusion, volume anisotropies, etc. all act to reduce the reflectance. Reflectance measurements were taken at NIST in Gaithersburg, MD. From these measurements the optical behavior results of a substrate, single films and two film combinations were determined by best fitting the measured reflectance values as a function of the angles of incidence with a functional form based on the theoretical reflectance as a function of the optical constants. By using these new optical constants in a multilayer design, the performance of a multilayer can be predicted.
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