Metal-substituted organic Cd-arachidate multilayers as soft-x-ray mirrors

Multilayers for soft x rays, lambda > 4.5 nm, have been made with Cd arachidate, a metal-substituted fatty acid. The multilayer period is found to be 5.53 nm, double the normal length of a Cd-arachidate molecule. The interfaces have a low roughness value of < 0.3 nm, which does not reduce the long-wavelength reflectance significantly. The soft-x-ray reflectance at 3.0 nm has been measured to be 0.13% for this prototypical multilayer that has 12 bilayers. The theoretical reflectance of these multilayers determined at a wavelength of 10.0 nm, suitable for x-ray lithography, is found to saturate at approximately 43% for approximately 150 bilayers.