Tungsten-beryllium multilayer mirrors for soft x rays

Multilayer structures of tungsten and beryllium were synthesized onto flat silicon single-crystal substrates by the neutral atom beam sputtering technique. Structures of constituent tungsten and beryllium thin films were evaluated. The standard deviation of the interface roughness of the multilayer was estimated to be ~2.5 A. Reflectivities of multilayer mirrors were measured at a grazing incidence of 5.0 degrees . The observed reflectivity of 30% at 1055 eV was in good agreement with the calculated value considering the interface roughness and oxygen contamination for a tungsten-beryllium structure having a period of 77.0 A.