Optical constants of superthin gold films for soft x rays

The optical constants, δ=1−n and k, of superthin gold films have been determined from the reflectance data obtained in the soft x-ray region of 60–900 eV. The gold films were prepared to various thicknesses, d=39–270 Å, by ion-beam sputtering (IBS) and electron-beam evaporation (EB). A plane-parallel slab model with due consideration for the surface and the interfacial roughness was used to analyze the data by least-squares curve fitting. The optical constants derived for the IBS samples definitely show variations in the vicinity of d=100 Å. It is also found that δ of the 201-Å-thick IBS film is smaller by about 7% than that of the 211-Å-thick EB film.