In situ reflectance measurements of soft-x-ray/extreme-ultraviolet Mo/Y multilayer mirrors

With a new ultrahigh-vacuum deposition/ref lectometer system, Mo/Y multilayer mirrors were deposited by dc-magnetron sputtering and characterized in situ with synchrotron radiation. The Mo/Y multilayer mirrors, measured before exposure to air, had near-normal-incidence reflectances as high as 46% at wavelengths near 11.4 nm. After several days of exposure these samples typically had a relative reflectance loss of ~10% as a result of oxidation of the top Mo layer. The best Mo/Y multilayers were fabricated with base pressures below the low 10(-9) Torr range and after a bakeout to reduce water vapor in the chamber.