Molybdenum-silicon multilayer mirrors for the extreme ultraviolet

Abstract

Multilayer structures of molybdenum and silicon have been synthesized by sputter deposition onto flat silicon single-crystal silicon substrates and spherically ground (0.5- and 22.0-m radii) fused silica substrates and the reflectivities for 170.4-Å (72.8-eV), 160.1-Å (77.4-eV), and 228-Å (54.4-eV) light measured at near normal incidence. Observed peak values ranged from 26.2 to 78%, the highest reflectivities occurring closest to normal incidence. Energy resolutions were ∼10 in all cases. Model calculations were performed using optical constants from the literature and experimentally determined multilayer structural parameters. In all cases the measured reflectivities were equal to or larger (by up to a factor of 2) than the calculated values, a result attributed to uncertainty in the optical constants used in the calculations. Experimental and calculated angular peak positions and energy resolutions were in good agreement. The high reflectivities of these molybdenum-silicon structures will make possible application of traditional optics approaches in the EUV and support new developments including free electron lasers.