Aging and thermal stability of Mg/SiC and Mg/Y2O3 reflection multilayers in the 25-35 nm region

Reflection measurements in the 25-35 nm region were made for Mg/SiC and Mg/Y2O3 multilayers kept in a low-humidity atmosphere for 4 or 5 years. Aged Mg/SiC multilayers keep their reflectances, and the reflectance value at 31.2 nm is 0.44 at 10(degree) of the normal angle of incidence. Aged Mg/Y2O3 multilayers change reflectance as top layer materials, and the best value at 30.1 nm is 0.40 at 10(degree). Reflection measurements are also made for Mg-based multilayers that are annealed from room temperature to 400 (degree)C at 50 (degree)C intervals. Both multilayers keep their reflectance at annealing temperatures of 200 (degree)C. These results suggest that both Mg-based multilayers can be applied to practical optics.