Development of Mo/Si multilayer for soft X-ray mirror with high heat stability

Mo/Si multilayers inserted with silicon oxide layers have been deposited by the ion beam sputtering method for the purpose of improving the heat stability of the Mo/Si multilayer. Multilayer samples were annealed at temperatures up to 600degC in the vacuum furnace for one hour. We have shown that Mo/Si multilayers inserted with SiO2 layers are thermally more stable than the conventional Mo/Si multilayer. The Mo/Si/SiO2 multilayer shows a relatively high soft X-ray reflectivity and keeps almost the same reflectivity as the as-deposited one after annealing at 400degC. The Mo/SiO2/Si/SiO2 multilayer is a promising system at temperatures over 500degC, because the small angle X-ray diffraction measurement has shown that the periodic structure of the Mo/SiO2/Si/SiO2 multilayer is hardly affected by annealing. (author)