Thermal stability of Co/SiO2 multilayers for use in the soft x-ray region

The thermal stability of Co/SiO2 multilayers was evaluated. Multilayer samples were deposited on Si substrates by means of the ion beam sputtering method and annealed at temperatures from 100 degrees C to 600 degrees C in a vacuum furnace. For the structural and optical evaluations, small-angle x-ray diffraction measurements, soft x-ray reflectivity measurement in the 1 keV energy region, and transmission electron microscopy observations were carried out. As the results, the Co/SiO2 multilayers annealed up to 400 degrees C maintained the initial multilayer structure, and kept almost the same soft x-ray reflectivity as the as-deposited sample. A deterioration of the multilayer structure caused by the growth of cobalt grains was found on the samples annealed over 500 degrees C, and the soft x-ray reflectivity dropped in accordance with the deterioration of the multilayer structure. (C) 2007 American Institute of Physics.