Thermal stability of Mo/Si multilayers

The thermal stability of Mo/Si multilayers for x-ray mirror applications was investigated by annealing studies at relatively low temperatures for various times. The as-deposited and annealed multilayers were examined using conventional small and large angle x-ray diffraction, normal incidence x-ray reflectance measurements using a synchrotron source, selected area electron diffraction, and high-resolution electron microscopy. The as-deposited structure consists of pure layers of crystalline Mo and amorphous Si separated by thin regions of amorphous Mo-Si. At temperatures between 200--400{degrees}C, the amorphous Mo-Si interlayers grow and hexagonal MoSi{sub 2} forms by a thermally activated process(es), and the bilayer spacing and x-ray reflectivity decrease. A determination of the effective activation energy of the process(es) suggests long-term stability at the mirror operating temperature, although additional low temperature testing is warranted. 11 refs., 5 figs., 2 tabs