STRUCTURAL STABILITY OF HEAT-TREATED CO C SOFT-X-RAY MULTILAYERS FABRICATED BY DUAL-FACING-TARGET SPUTTERING/

Thermal stability of Co/C multilayers prepared by a dual-facing-target sputtering system was studied. A picture of the thermally induced cha nges in the microstructure was obtained using complementary measuremen t techniques including low-angle and high-angle Xray diffraction, tran smission electron microscopy, Raman spectroscopy and X-ray photoelectr on spectroscopy. It was found that the period expansion, reflectivity change and compound formation, that were observed after annealing are caused by structural changes both in the sublayers and at the interfac es. Below 400 degrees C, the period expansion is mainly caused by the graphitization of the amorphous carbon layers, and a significant incre ase in the reflectivity at grazing incidence was observed. By 500 degr ees C, the crystallization and agglomeration of Co layers induce an en ormous period expansion and a serious decrease in reflectivity. A smal l amount of carbide is found to form at this temperature. Our results imply that new multilayer structures, e.g., compound multilayers will have to be developed for use at high temperatures or under high X-ray incident flux.