Evolution of Structure and Phase Composition of Multilayered Co/C Film Composition under Exposure to Temperature

The thermal-induced structural and phase transformations in dc-magnetron deposited Co/C multilayered periodical compositions (MPC) are studied by transmission electron microscopy, x-ray phase analysis, and small angle x-ray diffractometry. High level of periodicity is observed in Co/C MPC with Co thickness 2 nm at temperatures below 300 degrees C and in MPC with Co thickness 7 nm at temperatures below 400 degrees C. This thermal range can be used to control period increase. As shown, 2 nm-thick amorphous cobalt layers at T >= 330 degrees C are crystallized in f.c.c. phase with agglomeration of Co layers. As revealed, the agglomeration of 7 nm-thick Co layer begins after heating above 400 degrees C. Transition of h.c.p. Co to f.c.c. Co takes place after annealing above 500 degrees C. Agglomeration of Co layers proceeds in similar manner in both MPC, and mechanism of MPC damage is independent on initial structural state of Co layers. Textured graphite layers with (0002) planes parallel to the film surface occupy the space vacated during Co agglomeration.