Laminated structure in internally oxidized Ru-Ta coatings

► Laminated Ru-Ta coatings consisted of a cyclical gradient concentration. ► The as-deposited coatings showed a laminated structure with a period of 4-34 nm. ► Internal oxidation of Ru-Ta coatings executed after annealing in 1% O2-Ar atmosphere. ► Oxygen inward diffusion was dominated by lattice diffusion.