Surfactant controlled interfacial alloying in thermally evaporated Cu/Co multilayers

The effect of Ag surfactant on interfacial alloying in nm-range Cu/Co thin film multilayer structures is reported in this work. The multilayer were prepared by electron beam evaporation method with or without using Ag as a surfactant. When multilayers are annealed, the interdiffusion process get suppressed when Ag surfactant is introduced prior to deposition of the multilayer structures. In absence of a surfactant, the asymmetry in the free energy results in formation of a metastable CuCo-alloys. The Ag surfactant balances this difference in the surface free energy, resulting in reduced interdiffusion. The obtained results directly evidence the role of the Ag surfactant in balancing the asymmetry in the surface free energy of Cu and Co in Cu/Co multilayers and thereby controlling interfacial alloying.

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► Cu/Co multilayers were prepared using Ag surfactant.
► Ag surfactant results in smooth and symmetric Cu-on-Co and Co-on-Cu interfaces. Ag surfactant inhibits the interdiffusion across interfaces.
► Intermixed Cu–Co alloys are formed when no surfactant is added.
► By adding Ag surfactant formation intermixed Cu–Co alloys can be prevented. Obtained results can be understood in terms of balance of asymmetry in surface free energy by Ag surfactant.