Structural phase transition induced by ion irradiation in the equilibrium immiscible Ag–Co system

In the equilibrium immiscible Ag–Co system characterized by a large positive heat of formation (28 kJ/mol), interesting structural phase transitions were observed in Ag–Co multilayered films upon 200-keV xenon-ion irradiation at 300 K within a dose range of 5×1014 to 9×1015 Xe+/cm2. The formation of a new metastable HCP phase and observation of other structural phase transitions upon ion irradiation were quite in accordance with first principles and thermodynamic calculations. It was observed that in the as-deposited Ag–Co multilayered films, the stress from the Co layers resulted in a condensation effect on the Ag lattice, and that after irradiation to a dose of 5×1014 Xe+/cm2, the Ag lattice recovered to its original size along with the hcp Co transforming into its high-temperature-stabilized fcc structure. Besides, the mechanism of the metastable phase formation as well as the observed structural phase transitions induced by ion irradiation is discussed in terms of thermodynamics and growth kinetics.