Formation of a dodecagonal phase in an equilibrium immiscible Co-Cu system induced by ion irradiation and associated evolution

Abstract

Abnormal structural changes were observed in the equilibrium immiscible Co50Cu50 multilayers induced by 200 keV xenon-ion irradiation at 77 K. First, a dodecagonal quasicrystal phase was formed at an irradiation dose of 1×1015 Xe+ cm-2. Secondly, series of selected diffraction patterns taken later showed that the dodecagonal phase formed evolved to feature a high degree of ordering with increasing ion dose. Moreover, molecular dynamics simulations verified the possibility of formation of a metastable phase in the Co-Cu system. A mechanism possibly responsible for the observed structural changes upon ion irradiation is also discussed.