Microstructural evolution of Fe grown on a (001) Cu film and its implication to the elastic anomaly in metallic superlattices.

摘要

A large softening of the shear modulus has been reported in metallic superlattices composed of insoluble bcc/fcc metals. In an attempt to understand this elastic anomaly, we have studied the microstructure of Fe/Cu bilayers as a function of the Fe thickness with transmission electron microscopy (TEM). Analysis of the moire fringes observed in plan-view TEM images revealed that the fcc Fe structure epitaxially grows on the (001) Cu up to a thickness of 2.0 nm. At 2.3 nm. At 2.3 nm, the bcc Fe structure nucleates, accompanying lattice rotation around the growth direction with respect to the underlying fcc structure. As the Fe thickness further increases, the submicron polycrystalline grains formed. Based on these results, the microstructure of the metallic superlattices and its relation to the softening of the shear modulus will be discussed. 22 refs., 2 figs