Formation and structure of Fe/Cu(001) interfaces, sandwiches, and superlattices

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Abstract
We have used medium- and high-energy Auger-electron diffraction and low-energy electron diffraction to probe the structure of the Fe/Cu(001) interface, the Cu/Fe/Cu(001) sandwich, and the Fe/Cu/Fe/Cu(001) superlattice. Metastable epitaxial fcc overlayers of Fe with good structural quality grow on room-temperature Cu(001) for coverages up to five monolayers (ML). Above 5 ML, the structural quality of the overlayer diminishes. The first monolayer of Fe does not adsorb uniformly, but rather forms two-layer deep clusters. Above 1 ML, the film coalesces into a well-ordered fcc overlayer. When the substrate temperature is held at 125 °C or higher during evaporation, Fe atoms in-diffuse and displace Cu atoms at lattice sites. The fcc Fe overlayer formed at room temperature also acts as an excellent template for subsequent Cu overlayer growth. We show that Cu depositions on 8-ML Fe/Cu(001) adsorb uniformly (no clustering) and form a fcc film with the same level of structural quality as the substrate. Further Fe depositions on the Cu overlayer maintain an fcc structure, illustrating the feasibility of generating Fe/Cu superlattices in which ultrathin layers of metastable fcc Fe can be sandwiched between Cu layers of any thickness.