From high temperature phase formation to transition metal substitution in the Fe/Al9Co2(001) system

We report the formation of several complex intermetallics as surface alloys upon the adsorption of Fe on Al9Co2(001) for different dosing conditions. Up to 4 monolayers equivalent (MLE) of Fe deposited on the substrate held at 593 K, the low energy electron diffraction pattern consists of a (2×2)R45° phase with two additional domain types rotated by ±8∘ from it. The scanning tunneling microscopy (STM) measurements show that these three types of domains have the same crystallographic structure. The lattice parameters and structural motifs point towards the formation of the high-temperature Al8Fe5 phase (γ-brass of Zn8Cu5-type structure). For Fe deposition between 593 K and 873 K, we have identified the formation of two phases, tentatively assigned to a ternary disordered Al9(Co,Fe)2 overlayer and to the monoclinic Al13Fe4(100). The stoichiometric evolution of the grown structures have been characterized by angle-resolved x-ray photoelectron spectroscopy measurements. Density functional theory based calculations have been performed to model the Al8Fe5(100)/Al9Co2(001) interface, its structural stability and to simulate the corresponding STM images. [Display omitted] •Epitaxial growth of simple binary to complex metallic alloy phases.•Growth of the high-temperature Al8Fe5 phase as thin film on Al9Co2(001).•Identification of the Al8Fe5(100) surface termination by DFT calculations.•Substrate symmetry operations driving the alternating orientations of domains.•Formation of surface and interface structures of tuneable complexity.