The interaction of copper with a rhenium(0001) surface: structure, energetics, and growth modes

Abstract

Thin Cu films were vacuum-deposited onto Re(0001) and investigated by means of temperature-programmed desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). TDS (performed with a heating rate of 7.7K/s) reveals three (coverage-dependent) Cu binding states β3, β2, and β1 between 1000 and 1200K associated with Cu monolayer and multilayer formation, respectively. While the second and multilayer states β2 and β1 exhibit clear zero-order kinetics, the first monolayer state desorbs with more complicated desorption kinetics due to attractive mutual Cu–Cu interactions. The activation energy for desorption varies between ∼200kJ/mol for vanishing Cu coverage and ∼320kJ/mol near the monolayer saturation. Cu grows first pseudomorphically and forms, between 2 and 3ML, an incomplete (14×14) LEED structure (only first- and second-order diffraction spots are visible). At larger coverages, the formation of genuine Cu(111) crystallites is indicated by a Cu(1×1) LEED pattern. AES and XPS suggest an incomplete Stranski–Krastanov growth mode, since the Re signals remain visible even after deposition of 12 nominal Cu layers. The absence of any Cu and Re core level shifts in XPS (to within the resolution of our instrument) points to a negligible chemical interaction between the two elements at the interface.