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

Thin Cu films were vacuum-deposited onto Re(0001) and investigated by means of temperature-programmed desorption spectroscopy (TDS), X-ray photoelectr on spectroscopy (XPS), low-energy electron diffraction (LEED), and Auger el ectron spectroscopy (AES). TDS (performed with a heating rate of 7.7 K/s) r eveals three (coverage-dependent) Cu binding states beta(3), beta(2), and b eta(1) between 1000 and 1200 K associated with Cu monolayer and multilayer formation, respectively. While the second and multilayer states beta(2) and beta(1) exhibit clear zero-order kinetics, the first monolayer state desor bs with more complicated desorption kinetics due to attractive mutual Cu-Cu interactions. The activation energy for desorption Varies between similar to 200 kJ/mol for vanishing Cu coverage and similar to 320 kJ/mol near the monolayer saturation. Cu grows first pseudomorphically and forms, between 2 and 3 ML, an incomplete (14 x 14) LEED structure (only first- and second-o rder diffraction spots are visible). At larger coverages, the formation of genuine Cu(lll) crystallites is indicated by a Cu(1 x 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 a bsence 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. (C) 1999 Elsevier Science B.V. All rights re served.