Interaction of copper with the rhenium$(1 0\bar {1}0)$ surface

Abstract

We have studied the adsorption of copper on the clean Re(101[overline]0) surface between 300 and 900 K by means of low- and medium-energy electron diffraction (LEED and MEED) and temperature-programmed thermal desorption (TPD). The persistence of a (1 × 1) LEED pattern during Cu deposition suggests the formation of pseudomorphic Cu islands. Accordingly, the intensity-voltage behaviour of the (1 × 1) LEED beams can be quantitatively superimposed by the coverage-weighed fractions of the I(V)-curves of uncovered Re areas and of Cu-covered (1 × 1) islands. At a coverage of 1.625 × 10(19) Cu atoms m(-2) dynamical LEED I(V) calculations suggest a full hcp-oriented Cu bilayer (BL). Within this first BL, Cu wets the Re surface completely, while all following layers exhibit remnant roughness due to small Cu nuclei, as confirmed by in situ grazing-incidence MEED experiments. The completion of the first BL coincides with the saturation of a single β TPD state at 1180 K, whilst higher coverages produce an additional zero-order α state, which peaks at 1080 K at 2.6 BL. The energy of desorption rises from 320 kJ mol(-1) at small coverages to ~360 kJ mol(-1) for a bilayer Cu film, pointing to attractive lateral Cu-Cu interactions. An analysis of the leading edge of the multilayer α state yields a desorption energy of ~305 kJ mol(-1), somewhat lower than the sublimation enthalpy of bulk Cu. Our data are discussed and compared with previous results on related systems.