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The growth and morphology of cobalt thin films deposited onto a Re(0001) surface at 300, 400 and 550 K were followed in the coverage range 0 ML Θ T >400 K in that different (2×2) phases form within the first Re–Co bilayer, one within the rhenium substrate surface, the others within the cobalt islands. The (2×2) phases can be associated with Re/Co surface alloys of different stoichiometry, depending on cobalt coverage. As the cobalt coverages exceed two monolayers (ML), genuine but incomplete cobalt layers grow. Within the third and fourth cobalt layer, periodic triangular features with a lattice constant of ~28 A appear in STM, followed by a Moire pattern for Θ >4 ML. Both structures produce an incomplete (10×10) LEED pattern. After growth of the fifth or sixth layer the lattice misfit is overcome, and cobalt essentially grows layer-by-layer in a pseudo Frank–van der Merwe mechanism, the details being strongly temperature-dependent.

The energetics and kinetics of Ag thin film growth on Re(0001) were studied by means of temperature-programmed thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS), and work function change (ΔΦ) measurements. The formation of three individual Ag layers shows up in TDS as three distinct desorption maxima β1–β3 appearing between 950 and 1010 K (β3), between 900 and 960 K(β2), and between 870 and 970 K (β1). Except in the very low coverage (Θ) range, in which the desorption is a first-order process, the Ag desorption follows zero-order kinetics. For the first two layers, activation energy of desorption ( E ∗ des ) is strongly Θ dependent: within the first layer, E ∗ des increases almost linearly with Θ from ≈250 kJ mol−1 at Θ=0.05 to about 290 kJ mol−1, reflecting attractive Ag–Ag interactions. From Θ=0.5 to 0.9, E ∗ des rises by only some 10 kJ mol−1. A similar (but much less pronounced) Θ dependence appears for the second monolayer. A detailed shape analysis of the submonolayer TD spectra reveals a phase equilibrium between Ag condensed in islands and individual, mobile Ag atoms (2D gas phase). In XPS, the absence of any energy shift of the Ag and Re core levels underlines the weakness of chemical Ag–Re interactions. Two Ag layers lower the work function of the Re(0001) surface by about 750 meV, with a shallow minimum near the second monolayer. We discuss our data in conjunction with previous STM and LEED results for the same system and compare this system with other Ag-on-metal systems.

Ag thin films on an Re(0001) surface prepared by vapor deposition at 300, 400 and 600 K were studied by means of low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). At T = 300K, Ag atoms nucleate heterogeneously at every monoatomic Re step edge and diffusion-limited aggregation leads to dendritic Ag islands, which coalesce to a porous film near the monolayer. Still larger coverages result in more densified Ag layers, due to enhanced interlayer mass transport facilitated by low Schwoebel barriers for second-layer Ag islands. At T > 400K Ag atoms nucleate only at every second monoatomic step, indicating a preference for the formation of (111) microfacets and a pronounced mobility of Ag atoms perpendicular to the step edges. Compared to the 300 K situation, even more compact and better ordered layers are formed, resulting in a clear layer-by-layer growth (of Frank-van-der-Merwe type), but with a strongly layer-dependent morphology. Ag grows pseudomorphically in the first layer as indicated by misfit dislocation domains, uniaxially expanded lines of Ag atoms form in the second layer and STM moirestructures (paralled by appropriate LEED superstructures) appear for the third and fourth layer (at T ≥ 400K). In the fifth layer the 4.7% Ag Re lattice misfit is practically accommodated and clear epitaxial growth of Ag(111) crystallites occurs.

Al thin films were deposited at 873 K on a Re(1010) surface and examined by means of low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS), and work function (ΔΦ) measurements. In the submonolayer range (0