The initial stages of Pd thin film growth on clean and C- and O-precovered V(100) surfaces at room temperature (RT) and 200°C have been studied by means of scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). In the presence of C and O, the adsorption of Pd atoms in the clean four-fold hollow sites of the V surface is strongly preferred. Upon deposition of Pd in the submonolayer range, it was possible to stabilize single Pd adatoms and small clusters at RT. Annealing such a surface at 200°C leads to the formation of rectangular Pd islands (size approx. 40x40 Å2) and to the compression of the initial C and O adlayer in the areas between the Pd. For higher Pd coverages we found that oxygen acts as an anti-surfactant, shifting the onset of second layer growth dramatically. The reason for the change of the growth mode of Pd on V(100) from Stranski-Krastanov to a Volmer-Weber-type growth in the presence of oxygen can be found in a higher free energy of the film/substrate interface compared to the clean surface.
Corresponding author: P. Varga (varga).
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