Palladium (Pd) films have been grown and characterized in situ by low-energy electron diffraction (LEED) and microscopy in two different regimes: ultrathin films 2-6 monolayers (ML) thick on Ru(0001), and ∼20ML thick films on both Ru(0001) and W(110). The thinner films are grown at elevated temperature (750K) and are lattice matched to the Ru(0001) substrate. The thicker films, deposited at room temperature and annealed to 880 K, have a relaxed in-plane lattice spacing. All the films present an fee stacking sequence as determined by LEED intensity versus energy analysis. In all the films, there is hardly any expansion in the surface-layer interlayer spacing. Two types of twin-related stacking sequences of the Pd layers are found on each substrate. On W(110) the two fee twin types can occur on a single substrate terrace. On Ru(0001) each substrate terrace has a single twin type and the twin boundaries replicate the substrate steps. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

This research was partly supported by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, US Department of Energy under Contract Number DEAC04-94AL85000, by the Spanish Ministry of Science and Technology under Project Numbers MAT2006-13149-C02-02 and MAT2007-66719-C03-02 and by the Research Grants Council of the Hong Kong Special Administrative Region, China (CityU3/CRF/08).

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