Surface Investigation Of Au Monolayers On Pd(100)

Details of the growth and of the surface structure of 1, 2, and 3 monolayers of Au on Pd(100) have been investigated by reflection high-energy electron diffraction (RHEED), quantitative low-energy electron diffraction (LEED)-I(V) analysis and density-functional theory calculations (DFT). Despite the 4.7% misfit between Au- and Pd-lattice parameters, no change on the lateral lattice parameter was observed up to a thickness of 10 ML by RHEED, evidencing pseudomorphous growth. Up to 3 ML a (1 x 1) LEED pattern is observed, while at higher coverages a (7 x 1) superstructure is formed. The interlayer distances of the last atomic layers of n-ML-Au/Pd( 100) (n = 1, 2, 3) as determined by quantitative LEED and DFT calculations are compared and show only a reasonable agreement. However, DFT results indicate that surface alloying is energetically favorable, and a better match with the experimentally determined interlayer distances is obtained with surface alloy formation.