| Abstract
| - The low-temperature deposition of Au and Pd atoms on thin SiO2 films grown on Mo(112) has been studiedby scanning tunneling microscopy (STM), infrared reflection absorption spectroscopy, and CO adsorption.On the monolayer films, gold forms three-dimensional nanoparticles at temperatures as low as 10 K and doesnot affect the phonon spectra of the silica films. On the other hand, palladium exhibits structure-dependentbehavior. Pd deposition leads to a red-shift of the phonon frequency of the monolayer and not of the multilayerfilms. The amount of CO that may adsorb on the Pd particles formed on the “O-poor” monolayer films ismuch smaller than that on the “O-rich” films (with an additional O-layer on the Mo surface) and multilayerfilms. These experimental findings have been rationalized on the basis of density functional theory calculationsshowing that the Pd atoms penetrate into the hexagonal rings of the silica network and bind at the SiO2/Mointerface, which in turn depends on the atomic structure of the film. This bonding is very strong on theO-poor films so that Pd is unable to bind CO, while on the O-rich films CO may even pull out the Pd atomsfrom the interface thus promoting aggregation and particle formation. The Pd migration into the film hasbeen directly supported by low-temperature STM images.
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