Thin Pd films on SrTiO3 (001) substrates:: ab initio local-density-functional theory

The interface structure and energetic stability of Pd films adsorbed on SrTiO3 substrates is investigated by means of ab initio electronic-structure calculations based on the local-density-functional theory. For the Pd films, (002), mono-, bi- and tri-layers are considered, and (002) half-layers as approximants for the adsorption of single Pd atoms. For the SrTiO3 substrates with (001) surface orientation, the two possible surface terminations, with TiO2 and SrO composition, are discriminated. It is found that Pd atoms preferably adsorb on top of O atoms of the substrate. With increasing thickness of the adsorbed film, the TiO2 termination of the substrate is energetically advantageous for the film adsorption, and the structure of the surface atoms quickly becomes similar to the bulk crystal structure. The properties of the tri-layer film are already close to the ones of a coherent, atomically abrupt interface between bulk Pd and SrTiO3 crystals.