Tuning the electronic structure of ultrathin crystalline silica films on Ru(0001)

A combination of density functional theory calculations and photoelectron spectroscopy provides new insights into the atomistic picture of ultrathin silica films grown on Ru(0001). The silica film features a double-layer silicate sheet formed by corner-sharing [SiO4] tetrahedra and is weakly bound to the Ru(0001) substrate. This allows oxygen atoms to reversibly adsorb directly on the metal surface underneath the silica film. We demonstrate that the amount of adsorbed oxygen can be reversibly varied by vacuum annealing and oxidation, which in turn result in gradual changes of the silica/Ru electronic states. This finding opens the possibility for tuning the electronic properties of oxide/metal systems without altering the thickness or the structure of an oxide overlayer.