Oxidation of the Ru(0001) surface covered by weakly bound, ultrathin silicate films

Bilayer silicate films grown on metal substrates are weakly bound to the metal surfaces, which allows ambient gas molecules to intercalate the oxide/metal interface. In this work, we studied the interaction of oxygen with Ru(0001) supported ultrathin silicate and aluminosilicate films at elevated O₂ pressures (10^{- 5}-10 mbar) and temperatures (450-923 K). The results show that the silicate films stay essentially intact under these conditions, and oxygen in the film does not exchange with oxygen in the ambient. O₂ molecules readily penetrate the film and dissociate on the underlying Ru surface underneath. The silicate layer does however strongly passivate the Ru surface towards RuO₂(110) oxide formation that readily occurs on bare Ru(0001) under the same conditions. The results indicate considerable spatial effects for oxidation reactions on metal surfaces in the confined space at the interface. Moreover, the aluminosilicate films completely suppress the Ru oxidation, providing some rationale for using crystalline aluminosilicates in anti-corrosion coatings.