Support effects on the atomic structure of ultrathin silica films on metals

We studied the atomic structure of ultrathin silica films on Pt(111) in comparison with the previously studied films on Mo(112) and Ru(0001). The results obtained by scanning tunneling microscopy, photoelectron spectroscopy, and infrared reflection absorption spectroscopy suggest that the metal-oxygen bond strength plays the decisive role in the atomic structure of the silica overlayers on metal substrates. Metals with high oxygen adsorption energy favor the formation of the crystalline monolayer SiO 2.5 films, whereas noble metals form primarily vitreous SiO 2 bilayer films. The metals with intermediate energies may form either of the structures or both coexisting. In the systems studied, the lattice mismatch plays only a minor role.