Growth of ordered titanium oxide films on Ag(100)

Titanium oxide films grown on Ag(100) have been investigated with low-energy electron diffraction, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. As Ti is deposited on Ag(100) at room temperature in an O2 atmosphere at 10−5-10−7 Torr, a disordered TiO2-like film is formed. As the surface is subsequently heated at 600 ∘C, though the composition of the film is nearly unchanged, the film changes into an ordered film with (5×1) periodicity [(5×1) TiO2 film]. On the other hand, as Ti is deposited in O2 at 5.0×10−9-1.0×10−8 Torr, a disordered TiO-like film is formed. As the surface is subsequently heated at 600 ∘C, the composition of the film is nearly unchanged and the film changes into an ordered film with (1×1) periodicity [(1×1) TiO film]. Ultraviolet photoelectron spectroscopy measurements show that the (1×1) TiO film has an electronic state around the Fermi level, and the state is ascribed to a partially filled Ti 3d state which has been theoretically expected to exist in a TiO crystal.