Structural and electronic properties of transition-metal(001) interfaces

Electronic and structural properties of transition-metal/(Formula presented)(001) interfaces are studied by first-principles local-density full-potential linearized augmented plane-wave calculations with slab models. Equilibrium interlayer separations between metal overlayers (for the 5d metals Ta, W, Ir, and Pt) and the (Formula presented) substrate are calculated by total-energy determinations. It is found that the preferred adsorption site for metal atoms on the (Formula presented) surface is above the O site and the metal-oxygen distance increases from Ta to Pt while the binding energy decreases. Significant hybridization is found between metal d states and the O 2p-Ti 3d states. The Fermi levels of the metals lie in the gap of (Formula presented) and metal-induced gap states, as suggested by Heineșs theory [Proc. Phys. Soc. London 81, 300 (1962); Surf. Sci. 2, 1 (1964); Phys. Rev. 138, A1689 (1965)], are observed. The Schottky barrier in the interfaces is calculated by the position of (Formula presented) in the gap and the dependence of the barrier height on the metal work function is different from either Schottky and Mottșs or Bardeenșs [Phys. Rev. 71, 717 (1947)] speculation.