Metal or oxide electrodes (Pt, Au, Ag, (La,Sr)CoO 3 ) were deposited on single crystals of 0.02 mol% Nb doped SrTiO 3 by pulsed laser deposition. Current-voltage and capacitance-voltage responses were measured using three-terminal electrode configuration. Under high oxygen partial pressures, clear rectification behaviors were observed. Diffusion model well explained the current vs. voltage relationship with ideality factors close to unity. The barrier height varied reversibly with oxygen partial pressure, and was almost independent of the electrode materials, which suggested that the Fermi level at the interface was pinned by the surface states. The origin of the surface states was discussed in terms of oxygen adsorption or oxidative formation of metal vacancies around the surface. Chemical interaction between the surface and oxygen and resulting cation rearrangement was concluded to play an important role from the long stabilization time on oxygen partial pressure change. The water vapor pressure dependence of the barrier height was also explained by competitive adsorption of oxygen and water.

We have performed density-functional-theory calculations on seven [OOl]Si ,Ge, superlattices grown on substrates with lattice constants ranging from 5.36 to 5.66 A. We find that, with the exception of the L-derived conduction band states, the energies of principal levels vary linearly with the substrate lattice constant. The valence band offset as a function of substrate lattice constant exhibits a discontinuity at the silicon and the germanium lattice constants.

Investigation was made on the interface characteristics between various metal electrodes and SrTiO 3 single crystals at hightemperatures. The interfaces showed the non-linear current-voltage characteristics, which was caused by the Schottky barrier formed at the interface. The estimated Schottky barrier heights were approximately 1.5 eV, which were almost independent of the work function of electrode metal. These results indicated that the barrier formation obeys the diffusion mechanism for the Bardeen limit at high-temperature.