Transport properties have been studied for a perovskite heterojunction consisting of SrRuO3 (SRO) film epitaxially grown on SrTi0.99Nb0.01O3 (Nb:STO) substrate. The SRO/Nb:STO interface exhibits rectifying current-voltage (I-V ) characteristics agreeing with those of a Schottky junction composed of a deep work-function metal (SRO) and an n-type semiconductor (Nb:STO). A hysteresis appears in the I-V characteristics, where high resistance and low resistance states are induced by reverse and forward bias stresses, respectively. The resistance switching is also triggered by applying short voltage pulses of 1 µs -10 ms duration. 73.40.-c, 73.30.+y, 77.90.+k Recently, reversible resistance switching between two or multilevel resistance states has been found to take place by short voltage pulses at room temperature in capacitor-like devices composed of a wide variety of insulating perovskite oxides such as manganites, 1,2,3 titanates, 4 and zirconates 5 sandwiched between two metallic electrodes. This resistance switching attracts considerable attention due to the potential for device application such as resistance random access memories (RRAM). 6 The origin of resistance switching, however, is still an open question. One of the possibilities is the bulk effect 1,4,5,6 that a phase transition of perovskite takes place between insulating and conducting states, similar to the breakdown of charge-ordered insulating state in manganites induced by electric-field at low temperature. 7,8,9 The other is the interface effect, where voltage pulses reversibly alter the nature of potential barrier formed in the insulating (or semiconducting) perovskite in contact with metallic electrodes. 2,3 We have recently shown that the resistance switching occurs at a Ti/Pr 0.7 Ca 0.3 MnO 3 (PCMO) interface, 3 which exhibits Schottky-like currentvoltage (I-V ) characteristics, where Ti and PCMO can be regarded as a shallow work-function metal and a p-type semiconductor, respectively. A possible origin for the resistance switching is attributed to the change in Schottky barrier height (or width) by trapped charge carriers at the interface states. However, non-epitaxial structure and chemically incompatible materials combination make it difficult to characterize the transport properties and interface electronic structure in detail.In the present study, we have investigated the transport properties of a heteroepitaxial perovskite oxide interface consisting of SrRuO 3 (SRO) deposited on (001) SrTi 0.99 Nb 0.01 O 3 (Nb:STO) single crystal substrate. The SRO/Nb:STO interface exhibits rectifying Schottky-like I-V characteristics with large hysteresis and the resistance can be changed by applying pulsed-voltage stress.Epitaxial SRO thin films (100 nm) were grown on (001) Nb:STO single crystal substrates by a pulse laser deposition technique. Typical growth conditions were a substrate temperature of 700 • C and an oxygen pressure of 100 mTorr. After the deposition, the films were in-site annealed at 400 • C for 30 minutes under an oxygen pressure ...

The theory of quantum transport through a dot under a finite bias voltage is developed using perturbation theory in the Keldysh formalism. It is found that the Kondo resonance splits into double peaks when the voltage exceeds the Kondo temperature, eV > kBTK , which leads to the appearance of a second peak in conductance, in addition to the zero-bias peak. The possible relevance of the new peak to the 0.7 conductance anomaly observed in quantum point contact is discussed.

The magneto-optical (MO) Faraday effect of one-dimensional photonic crystals (1D-PCs) composed of Bi-substituted yttrium–iron–garnet films and dielectric films such as SiO2 and TiO2 films were studied theoretically. Because of considerable localization of light, these media exhibit a very large MO effect. For instance, when the film structure is chosen to be appropriate for supporting the localization of light, the 1D-PC films can possess a huge Faraday rotation angle reaching to −28 deg/μm at λ=1.15 μm. The analysis reveals that the MO characteristics of the 1D-PC films are almost governed by the degree of localization of light, which can be controlled by varying the number of reflection layers in the films.

Two types of one-dimensional photonic crystals composed of magnetic and dielectric materials (magnetophotonic crystals) driven, respectively, by Kerr (reflection) and Faraday (transmission) modes were constructed. Their optical and magneto-optical (MO) properties were studied in detail to confirm our theoretical results showing the large Kerr and Faraday effects of the media originating in the localization of light. For the Kerr-mode operation, films with (SiO2/SiN)×k/Co/(SiN/SiO2)×k (k: number of layers) structures were fabricated, while for the Faraday-mode operation, films with (SiO2/Ta2O5)×k/Bi:DyIG/(Ta2O5/SiO2)×k structures were formed. Excellent agreement between the theoretical and experimental results was obtained, where large enhancement in both Kerr and Faraday rotations appeared originating in the localization of light in the vicinity of the magnetic layers. Since the localized state of light can be controlled artificially, the one-dimensional magnetophotonic crystals will impact for various MO applications.