Fumio Komori

Epitaxial Rh-doped SrTiO3 thin film photocathode for water splitting under visible light irradiation

Epitaxial Rh-doped SrTiO3 thin film photocatalysts were fabricated by pulsed laser deposition under various deposition conditions. The oxygen pressure used during film growth was found to affect the valence of the Rh dopant in the Rh:SrTiO3 films, reproducing the known optical absorption behavior of powder samples. Evaporative Rh loss was observed at low growth pressures and high temperatures. Cyclic voltammetry measurements in a K2SO4 solution showed that Rh-doped SrTiO3 is a highly efficient hydrogen-producing photocathode with a characteristic p-type behavior under visible light irradiation.

ln T Dependence of Resistivity in Two-Dimensionally Coupled Fine Particles of Cu

Resistivity measurements were made on the emsemble of Cu fine particles on a quartz plate which are supposed to be coupled two-dimensionally through oxide layers. Particle size was 30 A in diameter. For samples with sheet resistivity at 4.2 K, \(R_{\square}\)(4.2 K), of several \(100{\varOmega}/{\square}\), resistivity was found to vary as R 0 + R 1 In T . On the other hand when \(R_{\square}\)(4.2 K)\({\gtrsim}10\) k\({\varOmega}/{\square}\), \(R_{\square}\) varied exponentially and when \(R_{\square}\)(4.2 K)\({\lesssim}100{\varOmega}/{\square}\), \(R_{\square}\) decreased with decreasing temperature.

The Anti-Localization Effect in Bi Thin Films

Temperature and magnetic field dependence of conductivity in Bi thin films is measured and compared with theories of the localization and the Coulomb interaction between electrons. The anti-localization effect in the case of strong spin-orbit interaction–logarithmic increase of conductivity with decreasing temperature–is found together with the other ln T term due to the interaction effect. From the analysis of the magnetic field dependence the inelastic scattering time is determined to vary as T -1 below 1.5 K and as T -2 above 4 K being consistent with the temperature dependence of conductivity.

Fine Tuning of Metal-Insulator Transition in Al0.3Ga0.7As Using Persistent Photoconductivity

We report experiments on the electrical conductivity of Al 0.3 Ga 0.7 As:Si in the critical region of the metal-insulator transition. The electron concentration is finely controlled in the vicinity of the transition using the persistent photoconductivity effect. The value of the critical exponent turns out to be 1. The metal-insulator transition due to the delocalization effect by the magnetic field is also studied.

Spin-Orbit Interaction and Electronic Conduction in Two-Dimensional Disordered Metals

Systematic change was observed in the magnetic field dependence of conductivity for the Cu films, Cu–Ag films and Cu–Au films while the temperature dependence is commonly written as σ 0 +σ 1 ln T . These features are discussed with theories of localization and the Coulomb interaction in two-dimensional disordered systems. It is shown that the magnetic field dependence is mainly due to the former effect with the spin-orbit interaction and that the temperature dependence is mainly due to the latter.

Robust protection from backscattering in the topological insulator Bi1.5Sb0.5Te1.7Se1.3.

Electron scattering in the topological surface state (TSS) of the topological insulator Bi1.5Sb0.5Te1.7Se1.3 was studied using quasiparticle interference observed by scanning tunneling microscopy. It was found that not only the 180° backscattering but also a wide range of backscattering angles of 100°-180° are effectively prohibited in the TSS. This conclusion was obtained by comparing the observed scattering vectors with the diameters of the constant-energy contours of the TSS, which were measured for both occupied and unoccupied states using time- and angle-resolved photoemission spectroscopy. The robust protection from backscattering in the TSS is good news for applications, but it poses a challenge to the theoretical understanding of the transport in the TSS.

Quantized Conductance through Atomic-sized Iron Contacts at 4.2 K

We studied the conductance of atomic-sized wires of iron made in a scanning tunneling microscope (STM) at 4.2 K. The conductance was measured as a function of the displacement between the iron substrate and the STM tip during the elongation and compression of the wires. The observed conductance curves were quantized, and some of the steps in the conductance curves display hysteresis for repeated displacements. The unit of the quantization is e 2 /h as expected in ferromagnetic materials. A magnetic field of up to 150 mT hardly affects the conductance. These results are discussed in terms of the ballistic transport accompanied with the sudden atomic rearrangements and the continuous deformation around the wires.

Local and Reversible Change of the Reconstruction on Ge(001) Surface between c(4×2) and p(2×2) by Scanning Tunneling Microscopy

The reconstruction on a Ge(001) surface is locally and reversibly changed between c (4×2) and p (2×2) by controlling the bias voltage of a scanning tunneling microscope (STM) at 80 K. It is c (4×2)...

Experimental Study of Electron Localization in a Two-Dimensional Metal

The electrical transport properties of highly resistive films of copper were studied. Logarithmic variations of the conductivity with temperature and magnetic field were observed. Magnetoconductivity was strongly anisotropic. The results are discussed with the recent theories of electron localization in a two dimensional metal.

Spin texture in type-II Weyl semimetal WTe 2

We determine the band structure and spin texture of