Inverse-Perovskite Ba BO (B = Si and Ge) as a High Performance Environmentally Benign Thermoelectric Material with Low Lattice Thermal Conductivity.

High energy-conversion efficiency (ZT) of thermoelectric materials has been achieved in heavy metal chalcogenides, but the use of toxic Pb or Te is an obstacle for wide applications of thermoelectricity. Here, high ZT is demonstrated in toxic-element free Ba BO (B = Si and Ge) with inverse-perovskite structure. The negatively charged B ion contributes to hole transport with long carrier life time, and their highly dispersive bands with multiple valley degeneracy realize both high p-type electronic conductivity and high Seebeck coefficient, resulting in high power factor (PF).

Destabilization of Sn 5s Lone-Pair States of SnO through Dimensional Crossover.

Materials exhibiting unique electronic properties arising from a characteristic crystal structure have physical properties that are sensitive to structural dimensionality. This study involves the destabilization of Sn 5s lone-pair states of SnO films by decreasing their structural dimensionality in the out-of-plane direction. The inherent dispersive band structure of the SnO films remained unchanged between 80 and 11 nm.

Control of Hole Density in Russellite BiWO via Intentional Chemical Doping.

Based on the fundamental design concept of modulating the valence band maximum of oxides and subsequent predictions through computational approaches, several lone-pair -based p-type oxide semiconductors, such as Sn- or Bi-based complex oxides, have been developed. Thus far, the bandgap can be modified via tuning of the chemical composition, whereas the hole density cannot be intentionally controlled because of the poor chemical stability of Sn and/or the formation of oxygen vacancies. The inability to control hole density prohibits the design and realization of emergent electronic devices based on p- and n-type oxide semiconductors.

Design, Synthesis, and Optoelectronic Properties of the High-Purity Phase in Layered N ( = Sr, Ba; = Ti, Zr, Hf) Semiconductors.

We report the synthesis and optoelectronic properties of high phase-purity (>94 mol %) bulk polycrystals of KCoO-type layered nitrides N ( = Sr, Ba; and = Ti, Zr, Hf), which are expected to exhibit unique electron transport properties originating from their natural two-dimensional (2D) electronic structure, but high-purity intrinsic samples have yet been reported. The bulks were synthesized using a solid-state reaction between NH and N precursors with NaN to achieve high N chemical potential during the reaction. The N bulks are n-type semiconductors with optical band gaps of 1.

Characteristic Electronic Structure of SnO Film Showing High Hole Mobility.

Actual knowledge of the intrinsic electronic characteristics of p-type oxide semiconductors should help guide the design of innovative electronic devices. The electronic characteristics of oxide semiconductors in thin-film form potentially differ from those in the bulk form owing to lattice strain. In this Letter, we report on the empirical band structure of stannous oxide (SnO) film, which has been shown to have a higher hole mobility than the theoretically expected values for SnO in the bulk form.

Resonant tunneling driven metal-insulator transition in double quantum-well structures of strongly correlated oxide.

The metal-insulator transition (MIT), a fascinating phenomenon occurring in some strongly correlated materials, is of central interest in modern condensed-matter physics. Controlling the MIT by external stimuli is a key technological goal for applications in future electronic devices. However, the standard control by means of the field effect, which works extremely well for semiconductor transistors, faces severe difficulties when applied to the MIT.

Bipolar Semiconducting Properties in α-SnWO Based on the Characteristic Defect Structure.

Diodes, memories, logic circuits, and most other current information technologies rely on the combined use of p- and n-type semiconductors. Although oxide semiconductors have many technologically attractive functionalities, such as transparency and high dopability to enable their use as conducting films, they typically lack bipolar conductivity. In particular, the absence of p-type semiconducting properties owing to the innate electronic structures of oxides represents a bottleneck for the development of practical devices.

Development of a high-precision XYZ translator and estimation of beam profile of the vacuum ultraviolet and soft X-ray undulator beamline BL-13B at the Photon Factory.

A high-precision XYZ translator was developed for the microanalysis of electronic structures and chemical compositions on material surfaces by electron spectroscopy techniques, such as photoelectron spectroscopy and absorption spectroscopy, utilizing the vacuum ultraviolet and soft X-ray synchrotron radiation at an undulator beamline BL-13B at the Photon Factory. Using the high-precision translator, the profile and size of the undulator beam were estimated. They were found to strongly depend on the photon energy but were less affected by the polarization direction.

Thickness-induced metal to insulator transition in Ru nanosheets probed by photoemission spectroscopy: Effects of disorder and Coulomb interaction.

We investigated the electronic structures of mono- and few-layered Ru nanosheets (N layers (L) with N = 1, ~6, and ~9) on Si substrate by ultra-violet and x-ray photoemission spectroscopies. The spectral density of states (DOS) near E of ~6 L and 1 L is suppressed as it approaches E in contrast to that of ~9 L, which is consistent with the Ru 3 d core-level shift indicating the reduction of the metallic conductivity. A power law g(ε) ∝ |ε - ε| well reproduces the observed spectral DOS of ~6 L and 1 L.

In-gap state generated by La-on-Sr substitutional defects within the bulk of SrTiO.

Local distortion in the conduction pathway has a significant influence on the conducting properties of oxides. The electronic states induced in the band gap of SrTiO3 by La doping were investigated using photoemission spectroscopy (PES) and soft X-ray emission spectroscopy (SXES); moreover, the local distortion in the conduction pathway was examined using extended X-ray absorption fine structure (EXAFS). An itinerant state and a localized state were observed as a metallic state and an in-gap state, respectively, in the PES spectra and as inelastic peaks in the SXES spectra.

Decreased Gray Matter Volume of Right Inferior Parietal Lobule Is Associated With Severity of Mental Disorientation in Patients With Mild Cognitive Impairment.

Mental disorientation in time, space, and with respect to people is common in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). Recently, a high-resolution functional MRI (fMRI) study revealed that the inferior parietal lobule (IPL) and precuneus are important regions related to mental orientation in healthy individuals. We hypothesized that the IPL and/or precuneus are crucial regions for mental disorientation in patients with amnestic MCI (aMCI).

Emergence of Quantum Critical Behavior in Metallic Quantum-Well States of Strongly Correlated Oxides.

Controlling quantum critical phenomena in strongly correlated electron systems, which emerge in the neighborhood of a quantum phase transition, is a major challenge in modern condensed matter physics. Quantum critical phenomena are generated from the delicate balance between long-range order and its quantum fluctuation. So far, the nature of quantum phase transitions has been investigated by changing a limited number of external parameters such as pressure and magnetic field.

Dielectric collapse at the LaAlO/SrTiO (001) heterointerface under applied electric field.

The fascinating interfacial transport properties at the LaAlO/SrTiO heterointerface have led to intense investigations of this oxide system. Exploiting the large dielectric constant of SrTiO at low temperatures, tunability in the interfacial conductivity over a wide range has been demonstrated using a back-gate device geometry. In order to understand the effect of back-gating, it is crucial to assess the interface band structure and its evolution with external bias.

Reversible Changes in Resistance of Perovskite Nickelate NdNiO Thin Films Induced by Fluorine Substitution.

Perovskite nickel oxides are of fundamental as well as technological interest because they show large resistance modulation associated with phase transition as a function of the temperature and chemical composition. Here, the effects of fluorine doping in perovskite nickelate NdNiO epitaxial thin films are investigated through a low-temperature reaction with polyvinylidene fluoride as the fluorine source. The fluorine content in the fluorinated NdNiOF films is controlled with precision by varying the reaction time.

Isotropic Kink and Quasiparticle Excitations in the Three-Dimensional Perovskite Manganite La_{0.6}Sr_{0.4}MnO_{3}.

In order to reveal the many-body interactions in three-dimensional perovskite manganites that show colossal magnetoresistance, we performed an in situ angle-resolved photoemission spectroscopy on La_{0.6}Sr_{0.4}MnO_{3} and investigated the behavior of quasiparticles.

Tuning Band Alignment Using Interface Dipoles at the Pt/Anatase TiO₂ Interface.

The Schottky barrier heights at the Pt/TiO2 (001) junctions are modulated over 0.8 eV by inserting <1 nm of LaAlO3. The large electric field in the LaAlO3 is stabilized by preserving the continuity of in-plane lattice symmetry at the oxide interface.

Controlling band alignments by artificial interface dipoles at perovskite heterointerfaces.

The concept 'the interface is the device' is embodied in a wide variety of interfacial electronic phenomena and associated applications in oxide materials, ranging from catalysts and clean energy systems to emerging multifunctional devices. Many device properties are defined by the band alignment, which is often influenced by interface dipoles. On the other hand, the ability to purposefully create and control interface dipoles is a relatively unexplored degree of freedom for perovskite oxides, which should be particularly effective for such ionic materials.

Enhanced electrical transparency by ultrathin LaAlO3 insertion at oxide metal/semiconductor heterointerfaces.

We demonstrate that the electrical conductivity of metal/semiconductor oxide heterojunctions can be increased over 7 orders of magnitude by inserting an ultrathin layer of LaAlO3. This counterintuitive result, that an interfacial barrier can be driven transparent by inserting a wide-gap insulator, arises from the large internal electric field between the two polar LaAlO3 surfaces. This field modifies the effective band offset in the device, highlighting the ability to design the electrostatic boundary conditions with atomic precision.

Atomically engineered metal-insulator transition at the TiO2/LaAlO3 heterointerface.

We demonstrate that the atomic boundary conditions of simple binary oxides can be used to impart dramatic changes of state. By changing the substrate surface termination of LaAlO3 (001) from AlO2 to LaO, the room-temperature sheet conductance of anatase TiO2 films are increased by over 3 orders of magnitude, transforming the intrinsic insulating state to a high mobility metallic state, while maintaining excellent optical transparency.

Self-energy on the low- to high-energy electronic structure of correlated metal SrVO3.

The correlated electronic structure of SrVO(3) has been investigated by angle-resolved photoemission spectroscopy using in situ prepared thin films. Pronounced features of band renormalization have been observed: a sharp kink ∼60 meV below the Fermi level (E(F)) and a broad so-called "high-energy kink" ∼0.3 eV below E(F) as in the high-T(c) cuprates, although SrVO(3) does not show magnetic fluctuations.

Selective impairment of optic flow perception in amnestic mild cognitive impairment: evidence from event-related potentials.

Alzheimer's disease (AD) patients have visuospatial deficits due to parietal dorsal stream dysfunction. Two distinct dorsal flows have been proposed: the inferior parietal (ventro-dorsal (v-d)) and superior parietal (dorso-dorsal (d-d)) streams. We aimed to elucidate how the two dorsal streams are altered in patients with amnestic mild cognitive impairment (aMCI) and AD.

Campylobacter jejuni DNA-binding protein from starved cells in Guillain-Barré syndrome patients.

Campylobacter jejuni enteritis is frequently associated with an axonal form of Guillain-Barré syndrome (GBS) and C. jejuni DNA-binding protein from starved cells (C-Dps) induces paranodal myelin detachment and axonal degeneration through binding with sulfatide in vivo. Here we investigated the invasion of C-Dps into hosts with C.

Preventive and therapeutic effects of the selective Rho-kinase inhibitor fasudil on experimental autoimmune neuritis.

We studied the effects of fasudil, a selective Rho-kinase inhibitor, on experimental autoimmune neuritis (EAN). Continuous parenteral administration of fasudil prevented the development of EAN induced by P0 peptide 180-199 in Lewis rats while it also reduced EAN severity when administered after disease onset. Immunohistochemical examination disclosed a marked decrease in the amount of inflammatory cell infiltration and attenuation of demyelination and axonal degeneration.