Kazuya Otsubo 교수

Fabrication of a crystalline ordered thin film based on the porous metal-organic frameworks (MOFs) is one of the practical applications of the future functional nanomaterials. Here, we report the creation of a highly oriented three-dimensional (3-D) porous pillared-layer-type MOF thin film on a metal substrate using a step-by-step approach based on liquid-phase epitaxy. Synchrotron X-ray diffraction (XRD) study clearly indicates that the thin film is crystalline and its orientation is highly con

The electrical resistivity and X-ray oscillation photograph measurements for an MMX-chain complex, Pt2(dtp)4I (dtp = C2H5CS2-), under high pressure were performed. We observed the most stable metallic phase (TMI = 70 K, under 2.2 GPa) in the 1-D purely d-electronic conductors and pressure-induced metal-insulator transition including the structural phase transition at 3.0 GPa.

This paper describes 1.3-mum AlGaInAs multiple-quantum-well semi-insulating buried-heterostructure distributed-feedback lasers for high-speed direct modulation. Combination of large differential gain AlGaInAs quantum wells and semi-insulating buried-heterostructure for reduction of active region achieved 25 and 40 Gb/s direct modulation with the device having the cavity length of 150 mum. The device whose Bragg wavelength is longer than gain peak wavelength showed 25 Gb/s direct modulation chara

Strained quantum well lasers emitting in the 1.2 µm region have been fabricated on In0.22Ga0.78As ternary substrates. The threshold current density of the laser with highly reflective facets is 176 A/cm2 at 20°C. The characteristic temperature (T0) of the device has reached 140 K, which is the highest value ever reported for long-wavelength semiconductor lasers.

Abstract We report the structural design and control of electronic states of a new series of ultrafine metal–organic right square prism‐shaped nanowires. These nanowires have a very small inner diameter of about 2.0 Å, which is larger than hydrogen and similar to xenon atomic diameters. The electronic states of nanowires can be widely controlled by substitution of structural components. Moreover, the platinum homometallic nanowire shows a 100 times higher proton conductivity than a palladium/pla

Metal–organic frameworks (MOFs) have attracted the attention of a variety of researchers because of their structural diversity and designability, and their varied physical properties based on their uniform microporosity. While MOFs are interesting as bulk materials, future applications in functional nanomaterials will require the use of MOFs as thin films, and to achieve this, several thin-film fabrication techniques have been developed. These techniques have provided rational design of a variet

Long-wavelength InGaAs-InAlGaAs strained quantum-well lasers have been fabricated on In/sub 0.22/Ga/sub 0.78/As ternary substrates grown by the Bridgman method. The threshold current density and lasing wavelength at 20/spl deg/C are 245 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 1.226 μm, respectively. The device has lased up to 210/spl deg/C, which is the highest operating temperature ever reported for long-wavelength semicond

Metal-organic frameworks (MOFs), made from various metal nodes and organic linkers, provide diverse research platforms for proton conduction. Here, we report on the superprotonic conduction of a Pt dimer based MOF, [Pt₂(MPC)₄Cl₂Co(DMA)(HDMA)·guest] (H₂MPC, 6-mercaptopyridine-3-carboxylic acid; DMA, dimethylamine). In this framework, a protic dimethylammonium cation (HDMA⁺) is trapped inside a pore through hydrogen bonding with an MPC ligand.

Metal-organic framework (MOF) thin films have recently attracted much attention as a new platform for surface/interface research, where unconventional structural and physical properties emerge. Among the many MOFs as candidates for fabrication of thin films, Hofmann-type MOFs {Fe(pz)[M(CN)₄]} [pz = pyrazine; M = Ni (<b>Nipz</b>), M = Pt (<b>Ptpz</b>)] are attractive, because they undergo spin transitions with concomitant structural changes. Here, we demonstrate the first example of a

Uncooled 25 Gbit/s direct modulation of 1.3 µm DFB lasers is demonstrated. The 150 µm-long semi-insulating buried-heterostructure AlGaInAs quantum-well DFB lasers show clear eye-openings with dynamic extinction ratio of 5 dB up to 70°C. 13 km singlemode-fibre transmission experiments using the devices show low power penalty within 1.3 dB between 25 and 70°C. These characteristics are the first achievement by 1.3 µm directly modulated lasers.

Ladder materials situated in a dimensional crossover region have attracted significant attention because of their unique physical properties, which depend strongly on the number of their constituent legs. Among them, metal–organic halogen-bridged ladder systems are currently of particular interest. These new series of ladder materials are composed of two or four halogen-bridged transition-metal complexes, the so-called MX-chains, as legs that are connected to each other by organic rung units. To

Ladder systems situated in a crossover from one dimensionality to two dimensionalities have been an attractive research target, because the physical properties, which are associated with dimensionality, are strongly dependent on the number of constituent legs. However, control of the intraladder configuration and electronic properties based on the substitution of structural components remain challenging tasks in materials science. On the other hand, structural design using coordination chemistry

The spin-crossover phenomenon in nanomaterials has been the subject of exploratory investigations for stimuli-responsive switching properties at nanoscale. Using variable-temperature Raman spectroscopy, we investigated changes in the temperature-driven spin-transition property of {Fe(py)₂[Pt(CN)₄]} (py = pyridine) induced by a size reduction from a bulk polycrystalline powder to an ultrathin film (crystallite size, 15 nm). When the crystallite size was reduced, the spin-tra