Hokkaido University Collection of Scholarly and Academic Papers
(65.390 recursos)
HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.
Mostrando recursos 1 - 20 de 3.064
1.
Luminescent properties of CdS nanoclusters dispersed in solution—Effects of size and surface termination - Okamura, Masayuki; Ebina, Kojiro; Akimoto, Seiji; Yamazaki, Iwao; Uosaki, Kohei
Steady-state and ultrafast transient luminescent properties of CdS nanoclusters prepared by the Aerosol-OT (AOT)/n-heptane reverse micelle method and those modified with 2-mercaptoethanesulfonate were investigated in heptane and water, respectively. A very short luminescence component (not, vert, similar200 fs) was observed for the first time for CdS nanoclusters dispersed in solution. The luminescence mechanism of CdS nanoclusters is proposed.
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Photoanodic formation of an organic monolayer on a hydrogen-terminated Si(111) surface via Si–C covalent bond using a Grignard reagent and its application for one-step monolayer-patterning - Takakusagi, Satoru; Miyasaka, Toyomitsu; Uosaki, Kohei
Alkyl monolayer (octadecyl) was formed on a hydrogen-terminated Si(1 1 1) (H–Si(1 1 1)) electrode via Si–C covalent bond by photoanodic reaction with C18H37MgCl in THF solution. The formation of the organic monolayer was confirmed by attenuated total reflection (ATR) FT-IR spectroscopy. This process was applied to a one-step patterning of an organic monolayer on a H–Si(1 1 1) by illuminating the H–Si(1 1 1) electrode through photomask in a C18H37MgCl/THF solution at positive potential. The formation of the pattern reflecting the shape of the photomask was confirmed by SEM observations.
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Epitaxial growth of a palladium layer on an Au(100) electrode - Naohara, Hideo; Ye, Shen; Uosaki, Kohei
The electrochemical deposition process of palladium from a PdCl42− complex on an Au(100) substrate was investigated using in situ scanning tunneling microscopy (STM). The reactant, i.e. the PdCl42− complex, was found to adsorb on the Au(100) surface with an ordered structure in the potential region where neither a cathodic nor an anodic current flowed. The electrochemical deposition of palladium on the Au(100) proceeded at potentials more negative than 1.0 V. The electrodeposition of the first palladium layer started not only on the terrace but also on gold islands which were formed as a result of the lifting process of the...
5.
Second harmonic generation study on electrochemical deposition of palladium on a polycrystalline gold electrode - Awatani, Tadashi; Yagi, Ichizo; Noguchi, Hidenori; Uosaki, Kohei
Electrochemical deposition (electrodeposition) and dissolution processes of Pd on a polycrystalline Au electrode surface in HClO4 solution containing PdCl42− were investigated by second harmonic generation (SHG) measurements. Both 1064 nm (near-IR) and 600 nm (visible) excitations were employed to monitor the SHG behavior in situ. Under the near-IR excitation, the resulting SHG signal contained contributions from both the Pd deposit and the adsorbed PdCl42−. On the other hand, the adsorption of the PdCl42− did not affect the SHG signal under the visible excitation. The SHG signal under the visible excitation was resonantly enhanced with the first and second monolayer depositions...
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In situ structural study on underpotential deposition of Ag on Au(111) electrode using surface X-ray scattering technique - Kondo, Toshihiro; Morita, Jun; Okamura, Masayuki; Saito, Toshiya; Uosaki, Kohei
In situ surface X-ray scattering (SXS) measurements were carried out to study the structure of a Ag layer on a Au(111) electrode formed by underpotential deposition (upd) in sulfuric acid solution. Specular rod profiles showed that a monolayer of Ag was formed at a potential between the second and third upd peaks, and a bilayer of Ag was formed at a potential between the third upd peak and bulk deposition. Non-specular rod profiles demonstrated that electrochemically deposited Ag atoms both in the first and second layers were situated at the threefold hollow cubic closest packing (ccp) site of the underlying...
7.
Electrochemical oxidative adsorption and reductive desorption of a self-assembled monolayer of decanethiol on the Au(111) surface in KOH+ethanol solution - Sumi, Takayoshi; Wano, Hiromi; Uosaki, Kohei
The electrochemical characteristics of an Au(111) electrode were investigated in 0.1 M KOH ethanol solutions containing various concentrations of decanethiol. Anodic and cathodic peaks corresponding to the oxidative adsorption and reductive desorption, respectively, of a self-assembled monolayer (SAM) of decanethiol were observed. Both peaks shifted negatively with an increase in the thiol concentration by ca. 57 mV/decade, showing that the redox process is a one-electron process. The adsorbed amount determined from the charge corresponding to the reductive desorption increased with an increase in the decanethiol concentration but never reached the saturated amount as long as the cyclic voltammograms were recorded...
8.
Electron and ion transport through multilayers of Au nanoclusters covered by self-assembled monolayers - Song, Wenbo; Okamura, Masayuki; Kondo, Toshihiro; Uosaki, Kohei
Two types of gold nanoclusters (GNCs), one covered by self-assembled monolayers of mercaptoundecanoic acid (MUA), hexanethiol (C6SH), and ferrocenylhexanethiol (FcC6SH), MHF-GNC, and the other with MUA and C6SH, MH-GNC, were used for the construction of ten GNC layers of two different sequences on an MUA modified Au(1 1 1) surface based on the carboxylate/polycation (poly(allylamine hydrochloride), PAH)/carboxylate electrostatic interaction. MHF-GNC was placed either as the layer closest to the gold electrode, i.e. the first layer, or as the outermost layer with MH-GHC in the other layers. A quasi-reversible redox peak with a constant charge corresponding to the redox reaction of...
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Potential-dependent structure of the interfacial water on the gold electrode - Nihonyanagia, Satoshi; Yea, Shen; Uosaki, Kohei; Dreesen, Laurrent; Humbert, Christphe; Thiry, Paul; Peremans, Andre
Doubly tunable sum frequency generation (SFG) spectra demonstrate that the water molecules at gold/electrolyte interface change their orientation with applied potential. At negative potentials, water molecules in the double layer align with their oxygen atom pointing to the solution. As potential became positive to be close to the potential of zero charge (PZC), the SFG signal decreased, suggesting the OH groups of the water molecule are either in random orientation or parallel to the electrode. As potential became more positive than the PZC, the SFG signal increased again with the oxygen-up orientation as same as in the negative potential region,...
10.
Effects of heat treatment on the composition and semiconductivity of electrochemically deposited CdTe films - Takahashi, Makoto; Uosaki, Kohei; Kita, Hideaki; Suzuki, Yoshikazu
Effects of heat treatments on crystalline diameter, composition, and semiconductivity of CdTe films deposited electrochemically at –0.35 V (vs Ag/AgCl) from an acidic solution containing 1-M CdSO4 and 1-mM TeO2 were studied. As-grown films contained free Te in addition to CdTe. The intensity of x-ray diffraction peaks due to CdTe became stronger by the heat treatment at higher temperatures but x-ray diffraction peak due to metallic Te disappeared at the films annealed above 350 °C in a He atmosphere. The intensity of Auger peaks due to Cd increased and that due to Te decreased by increasing the annealing temperature. The...
11.
Resistivity, carrier concentration, and carrier mobility of electrochemically deposited CdTe films - Takahashi, Makoto; Uosaki, Kohei; Kita, Hideaki; Yamaguchi, Shoji
The electrical type, resistivity, and donor or acceptor concentration of CdTe films deposited electrochemically at various potentials were measured. The carrier mobilities of the films were determined from these results. The deposition potential dependence of the mobility was small and the deposition potential dependence of the resistivity was mainly controlled by the deposition potential dependence of the donor or acceptor concentration. The carrier mobilities were very small compared with those in single crystals due to the scattering of the carriers at grain boundaries. Journal of Applied Physics is copyrighted by The American Institute of Physics.
The electrical type, resistivity, and...
12.
Laser spot scanning in photoelectrochemical systems, relation between spot size and spatial resolution of the photocurrent - Eriksson, S.; Carlsson, P.; Holmström, B.; Uosaki, K.
Laser spot scanning studies of single-crystalline p-InSe in contact with a neutral aqueous solution reveal a dramatic difference in lateral resolution between the material ``as cleaved'' and after platinization by brief dipping in a dilute H2PtCl6 solution. A model is developed to explain these observations, and the resolution is calculated as a function of the diffusion coefficient and the life time of minority carriers, and of the charge transfer rate. The improvement of the resolution is found to be due to the increase of the rate of hydrogen evolution at the illuminated semiconductor by Pt catalyst. The model also provides...
13.
Atomic imaging of an InSe single-crystal surface with atomic force microscope - Uosaki, Kohei; Koinuma, Michio
The atomic force microscope was employed to observed in air the surface atomic structure of InSe, one of III-VI compound semiconductors with layered structures. Atomic arrangements were observed in both n-type and p-type materials. The observed structures are in good agreement with those expected from bulk crystal structures. The atomic images became less clear by repeating the imaging process. Wide area imaging after the imaging of small area clearly showed that a mound was created at the spot previously imaged. Journal of Applied Physics is copyrighted by The American Institute of Physics.
15.
A 50-70 year climatic oscillation over the North Pacific and North America - Minobe, Shoshiro
The chronology of interdecadal climatic regime shifts is examined, using instrumental data over the North Pacific, North America and the tropical oceans, and reconstructed climate records for North America. In the North Pacific and North America, climatic regime shifts around 1890 and in the 1920s with alternating polarities are detected, whose spatial structure is similar to that of the previously-known climatic shifts observed in the 1940s and 1970s. Sea-surface temperatures in the tropical Indian Ocean-maritime continent region exhibit changes corresponding to these four shifts. Spectra obtained by the Multi-Taper-Method suggest that these regime shifts are associated with 50–70 year climate...
16.
Resonance in bidecadal and pentadecadal climate oscillations over the North Pacific : Role in climatic regime shifts - Minobe, Shoshiro
The roles of interdecadal oscillations in climatic regime shifts, which are observed as rapid strength changes in the Aleutian low in winter and spring seasons, have been analyzed. A regime shift results from simultaneous phase reversals between pentadecadal and bidecadal variations, which synchronize with one another at a relative period of three. The pentadecadal variation, which is observed in both winter and spring seasons, provides the basic timescale of regime shifts, while the bidecadal variation, which is observed only in winter, characterizes the rapidity of the shifts. A Monte-Carlo simulation has shown that the simultaneous phase reversals or resonance between...
17.
Slow postseismic recovery of geoid depression formed by the 2004 Sumatra-Andaman Earthquake by mantle water diffusion - Ogawa, Ryoko; Heki, Kosuke
Earthquakes are accompanied with mass redistributions and cause changes in gravity field and shape of geoid, an equipotential surface coincident with the mean sea surface. Such coseismic changes were detected by satellite gravimetry after the 2004 Sumatra-Andaman Earthquake [Han et al., 2006], but little has been known on what happens on geoid after the earthquake. Here we report slow postseismic recovery of coseismic geoid depression from satellite measurements. This cannot be explained with simple afterslip or viscous relaxation of Maxwellian upper mantle. It suggests the relaxation of coseismic dilatation and compression by the diffusion of supercritical H2O abundant in the...
18.
The Nine Morse Generic Tetrahedra - Siersma, Dirk; van Manen, Martijn
There are two types of shapes for a generic triangle-acute and obtuse. These shapes are also distinguished by the (topological) Morse theory of the minimal distance function to the vertices. We can use the same method for a tetrahedron, and we show in this paper that there exist nine generic shapes. These can be described by a Morse poset or by a Gabriel graph. We also report on some computer experiments and compare our classification to another criterion used in computational geometry.
19.
An ab initio molecular dynamics study on the dissociative recombination reaction of HD2O+ + e− - Kayanuma, Megumi; Taketsugu, Tetsuya; Ishii, Keisaku
An ab initio molecular dynamics simulations have been carried out for the dissociative recombination reaction of the deuterium-substituted hydronium cation, HD2O+ + e(-), at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD2O were included explicitly, and non-adiabatic transitions among adiabatic electronic states were taken into account by the Tully's fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% of trajectories, indicating that the release of a light fragment H is...
20.
Characteristic precipitation patterns of El Niño/La Niña in time-variable gravity fields by GRACE - Morishita, Yu; Heki, Kosuke
El Niño and La Niña are known to bring about characteristic patterns of anomalous precipitation in various regions of the world. We extracted temporary and regional gravity changes from monthly gravity fields recovered by the GRACE satellites, and converted them to the changes in surface mass, possibly ground or subsurface water in land area. Such mass changes in the 2006-2007 El Niño and 2005-2006 La Niña episodes agreed well with precipitation anomaly patterns inferred from meteorological records in tens of past such episodes. We further compared them with anomalies of soil moisture numerically simulated by integrating monthly precipitation and evapotranspiration....
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