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Search Results: 1 - 10 of 2900 matches for " Satoshi Yamauchi "
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ZnO Heteroepitaxy on Sapphire Using a Novel Buffer Layer of Titanium Oxide: Crystallographic Behavior  [PDF]
Satoshi Yamauchi, Yoh Imai
Crystal Structure Theory and Applications (CSTA) , 2013, DOI: 10.4236/csta.2013.22006
Abstract: A novel buffer layer consists of titanium oxide grown on a-sapphire by low-pressure chemical vapor deposition using titanum-tetra-iso-propoxide and oxygen gas was used for ZnO epitaxial growth at temperature as low as 340 by plasma-assisted epitaxy using radio-frequency oxygen-gas plasma. XRD and RHEED indicated (0001)Ti2O3 layer in corundum crystal system was epitaxially grown on the substrate in an in-plane relationship of [1-100]Ti2O3// [0001]Al2O3 by uniaxial phase-lock system. Growth behavior of ZnO layer was significantly dependent on the Ti2O3 buffer-layer thickness, for example, dense columnar ZnO-grains were grown on the buffer layer thinner than 10 nm but the hexagonal pyramid-like grains were formed on the thin buffer layers below 2 nm. RHEED observations showed ZnO layer including the pyramid-like grains was epitaxially grown with single-domain on the thin buffer layer of 0.8 nm in the in-plane relationship of [1-100]ZnO//[1-100]Ti2O3//[0001]Al2O3, whereas the multi-domain was included in ZnO layer on the buffer layer above 10 nm.
Plasma-Assisted Chemical Vapor Deposition of TiO2 Thin Films for Highly Hydrophilic Performance  [PDF]
Satoshi Yamauchi, Yoh Imai
Crystal Structure Theory and Applications (CSTA) , 2013, DOI: 10.4236/csta.2013.21001
Abstract: Titanium-oxide layer was grown on glass substrate by plasma-assisted chemical vapor deposition (PCVD) using oxygen gas plasma excited by radio-frequency power at 13.56 MHz in the pressure as low as 3mtorr at relatively low temperature below 400oC, and studied on the crystallographic properties with the hydrophilic behavior comparing to the layer deposited by low-pressure chemical vapor deposition (LPCVD). Raman spectra indicated anatase-phase TiO2 layer without amorphous-phase could be formed above 340oC by simultaneous supply of plasma-cracked and non-cracked titanium-tetra-iso-propoxide (TTIP) used as preliminary precursor. Surface Scanning Electron Microscope images indicated the PCVD-layer consists of distinct nanometer-size plate-like columnar grains, in contrast to rugged micrometer-size grains in the LPCVD-layer. Extremely small water contact angle about 5o in dark and the quick conversion to super-hydrophilicity by UV-irradiation with a light-power density as low as 50 W/cm2 were observed on the PCVD- layer grown at 380oC, while the large initial contact angle was above 40o and the response for the UV-irradiation was gradual on the LPCVD-layer.
ZnO Heteroepitaxy on Sapphire Using a Novel Buffer Layer of Titanium Oxide: Optoelectronic Behavior  [PDF]
Satoshi Yamauchi, Yoh Imai
Crystal Structure Theory and Applications (CSTA) , 2013, DOI: 10.4236/csta.2013.23014
Abstract:

Optoelectronic property of ZnO epitaxial layer grown by plasma-assisted epitaxy at temperature as low as 340°C using Ti2O3 buffer layer on a-sapphire were studied by low temperature photoluminescence at 10 K comparing to the layers on c-sapphire and a-sapphire without the buffer layer. The near band-edge emission consisting of free-exciton emissions and neutral-donor bound exciton emissions was significantly dependent on the buffer thickness and dominated by the free-exciton emissions in the layer grown on the very thin buffer layer about 0.8 nm, whereas the intense emissions by neutral-donor bound excitons were observed in the ZnO layer on c-sapphire. The structural behavior indicated the donor was originated from the three-dimensional growth of ZnO layer and details of the optoelectronic feature suggested the residual donors were Al and interstitial-Zn.

A Pilot Clinical Trial on L-Carnitine Supplementation in Combination with Motivation Training: Effects on Weight Management in Healthy Volunteers  [PDF]
Satoshi Odo, Koji Tanabe, Masamitsu Yamauchi
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.42030
Abstract:

A 4-week low dosage (500 mg/day) L-carnitine supplementation in combination with motivation training was carried out in 24 overweight (BMI 25.8 - 26.6 kg/m2) Japanese males in the course of a double-blind randomized placebo-controlled study. L-carnitine motivated group showed significant body weight loss and a decrement of serum triglyceride level vs. the non-motivated placebo group. Serum adiponectin levels increased in both L-carnitine supplemented groups. The beneficial effects of L-carnitine were amplified by motivation training. For clinical evaluation of supplements, whose efficacy is potentially affected by inter-individual life style variability, supportive motivation training might be advisable for future clinical trials.

Remote-Plasma-Assisted Deposition of Pentacene Layer Using Atomic-Hydrogen  [PDF]
Satoshi Yamauchi, Takatoshi Minakuchi, Miyuki Onodera
Journal of Crystallization Process and Technology (JCPT) , 2014, DOI: 10.4236/jcpt.2014.41002
Abstract:

Pentacene thin layers were deposited on Si with the native oxide at 80°C by remote-plasma-assisted deposition (RPAD) using hydrogen-plasma cell to supply atomic hydrogen radicals. The deposition rate was increased by RPAD comparing to that by non-excited hydrogen gas supply whereas thermal evaporation rate of pentacene from crucible was same in the both process. DFM and XRD studies showed the grain laterally grew in the thin film phase with the size above 10 μm by RPAD. First-principles molecular orbital calculations suggested pentacene is evaporated from crucible as the trimer or larger cluster but atomic hydrogen penetrated into the cluster enhances cracking of pentacene clusters to the monomer.

Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Layer at Room-Temperature  [PDF]
Satoshi Yamauchi, Hiromi Suzuki, Risa Akutsu
Journal of Crystallization Process and Technology (JCPT) , 2014, DOI: 10.4236/jcpt.2014.41003
Abstract:

Plasma-assisted chemical vapor deposition (PCVD) at pressure as low as 3 mtorr using titanium-tetra-isopropoxide (TTIP) and oxygen mixed gas plasma generated by 13.56 MHz radio frequency power (RF-power) below 70 W were applied to deposit titanium-oxide layer at temperature under 40°C. Plasma optical emission spectroscopy and FTIR indicated that density of OH group in the amorphous layer was related to the density of OH or H2O in the plasma and the species was formed on electrode to induce the RF-power. Hydrophilicity on the layer was dependent on the density of chemisorbed OH, but was degraded by the excess OH. The PCVD-TiOx coating was demonstrated on polyethylene terephthalate and showed good hydrophilic property with the contact angle of water about 5°.

Low Pressure Chemical Vapor Deposition of TiO2 Layer in Hydrogen-Ambient  [PDF]
Satoshi Yamauchi, Kazuhiro Ishibashi, Sakura Hatakeyama
Journal of Crystallization Process and Technology (JCPT) , 2014, DOI: 10.4236/jcpt.2014.44023
Abstract: Low pressure chemical vapor deposition (LPCVD) of anatase TiO2 as a reduction gas was demonstrated at pres- sure of 3 mtorr in comparison to that using TTIP and O2 with study for the property of the layers. Dissociation energy of TTIP in H2 was higher than that in O2 but resistivity of the layer deposited in H2 was significantly decreased to 0.2 Ω cm in contrast to the high resistivity beyond 100 Ω cm of the layer deposited in O2. UV-Vis optical transmission spectra showed absorption around 2.2 eV was increased in the layer deposited by TTIP + H2 in addition to decrease of forbidden energy gap due to increase of Urbach tail. Resistivity at low temperature below 100 K indicating the layer deposited in H2-ambient was degenerated by the high electron density but the resistivity was decreased with temperature above 100 K with the activation energy about 100 meV. A possible electronic conduction model based on kernel, grain boundary and surface trap to clarify the temperature dependent resistivity suggesting resistivity of the layer was limited by depletion region in the grain-boundary extended from the surface and the kernel with significantly low resistivity in 10-3 Ω cm order was formed in the layer.
Low Resistive TiO2 Deposition by LPCVD Using TTIP and NbF5 in Hydrogen-Ambient  [PDF]
Satoshi Yamauchi, Kazuhiro Ishibashi, Sakura Hatakeyama
Journal of Crystallization Process and Technology (JCPT) , 2015, DOI: 10.4236/jcpt.2015.51003
Abstract: Low resistive TiO2 layer was deposited by low pressure chemical vapor deposition (LPCVD) at pressure around 0.25 Pa using titanium-tetra-iso-propoxide (TTIP) and NbF5 in H2-ambient. Acti-vation energy for the deposition rate on the temperature was significantly decreased to 120 kJ/mol as compared with 228 kJ/mol for the deposition in H2 without NbF5. The deposition rate linearly increased with NbF5 supply rate but gradually decreased with H2 supply rate indicated that F on the deposition surface acts as catalyst for TTIP-dissociation but is non-activated by hydrogen. Resistivity of the layer was decreased by NbF5 supply depending on the deposition temperature with the activation energy of 319 kJ/mol, whereas the energy was 244 kJ/mol for the layer deposited in H2 without NbF5. The dependence of resistivity on NbF5. and H2 supply rates suggested that the doping should be performed by sufficient NbF5 and H2 supply rate to improve the crystallinity. As a result of the optimization, the resistivity was successfully reduced to 5 × 10-2 Ω·cm. Optical transmission spectra in UV-Vis region indicated that significant absorption observed for the layer deposited in H2 was notably decreased by using NbF5. The improved optical property was better than that for the layer deposited in O2-ambient.
Drastic Resistivity Reduction of CVD-TiO2 Layers by Post-Wet-Treatment in HCl Solution  [PDF]
Satoshi Yamauchi, Kazuhiro Ishibashi, Sakura Hatakeyama
Journal of Crystallization Process and Technology (JCPT) , 2015, DOI: 10.4236/jcpt.2015.51004
Abstract: Poly-crystalline anatase TiO2 layer fabricated by LPCVD using titanium-tetra-iso-propoxide and NbF5 in H2-ambient was treated in conc.-HCl solution after thin layer of IIIb-group metal was deposited on the TiO2 layer. Resistivity of the as-deposited layer about 1 × 10-1 Ω·cm was drastically reduced to 3 × 10-3 Ω·cm by the wet-treatment using indium. Temperature dependence of the resistivity increased with temperature above 100 K for the wet-treated layer was quite different from that decreased above 100 K for the as-deposited layer, whereas the resistivity was saturated at lower temperatures. The resistivity at room-temperature was decreased with the thickness before the wet-treatment but independent on the thickness above 100 nm for the wet-treated layer. Indium was more effective for the resistivity reduction than gallium but aluminum was not useful for the treatment. As the results that the wet-treatment using indium was examined for the TiO2 layers deposited by various conditions, the optimum deposition condition to reduce the resistivity of the layer after the wet-treatment was clearly different from that for the as-deposited layer.
Enhanced Photo-Induced Property of LPCVD-TiO2 Layer on PCVD-TiOx Initial Layer  [PDF]
Satoshi Yamauchi, Keisuke Yamamoto, Sakura Hatakeyama
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.37004
Abstract: Plasma-assisted chemical vapor deposition (PCVD) was applied for amorphous TiOx deposition on Pyrex-glass substrate at low temperature below 90°C to control orientation of anatase-TiO2 layer by low pressure chemical vapor deposition (LPCVD) using TTIP-single precursor. Preferentially <112>-oriented anatase-TiO2 layer was successfully deposited with the orientation ratio as high as 68% on the initial layer of the thickness around 70 nm. Contact angle water was quickly decreased by UV-irradiation on the highly <112>-oriented TiO2 layer comparing with the layer directly deposited on glass, whereas surface roughness on the former was significantly reduced in comparison to that on the latter. Methyleneblue (MB) aqueous solution with the concentration of 2 mmol/L was used to evaluate photocatalytic property on the layer. Rate constant of MB-decomposition via first order kinetics increased with the orientation ratio above 60% was resulted in 2.3 × 10-1?min-1 for the layer with <112>-orientation ratio of 68%, whereas the constant was 2.8 × 10-3 min-1 for the layer directly deposited on glass.
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