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(100) films by helium irradiationYamamoto, Shunya; Nagata, Shinji*; Takeyama, Akinori; Yoshikawa, Masahito
Nuclear Instruments and Methods in Physics Research B, 249(1-2), p.374 - 376, 2006/08
Times Cited Count：8 Percentile：50.31(Instruments & Instrumentation)no abstracts in English
films by RBS/CYamamoto, Shunya; Takeyama, Akinori; Yoshikawa, Masahito
Nuclear Instruments and Methods in Physics Research B, 242(1-2), p.377 - 379, 2006/01
Times Cited Count：9 Percentile：53.56(Instruments & Instrumentation)no abstracts in English
(100) thin films by helium ion implantationYamamoto, Shunya; Nagata, Shinji*; Takeyama, Akinori; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 30(3), p.789 - 792, 2005/09
no abstracts in English
optical spectroscopy of ablation plume for preparations of nanostructured TiO thin films by pulsed laser depositionKitazawa, Shinichi
Japanese Journal of Applied Physics, Part 1, 43(9A), p.6335 - 6341, 2004/09
Times Cited Count：17 Percentile：54.99(Physics, Applied)Nanostructured TiO thin films on 
-AlO
(0001) substrates prepared by pulsed laser deposition (PLD) were analyzed and evaluated in terms of the buffer O gas pressure (0 - 80 Pa) dependencies by optical spectroscopy and surface morphology. Optical emission spectra of the ablation plume from Ti and TiO targets were measured in-situ. The contribution from TiO molecules was observed by narrow-band photometry. The surface morphology was observed by an atomic force microscope (AFM), revealing the pressure dependence of nanostructures. The crystallographic structures of prepared TiO thin films were observed by X-ray diffraction (XRD). The optically observed band-gaps of the prepared thin films show that the crystallographic structures are mixed crystals of rutile and anatase. Evaporated Ti particles combine with buffer O gas thereby producing TiO molecules, which affect the formation of nanostructures on TiO thin films.
/ZnO films by pulsed laser depositionYamamoto, Shunya; Choi, Y.; Umebayashi, Tsutomu; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 29(6), p.2701 - 2704, 2004/00
no abstracts in English
thin filmsKitazawa, Shinichi; Yamamoto, Shunya
Transactions of the Materials Research Society of Japan, 28(4), p.1133 - 1136, 2003/12
The epitaxial growth of high quality TiO films has attracted much interest from the viewpoints of basic science and applications. In the synthesis process of TiO films, the pulsed laser deposition (PLD) method is widely employed because of its advantage for materials with high melting point. The laser irradiation generates plasmas from Ti bulk targets, and the evaporated Ti particles have interactions with buffer dioxide gas before/after the epitaxial growth. We observed the optical emission spectra from the plumes generated by laser ablation in order to improve on the epitaxial growth under proper conditions. The spectra show dependences of energy densities and wavelengths of the laser. The spectra are investigated for relevancies to the quality of films and crystallographic relationships that were assessed by x-ray diffraction, x-ray pole figures and Rutherford backscattering spectroscopy.
under visibel light irradiationUmebayashi, Tsutomu; Asai, Keisuke*; Yamaki, Tetsuya; Yoshikawa, Masahito
Kogyo Zairyo, 51(7), p.34 - 36, 2003/07
no abstracts in English
by ion implantationUmebayashi, Tsutomu; Yamaki, Tetsuya; Yamamoto, Shunya; Tanaka, Shigeru; Asai, Keisuke*
Transactions of the Materials Research Society of Japan, 28(2), p.461 - 464, 2003/06
TiO is promising as a photocatalytic material. However, it is active only under UV light irradiation because of its wide band gap (
3.0 eV). We recently reported that sulfur (S) doping caused the optical absorption edge of TiO to be shifted into the lower energy region. Based on the theoretical analyses using first principles band calculations, mixing of the S 3p states with the valence band was found to contribute to the bandgap narrowing. In this study presented here, S-doped TiO was prepared by ion implantation and subsequent thermal annealing. S
was implanted into the single crystals of rutile TiO with a fluence of 8 
10
ions/cm
. According to the results of RBS/channeling analysis, irradiation damage recovered after the annealing at 600 
C in air. In the annealed crystal, S atoms occupied O sites to form Ti-S bonds, as assessed by XPS.
Umebayashi, Tsutomu; Yamaki, Tetsuya; Yamamoto, Shunya; Miyashita, Atsumi; Tanaka, Shigeru; Sumita, Taishi*; Asai, Keisuke*
Journal of Applied Physics, 93(9), p.5156 - 5160, 2003/05
Times Cited Count：300 Percentile：98.62(Physics, Applied)Sulfur (S)-doped titanium dioxide (TiO) was synthesized by ion implantation and subsequent thermal annealing. Compared to the pure TiO, a photocurrent was observed in the lower energy regions for the S-doped TiO. Based on the theoretical analyses by the first principles band calculations using the full potential linearized augmented plane wave methods within the generalized gradient approximation, the mixing of the S 3p states with the valence band (VB) was found to contribute to the increasing width of the VB. This leads to the bandgap narrowing in the S-doped TiO. Therefore, the photon-to-carrier conversion was induced during irradiation by visible light above 420 nm (
2.9 eV).
Umebayashi, Tsutomu; Yamaki, Tetsuya; Sumita, Taishi*; Yamamoto, Shunya; Tanaka, Shigeru; Asai, Keisuke*
Nuclear Instruments and Methods in Physics Research B, 206, p.264 - 267, 2003/05
Times Cited Count：24 Percentile：81.86(Instruments & Instrumentation)Chromium (Cr) and niobium (Nb) were implanted into single-crystalline titanium dioxide (TiO; rutile). After annealing at 600C for the Cr-implanted sample or at 1000C for the Nb-implanted sample, the radiation damage was recovered. The implanted metals occupied titanium (Ti) sites in TiO to form metal-oxygen bonds. According to the ultraviolet-ray photoelectron spectra, a localized level due to the implanted metals was formed in band gap of both the crystals. This position was close to the VB edge for the Cr-doped TiO, while the Nb-doped TiO had the small peak far from the edge. This is in good agreement with the ab-initio band calculation results. It is considered that the midgap states of Cr- and Nb-doped TiO consist of the Cr t
or Ti t state, respectively.
films by RBS/channelingYamamoto, Shunya; Yamaki, Tetsuya; Naramoto, Hiroshi; Tanaka, Shigeru
Nuclear Instruments and Methods in Physics Research B, 206(1-4), p.268 - 271, 2003/05
Times Cited Count：13 Percentile：64.66(Instruments & Instrumentation)no abstracts in English
Yamaki, Tetsuya; Umebayashi, Tsutomu; Sumita, Taishi*; Yamamoto, Shunya; Maekawa, Masaki; Kawasuso, Atsuo; Ito, Hisayoshi
Nuclear Instruments and Methods in Physics Research B, 206(1-4), p.254 - 258, 2003/05
Times Cited Count：136 Percentile：98.91(Instruments & Instrumentation)Single crystalline titanium dioxide (TiO) rutile were implanted with 200keV F at a nominal fluence of 110
to 110
ions cm
and then thermally annealed in air up to 1200
for 5h. The radiation damage and its recovery during the subsequent annealing were analyzed by Rutherford backscattering spectrometry in channeling geometry and variable-energy positron annihilation spectroscopy. The lattice disorder was completely annealed at 1200 by the diffusion of point defects to the surface acting as a sink. According to the secondary ion mass spectrometry, the F depth profile was shifted to a shallower region along with the damage recovery, finally producing an F-doped layer where the impurity concentration increased steadily towards the surface. The F doping proved to provide a small modification to the conduction-band edge of TiO, as assessed by theoretical band calculations.
Kuratomi, Takashi*; Yamaguchi, Kenji; Yamawaki, Michio*; Bak, T.*; Nowotny, J.*; Rekas, M.*; Sorrell, C. C.*
Solid State Ionics, 154-155, p.223 - 228, 2002/12
Times Cited Count：14 Percentile：57.58(Chemistry, Physical)no abstracts in English
films prepared by pulsed laser depositionYamamoto, Shunya; Sumita, Taishi; Yamaki, Tetsuya; Miyashita, Atsumi; Naramoto, Hiroshi
Journal of Crystal Growth, 237-239(Part1), p.569 - 573, 2002/04
The epitaxial growth of TiO films has attracted much interest from the viewpoints of basic science and applications. In the present study, it is shown that TiO films with anatase or rutile structure can be grown by pulsed laser deposition(PLD) with an ArF excimer laser under the controlled O atmosphere. The TiO films were prepared on the LaAlO, LSAT SrTiO and -AlO single crystal substrates. The epitaxial films were analyzed by RBS and X-ray diffraction for investigating the crystallographic relationships with the substrates. The high quality anatase TiO(001) films have been successfully grown on the LaAlO (001), LSAT (001) and SrTiO (001) substrates at temperatures above 500C. Also the high quality rutile TiO(100) and (001) films were obtained on the -AlO (0001) and (10-10), respectively.The optical properties were characterized by optical absorption measurements. The optical band gaps for anatase and rutile TiO epitaxial films were evaluated to be 3.22 eV and 3.11 eV, respectively.
Aoki, Yasushi; Yamamoto, Shunya; Takeshita, Hidefumi; Naramoto, Hiroshi
Nuclear Instruments and Methods in Physics Research B, 136-138, p.400 - 403, 1998/00
Times Cited Count：7 Percentile：53.8(Instruments & Instrumentation)no abstracts in English
