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Author: search.filters.author.Katayama, Mitsuhiro

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    Ultraviolet photoresponse properties of single-walled carbon nanotubes decorated with thickness-controlled ZnO layer by pulsed laser deposition
    (2012-05-01)
    Itabashi, Kenta
    ;
    Tabata, Hiroshi
    ;
    Wongwiriyapan, Winadda
    ;
    Minami, Shinji
    ;
    Matsushita, Kazutoshi
    We fabricated single-walled carbon nanotubes (SWNTs) covered with a thickness-controlled ZnO layer (ZnO-SWNTs) by pulsed laser deposition (PLD) and investigated their UV photoresponse, induced by the photodesorption of oxygen molecules from the ZnO surface. The magnitude of the negative photocurrent and the recovery time were strongly dependent on the thickness and morphology of the ZnO layer, and were highest when the ZnO layer was 3-4nm thick. The observed recovery curves of the negative photocurrent were fitted with double-exponential-function curves, which indicate the coexistence of two types of adsorption sites for oxygen molecules on the ZnO surface. The light intensity dependence of the negative photocurrent was also measured. © 2012 The Japan Society of Applied Physics.
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    Highly stable and sensitive gas sensor based on single-walled carbon nanotubes protected by metal-oxide coating layer
    (2009-09-01)
    Wongwiriyapan, Winadda
    ;
    Inoue, Satoshi
    ;
    Okabayashi, Yusuke
    ;
    Ito, Tatsuya
    ;
    Shimazaki, Ryotaro
    We fabricated a highly stable and sensitive gas sensor based on single-walled carbon nanotubes (SWNTs) protected by metal-oxide coating layer. SWNTs were deliberately decorated with 2-5 nm of oxygen-deficient SiO <inf>x</inf> and AlO<inf>x</inf> by pulsed laser deposition, followed by annealing under Ar/H<inf>2</inf> ambient. Surpassing the as-grown SWNTs, the metal-oxide coated SWNTs showed an excellent sensing stability with a variation of sensor response less than 7-8%. The obtained sensitivity to NO<inf>2</inf> was also improved. Moreover, the relationship between NO<inf>2</inf> concentration and sensor response can be described by the Frumkin-Temkin isotherm. © 2009 The Japan Society of Applied Physics.
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    Adsorption kinetics of NO2 on single-walled carbon nanotube thin-film sensor
    (2008-10-01)
    Wongwiriyapan, Winadda
    ;
    Inoue, Satoshi
    ;
    Honda, Shin ichi
    ;
    Katayama, Mitsuhiro
    The adsorption kinetics of NO<inf>2</inf> on a single-walled carbon nanotube (SWNT) thin-film sensor was investigated. To avoid the influence of ambient air, the adsorption property of SWNTs was explored under high vacuum. By virtue of the suppression of the influence of residual gases and the cleanness of the SWNT surface in vacuum, the SWNTs exhibited high sensitivity with a detection limit of lower than 1 ppb. On the basis of the Langmuir adsorption isotherm, the sticking probability and adsorption energy of NO<inf>2</inf> molecules on SWNTs were experimentally estimated. © 2008 The Japan Society of Applied Physics.
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