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Proceedings Paper

Fabrication, characterization, and gas sensing properties of three-dimensional network of ZnO tetrapods
Author(s): Jean-Jacques Delaunay; Naoki Kakoiyama; Ichiro Yamada
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Paper Abstract

We fabricated ZnO nanostructures via a thermal oxidation reaction in air from Zn pellets placed in an open quartz tube heated in a furnace. The reaction started at a temperature of about 900°C and consumed the Zn pellets very rapidly. The fabrication process employed did not rely on metal catalysts. The nanostructures obtained were in the form of powder and thick layers deposited on quartz substrates. X-ray diffraction analysis showed that the crystal structure of the obtained material matched that of the hexagonal wurtzite structure of ZnO. X-ray fluorescence analysis showed no trace of metallic contamination, which confirmed that our material was synthesized without metal catalysts. Scanning electron microscope and transmission electron microscope observations revealed needle-like nanostructures, with a high yield for nanostructures having 4 legs assembled in a tetrapod-like shape. The diameter of the needles/legs varied in the 0.1 - 1 μm range while their lengths varied in the 1 - 10 μm range. Connections between long legs of different tetratpods were observed. Most of the legs were in the form of monocrystals. Material made of these tetrapods exhibited a sharp near-band-gap photoluminescence peak having its maximum at 390 nm together with a weak green below-band-gap emission. We found that a three-dimensional network made up of interconnected tetrapods could be deposited on quartz substrates. The ZnO tetrapod network formed a porous layer with a very high surface to volume ratio. The tetrapod network layer was tested as a gas sensing element by measuring changes in its electrical resistance upon exposure to ethanol vapor. A maximum in ethanol sensitivity was found at an operating temperature of 400°C. Ethanol concentration as low as 0.5 ppm was detected with a sensitivity of 2.5, suggesting a high sensitivity to ethanol vapor and possible applications in trace gas detection for the three-dimensional tetrapod network.

Paper Details

Date Published: 2 March 2006
PDF: 8 pages
Proc. SPIE 6122, Zinc Oxide Materials and Devices, 612208 (2 March 2006); doi: 10.1117/12.645181
Show Author Affiliations
Jean-Jacques Delaunay, The Univ. of Tokyo (Japan)
Naoki Kakoiyama, The Univ. of Tokyo (Japan)
Ichiro Yamada, The Univ. of Tokyo (Japan)

Published in SPIE Proceedings Vol. 6122:
Zinc Oxide Materials and Devices
Ferechteh Hosseini Teherani; Cole W. Litton, Editor(s)

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