Regensburg 2007 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 15: Poster Session
DS 15.12: Poster
Dienstag, 27. März 2007, 15:00–17:00, Poster B
Sensing investigations of tungsten oxide nano-particle thin films using Impedance Spectroscopy — •Tim Hülser1,2, Hartmut Wiggers2, Sonja Hartner1, and Axel Lorke1 — 1Department of Physics, University of Duisburg-Essen, 47057 Duisburg, Germany — 2Institute of combustion and gas dynamics, University of Duisburg-Essen, 47057 Duisburg, Germany
Tungsten oxide nanoparticles particles are synthesized in a low pressure premixed H2/O2/Ar flame reactor using WF6 as precursor material. The parameters can be adjusted to synthesize WOx particles with 2.6 < x < 3. Thin films of particles in the size range from 5 nm to 9 nm deposited on interdigital structures are investigated. Impedance spectroscopy on the as-prepared WOx thin films have been performed under synthetic air and synthetic air with 1000 ppm NO or CO in the range from 553 K to 583 K. The overall impedance data reveal sensitivities of S=3.8 for CO at 553 K and a maximum of sensitivity S = 5 for NO at 573 K. Fits of the overall impedance data using equivalent circuit reveal two contributions to the overall impedance which are assigned to grain-boundary contacts on the surface of each particle and a semi-conducting core conductivity. Furthermore, we have been able to calculate the sensitivity for both processes separately. From this investigation we show that the sensitivity of the grain boundary contribution in presence of CO exhibits values up to S =12, much higher than the core sensitivity with S = 2.6 at 553 K. A similar behaviour is observed under the presence of NO.