Dresden 2006 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 23: Nanowires, nanoparticles and nanostructures
DS 23.5: Vortrag
Donnerstag, 30. März 2006, 17:00–17:15, GER 38
Electrical investigations of tungsten oxide nano-particles using Impedance Spectroscopy — •Tim Patrick Hülser1,2, Hartmut Wiggers2, and Axel Lorke1 — 1Institute of physics, University Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg — 2Institute of combustion and gas dynamics, University Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg
We report on the electrical properties of tungsten oxide nanoparticles, which are analyzed using Impedance Spectroscopy. The particles are synthesized in a low pressure premixed 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 capacitors as well as small discs of this material are investigated by AC-methods.
Impedance Spectroscopy on the as-prepared WOX thin films have been carried out under air in the range from 313 K to 503 K. Two contributions to the overall impedance are detected and analyzed by fitting the data using equivalent circuits. Two contributions can be identified, one from the grain-boundary contacts (GB), the other from the electrode-particle (EC) contacts. The resistance of both decreases with increasing temperatures as expected for semi-conducting materials. Activation energies of -1.93 eV for the GB and -201 meV for the EC contacts have been found.
The conductivity of compacted, understoichiometric WOX is higher than that of stoichiometric WO3. Furthermore, compacted material also shows GB and EC contributions in agreement with the results from the interdigitated capacitors.