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Proceedings Paper

Investigation of the Anderson transition in substoichiometric sputtered WOx by measurements of conductivity and the dielectric constant
Author(s): Andreas Georg; Volker Wittwer
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Paper Abstract

Thin substoichiometric WOx films were produced by reactive sputtering with variation of the oxygen partial pressure and the temperature of the substrate to get samples with different degrees of crystallinity and colorations. Measurements were done on the conductivity, the transmittance and reflectance from 100 K up to 300 K. The dielectric constant was evaluated by ellipsometry. As observed in earlier works, with increasing coloration a sudden increase in conductivity and a decrease of the temperature dependence of the conductivity takes place, which is attributed to an Anderson transition. But based on Hall measurements and the ellipsometrically evaluated dielectric constants the formation of Drude electrons with a plasma edge in the visible or NIR range is unlikely. Rather the measured dielectric constant suggests a strong Lorentz oscillator with a weak bond of the coloring electrons. Reflectance and transmittance did not change when cooling the samples from 300 K to 100 K. At very high colorations a second qualitative change of the conductivity and the optical properties was observed. Here perhaps the first metallic clusters are formed.

Paper Details

Date Published: 9 September 1994
PDF: 8 pages
Proc. SPIE 2255, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, (9 September 1994); doi: 10.1117/12.185435
Show Author Affiliations
Andreas Georg, Fraunhofer-Institut fuer Solare Energiesysteme (Germany)
Volker Wittwer, Fraunhofer-Institut fuer Solare Energiesysteme (Germany)

Published in SPIE Proceedings Vol. 2255:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII
Volker Wittwer; Claes G. Granqvist; Carl M. Lampert, Editor(s)

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