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Electrical conductivity and gas-sensing properties of Mg-doped and undoped single-crystalline In2O3 thin films: Bulk vs. surface

 
: Rombach, J.; Bierwagen, O.; Papadogianni, A.; Mischo, M.; Cimalla, V.; Berthold, T.; Krischok, S.; Himmerlich, M.

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Postprint (PDF; )

Procedia Engineering 120 (2015), pp.79-82
ISSN: 1877-7058
European Conference on Solid-State Transducers (Eurosensors) <29, 2015, Freiburg>
English
Journal Article, Conference Paper, Electronic Publication
Fraunhofer IAF ()
conductometric gas sensors; MBE; single crystalline; doping; indium oxide; ozone sensors

Abstract
This study aims to provide a better fundamental understanding of the gas-sensing mechanism of In(2)O(3)-based conductometric gas sensors. In contrast to typically used polycrystalline films, we study single crystalline In(2)O(3) thin films grown by molecular beam epitaxy (MBE) as a model system with reduced complexity. Electrical conductance of these films essentially consists of two parallel contributions: the bulk of the film and the surface electron accumulation layer (SEAL). Both these contributions are varied to understand their effect on the sensor response. Conductance changes induced by UV illumination in air, which forces desorption of oxygen adatoms on the surface, give a measure of the sensor response and show that the sensor effect is only due to the SEAL contribution to overall conductance. Therefore, a strong sensitivity increase can be expected by reducing or eliminating the bulk conductivity in single crystalline films or the intra-grain conductivity in polycrystalline films. Gas-response measurements in ozone atmosphere test this approach for the real application.

: http://publica.fraunhofer.de/documents/N-366606.html