Mechanism of the conductivity and sensor response of nanostructured In2O3+ZnO films

Abstract

The conductivity and sensor properties of mixed nanostructured In2O3+ZnO metal oxide systems with different component ratios are investigated. It is found that maximum sensor sensitivity in detecting hydrogen and CO in composite films containing 15 and 80 wt % In2O3 considerably exceeds the sensitivity of individual oxides. A mechanism of the sensor action, which is largely determined by the dependency of the paths of conductivity in a composite metal-oxide film on its composition, is proposed. It is established that the main factors determining the conductivity and sensor sensitivity of In2O3 + ZnO composite are modifications in the electron structure of crystals (mainly by In2O3) during the formation of composites, electron transfer from In2O3 to ZnO, and the catalytic activity of ZnO. It is shown in particular that ZnO effectively catalyzes the reaction of hydrogen dissociation and, in contact with In2O3, favors the chemical sensibilization of the sensor response of such mixed metal oxide systems in detecting H2 and CO.