Conductivity and sensing properties of In2O3Â +Â ZnO mixed nanostructured films: Effect of composition and temperature

The conductivity and conductometric sensor response of mixed In2O3 + ZnO nanocrystalline composite systems to H2 and CO in air ambience are investigated for varying oxide compositions. The maximum sensor response to H2 and CO is obtained for composite films containing 15 wt% and 80 wt% In2O3. This sensor response is also much higher than the values obtained for the individual oxides. The sensory mechanism is proposed to be largely determined by the dependence of the conduction paths on the film composition. The major factors determining the conductivity and sensor response of the In2O3 + ZnO composite are: (i) the modification of the electronic structure of the crystals (mainly, In2O3) during the synthesis of the composite, (ii) the electron transfer from In2O3 to ZnO, and (iii) the catalytic activity of ZnO in the dissociation reactions of O2 and H2.