Effect Of Composition On Sensing Properties Of Sno 2 + In 2O 3 Mixed Nanostructured Films

The conductometric response of SnO 2 + In 2O 3 nanocomposite films to hydrogen and carbon monoxide in air are investigated experimentally for varying oxide compositions. The fundamental mechanism of sensory phenomena in such nanocomposite films is also discussed. The experimental results indicate that the response (θ com) of the sensor is determined by the current flow path in the film. For composites with In 2O 3 composition (X In) less than 20 wt.%, current flows through the SnO 2 crystals. Due to electron transfer from the In 2O 3 inclusions to the SnO 2 matrix, an increase in X In up to 20 wt.% leads to a significant increase in the conductivity of the composite sensor and θ com for both CO and H 2. A further increase in X In results in percolation transition for In 2O 3 nanocrystals, which form conducting clusters (threads) of In 2O 3, with electrical conductivity that is much higher than that of SnO 2. The transition from conduction through the SnO 2 crystals to conduction through the In 2O 3 crystals in the composite films occurs at X In in the range about 20-50 wt.%. For X In ≥ 50 wt.%, θ com is entirely determined by the sensory properties of the In 2O 3 conducting clusters, and electron transfer from In 2O 3 clusters to SnO 2 results in a decrease of θ com. © 2012 Elsevier B.V. All rights reserved