Ultrathin percolated WO3 cluster film and its resistive response to H2

• Ultrathin percolated network of WO3 clusters was fabricated.
• The WO3 clusters are modeled by spherical caps connected by ultrafine linkages.
• The ultrathin percolated network of WO3 clusters shows fast response rate to H2.
• The fast response is attributed to the rapid electrical switching of the linkages.
• Improved H2 sensing properties may be achieved if narrower linkages are used.

Thin films composed of tungsten oxide (WO3) nanoclusters were fabricated by oxidizing supersonic cluster beam deposited tungsten films at various temperatures. Oxidation at 700 °C resulted in aggregation of the deposits, forming a percolated network of WO3 spherical caps connected by fine links. The resistance response of the palladium-(Pd-) coated film sample to hydrogen (H2) was investigated. The response rate was faster than those of other samples oxidized at lower temperatures. This is the result of the rapid electrical switching of the intercluster links between the highly resistive depleted state and conducting hydrogenated state. The possibility of improving the H2 sensing response rate with the use of the percolated WO3 film structure is illustrated.

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