Ultrathin percolated WO3 cluster film and its resistive response to H2

Abstract Thin films composed of tungsten oxide (WO 3 ) 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 WO 3 spherical caps connected by fine links. The resistance response of the palladium-(Pd-) coated film sample to hydrogen (H 2 ) 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 H 2 sensing response rate with the use of the percolated WO 3 film structure is illustrated.