Atomic layer deposition of Rh nanoparticles on WO3 thin film for CH4 gas sensing with enhanced detection characteristics

CH4 gas sensor was fabricated by depositing WO3 film (200 nm) on a ceramic substrate through E-beam evaporation, followed by depositing Rh nanoparticles on WO3 through Atomic Layer Deposition (ALD). The amount of Rh nanoparticles was regulated by ALD cycles. The TEM characterization showed that Rh nanoparticles were homogeneously distributed on WO3 thin film, and the XPS investigation indicated the interactions between Rh nanoparticles and WO3 thin film. The gas-sensing performance testing showed that, when the Rh ALD deposition cycle is 20, the sample showed the highest selectivity, which is increased by similar to 110% compared with pure WO3, which could be attributed to the surface catalytic effect contributed by Rh nanoparticles, while over high concentration of Rh could be harmful to the gas sensing performance, which blocks the active sites on the surface of WO3 thin film. The sensing stability of WO3/Rh composite (with ALD cycle of 20) was further investigated by exposing the sensor in CH4 gas environment for one week.