Ethanol and ozone sensing characteristics of WO3 based sensors activated by Au and Pd

Abstract The sensitivity towards ethanol (C 2 H 6 O) and ozone (O 3 ) of WO 3 thin films based conductometric sensors was investigated. The performances of three sensing layers were compared: bare WO 3 , palladium (Pd) and gold (Au) activated surface WO 3 . The WO 3 thin films were deposited by thermal evaporation of oxide powders onto SiO 2 /Si transducers with platinum interdigited electrodes. All the tests were performed at the same working temperature T work  = 300 °C and under fixed gas concentrations: 2% ethanol and 0.8 ppm ozone using dry air as carrier gas. The morphology of the sensor surfaces were analyzed before and after working runs by atomic force microscopy (AFM) and scanning electron microscopy (SEM) in order to control the stability of the metal deposits. DC and AC electrical responses under 50 l h −1 gas flows are presented and discussed.