Sensitivity of CoWO4 thin films to CO

A new p-type thin film material for gas sensing was prepared and investigated for CO response. The films of CoWO4 were fabricated by pulsed laser deposition (PLD) and characterised by XRD, XRR, XPS and SEM. The substrate temperature and oxygen pressure in PLD chamber were varied in order to examine the relations between deposition parameters, film structure and gas sensitivity. Conductometric response to CO was measured at 150–350 ∘C and was found to be the highest at relatively low temperatures, at 200–250 ∘C depending on relative humidity or annealing time in ambient atmosphere. Highest sensitivity was obtained for the films grown on silicone nitrite substrates at 400–500 ∘C at oxygen pressures 10−3 to 10−2 mbar. At higher oxygen pressures or after annealing in oxygen environment the film stoichiometry was seriously altered and the conductivity of the films was significantly decreased.