Kinetics of gas response to reducing gases of SnO2 films, deposited by spray pyrolysis

The present paper is devoted to systematic measurements of SnO2 gas response to reducing gases in transient mode. SnO2 films were deposited by spray pyrolysis from SnCl4–water solution. The influence of operation temperature (25–500 °C) on gas response (S) to CO and H2 (0.1–0.5%), response time (τ), shape of S(T) curves, and activation energy of τ(1/kT) dependencies is discussed. Three operating temperature ranges with different activation energies of 0.3–0.38, 0.6–0.7, and 1.1–1.4 eV were selected on τ(1/kT) dependencies. The mechanism of oxygen and water influence on gas sensing characteristics of SnO2 films has been proposed. It was concluded that adsorption/desorption processes of molecular oxygen, hydroxyl groups, and atomic oxygen have dominant influence on electro-physical and gas sensing characteristics of SnO2 films in the temperature ranges of 25–150; 200–400 and >450 °C, respectively.