Effect of gold on the properties of nitrogen dioxide sensors based on thin WO3 films

The microstructure and properties of gold-doped WO3 (WO3:Au) thin films before and after deposition of dispersed Au layers have been studied. It is shown that the gamma-WO2.72 phase arises in WO3:Au layers, which leads to a significant increase in the film conductivity. Deposition of a dispersed gold layer results in an increase in the sensor response to NO2 by several times. The concentration dependences and the dynamics of sensor responses to nitrogen dioxide are described by the analytical expressions derived under the assumption that WO3 films contain grains connected by conducting bridges. An analysis of the experimental data using these expressions made it possible to determine the activation energies of NO2 adsorption and desorption and the adsorption heat.