Effect of water vapour on gallium doped zinc oxide nanoparticle sensor gas response

Zinc oxide is a wide band gap (~3.4 ev) semiconductor material, making it a promising material for high temperature applications, such as exhaust and flue environments where NO and NO₂ monitoring is increasingly required due to stricter emission controls. In these environments water vapour and background levels of oxygen are present and, as such, the effect of humidity on the sensing characteristics of these materials requires further study. The reaction mechanisms in the presence of water vapour are poorly understood and there is a need for deeper understanding of the principles and mechanisms of gas response of these materials. An investigation of the influence of changing water vapour (H₂O) and oxygen (O₂) backgrounds on the response of nanoparticulate Ga-doped ZnO resistive sensors is presented.