On the origin of sensing properties of the nanodispersed layers of semiconducting metal oxide materials

A model for the electronic states in the nanodispersed metal oxide-based semiconducting materials (NDSM) explaining the mechanism of their sensing properties is suggested. It is shown that as the nanoparticle diameter a is decreased down to the redistribution of the electrons from the bulk donors to the surface vacancies (“surface electron traps”) is taking place. This leads to a significant (by three orders of magnitude) drop in the bulk conduction electron density (we call it as the effect of “charge carrier self-exhaustion” of the nanodispersed materials) and its strong dependence on the concentration of gas molecules adsorbed on the surface. Due to that physical phenomenon NDSM with a