Fabrication and humidity sensing properties of nanostructured TiO2–SnO2 thin films

Nanostructured TiO2–SnO2 thin films have been prepared using a sol–gel process and the humidity sensing properties of the films were investigated. The films possess nano-sized grains and nanoporous structure. The TiO2–20 wt.% SnO2 film exhibits the highest sensitivity for the humidity, which shows over three orders change in the resistance during the relative humidity (RH) variation from 20 to 90%. The high humidity sensitivity is due to the protonic and electrolytic conduction between hydroxyl ions and water molecules adsorbed on the film surfaces with capillary nanopores.