Nanocrystalline tin dioxide thin films as oxidizing gas sensor

Nanocrystalline tin dioxide has been employed to develop two types of sensor devices. Two electrical properties, resistivity and work function, increase with oxidizing gas adsorption. The first leads to the classical thin film resistive sensor. The other property is used to design a switching diode. Both devices show a ligh sensitivity and linearity under proper design and operating parameters. Typival figures are 100% resistance change and 50 mV voltage shift for 50 ppb of NO₂ in air. A theoretical model is proposed to explain the results.