Zinc oxide as an ozone sensor

This work presents a study of intrinsic zinc oxide thin film as ozone sensor based on the ultraviolet $\left(\mathrm{UV}\right)$ photoreduction and subsequent ozone re oxidation of zinc oxide as a fully reversible process performed at room temperature. The films analyzed were produced by spray pyrolysis, $\mathrm{dc}$ and $\mathrm{rf}$ magnetron sputtering. The $\mathrm{dc}$ resistivity of the films produced by $\mathrm{rf}$ magnetron sputtering and constituted by nanocrystallites changes more than eight orders of magnitude when exposed to an $\mathrm{UV}$ dose of $4\mathrm{mW}∕{\mathrm{cm}}^2$ . On the other hand, porous and textured zinc oxide films produced by spray pyrolysis at low substrate temperature exhibit an excellent ac impedance response where the reactance changes by more than seven orders of magnitude when exposed to the same $\mathrm{UV}$ dose, with a response frequency above $15\mathrm{kHz}$ , thus showing improved ozone $\mathrm{ac}$ sensing discrimination.