Growth of titanium dioxide films by cluster supersonic beams for VOC sensing applications

We developed and tested gas sensing devices based on TiO₂ nano-crystalline films produced at room temperature by the novel growth method of cluster beam deposition. The devices show a very good response to ethanol, methanol, and propanol and an overall performance comparable or better to the best devices reported in literature, based on films grown with other techniques. The major advantage of our growth method is that there is no need of the thermal annealing or doping processes usually required to improve sensitivity and reliability of gas sensing devices based on nanostructured thin film. The sensors dynamic response gives a maximum sensitivity for ethanol at about 250°C. As the morphological (AFM) and structural (XRD) characterizations of the films show, the high performance of our sensors could only be achieved because their nano-crystalline structure was well controlled by the properties of the cluster precursors in the supersonic beam. We envisage possible further developments in terms of sensitivity and selectivity of gas sensing devices based on films grown by cluster beam deposition.