Atmospheric pressure, low temperature deposition of photocatalytic TiOx thin films with a blown arc discharge

Thin film deposition of TiOx is performed with an atmospheric pressure plasma afterglow from a nitrogen-fed blown arc discharge. Titanium tetraisopropoxide is used as titanium precursor molecule and injected in the afterglow by an ultrasonic nebuliser. The coatings are made of a homogenous thin film and agglomerates, whose mean size and number depend on the deposition time and on the reactivity of the afterglow. These agglomerates are created by aggregation of nanoparticles synthesised in the gas phase. The latter are crystalline and responsible for the photocatalytic activity of the coating. The presence of a crystalline phase with a high specific surface area induces a photodegradation of the stearic acid with kinetics close to that obtained with an anatase sample deposited by magnetron sputtering at 523 K. The substrate temperature is always lower than 523 K. Significant photocatalytic activity has even been achieved with a substrate temperature as low as 460 K.