Nitrogen doped spongy TiO 2 layers for sensors application

Nanostructured materials represent a breakthrough in many fields of application. For sensing, the use of structures with high surface/volume ratio is crucial to obtain a good sensitivity. Chemical growth approaches are preferred to reach this goal but thick micrometers layers are usually needed. To reduce the layer thickness, methods are required to guaranteelarge exposed surfaces in a small volume. We have indeed designed new spongy TiO2 layers by a reactive sputtering method based on a grazing-incidence source combined with the local oxidation of the sputtered species (gig-lox). The process has been implemented with a doping procedure during growth consisting of adding in the reactive environment nitrogen at low flow rate in close proximity of the growing front. We have characterized the layers in terms of porosity, roughness and electrical behaviour with respect an undoped films. The doping procedure allowed improving the electrical response of the material with the best electrical performances achieved using 2 standard cubic centimeter per minute (sccm) of nitrogen. Unexpectedly, using a higher content of nitrogen is detrimental for the electrical response of the deposited layers.