Nanostructured sol-gel silica thin films doped with NiO and SnO2 for gas sensing applications

Nanoporous SiO2 thin films containing different functional oxide nanoparticles (NiO, SnO2) have been synthesized by sol–gel methods and the gas response to H2, CO and humidity has been determined by volt amperometric techniques. The structure development of the nanocomposite films has been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and secondary ion mass spectrometry (SIMS). Films of molar composition 60SiO2–40NiO and 60SiO2–40SnO2 showed homogeneously dispersed round shaped oxide nanocrystals of 3–4 nm mean diameter. The gas response of films deposited on Si/Si3N4 substrates provided with Pt interdigital electrodes has been measured at different operating temperatures ranging from 25 to 350 uC and gas concentrations between 10 and 1000 ppm. NiO and SnO2 nanocomposite films have shown a p-type and n-type response, respectively, with greater sensitivity to H2 gas than CO in the whole range of the investigated operating temperatures.