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

Abstract

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 °C 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.