Formation of NiO–SiO2 nanocomposite thin films by the sol–gel method

Nanocomposite thin films with a molar composition of 40NiO–60SiO2 were obtained by the sol–gel method on silicon and glass substrates using the dip coating technique. The formation process was studied using thermogravimetric analysis, X-ray diffraction, infrared spectroscopy and optical reflectance and transmittance measurements. The data show that the NiO particles are formed at temperatures lower than 300 °C. X-ray diffraction measurements confirm the presence of NiO nanoparticles in the films with a size of about 4 nm. From the infrared spectra it was obtained that the porous structure of the SiO2 matrix is retained even at temperatures of 800 °C. Using the Maxwell–Garnett effective dielectric function for NiO–SiO2 composite films, the volume fraction occupied by the nanoparticles was obtained for different annealing temperatures.