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

Nanocomposite thin films with a molar composition of 40NiO-60SiO(2) 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 degrees 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 degrees 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. (c) 2005 Elsevier B.V. All rights reserved.