Cobalt oxide films grown by a dipping sol-gel process

Cobalt oxide thin films were prepared by the dipping sol-gel process, using two different inorganic precursors: cobalt chloride and cobalt nitrate salts. Also, samples with a different number of dipping-annealing cycles (3, 5, and 7) where prepared. Composition, structure, surface morphology and optical properties of such films have been characterised by means of X-ray diffraction, differential thermogravimetric analysis (DTA), transmittance spectra and atomic force microscopy (AFM). The results show that starting from distinct precursors leads to different properties: film water contents, surface roughness, crystallite size, total film transmittance, absorption coefficient and refractive index. Absorption coefficients higher than 10(4) cm(-1) where found for all the samples. Refractive indices vary from n similar to 1.9-2.8 in the near infrared region. Our study shows that using a relatively simple preparation method like the sol-gel process, cobalt oxide films with specific properties, can be made. (C) 1999 Elsevier Science S.A. All rights reserved.