Preparation and microstructure of the porous TiO2 nanometer thin films by sol-gel method

The porous TiO2 anatase nanometer thin films were prepared from alkoxide solutions containing polyethylene glycol (PEG) by sol-gel method. The effects of PEG addition to the precursor solution on the microstructure of the resultant thin films were studied. The larger amount and the larger molecular weight of PEG, the larger size and more pores produce in the resultant films on the decomposition of PEG during heat-treatment. However, the transmittance of the films decreases due to the light scattering by the larger size and more pores. The film thickness was measured by SEM and weight method, and the thickness of TiO2 films prepared by 1 cycle (from dipping to teat-treatment at 500 degrees C1h) was 0.08 mu m or so. The chemical composition and The adsorbed hydroxyl content of the films were analyzed with X-ray photoelectron spectroscopy(XPS) and IR spectra. Experiment results show that in the film, besides Ti and O elements, there are a certain amount of residual carbon from the starting organometallic components and a small amount of sodium and calcium ions diffused from the glass substrates. The adsorbed hydroxyl content of such porous thin films increases due to the larger size and more pores in the films.