Preparation of TiO2 nanoparticle thin film with sol-gel process

TiO2 nanoparticle thin films are fabricated via sol-gel process followed by dip and spin coating technique, using Ti(OC4H9)4 as raw material. A complexing agent is used in order to form a stable sol. Experiments show that the colloidal particles in the sols are relatively large under basic catalyst conditions, while under acidic conditions, the colloidal particles are only about several nanometers. The properties and structures of the films are studied. The films are normally homogenous and crack-free. TEM shows that the films are composed of nanoparticles with a certain porosity. Under the thermal treatment of 80 degrees Celsius, the porosity and thickness of the film decrease while the refractive index increases from the original 1.70 to the final 1.89. When the temperature of the thermal treatment goes up, the size of the nanoparticles increases and crystallization occurs.