THE ROLE OF GAS-PHASE NUCLEATION IN THE PREPARATION OF TIO2 FILMS BY CHEMICAL-VAPOR-DEPOSITION

TiO2 thin films were deposited by chemical vapor deposition using the thermal decomposition of titanium tetra-iso-propxoide (TTIP), in a temperature range from 400-degrees-C to 700-degrees-C under a reduced pressure of 2.66 x 10(3)-2.66 x 10(4) Pa. The TTIP partial pressure and the temperature dependence of deposition rates were investigated under a total gas flow rate of 2000 sccm and a reactor pressure of 2.66 x 10(4) Pa. The microstructure and the X-ray diffraction peak intensity of TiO2 filMs depended dramatically on the reaction temperature and pressure. Using the modified homogeneous reaction theory, the experimental results were explained. As the reaction temperature increased, the adsorbed species on the substrate, varied from TTIP vapor to TiO2 monomers, and finally TiO2 particles.