CRYSTALLITE GROWTH-KINETICS IN ISOTHERMALLY ANNEALED SOL-GEL FILMS

Raman scattering methods were used to investigate the isothermal devitrification kinetics of sol-gel deposited amorphous titania films as a function of annealing temperature. Time-dependent line intensity variations, indicative of a crystalline anatase phase, generated a sigmoidal growth curve which was analyzed in terms of a modified Avrami equation based on the diffusion-limited mass transport model. The observed spheroidal growth morphology evident in transmission electron micrographs supports this model. Both film refractive index and crystallization rate are influenced by solution equilibration time which controls the condensation of titania precursors into titanium-oxygen oligomers in these low pH solutions.