Influence of anatase-rutile phase transformation on dielectric properties of sol-gel derived TiO2 thin films

Effects of annealing temperature on the structural and dielectric properties of sol-gel derived TiO2 thin films were systematically investigated. Thin films annealed at various temperatures showed pure or mixed phases of anatase and rutile. As-deposited films started crystallization below 600 degrees C and fully crystallized into the anatase phase at 800 degrees C, followed by transformation to the rutile phase above 850 degrees C. Dielectric properties of thin films with various phases were studied by LCR-meter using the Metal-insulator-metal (MIM) structure. Dielectric constants of thin films increased from 40 to 147 as the portion of rutile phase increased from 0 to 95%, while dielectric losses decreased from 0.011 to 0.001. Temperature dependence of dielectric constants of thin films was also investigated. The dielectric properties of TiO2 thin films were discussed in terms of phase constitution, crystallinity, and preferred orientation.