Microstructure and dielectric properties of pyrochlore Bi2Ti2O7 thin films

Bi 2 Ti 2 O 7 thin films were grown by radio-frequency magnetron sputtering on bare and Pt-coated sapphire substrates at low substrate temperatures (∼200 °C). Postdeposition anneals were carried out at different temperatures to crystallize the films. Nearly phase-pure Bi2Ti2O7 thin films with the cubic pyrochlore structure were obtained at annealing temperatures up to 800 °C. Impurity phases, in particular Bi4Ti3O12, formed at higher temperatures. At 1 MHz, the dielectric constants were about 140–150 with a very small tunability and the dielectric loss was about 4×10−3. The dielectric loss increased with frequency. The dielectric properties of Bi2Ti2O7 films are compared to those of pyrochlore bismuth zinc niobate films.