Effect of grain size on Bi4Ti3O12 thin film properties

Bismuth titanate (Bi4Ti3O12) thin films with a c-axis orientation were prepared on (100) silicon wafers by rf magnetron sputtering. The average grain size and the c-axis lattice constant depend on the substrate temperature. The c-axis lattice constant was decreased with increasing grain size. The leakage current characteristics of the Bi4Ti3O12 thin film consisting of small grains with a closely packed structure, are superior to those of others. The apparent remanent polarization and the apparent coercive field of the film with small grain sizes were estimated to be 2.4 μC&middotcm-2 and 2.3 kV&middotcm-1, respectively. The refractive index dispersion characteristics for the film show that the large grains increase the distortion of the oxygen-octahedra. Consequently, this result indicates that the small grain size of Bi4Ti3O12 thin films can improve the ferroelectric properties.