Effects of rare earth incorporation on the ferroelectric and dielectric properties of sol-gel derived PbTiO₃ films

Ferroelectric (FE) films, especially PZT films, have received increasing attention for microelectronics applications such as FE memory and in high density DRAM's. While rare earth doped PbTiO₃ ceramics has been studied for SAW and piezoelectric applications, rare earth-doped films seldom have been systematically explored. A series of sol-gel derived PbTiO₃ films with varying amounts (5-15 mole %) of rare earths (such as, Nd, Sm, Tb, Dy, Er, Yb and La) have been prepared using acetates and alkoxides as precursors. The solutions were spin coated onto platinized Si wafers. The effects of the type and amount of rare incorporation on the phase assembly and microstructure have been quantified. The results of dielectric characterization (e.g., dielectric constant, dissipation factor and leakage currents) and FE behaviors (viz.remanent polarization, and coercive field) are presented; these films exhibited low leakage currents (3E-10 A/cm²) and much higher dielectric constant (up to 525) compared to undopeal PbTiO₃ films.