Structural and electrical characteristics of chemical-solution-derived (Bi,La)4Ti3O12 thin films with various Bi2O3 template layers

Abstract

Ferroelectric (Bi,La)4Ti3O12 (BLT) thin films with different Bi2O3 template layers were prepared on Pt/Ti/SiO2/Si substrates by a chemical-solution deposition method. The BLT films with a thin Bi2O3 bottom layer and those with a thin Bi2O3 intermediate layer had a (117) preferentially oriented growth after annealing at 750 °C, while those with a thin Bi2O3 upper layer and those without a Bi2O3 template layer exhibited a high c-axis orientation. The surface morphologies changed with different preferential orientations. The electrical measurements showed that the use of Bi2O3 template layers improved significantly the P–E hysteresis loops of BLT thin films. The remanent polarization (2Pr) and coercive field (Ec) values of BLT films without a Bi2O3 template layer, with a Bi2O3 upper layer, with a Bi2O3 bottom layer, and with a Bi2O3 intermediate layer annealed at 750 °C were 10.8, 29.12, 26.17, and 19.67 μC/cm2; 79.0, 74.5, 75.5, and 76.3 kV/cm, respectively, at an applied electric field of 350 kV/cm. The dielectric constants and dissipation factors were 184, 303, 243, and 217; 0.036, 0.044, 0.039, and 0.039, respectively, at the frequency of 100 kHz, for these BLT films without a Bi2O3 template layer, with a Bi2O3 upper layer, with a Bi2O3 bottom layer, and with a Bi2O3 intermediate layer. All the capacitors with Bi2O3 template layers showed good polarization fatigue characteristics at least up to 3×1010 bipolar pulse cycles and excellent retention properties up to 3×104 s.