Ferroelectric properties of heteroepitaxial PbTiO₃ and PbZr_1–xTi_xO₃ films on Nb-doped SrTiO₃ fabricated by hydrothermal epitaxy below Curie temperature

PbTiO₃ (PTO) and PbZr_1-xTi_xO₃ (PZT) films on a (100) Nb-doped SrTiO₃ (NSTO) substrate were fabricated at 160 and 210 °C, respectively, by hydrothermal epitaxy below the Curie temperature, T_C. The PTO capacitor had a square hysteresis curve compared to the rounded hysteresis curve of the PZT capacitor. These differing behaviors in the polarization-electric hysteresis curves can be explained by the existence of an interfacial layer formed between the PZT film and the NSTO substrate. The PZT capacitor showed almost no polarization fatigue after 10¹¹ switching cycles. However, the PTO capacitor revealed a slightly different fatigue behavior due to the microvoids that formed as a result of the agglomeration of the island growth mode. However, the fatigue behavior of both capacitors revealed that defects, such as the lead or oxygen vacancies, were suppressed by the hydrothermal epitaxy using a very low fabrication temperature below T_C.