Phase development and electrical properties of Pb(Yb_1/2Nb _1/2)O₃-PbTiO₃ epitaxial films

The growth and electrical properties of Pb(Yb_1/2Nb _1/2)O₃-PbTiO₃ (PYbN-PT) epitaxial films were investigated. PYbN-PT epitaxial films with SrRuO₃ bottom electrodes were grown by pulsed laser deposition. Optimization of the growth conditions for the PYbNPT epitaxial films was carried out on (100) SrRuO₃(100) LaAlO₃ substrates using the (50/50) composition target. It was found that formation of pyrochlore phase could be caused not only by low growth temperatures or lead deficiency, but also by poor surface condition of the SrRuO₃ bottom electrodes. (001) PYbN-PT epitaxial films with good crystalline quality were obtained for a range of deposition rates (60-100 nm/min) and temperatures (620-680°C) after vacuum annealing the SrRuO ₃ bottom electrodes. The ferroelectric and piezoelectric properties of 1 μm-thick PYbN-PT epitaxial films with (50/50) and (60/40) compositions and with (001) and (111) orientations were investigated using (100) LaAlO ₃, (100) SrTiO₃, and (111) SrTiO₃ substrates with SrRuO₃ bottom electrodes. The highest remanent polarization (29 μC/cm²) and effective piezoelectric coefficient e_31.f (-14 C/m²) were observed in the (001) PYbN-PT (50/50) film. The transition temperature of the (001) PYbN-PT (50/50) film was about 380°C. Because of the degradation of the target during the deposition, a 3 nm-thick film was prepared by three depositions (1 μm each layer). The 3 μm-thick film exhibited a higher e_31.f coefficient of -19 C/m².