Ferroelectric properties of highly (1 1 1)-oriented Pb(Zr_1-x, Ti_x)O₃ thin films with different Zr/Ti ratios

Pb(Zr_1-x, Ti_x)O₃ thin films with different Zr/Ti ratios (0.45 ≤ x ≤ 0.49) were prepared by a sol-gel method using nitrate zirconium as starting material and 2-methoxyethanol as solvent. The films were deposited on Pt (1 1 1)/Ti/SiO₂/Si (1 0 0) substrates by spin-coating process and annealed at 650 °C for 3 min by rapid thermal annealing (RTA). X-ray diffraction (XRD) revealed that the films crystallized in perovskite phase and were all (1 1 1)-oriented. The effect of Zr/Ti ratios on the phase components and ferroelectric properties of the thin films was investigated. The result suggests that monoclinic phase and tetragonal phase coexists for the films with 0.47 ≤ x ≤ 0.49 and there is a pure monoclinic phase for the films with x ≤ 0.46. The films with x ≤ 0.46 exhibit higher remnant polarizations (2 P_rmax = 44.9 μ C/c m²) compared with the other films, as is explained by more monoclinic phase content and higher (1 1 1) orientation degree.