Effects of sputtering gas pressure on physical properties of ferroelectric (Bi3.25Nd0.65Eu0.10)Ti3O12 nanoplate films

(Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT-0.1) films with a- and b-axis orientations and thicknesses of 1.8-2.3 µm were sputter-deposited on conductive Nb:TiO2(101) substrates containing 0.79 mass % Nb. The deposition temperature was fixed at 650 °C, and the sputtering gas pressure was varied from 0.4 to 5.0 Pa in order to examine its effect on the structural, ferroelectric and piezoelectric properties of the films. The films were found to have a mostly single-phase orthorhombic structure, with a high degree of a- and b-axis orientations (93-98%). The films had a nanoplate microstructure, with the plates being aligned along the [100]/[010] direction, and porosities of 15-25%. A maximum room-temperature remanent polarization (2Pr) of 93 µC/cm2 was obtained for a sputtering gas pressure of 5.0 Pa. All the films were strongly a-axis oriented, according to the results of X-ray diffraction measurements and vertical amplitude images in piezoresponse force microscopy. The optimal sputtering gas pressure for heteroepitaxial growth of BNEuT-0.1 nanoplates with a high degree of a-axis orientation of 96.5%, a maximum orthorhombicity of 0.0017, a comparatively large remanent polarization of 2Pr = 66 µC/cm2, and a high porosity of 24% was found to be 0.4 Pa.