Microstructural, electrical, and ferroelectric properties of M0.5Bi4.5-xSmxTi4O15 (M = Na or K) thin films

Aurivillius type M0.5Bi4.5-xSmxTi4O15 (x = 0 and 0.5, M = Na or K) thin films were prepared on Pt(111)/Ti/Si/SiO2(100)substrates by using a chemical solution deposition method. Fabricated thin films were crystallized in pure Aurivillius phaseorthorhombic structures, which were confirmed by X-ray diffraction and Raman spectroscopy studies. The use of Sm3+-ionsfor doping purposes results in remarkable improvements in electrical and ferroelectric properties of the M0.5Bi4.5-xSmxTi4O15thin films. A study of the ferroelectric hysteresis loops enabled the remnant polarization (2Pr) and coercive field (2Ec) valuesfor the Na0.5Bi4Sm0.5Ti4O15 and the K0.5Bi4Sm0.5Ti4O15 thin films to be measured as 34.4 mC/cm2and 220 kV/cm at an appliedelectric field of 475 kV/cm and 36.0 mC/cm2and 103 kV/cm at 231 kV/cm, respectively. The 2Pr values measured for the thinfilms doped with Sm3+-ions were much larger than those of the un-doped thin films. The 2Ec values of the M0.5Bi4.5-xSmxTi4O15thin films were also drastically lowered. Furthermore, low leakage current densities were measured for the M0.5Bi4.5-xSmxTi4O15thin films.