Microstructural, electrical, and ferroelectric properties of M_0.5Bi_4.5-xSm_xTi₄O₁₅ (M = Na or K) thin films

Aurivillius type M_0.5Bi_4.5-xSm_xTi₄O₁₅ (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 phase orthorhombic structures, which were confirmed by X-ray diffraction and Raman spectroscopy studies. The use of Sm³⁺-ions for doping purposes results in remarkable improvements in electrical and ferroelectric properties of the M_0.5Bi_4.5-xSm_xTi₄O₁₅ thin films. A study of the ferroelectric hysteresis loops enabled the remnant polarization (2P_r) and coercive field (2E_c) values for the Na_0.5Bi₄Sm_0.5Ti₄O₁₅ and the K_0.5Bi₄Sm_0.5Ti₄O₁₅ thin films to be measured as 34.4 mC/cm² and 220 kV/cm at an applied electric field of 475 kV/cm and 36.0 mC/cm² and 103 kV/cm at 231 kV/cm, respectively. The 2P_r values measured for the thin films doped with Sm³⁺-ions were much larger than those of the un-doped thin films. The 2E_c values of the M_0.5Bi_4.5-xSm_xTi₄O₁₅ thin films were also drastically lowered. Furthermore, low leakage current densities were measured for the M_0.5Bi_4.5-xSm_xTi₄O₁₅ thin films.