Effects of rare-earth (Tb, Yb, and Lu)-doping on the structural, electrical and ferroelectric properties of K0.5Bi4.5Ti4O15 thin films

The electrical and the ferroelectric properties of pure K0.5Bi4.5Ti4O15 and a series of rare-earth-doped K0.5RE0.5Bi4Ti4O15 (RE = Tb, Yb, and Lu) thin films deposited on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method have been investigated. Compared to the pure K0.5Bi4.5Ti4O15 thin film, there were no structural changes in the K0.5RE0.5Bi4Ti4O15 thin films while the leakage current and the ferroelectric properties were significantly improved. Among the thin films, the K0.5Lu0.5Bi4Ti4O15 thin film exhibited wellsaturated hysteresis loops with a large remnant polarization (2Pr) of 32 μC/cm2 and a coercive field (2Ec) of 307 kV/cm at an applied electric field of 886 kV/cm. Furthermore, a low leakage current density of 2.95 × 10−9 A/cm2, which is about two orders of magnitude lower than that of the K0.5Bi4.5Ti4O15 thin film, was measured in the K0.5Lu0.5Bi4Ti4O15 thin film at an applied electric field of 100 kV/cm. The enhanced electrical and ferroelectric properties observed in the rare-earthdoped K0.5RE0.5Bi4Ti4O15 thin films can be correlated to a decrease in the number of ionic defects, such as bismuth and oxygen vacancies, structural distortion, and improved microstructure.