Effects of LSMO Buffer Layer on Crystalline Orientation and Ferroelectric Properties of Bi_2.9Pr_0.9Ti₃O₁₂ Thin Films Prepared by Radio-Frequency Magnetron Sputtering

Ferroelectric Bi_2.9Pr_0.9Ti₃O₁₂/La_0.67Sr_0.33MnO₃ (BPT/LSMO) films are fabricated on Pt(111)/TiO₂/SiO₂/Si substrates by rf-magnetron sputtering method. The influences of the LSMO deposition conditions and LSMO layer thickness on properties of BPT thin films are studied. The LSMO layer deposited at 300°C and 450°C favours preferred (117) orientation of BPT films, while deposited at 600°C for LSMO layer leads to strong (111)-preferred orientation of BPT film. With the LSMO buffer layer, the films exhibit improved ferroelectric properties and Pt/BPT/LSMO(20nm)/Pt capacitor shows the largest remnant polarization P_r of 18.4μC/cm² at 14V. A similar change in dielectric constant with the increase of LSMO layer thickness is also observed and the highest dielectric constant of 342.7 is obtained for the Pt/BPT/LSMO(20nm)/Pt film. Compared with the Pt/BPT/Pt film, the Pt/BPT/LSMO/Pt films exhibit better fatigue endurance after 5×10⁹ switching cycles. Moreover, the LSMO layer has apparent effect on leakage current density and the Pt/BPT/LSMO(20nm)/Pt film exhibits the lowest leakage current density.