Energy Storage Characteristics of BiFeO₃/BaTiO₃ Bi-Layers Integrated on Si.

BiFeO₃/BaTiO₃ bi-layer thick films (~1 μm) were deposited on Pt/Ti/SiO₂/(100) Si substrates with LaNiO₃ buffer layers at 500 °C via a rf magnetron sputtering process. X-ray diffraction (XRD) analysis revealed that both BiFeO₃ and BaTiO₃ layers have a (00l) preferred orientation. The films showed a small remnant polarization (Pr ~ 7.8 μC/cm²) and a large saturated polarization (Ps ~ 65 μC/cm²), resulting in a slim polarization-electric field (P-E) hysteresis loop with improved energy storage characteristics (Wc = 71 J/cm³, η = 61%). The successful "slim-down" of the P-E loop from that of the pure BiFeO₃ film can be attributed to the competing effects of space charges and the interlayer charge coupling on charge transport of the bi-layer film. The accompanying electrical properties of the bi-layer films were measured and the results confirmed their good quality.