Multiferroic and energy-storage characteristics of polycrystalline Ca-doped BiFeO3 thin films on Si substrates

Significant progress has been made in the enhancement of multiferroic properties with possibilities for energy harvesting and storage applications. In this study, BiFeO3 (BFO) thin films were doped with Ca, and the multiferroic, piezoelectric, and energy-storage properties of Bi1−xCaxFeO3−δ (x = 0.3, BCFO) thin films were compared with those of BFO to investigate the effects of the doping. The BCFO thin films were deposited on Pt/TiO2/SiO2/Si substrates using pulsed laser deposition. The BCFO thin films having a polycrystalline structure, exhibited improved crystallinity and larger grains, compared with the BFO thin films. The high crystallinity further resulted in the BCFO thin films exhibiting improved leakage current, ferroelectric, and ferromagnetic characteristics, compared with the BFO thin films. The morphotropic phase boundary formed in the mixed crystal phase, which was driven by the Ca doping, and it improved the piezoelectric coefficients of the BCFO thin films. Additionally, we found that the BCFO thin films have superior energy-storage characteristics, compared with the BFO thin films, owing to the improved ferroelectric properties. Our findings suggest that the Ca doping of the BFO thin films improves their multiferroic properties, piezoelectric response, and energy-storage characteristics.