Multiferroic properties of Bi0.89Ho0.08Sr0.03Fe0.97−xMn0.03NixO3 thin films modulated by F-N tunneling effects

Bi0.89Ho0.08Sr0.03Fe0.97−xMn0.03NixO3 (BHSFMNixO) films were prepared via a chemical solution deposition method. X-ray diffraction (XRD) patterns and Raman spectroscopy revealed that BHSFMNixO films showed (100) preferential orientation and the structural transition. The structure of BHSFMNi0.02O was close to the morphotropic phase boundary (MPB) (R3c:H:R3m:R = 1:1). The oxygen vacancies were increased with an increase in Ni2+ doping, and there were many defect dipoles. The BHSFMNixO thin films exhibited an Ohmic or a space-charge-limited conduction (SCLC) mechanism in a low electric field, and the interface-limited Fowler-Nordheim (F-N) tunneling or the trap-assisted F-N tunneling in a high electric field. The interface-limited F-N tunneling effects of BHSFMNi0.01O and BHSFMNi0.02O were due to an interface effect. The large remnant polarizations of BHSFMNi0.01O and BHSFMNi0.02O contributed to the intrinsic polarization and the interface-limited F-N tunneling. The fake polarizations of BHSFMNi0.03O and BHSFMNi0.04O were dominated by the trap-assisted F-N tunneling in which the interface traps helped the carrier tunnel the potential barrier. These results demonstrate that the polarizations of BHSFMNixO are related not only to the structural transformation, but also to the defects and conduction mechanisms.