Effects of Various Substrates on the Structure and Properties of BiFe0.91Zr0.09O3 Thin Films

Abstract

BiFe_0.91Zr_0.09O₃ (9BFZrO)/LaNiO₃ (LNO)/MgO and 9BFZrO/LNO/Si multilayers were prepared by the sol–gel method using MgO and Si single crystals as substrates, and LNO films with a thickness of approximately 50 nm were deposited by magnetron sputtering to form bottom electrodes and transition layers. The effects of different substrates on the crystal structure, phase composition, oxygen vacancy content, ferroelectric properties, dielectric properties, leakage mechanism, and ageing properties of the 9BFZrO films were systematically analysed. X-ray diffraction showed that the prepared 9BFZrO thin films had a structure composed of both rhombic R3c and orthogonal Pnma phases, and the films prepared on the MgO substrate contained a significant amount of the R3c phase. SEM analysis showed that the thin film prepared on the MgO substrate had a relatively large grain size. X-ray photoelectron spectroscopy showed that the Fe²⁺ content and oxygen vacancy defect concentration of the MgO substrate samples were relatively low. The thin film prepared on the MgO substrate has a high residual polarization strength (2P_r = 60.28 μC/cm²) and a low leakage current density (4.71 × 10⁻⁶ A/cm²). After 90 days of room-temperature ageing, the residual polarization strength (2P_r) of the film on the MgO substrate decreased by 16.8%, with a lower ageing degree and better stability.