Structural, ferroelectric, aging properties of Eu-substituted BiFeO3 thin films

The aging phenomenon represents a major challenge for to the practical application of ferroelectric devices, primarily because of its detrimental impact on the material's physical and ferroelectric properties. In the present study, Bi 1-x Eu x FeO 3 (x = 0.0, 0.02, 0.04, 0.06) thin films with varying Eu doping concentrations were synthesized on ITO/glass substrates via the sol-gel method. A comprehensive investigation was conducted to analyze the impact of Eu doping on the structural, ferroelectric, ferromagnetic, leakage, and aging properties of the BFO films. X-ray diffraction (XRD) and Raman spectroscopy analyses confirmed the coexistence of R3c and Pnma phases in the film samples. X-ray photoelectron spectroscopy (XPS) analysis revealed the prevalent presence of Fe³ ⁺ and Fe²⁺ in all BEFO films, which effectively inhibited the formation of oxygen vacancies and the Fe³ ⁺ → Fe²⁺ charge transfer. Piezoresponse force microscopy (PFM) results revealed that the film with x = 0.04 exhibited the lowest surface roughness (R a ≈ 4.22 nm). Notably, at x = 0.02, the remanent magnetization (2.5 × 10⁻⁶ emu/g) was twice that of pure BFO. Additionally, at a doping concentration of 0.04, the BEFO₄ film sample exhibited significant, such as a high remanent polarization (88.82 μC/cm²) and a significantly reduced leakage current density (5.92 × 10⁻⁶ A/cm²), which corresponds to a 1.5-order-of-magnitude reduction compared to pure BFO. Furthermore, after 30 days of aging, the BEFO4 sample exhibited superior aging resistance to aging, suggesting its potential for long-term stability and reliability.