Enhanced ferroelectric properties of BiFeO3 thin films utilizing four buffer layers: Nd2O3, Eu2O3, Ho2O3, and Er2O3

This paper investigates the ferroelectric and structural properties of BiFeO 3 thin films with four different RE 2 O 3 (Nd 2 O 3 , Eu 2 O 3 , Ho 2 O 3 , and Er 2 O 3 ) buffer layers fabricated on a SrRuO 3 /n + -Si substrate through spin-coating. To analyze the BiFeO 3 films with RE 2 O 3 buffer layers, various techniques, such as X-ray diffraction, secondary ion mass spectrometry, atomic force microscope, and X-ray photoelectron spectroscopy were employed to investigate the crystalline structures, depth profiles, surface topographies, and chemical compositions. It was found that the BiFeO 3 film with RE 2 O 3 buffer layers exhibited improved electrical properties such as leakage current, remnant polarization, and coercive field compared to the control BiFeO 3 film without a buffer layer. Moreover, the Eu 2 O 3 buffer layer exhibited the lowest leakage current of 2.05 × 10 –6 A/cm 2 , the highest remnant polarization of 43.76 μC/cm 2 , and the smallest coercive field of 188 kV/cm among all the RE 2 O 3 buffer layers. The outcome is likely to have been caused by the introduction of Eu 3+ ion to the BiFeO 3 film, which resulted in a reduction in surface roughness, a significant preferred orientation of (110), and an increased concentration of Fe 3+ ion. Consequently, this inhibited the fluctuation of Fe 3+ to Fe 2+ ions and reduced the occurrence of oxygen vacancies.