The Effect Of TiO₂ Buffer Layer On The Microstructure And Ferroelectric And Magnetic Properties Of BiFeO₃ Films

Multiferroic materials have attracted much attention for their coexistent ferroelectric and magnetic properties, in which the magnetization (and, respectively, the dielectric polarization) is expected to be modulated by the electric field (and, respectively, by the magnetic field), which is known as magnetoelectric effect. This magnetoelectric effect is expected to be the basis of information storage and spintronics devices by a combination of ferroelectric and ferromagnetic properties.As a typical single phase multiferroic materials, BiFeO₃(BFO) was reported as simultaneously exhibiting ferroelectric ordering with Curie temperature of 810℃and magnetic ordering with Néel temperature of 350℃, Which is a suitable candidate to attain the ferroelectric and antiferromagnetic domain coupling at room temperature(RT).At present, TiO₂ thin films have been investigated for numerous integrated microelectronic device applications such as high-K materials and gate dielectrics. Results of these studies have shown that TiO₂ thin films have high dielectric constants, low dielectric loss, low leakage currents, and low defect densities. Recently, there are a few reports on the potential of TiO₂ as a buffer layer for perovskite ferroelectric films, such as Bi₄Ti₃O₁₂ related compounds, (Ba,Sr)TiO₃, and Pb(Zr,Ti)O₃. However, there is no report on the effects of TiO₂ buffer layers on the microstructure and electrical properties of the BFO films on Si substrates. Since it is difficult to get pure-phase BFO films on silicon substrates, it is our motivation to modulate the growth of BFO films on silicon substrates using the TiO₂ buffer layer in this study.The effect of TiO₂ buffer layer on the microstructure and ferroelectric and magnetic properties of BFO films produced by a Sol-Gel method on both Si(100) and Pt(111)/Ti/SiO₂/Si(100) substrates was studied. X-ray diffraction and Atomic force microscope showed that the TiO₂ buffer layer is critical for improving the crystallinity and surface roughness. Comparing with the films crystallized directly onto the Si and Pt/Ti/SiO₂/Si substrates, the BFO films on the TiO₂ buffer layer have pure perovskite phase without Bi2O₃, Fe2O₃ or Bi2Fe4O9 phases. At room temperature, obvious multiferroic behavior with the remanent polarization of 9.8μC/cm2 and saturation magnetization of 17 emu/cm3 was observed in the films having TiO₂ buffer layer.