Effects of Bismuth Oxide Buffer Layer on BiFeO3 Thin Film

Bismuth ferrite (BiFeO₃) thin films with Bi₂O₃ buffer layers were prepared on Si/SiO₂/TiO₂/Pt substrates by sol–gel‐derived spin‐coating method. The structural and electrical properties of BiFeO₃ was effectively improved by adding a Bi₂O₃ buffer layers either at Pt/BiFeO₃ interface or on BiFeO₃ surface, also strongly depending on the positions and the annealing conditions of buffer layers. A 500°C‐annealed Bi₂O₃ buffer layer could act as a Bi source for compensating Bi volatilization and a diffusion barrier for species from BiFeO₃. A near stoichiometric BiFeO₃ with less defects and substrate contamination was obtained by employing a 500°C‐annealed Bi₂O₃ buffer layer in between Pt substrate and BiFeO₃. The structure change in BiFeO₃ led by such a buffer layer should result from the interfacial constraint between buffer layer and BiFeO₃. Furthermore, this crystalline BiFeO₃ specimen exhibited a highly (100)‐textured, where this preferred orientation was attributed to the accumulation of Bi at Pt/BFO interface. Therefore, the Pt/500°C‐annealed Bi₂O₃/BiFeO₃/Pt thin film exhibited the good ferroelectric and magnetic properties. As compared to the usual method for controlling BiFeO₃ composition by adding excess Bi, this study indicates the more advantages using a Bi₂O₃ buffer layer.