Synthesis of epitaxial BiFeO3 films by chemical solution deposition on Pt(100)

Thin (012) oriented epitaxial films of rhombohedral (R3c) BiFeO3, ∼120 nm thickness, were obtained by means of chemical solution deposition on MgO(100)/Pt(100) substrates using an alkoxide based precursor system. X-ray diffraction and transmission electron microscopy (TEM) analysis confirmed good epitaxial matching to the substrate. The results show that careful control of the bismuth excess used for counterbalancing evaporation during crystallization is required. In contrast to lead-containing systems such as PZT, where Pb is pushed to the surface by the crystallization front where it evaporates, the Bi excess forms a Bi-rich phase at the BiFeO3/Pt interface. This phase is believed to represent a Fe substituted version of the high temperature phase δ-Bi2O3. TEM analysis shows that this phase grows on the substrate with (111) and (001) orientation. It is further found that BiFeO3 grows with (012) orientation on this phase as well, making an overall epitaxial film of BiFeO3 possible. Crystallization theory was applied to explain the presence of a Bi-rich secondary phase.