Short range biaxial strain relief mechanism within epitaxially grown BiFeO(3)

Lattice mismatch-induced biaxial strain effect on the crystal structure and growth mechanism is investigated for the BiFeO(3) films grown on La(0.6)Sr(0.4)MnO(3)/SrTiO(3) and YAlO(3) substrates. Nano-beam electron diffraction, structure factor calculation and x-ray reciprocal space mapping unambiguously confirm that the crystal structure within both of the BiFeO(3) thin films is rhombohedral by showing the rhombohedral signature Bragg’s reflections. Further investigation with atomic resolution scanning transmission electron microscopy reveals that while the ~1.0% of the lattice mismatch found in the BiFeO(3) grown on La(0.6)Sr(0.4)MnO(3)/SrTiO(3) is exerted as biaxial in-plane compressive strain with atomistically coherent interface, the ~6.8% of the lattice mismatch found in the BiFeO(3) grown on YAlO(3) is relaxed at the interface by introducing dislocations. The present result demonstrates the importance of: (1) identification of the epitaxial relationship between BFO and its substrate material to quantitatively evaluate the amount of the lattice strain within BFO film and (2) the atomistically coherent BFO/substrate interface for the lattice mismatch to exert the lattice strain.