Growth temperature and thickness dependences of crystal and micro domain structures of BiFeO3 epitaxial films

Crystal structure and microstructure such as surface morphology and ferroelectric domain structure of 0.2- to 2.0-μm-thick BiFeO₃ epitaxial films deposited between 400 and 700°C were evaluated. For the films deposited at 500°C, tetragonal BiFeO₃ was grown The relaxation of the lattice strain drastically occurred by increasing the film thickness. On the other hand, rhombohedral BiFeO₃ with tetragonal distortion was grown and the relaxation of the lattice strain occurred by the grain growth for the films deposited at 650°C. The grains consist of single domain for the films deposited at 500°C, while those of films deposited at 650°C consist of multi domains. It is suggested that the domain walls existing inside the grains contributes the piezoelectric response.