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.