Growth mechanism and ferroelectric domain structure study on epitaxial BiFeO_3 film grown on (La_(0.3)Sr_(0.7))(Al_(0.65)Ta_(0.35))O_3

摘要

BiFeO_3 (BFO) film is epitaxially grown on the (La_(0.3)Sr_(0.7))(Al_(0.65)Ta_(0.35))O_3 (LSAT) substrates to investigate lattice mismatch effect on domain structure and lattice strain status within the BFO film. Atomic resolution scanning transmission electron microscope image, [Fig. 1(a)] selected area electron diffraction (SAED) pattern, and X-ray reciprocal space mapping (XRSM) clearly reveal that the lattice strain originating from the lattice mismatch between BFO and LSAT is relaxed by causing misfit dislocations in BFO film. [Fig. 1(a)] The SAED and XRSM data indicate crystal structure of BFO film is rhombohedral with space group of R3c assigned rhombohedral specific diffraction spots. In particular, XRSM acquired along two different in-plane orientations reveal that BFO layer consists of two different domains that were 90° off each other around surface normal orientation. Atomistic model based on the orientation relation found by SAED and XRSM shows the domain structure is consistent with so called 71° ferroelectric domain reported previously. [Fig. 1(b)] The lattice mismatch of ï½2.8% calculated based on the epitaxial relation is proposed to be too large to be stored as elastic strain within BFO layer.