Scanning X-ray nanodiffraction with 100 nm spatial resolution has been applied to investigate the ferroelectric domain structure of K 0.75Na 0.25NbO 3 epitaxial layers grown on a (110) TbScO 3 substrate using metal–organic chemical vapour deposition. Two variants differing in domain wall alignment and vertical lattice parameters have been identified and independently analysed.
Scanning X-ray nanodiffraction on a highly periodic ferroelectric domain pattern of a strained K 0.75Na 0.25NbO 3 epitaxial layer has been performed by using a focused X-ray beam of about 100 nm probe size. A 90°-rotated domain variant which is aligned along [1 2] TSO has been found in addition to the predominant domain variant where the domains are aligned along the [ 12] TSO direction of the underlying (110) TbScO 3 (TSO) orthorhombic substrate. Owing to the larger elastic strain energy density, the 90°-rotated domains appear with significantly reduced probability. Furthermore, the 90°-rotated variant shows a larger vertical lattice spacing than the 0°-rotated domain variant. Calculations based on linear elasticity theory substantiate that this difference is caused by the elastic anisotropy of the K 0.75Na 0.25NbO 3 epitaxial layer.