Hierarchy and scaling behavior of multi-rank domain patterns in ferroelectric K 0.9 Na 0.1 NbO 3 strained films

• Published in: Nanotechnology 2018-01, Vol.29 (1), p.015701
• Main Authors: Braun, Dorothee, Schmidbauer, Martin, Hanke, Michael, Schwarzkopf, Jutta
• Format: Article
• Language: English
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/aa98a4

The formation process of a ferroelectric multi-rank domain pattern in the thickness range of 7-52 nm is investigated for monoclinic K Na NbO strained epitaxial films on (110) NdScO substrates. Although the elastic strain energy density is degenerated for two pseudocubic orientations, a distinctive hierarchy of domain evolution is observed with exclusive in-plane a a domains for very thin films and the retarded onset of a ferroelectric M phase at larger film thickness. This is accompanied by a thickness dependent transformation from stripe domains to a herringbone pattern and, eventually, for the thickest film, to a checkerboard-like structure. These transformations in the domain arrangement and width are correlated to energetic aspects as depolarization field and anisotropic strain relaxation in the film. While for the M domains plastic strain relaxation is throughout observed, the a a domains show a two-step strain relaxation mechanism starting with an in-plane elastic shearing, which is followed by plastic lattice relaxation. Our results highlight a pathway for engineering and patterning of periodic ferroelectric domain structures.