Strain engineering of monoclinic domains in K x Na 1-x NbO 3 epitaxial layers: a pathway to enhanced piezoelectric properties

• Published in: Nanotechnology 2017-06, Vol.28 (24), p.24LT02
• Main Authors: Schmidbauer, Martin, Braun, Dorothee, Markurt, Toni, Hanke, Michael, Schwarzkopf, Jutta
• Format: Article
• Language: English
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/aa715a

A novel concept to obtain a ferroelectric material with enhanced piezoelectric properties is proposed. This approach is based on the combination of two pathways: (i) the evolution of a ferroelectric monoclinic phase and, (ii) the coexistence of different types of ferroelectric domains leading to polarization discontinuities at the domain walls. Each of these pathways enables polarization rotation in the material which is responsible for giant piezoelectricity. Targeted incorporation of anisotropic epitaxial lattice strain is used to implement this approach. The feasibility of our concept is demonstrated for K Na NbO epitaxial layers grown on NdScO substrates where the coexistence of (100) and (001) pseudocubic oriented monoclinic domains is experimentally verified. This coexistence results in a complex periodic domain pattern with alternating emergence of ferroelectric in-plane a a and inclined M monoclinic phases, which differ in the direction of the electrical polarization vector. Our approach opens the possibility to exploit ferroelectric properties in both vertical and lateral directions and to achieve enhanced piezoelectric properties in lead-free material caused by singularities at the domains walls.