Teilprojekt 5
TP5
Tailored domain structures in LiNb1-xTaxO3 solid solutions
This project aims at the fabrication of tailored ferroelectric domain structures in the model system lithium niobate–tantalate via electric field poling. Structured ferroelectric domains are the fundamental building block to enable various applications of ferroelectric materials, such as in nonlinear and quantum optics, ferroelectric surface structuring, piezotronics, or electronics. The reliable and reproducible fabrication of homogeneous ferroelectric domain structures requires a profound understanding of the underlying physical mechanisms related to the poling process over the complete range of stoichiometric compositions in the mixed crystals. In the context of the mixed crystals, the defects and local variations in the Nb/Ta stoichiometry create new challenges for realizing homogeneous domain structures. At the same time, the mixed crystals offer novel possibilities to control and structure ferroelectric domains and domain walls
via control of stoichiometry.
The fabrication of structured domain grids is realized with electric field poling at room temperature. In combination with standard lithography or local UV illumination this enables the realization of two-dimensional ferroelectric domains in tailored, arbitrary patterns. To achieve a complete picture of the poling process in the model system, investigations are performed on the polar (c-surface), as well as non-polar surfaces (a- and b-surfaces). To analyze the poling process and the influence of various parameters, complementary methods will be used to investigate the fabricated domain structures, such as nonlinear microscopy, piezo-response force microscopy, polarization microscopy and μ-Raman spectroscopy. This will allow for the analysis of material constants directly related to the poling process, such as coercive fields or domain propagation speeds, as well as for the analysis of the influences of defects or local stoichiometry on the formation of ferroelectric domains and domain walls. The fabricated domain structures and their domain walls, which can be understood as low dimensional extended defects, will be used to investigate the interaction of domain structures with other material parameters, such as ion and electronic transport, the electromechanical properties, thermal stability or polarons, which are investigated within the research group.
Objectives
- Reliable and reproducible fabrication of ferroelectric domain structures
- Analysis of the specific poling properties of the mixed crystals
- Investigation of the domain and domain wall properties
