Tailored domain structures in LiNb_(1-x)Ta_xO_3 solid solutions

• Applicant: Dr. Michael Ruesing
• Subject Area: Synthesis and Properties of Functional Materials ; Experimental Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426703838

The proposal is part of the research group “Periodic low dimensional defect structures in polaroxides”, which is dedicated to the correlation of defect structure, electron and ion transport, andelectromechanical properties using the model system lithium niobate - lithium tantalate (LiNb_(1-x)Ta_xO_3, LNT).This proposal aims at the fabrication of tailored ferroelectric domain structures in the modelsystem via electric field poling. Structured ferroelectric domains are the fundamental buildingblock to realize various applications in ferroelectric materials, such as in nonlinear and quantumoptics, ferroelectric surface structuring, piezotronics, or novel electronics. The reliable andreproducible fabrication of homogeneous ferroelectric domains structures requires a profoundunderstanding of the underlying physical mechanism related to the poling process over thecomplete range of stoichiometric compositions in the model system. In the context of the mixedcrystals defects and local variations in the Nb/Ta stoichiometry create new challenges forrealizing homogeneous domain structures. At the same time the mixed crystals promise novelpossibilities to control and structure ferroelectric domains and domain walls.The fabrication of structured domain grids is realized with electric field poling at roomtemperature. In combination with standard lithography this enables the realization of two-dimensional ferroelectric domains in tailored, arbitrary patterns. To achieve a complete picture ofthe poling process in the model system, investigations are performed on the polar, as well asnon-polar surfaces To analyze the poling process and the influence of various parameters,complementary methods will be used to investigate the fabricated domain structures, such asnonlinear microscopy, piezo-response force microscopy, polarization microscopy and µ-Ramanspectroscopy. This allows for the analysis of material constants directly related to the polingprocess, such as coercive fields or domain propagation constants, as well as for the analysis ofthe influences of defects or local stoichiometry on the formation of ferroelectric domains anddomain walls. The fabricated domain structures and their domain walls, which can beunderstood as low dimensional extended defects, will be used to investigate the interaction ofdomain structures with other material parameters, such as ion and electron transport, theelectromechanical properties, thermal stability or polarons, which are investigated within theresearch group.

• DFG Programme: Research Units
• Subproject of: FOR 5044: Periodic low-dimensional defect structures in polar oxides
• Co-Investigator: Professor Dr. Lukas M. Eng