FOR 5044:  Periodic low-dimensional defect structures in polar oxides

• Subject Area: Materials Science and Engineering ; Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426703838

The research unit FOR5044 focuses on the correlation of defect structure, electronic and ionic transport, and electromechanical properties in polar oxides using the model system Li(Nb,Ta)O3 (LNT) as an example. Based on the successful growth of high-quality solid solution crystals, fundamental insights into the special defect structure, the dominant charge carriers and transport mechanisms, the extraordinary polaron dynamics, and the acoustic losses were achieved in the first funding period. This was only possible by a coherent combination of experimental and theoretical research in close cooperation. The transport phenomena in domain walls were investigated and interpreted over a wide temperature range, resulting in a comprehensive overall picture, that is reflected in more than 50 mostly joint publications. Far-reaching application prospects for LNT are becoming apparent, e.g. in the field of piezoelectric sensors and nanoelectronics, even at high temperatures. Of particular importance to the research area are 6 international workshops, conferences and symposia, initiated and organized by FOR5044. The close cooperation between the subprojects is also reflected in the promotion of young scientists, which includes knowledge transfer through the exchange of PhD students and the joint supervision of theses. Based on new and follow-up research questions from the first funding period, the strategic orientation of the second phase is defined in particular by further fundamental research, the addition of thin films or heterostructures and doping. By limiting dimensionality and by deliberately introducing mechanical stresses, films are expected to provide access to further new physical phenomena in LNT. Doping allows the control of ion and electron transport as well as optical and photoelectric properties. In combination with domain walls, film systems of different compositions are expected to produce novel structures or interfaces whose properties can be locally tailored and, eventually, form a 2D electron gas. This will provide the basis for the development of novel high-tech components for piezotronics, micro-actuators, integrated acoustics and photonics as well as quantum technologies based on LNT. The results can be transferred to other material systems such as multiferroics and perovskite-related materials. The scientists involved have complementary competences, ranging from crystal growth and thin film preparation to the investigation of polaron dynamics, domain structures, ion transport, electromechanical properties and modelling. The decentralized research unit ensures collaborative research of complementary working groups, which is not the case in individual research institutions.

• DFG Programme: Research Units
• International Connection: Hungary, Italy

Projects

• Acoustic loss and electromechanical properties of LiNb_(1-x)Ta_xO_3 (Applicant Fritze, Holger )
• Control of non-linear self-localization phenomena of strongly coupling charge carriers in LiNb_(1-x)Ta_xO_3 (LNT) - solid solutions (Applicant Imlau, Mirco )
• Control of nonlinear self-localisation phenomena of charge carriers with strong coupling in LiNb1-xTaxO3 (LNT) solid solutions (Applicant Imlau, Mirco )
• Coordination Funds (Applicant Fritze, Holger )
• Crystal Growth and Basic Properties of Lithium Niobate - Lithium Tantalate Solid Solution Crystals (Applicant Ganschow, Steffen )
• Domain Walls in LNT Mixed Crystals (Applicant Eng, Lukas M. )
• Domain Walls in LNT Mixed Crystals (Applicant Eng, Lukas M. )
• Epitaxial LiNb1-xTaxO3 Films (Applicant Schwarzkopf, Jutta )
• Ion transport and point defects in LiNb_(1-x)Ta_xO_3 solid solutions (Applicant Schmidt, Harald )
• Modeling ferroelectric LiNb_(1-x)Ta_xO_3 solid solutions and their defect structure (Applicant Sanna, Simone )
• Tailored domain structures in ferroelectric heterostructures (Applicants Eng, Lukas M. ;  Silberhorn, Christine )
• Tailored domain structures in LiNb_(1-x)Ta_xO_3 solid solutions (Applicant Ruesing, Michael )
• Thermal Stability and Application Limits of LiNb_(1-x)Ta_xO_3 solid solutions (Applicant Suhak, Yuriy )

• Spokesperson: Professor Dr.-Ing. Holger Fritze