Nanoscale multifunctionale oxides
Materials- and Interface design for new concepts in data storage and renewable energy conversion
Prof. Dr. Christian Jooss
Complex transition metal oxides show a rich world of properties such as magnetism, high-temperature superconductivity, insulator-metal transitions and optical properties which are rarely understood. They represent emergent behavior based on the correlations between electronic states, lattice structure and defects.
Nanostructures and interfaces in such materials allow for new functionalities in electronic data storage and in energy conversion. We investigate new mechanisms in photovoltaic energy conversion at interfaces via polarons and optically induced phase transitions in strongly correlated systems. The study of the change of the atomic and electronic structure of oxide electrodes in their active state during electro-catalytic water splitting allows us to gain an understanding of the mechanisms and in the long term the development of better catalysts. Electrochemical redistribution of vacancies in oxides under electric stimulation can give rise to the development of new concepts of data storage similar to those in neurons. Furthermore, we study thermal transport in nanoscale oxides which have a great potential for thermoelectric applications.
Figure: High resolution transmission electron microscopy images of interfaces involving complex oxides.
The following fundamental questions drives our research:
- What determines the atomic and electronic structure of interfaces and their properties in complex oxides?
- How can we understand mechanisms of energy conversion in strongly correlated systems in nanoscale oxides and how can they be utilized in future applications?
- Which synthesis processes are suitable for the design of interfaces and nanostructures on atomic scales?
In order to contribute to answering these questions, we develop new approaches for in-situ studies in electron microscopes of materials from nano- to atomic scales. This involves studies under electric, optic, thermal and chemical stimulation, using an environmental TEM. The methods allow for gaining an improved understanding of complex oxides on smallest length scales and various time scales during external stimuli. Such capabilities are required for the further development of established concepts and theories in materials physics.
Figure: Electrical stimulation and measurement of a metal-oxide heterostructure in a transition electron microscope via a piezo-controlled nanotip.
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