Single crystal low temperature ultrafast fluorescence microscope

• Subject Area: Condensed Matter Physics
• Term: Funded in 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 443153421

The new large apparatus will be used to probe the fundamental optical, electronic and optoelectronic properties of novel materials. The large question is how the composition and structure of these materials determine these properties. With this knowledge, the materials can be tailored and optimized for specific optoelectronic applications, such as lasers, LEDs or solar cells. The base for the investigations will be nanostructured materials, as they are often easy to synthesize reproducibly. Moreover, once shrunk down sufficiently, they exhibit quantum confinement effects, which can be beneficial for understanding the inner workings of these materials. These effects also offer an additional way to tune the material properties. The laser source included in the device with its short excitation wavelengths (<400 nm) and extra short pulses (300 fs) as well as the ultrafast detector is an important component for the plans of the group. They will allow the group’s experiments to focus more on single crystals and ultrafast processes occurring therein, such as nonradiative energy transfer (FRET) or exciton-exciton annihilation.Four material systems will be the foundation of the experiments: a) halide perovskite nanocrystals, b) carbon dots, c) ZnO crystals doped with amino acids (ZnO-AA) and d) hybrid plasmonic-excitonic nanostructures. The main goal for the halide perovskites is overcoming the stability problems as well as their poor performance in the blue part of the visible spectrum. The approach to enhance stability involves growing the nanocrystals inside polymer micelles, enabling fine-tuning of the sizes and protection against environmentally-induced degradation. A promising candidate for enhancing the blue emission are two-dimensional nanoplatelets. Both of these nanosystems have great potential, but much needs to be understood about their synthesis and fundamental properties, especially on the single crystal level. There is also more room for improvement in their overall performance and for developing strategies for optoelectronic integration. Both the carbon dots and the ZnO crystals are interesting hybrid materials with organic and inorganic components. Usages are widespread, typically in the blue/ultraviolet spectrum, ranging from LEDs to biomarkers and even photocatalysis. Carbon dots have proven elusive to understand and require single crystal studies to unravel the interplay between morphology and optical properties. These studies have proven elusive due to the carbon dots' small size and the necessary ultraviolet optical excitation. Incorporation amino acids into the ZnO crystal structure enables tuning of the crystal properties, however, the exact mechanism behind this is far from being understood. Plasmonic structures will be coupled with these (mainly excitonic) nanomaterials to enhance and tune their absorption and emission properties, enabling, for examale, strong single-photon sources.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Einzelkristall Tieftemperatur Ultrakurzzeitfluoreszenzmikroskop
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Ludwig-Maximilians-Universität München
• Leader: Professor Dr. Alexander Urban