Materials science

Investigating plasmonic and dielectric nanostructures with cathodoluminescence
Dr. Saskia Fiedler is a Postdoc at SDU (University of Southern Denmark) Nano Optics and The Mads Clausen Institute. Her research is focused on electron beam-based spectroscopy, namely CL and EELS, of plasmonic and dielectric nanostructures. Next to physics, her biggest passion is dressage. Other than that, Dr. Fiedler enjoys lots of different sports such as badminton, scuba diving, weightlifting, hiking, boxing.

Her current journey and passion for cathodoluminescence started from traveling in a camper van across Australia for 7 months, which made her fall in love with the country and the lifestyle. So, Dr. Fiedler decided to stay another 3.5 years to do her PhD at the University of Technology Sydney in nanophotonics. Subsequently, the extensive cathodoluminescence experience from her work at UTS helped her to get a postdoc position in a prestigious nano optics group at the University of Southern Denmark.

In her research, Dr. Fiedler is taking advantage of the up to sub-nanometer spatial resolution in combination with a high spectral resolution, which allows for correlation of the morphology with the spectral response of the sample under investigation. Additional conventional optics such as photoluminescence, dark-field scattering, and Raman spectroscopy are being used to complement and compare near- and far-field techniques. Her extensive experimental investigation of different types of materials, such as metallic and dielectric nanostructures, 2D-material stacks and single photon emitters in nanodiamonds, is being complemented by in-depth theoretical calculations performed by her colleagues.

The cathodoluminescence detection system is actively used by Dr Fiedler in her research. To study nanostructures at the true nanoscale, the very local excitation by an electron beam is essential. Therefore, SPARC Spectral system is used to investigate, for example, the mode distribution of plasmonic and Mie resonances in single metallic and dielectric nanoparticles, respectively. Dr. Fiedler and her group were able to demonstrate that optically dark plasmonic modes in single gold nanodisks can be mapped out by electron beam excitation and their visibility can be increased by taking advantage of substrate effects (read the paper here). Similarly, the distribution of Mie resonances within a single high-index dielectric nanosphere can be studied and mapped in CL.

Furthermore, her group extended the system with a g(2) setup to investigate (anti-) bunching effects in nanodiamonds, showing electron beam current-dependent bunching/anti-bunching. The SPARC Spectral system was also used for another interesting project which focused on the electron beam excitation of TMDC monolayers encapsulated in hBN, where giant photon bunching was observed.

It was very reassuring to know that the SPARC system was developed by a trusted and esteemed colleague in our field, rather than being some general-purpose solution in material science.

Dr. Fiedler also mentions that she was overall happy with the Delmic service team.

Technicians have been easy to get in touch with, knowledgeable and fast. The support and help by the application specialists were outstanding – they were very helpful in discussing ideas and design possibilities to further expand our CL capabilities.
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