For the Autumn 2023 semester the LSME is offering the following student projects. These can be taken as masters thesis as semester projects in materials (SMX) or physics (SPH). The photonics project is also suitable for the EPFL minor in photonics.
Simulating atomic resolution analytical STEM data
In the LSME we regularly record analytical spectroscopic datasets (EDXS or EELS) at an atomic resolution using the aberration-corrected microscope at EPFL. While these datasets readily give qualitative insights into the atomic distributions of different elements, obtaining quantitative information is not straightforwards owing to complex effects of electron probe channeling in the sample. In order to address this deficit, it is necessary to simulate the atomic resolution maps for comparison with experimental datasets. Correct simulations should, in turn, allow us to correctly identify chemical intermixing across atomic boundaries. This project will focus on making such simulations, using various open or closed source software packages such as muSTEM. Simulated data will be compared to experimental data recorded on samples of interest by LSME researchers or project collaborators.
Contact: [email protected]
EELS simulations of dielectric photonic nanocavities
In a recent study of optical nanocavities, made from dielectric silicon, using low-loss electron energy-loss spectroscopy (EELS), we identified that the EELS data give valuable insights into different optical eigenmodes with a spatial resolution of a few 10s of nanometers – so far below the diffraction limit. While data correlations could be made, it is also valuable to be able to simulate the recorded EEL spectra. Recently, this has been shown possible using an approach within the COMSOL package. This project will be focused on developing and implementing such simulations, both for reference plasmonic spectra and more specifically for the dielectric nanocavities. Extensive experimental data is already available for comparison with, and validation of, the EELS simulations. Note that this project is suitable for the EPFL minor in photonics.
Contact: [email protected]
4D-STEM for atomic imaging of oxide thin films
Recently, a pixelated detector was installed on the flagship Titan Themis microscope at CIME, EPFL’s electron microscopy platform, that allows the acquisition of diffraction patterns while rastering an atomic resolution probe in scanning transmission electron microscopy (STEM) mode. In this project, this “4D-STEM” technique will be applied to the study of perovskite oxide thin films. The goal will be to retrieve images of the atomic lattices from the 4D-STEM data that have a higher quality than those recorded using the conventional monolithic STEM detectors. After acquiring data at the microscope, the focus of the project will be on the data analysis and lattice image reconstruction.
Contact: [email protected]