Events in Physics
CMP seminar - Ralf Hambach
Inelastic Electron scattering in the Transmission Electron Microscope: Experiment and Theory
By combining the spatial resolution of transmission electron microscopes (TEM) with the analytical power of electron energy-loss spectroscopy (EELS), it is now possible to study electronic excitations of nano-objects with a resolution of a few Angstrom. At this scale, theoretical simulations become indispensable to understand experimental spectra and high-resolution images.
First, low-energy excitations (e.g., plasmons) in free-standing single-layer graphene will be considered. We compare EELS experiments at the SALVE-I (sub-angstrom low-voltage) microscope with corresponding time-dependent density-functional theory calculations. Starting from the 2D system, plasmons in more complex materials like graphene multilayers and single-wall carbon nanotubes can be understood by means of simple dielectric models.
Second, we discuss energy-filtered TEM imaging of high-energy excitations (core-loss). Reaching atomic dimensions, extensive numerical simulations using quantum mechanical scattering theory are necessary to understand TEM images formed by inelastically scattered electrons. Theoretical and experimental challenges for mapping unoccupied orbitals in real-space will be assessed.