Public Physic Colloquium in the Winterer Terms 2012 /2013 in Münster
Place:     Germany, 48149 Münster, Wilhelm-Klemm-Str. 10, IG I, HS 2
Time:     Thursday, 08.11.2012  16:00 h c.t.
Colloquium Coffee at 15:45 h  at the Lecture Hall

Basics and applications of low-loss EELS
Dr. Wilfried Sigle, MPI für intelligente Systeme, Stuttgart

Energy loss of fast electrons penetrating a slab of material is dominated by losses in the energy range below 100 eV. These losses are either due to collective excitations of the electrons or to single-electron excitations from occupied to unoccupied states. Less pronounced are losses due to Cerenkov radiation, transition radiation, phonons, and bremsstrahlung. The material response can be described by the dielectric function ε(ω)=ε₁(ω)+iε₂(ω), where ε₁ is determined by the polarizability of the material and ε₂ by the single-electron absorption.

The multitude of processes and the high signal intensity makes low-less EELS a rich playground for materials characterization. Various examples will be presented how low-energy-loss data are acquired, analyzed, and interpreted:

1. Use of volume plasmon energies for material characterization.
2. Measurement of band-gaps in semiconductor systems.
3. Detection of interface plasmons.
4. Mapping of surface-plasmon resonances in metallic nanostructures.

Special emphasis will be devoted to the final issue.

Invited from: Prof. Dr. Helmut Kohl

By Order of the Professors of the Department of Physics

Prof. Dr. Nikos Doltsinis