Talk given by
 

Prof. Klaus Leifer

Abstract:

EELS spectroscopies have become a standard tool in materials analysis in the TEM. In this talk, we will present selected examples of EELS spectroscopies applied to magnetic materials and third generation solar light absorber layers.

In the first part, we show how the technique of EMCD (electron magnetic circular dichroism) was developed to obtain quantitative orbital to spin magnetic moments and show first results of magnetism at buried interfaces. We have used several acquisition geometries in energy filtered electron spectroscopy to obtain EMCD signals. When magnetic samples were analysed in the spectroscopy geometry of the energy filter, we could show that magnetic signals from different layers, stacked upon each other along the electron beam direction, could be resolved by changing the position of the detector aperture. Besides electron channeling and, of course, the very high spatial resolution of the EMCD technique, the q-selection of the signal is one of the unique features of the EMCD as compared to other techniques analysing magnetic signals.

In the second part, we analyse, using spectroscopic 3D electron tomography, Si rich silicon carbide (SRSC) absorber layers that has undergone an annealing treatment. The thermal treatment leads to the SRSC films spinodally decomposed into a Si-SiC nanocomposite. The nanostructures of the phase separated Si and SiC should have, in principle a very simple structure containing the SiC matrix hosting the Si-nanoparticles. In fact a three dimensional analysis of this system with nanometer resolution is necessary to reveal the complex nanostructure of this system. Whereas typically, one would expect in the two components in the system the Si NPs and the SiC matrix, using the plasmonic signal, we could discover an additional phase. From tomograms, we could localize these phases at three dimensional interfaces in the thin film system.