Fraunhofer Institute for Microstructure of Materials and Systems IMWSA new generation of spectrometers extends the application range of electron energy loss spectroscopy (EELS) to up to 30 keV. This method allows for very precise and comprehensive material analyses, as EELS spectra provide a wide range of information about the elements present in the sample, including their valence. Unlike comparable methods such as X-ray absorption spectroscopy (XAS), however, it offers spatial resolution on the nanometer scale. A device that utilizes these capabilities, the first of its kind in Europe, is now in operation at the Fraunhofer Institute for Microstructure of Materials and Systems IMWS in Halle (Saale). The research team is using the new capabilities for application-related questions concerning glasses, glass ceramics, and components from microelectronics and photovoltaics.
Electron energy loss spectroscopy (EELS) is an important analytical method in materials science. It complements transmission electron microscopy (TEM) – a method of electron microscopy that offers particularly high lateral resolution – to provide comprehensive and valuable information about the material under investigation.
In transmission electron microscopy, when high-energy electrons pass through a thin material sample, they lose some of their primary energy through interaction with the material via various processes. The energy loss depends, among other things, on the chemical composition, the bonding states, and the crystal structure of the material under investigation. Analyzing the energy loss thus provides access to knowledge of these material properties – with spatial resolution in the nanometer range. This technique can be used, for example, to detect defects in semiconductor materials or analyze nanostructures in glass ceramics.
Traditionally, EELS was limited to the detection of energy losses of less than 2 keV for technical reasons. The newly available device overcomes these limitations. With a new monochromatized and double-corrected high-end TEM (Spectra Ultra, Thermo Fisher Scientific) available at Fraunhofer IMWS, in combination with an innovative Iliad EEL spectrometer, a significantly expanded range of energy losses up to 30 keV can be addressed.
In the project "Ultimate EELS – Valence, Coordination, Band Structure, and Vibrational Spectroscopy at the Atomic Level," which will run until June 2027, Fraunhofer IMWS is developing suitable use cases to make this new method usable for nanostructure-based material development and failure diagnostics. The focus is on three areas with high application relevance:
- Glass, ceramic, and enamel characterization
- Characterization and failure diagnostics of novel microelectronic devices such as memristors and power electronics components
- Analysis of novel components for photovoltaics, photocatalysis, and electrolysis (such as TOPCon solar cells, tandem solar cells, or PEC cells)
The aspired competence development also includes the development of suitable solutions for sample preparation.
"We now have the ideal equipment for addressing these issues. We will use the project to underpin this enormously valuable expansion of our technical equipment with the corresponding expertise in the use of the complex EELS technology. This will enable us to offer our clients completely new possibilities," says Dr. Christian Patzig, who is leading the project at Fraunhofer IMWS.
(October 20, 2025)