E138
Institut für Festkörperphysik

RESEARCH

Properties

ELNES - Density of states


Core loss spectroscopies such as XAS (X-Ray Absorption Spectroscopy) and EELS (Electron Energy Loss Spectroscopy) are powerful tools for the analysis of the electronic structure of materials.

The fine structure of ionisation edges detected by EELS (ELNES - electron energy loss near edge structure) has long been used as a source of information on the local chemistry of the specimen. Surpassing pure quantification it is the density of unoccupied states above the Fermi level that determines the ELNES, and consequently the bonding of the ionised atom in its crystalline environment plays an important role.

ELNES are recorded in the TEM with an energy resolution of 0.7 eV and a lateral resolution of less than 1 nm. Comparison with calculation based on the density functional theory (full potential augmented plane waves code WIEN2k) allow a detailled interpretation of the fine structures.

Fig.1: The figure shows the O-K edge in diferent Vanadium oxides. The experiment (left) compared with theoretical calculations (right). Investigation done in cooperation with the Friz Haber Institute Berlin.
Contact: M. Stöger-Pollach