Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 20: Poster session

MM 20.10: Poster

Tuesday, March 27, 2007, 14:45–18:00, Poster C

Removing relativistic effects for the determination of optical properties using EELS — •Michael Stöger-Pollach, Anita Laister, and Peter Schattschneider — Institute for Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10/138, A-1040 Vienna, Austria

Since the energy resolution of modern energy loss (EELS) experiments in a transmission electron microscope (TEM) has improved to less than 0.2 eV full width at half maximum in the elastic peak, valence EELS has attracted interest again. However, due to the fact that the acceleration voltages of conventional TEMs are in the range of 100-300 kV retardation effects become important. The condition for Cerenkov radiation is fulfilled if v > c/n, with c as the speed of light, v as the speed of the probe electron and n as the refractive index of the material.

For determination of optical properties Kramers-Kronig Analysis (KKA) is applied after an iterative removal of relativistic effects and surfce plasmons. Conventinal software does not take relativistic effects into account. Our method therefore gives more precise information on the optical properties of materials. Moreover faint differences of the response function between similar layers can be probed with very high accuracy.

We present the result on two similar SiN:H layers with different H concentration. The difference in the optical refractive index is 2% and can be identified with an accuracy of less than 1%.