Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 25: Poster

KFM 25.22: Poster

Donnerstag, 8. September 2022, 15:00–18:00, P2

A Doppler-Broadening Spectrometer for Defect Studies and Thin-Film Analysis — •Lucian Mathes, Vassily Vadimovitch Burwitz, and Christoph Hugenschmidt — Heinz Maier-Leibnitz Zentrum (MLZ), Technical University of Munich, Lichtenbergstr. 1, 85748 Garching, Germany

The laboratory positron source for Doppler-broadening spectroscopy (Labbeam) is the most recent addition to the instrument fleet of the TUM research group “Physics with Positrons”. It complements the Coincidence Doppler-broadening Spectrometer (CDBS) at NEPOMUC in many ways. Positrons are provided by a 22Na source, then moderated in a thin tungsten foil from which they are guided to the sample chamber by a system of longitudinal and transverse magnetic fields. The positrons are accelerated electrostatically by a potential difference applied between moderator and sample to a kinetic energy from a few electronvolts up to 40 keV.

Depth resolved measurements of so-called lineshape parameters of the 511 keV annihilation line (S/W/Valley-to-Peak) are characteristics of different material properties. Valley-to-Peak, for instance, enables the observation of Ps formation at the surface, while an S(E) profile allows for determination of the positron diffusion length (which is cor- related to the defect concentration). The Labbeam setup is especially suitable for surface, near-surface, and thin-film analysis due to its pos- sible implantation energies down to a few eV. Experimental results on tungsten, oxides, and thin films will be presented.

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