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O: Fachverband Oberflächenphysik

O 95: Other And Miscellaneous

O 95.4: Vortrag

Donnerstag, 15. März 2018, 12:45–13:00, MA 144

Development of a Novel Reflection High-Energy Positron Diffractometer at NEPOMUC — •Matthias Dodenhöft, Sebastian Vohburger, and Christoph Hugenschmidt — Heinz Maier-Leibnitz Zentrum (MLZ) and Physik Department E21, Technische Universität München, 85748 Garching, Germany

The arrangement of surface atoms is an important input parameter for density functional theory (DFT) calculations of the electronic structure at the surface. It has been shown that Total Reflection High-Energy Positron Diffraction (TRHEPD) is an ideal technique to determine the structure of the topmost and the immediate subsurface atomic layer of crystal surfaces. In contrast to electrons that are used in Reflection High-Energy Electron Diffraction (RHEED), positrons exhibit the phenomenon of total reflection for glancing angles smaller than the critical angle θc leading to the outstanding surface sensitivity of TRHEPD. Additional information about near-surface layers can be obtained by increasing the glancing angle above the critical angle.
Currently, we develop a new TRHEPD setup that will be coupled to the high-intensity positron source NEPOMUC in 2018. The TRHEPD setup features UHV down to 10^-10mbar, sample temperatures up to 1000^∘C and a RHEED system for complementary measurements. In combination with the existing Surface Spectrometer (SuSpect), NEPOMUC will provide a unique ensemble to characterize surfaces using positrons. This project is supported by the BMBF (funding number 05K16WO7).