Regensburg 2019 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 12: Poster session I

MM 12.31: Poster

Montag, 1. April 2019, 19:15–20:45, Poster C

Determination of the Vacancy Formation Enthalpy of La by Positron Annihilation Spectroscopy — •Lucian Mathes, Thomas Gigl, and Christoph Hugenschmidt — Heinz Maier-Leibnitz Zentrum (MLZ) and Physik Department E21, Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany

The coincident Doppler broadening (CDB) spectrometer at the positron beam facility NEPOMUC of the FRM II enables spatially resolved defect studies by using Doppler broadening spectroscopy (DBS) of the positron-electron annihilation line. In order to perform depth dependent measurements of the near-surface region and the bulk of a sample, the positron implantation energy can be set up to 30 keV. A heatable sample holder enables temperature dependent in-situ defect spectroscopy from room temperature up to 1000 K. By using temperature dependent DBS we succeeded in determining the vacancy formation enthalpy of La for the first time. First, the as-received samples were annealed in situ, i.e. the decrease of the so called S-parameter indicated the annealing of lattice defects. For comparison, Cu served as reference material. During a second heating cycle the increase of the vacancy concentration was clearly observed which allowed a calculation of the vacancy formation enthalpy. In addition, a temperature dependence of the vacancy formation enthalpy in La was observed. Financial support by BMBF (project no. 05K10WOB) is gratefully acknowledged.