Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 12: Materials for the Storage and Conversion of Energy III / Functional Materials I

MM 12.8: Talk

Tuesday, March 10, 2026, 12:15–12:30, SCH/A216

Positron annihilation spectroscopy for atomic defects in functional materials — •Maciej Oskar Liedke, Eric Hirschmann, Jyoti Verma, Sebastian Klug, and Andreas Wagner — Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328, Germany

Positron annihilation spectroscopy (PAS) is a highly effective method for the characterization of point defects and their agglomerates in functional bulk materials and thin films. The method provides access to defect concentration in the range of 0.01-100 ppm, which is common for most material classes, including metals, semi-, and superconductors. The utilization of the radiation source ELBE at HZDR in Dresden, which delivers a pulsed positron beam, enables depth profiling by varying the kinetic energy of positrons. The integration of PAS techniques with density functional theory calculations facilitates understanding of defect types and local chemistry at the defected crystal sites. In this contribution, we will present few highlights from positron studies and discuss the role of defects in wide-bandgap semiconductors, such as Ga2O3, in addition to superconducting Nb-based coatings, and high-entropy alloys intended for fusion applications. The presentation will emphasize the control over transitions between different polymorphs of Ga2O3 driven by ion irradiation and resulting defect microstructure. Furthermore, we will demonstrate the correlations between deposition parameters and defect landscapes in Nb alloys. We will conclude discussing healing processes in CrFeMnNi subjected to Fe-ion irradiation, which is analogous to neutron radiation in nuclear systems.

Keywords: positron annihilation spectroscopy; semiconductors; high-entropy alloys; superconductors