Department Seminar: Defect Hunting in Materials with Variable Energy Positron Beam System (VEPOS)

  • Date: 18 October 2025

Defect Hunting in Materials with Variable Energy Positron Beam System (VEPOS)

Uğur YAHŞİ and Cumali TAV

Marmara University, Faculty of Science, Department of Physics, 34722 Göztepe, Istanbul
e-mail: uyahsi@marmara.edu.tr  lab: http://positron-fzk-fen.marmara.edu.tr/

Seminar Place: Faculty of Science, Department of Physics, GZF-C114
Seminar Date: 22 October 2025 - 13:00-14:00

Summary
The positron, which is an antimatter particle, serves as an important research tool in the fields of medicine, atomic physics, and materials science. This presentation will describe the determination of defect profiles on surfaces and interfaces using the Variable Energy Positron Beam System (VEPOS). Positrons emitted from a Na-22 source are cooled in a neon (Ne) film moderator at a temperature of 6-7 K, reduced to eV, and directed to the target with adjustable energy values between 0 and 30 keV. Thus, high precision is achieved in extracting surface depth profiles.
PPositron Annihilation Lifetime Spectroscopy (PALS) and Doppler Broadening Spectroscopy (DBS) are the two main methods in positron spectroscopy that play an important role in studying void defects and electron density distributions in materials.
TThese studies, conducted at the Marmara Positronium Laboratory (MARPOS), contribute to advanced research in defect analysis and structural characterization of technological materials.

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Notices

Our paper titled “Depth Defect Analysis of BaO Thin Films Doped with Cd via Positron Annihilation Techniques” has been accepted in Philosophical Magazine.

Our paper has been published in Radiation Effects and Defects in Solids, titled “Swift heavy ion induced damage in nanostructured ZrN film elaborated by magnetron sputtering technique”

Our paper has been published in Journal of Alloys and Compounds titled "Defect Engineering and Magnetic Properties of Cu/Cr Codoped ZnO Nanoparticles."

Our paper has been published: “Graphene oxide-induced free volume effects in proton conductive CS/PVA-based composite electrolytes: a PALS study"

ADEP project has been accepted: "Obtaining high-density materials from nanomaterials synthesized by different methods by flash sintering technique and ..."

BAP project has been accepted: "Investigation of the Conductivity-Free Volume Mechanism of Li Solid Polymer Electrolytes Using Positron Techniques"

Our PhD student Dr. Zainab Raad successfully defended and completed her PhD thesis titled "Point defect investigation in Cu and Cr codoped ZnO with varying Cr content prepared via Sol-Gel method".

Our paper is published in Physica Scripta online by the title: "The impact of reactor neutrons on 6H-SiC followed by irradiation of 91.3 MeV Xe ions - Defects studies using positron annihilation spectroscopy"

A seminar on the introduction of the MARPOS laboratory and positron studies at the Institute of Clean Energy Technologies at Yıldız Technical University.

A seminar on the presentation of the MARPOS laboratory and positron studies at Istanbul University - Cerrahpaşa Institute of Nanotechnology and Biotechnology.

"Preparation and characterization of an acrylated-coumarin-containing photo-crosslinked thiol-ene network: Investigation of ..." has been published in Polymer Engineering and Science.

PhD student NourelHouda Ketita from Univ. of Skikda is visiting our lab. for her thesis study of Cu based films during 2-28.12.2024.

The paper with the title "Cation Vacancy-Mediated Ultrafast Hole Transport in CuBi2O4 Photocathodes” published in ChemSusChem

Muhamed Walid Khalimi, a PhD student at the University of Blida, is visiting our laboratory during October for his studies.

Prof. Mahdi Ghasemifard from Esfarayen University of Technology-Iran visits us for a year to work on the defects of nano-electroceramics materials.

Accepted paper in Materials Research Bulletin titled “A Novel Approach for the Atomic Scale Characterization of Li-ion Battery Components probed by Positron Annihilation Lifetime Spectroscopy,"

Accepted paper in J. Mol. Structure: "The Influence of Defects on the Structural, Optical, and Antibacterial Properties of Cr/Cu Co-Doped ZnO Nanoparticles"

Accepted paper: “Structural and dielectrical properties of PMMA/TeO2 composites in terms of free volume defects probed by positron annihilation lifetime spectroscopy”,

Emir Ardalı from Koç University has completed his MSc thesis in which some work has been contributed from MARPOS Lab.

The paper with the title “Proton pathways via free volumes: A positron annihilation lifetime spectroscopy (PALS) investigation of proton conductivity in SPEEK-PEG-TMOS composites” has been published at Colloids and Surfaces A: Physicochemical and Eng

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