Regensburg 2013 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 17: Glasses III (joint session with CPP, DY)

DF 17.2: Vortrag

Mittwoch, 13. März 2013, 12:50–13:10, H11

Pressure dependent void size in SiO₂ investigated with the Pulsed Low Energy Positron System (PLEPS) — •Luca Ravelli¹, Werner Egger¹, Marco Zanatta², Roberto Sennen Brusa², and Günther Dollinger¹ — ¹Universität der Bundeswehr, München, Germany — ²Università di Trento, Trento, Italy

Positron annihilation lifetime spectroscopy (PALS) is a very powerful tool for the non-destructive detection and characterization of open volume defects such as vacancies, vacancy clusters and voids in different materials, ranging from metals to semiconductors and insulators. In combination with a mono-energetic pulsed beam of variable energy it is possible to tune the positron implantation depth. The analysis of the lifetime spectra as a function of the implantation energy allows to measure defect depth profiles from the surface to the bulk of the sample.

As an example we show a study of the evolution of defects, and in particular of voids, present in SiO₂ glasses compressed with 0, 2, 4, 6 and 8 GPa. Because of the small size and the shape of the samples (small cylinders with diameter from 3 mm for the reference sample to 2 mm for one subjected to the highest pressure) a conventional positron lifetime measurement in sandwich configuration was impossible. The measurements were performed with the Pulsed Low Energy Positron System (PLEPS) at the high intensity positron source NEPOMUC (NEutron-induced POsitron source MUniCh) at the research reactor FRM-II. The results have shown a decrease of the void-size with increasing pressure.