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Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 44: Functional Materials II

MM 44.5: Talk

Friday, March 18, 2011, 11:30–11:45, IFW A

Positron lifetime measurements for monitoring vacancies and vacancy clusters in hydride forming free standing Mg films. — •Luca Ravelli1, Werner Egger1, Günther Dollinger1, Roberto Brusa2, and Riccardo Checchetto21Institut für Angewandte Physik und Messtechnik, Universität der Bundeswehr München, Neubiberg, Deutschland — 2Dipartimento di Fisica, Università degli Studi di Trento, Trento, Italy

Pd-capped free-standing Mg-based film samples (thickness 10 micrometers) were produced by r.f. magnetron sputtering[1]. The presence of vacancies and the formation of vacancy clusters were studied in the as-prepared sample and in samples submitted to 1, 2, 4 and 8 H2 absorption and desorption cycles by positron annihilation lifetime spectroscopy. For this task a monoenergetic pulsed positron beam of variable energy is necessary to control the implantation depth of the positrons and to depth-profile the defect structure in the Mg films. The measurements were performed with the Pulsed Low Energy Positron System (PLEPS)[2] at the high intensity positron source NEPOMUC (NEutron-induced POsitron source MUniCh) of the research reactor FRM II. Disappearence of vacancies due to their clustering was observed after the second H2 sorption cycle.

[1] N. Bazzanella et al., Appl. Phys. Lett. 85 (2004) 5212-5214.

[2] P. Sperr et al., Appl. Surf. Science 255 (2008) 35-38.

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