Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 12: Thin Film Characterisation: Structure Analyse and Composition (XRD, TEM, XPS, SIMS, RBS, ...)
DS 12.4: Vortrag
Dienstag, 26. Februar 2008, 12:30–12:45, H 2013
Depth Resolved Doppler Broadening Measurement of Layered Al-Sn-Samples — •Philip Pikart1,2, Martin Stadlbauer1,2, Klaus Schreckenbach1,2, and Christoph Hugenschmidt1,2 — 1TU Munich, Department of Physics E21, James-Franck-Strasse, 85478 Garching — 2TU Munich, ZWE FRM II, Lichtenbergstrasse 1, 85748 Garching
The accumulation of positrons in a 2-dimensional layer of tin embedded in aluminum is examined by Doppler Broadening Spectroscopy (DBS). For this purpose samples are grown out of high purity materials consisting of a step-shaped layer (0.1 to 200 nm) of tin on a substrate of aluminum and covered by an aluminum layer of constant thickness (200 nm). The positron implantation profile is varied by different positron acceleration energies of up to 15 keV. The pre-thermal implantation profile of the monoenergetic positron beam is examined since the effect of thermal positron diffusion is less significant at tin layers thicker than 50 nm. At thin layers (< 50 nm), the positrons greatly accumulate either at the aluminum-tin interface or in the tin layer due to its higher positron affinity compared to aluminum. Thus a very high sensitivity of the measurement for low densities of tin is observed. Consequently from the experimental results, a sensitivity threshold for the detection of a low amount of tin in an aluminum matrix with DBS is determined. The DB results are compared to theory by an approximation for pre-thermal implantation in layered materials.