Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DS: Fachverband Dünne Schichten
DS 37: Thin Film Characterisation: Structure Analyse and Composition (XRD, TEM, XPS, SIMS, RBS, ...) II
DS 37.6: Vortrag
Donnerstag, 25. März 2010, 12:30–12:45, H8
Coincident Doppler Broadening measurement on embedded thin layers of different materials with a positron beam of variable energy — •Philip Pikart1,2, Christoph Hugenschmidt1,2, and Klaus Schreckenbach1,2 — 1ZWE FRM II, Lichtenbergstraße 1, 85747 Garching — 2Technische Universität München, Physik Department E21, James-Franck Straße, 85748 Garching
Coincident Doppler Broadening (CDB) is particularly suited to study thin layers in a non-destructive way. Further, CDB is outstanding in its sensitivity to defects and precipitates, because the positron is used as a "nanoprobe". It diffuses thermally inside the sample, can be localized at a defect and then annihilates with an electron by the emission of gamma-radiation. The shape of the annihilation line is characteristic for chemical elements and defect types. Defects have a highly attractive potential for the diffusing positron, which leads to trapping in open volume defects. But also the trapping at precipitates and small clusters of a different material is possible. The aim of the presented experiment is to study the trapping at interfaces and thin layers. For this purpose, samples consisting of aluminum are grown with an embedded layer of gold, copper and chrome. These materials cover a wide range of positron affinities, so the trapping probability of a positron at the layer depends on the material and the layer thickness. CDBS-results of these samples are presented and explained by a one-dimension potential well model.