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MM: Fachverband Metall- und Materialphysik
MM 9: Topical Session TEM III
MM 9.4: Vortrag
Montag, 14. März 2011, 17:00–17:15, IFW A
Annealing in InGaNAs studied by TEM three-beam imaging — •Knut Müller1, Marco Schowalter1, Michael Hetterich2, Dongzhi Hu2, Daniel Schaadt2, Philippe Gilet3, Kerstin Volz4, and Andreas Rosenauer1 — 1Univ. Bremen, D-28359 Bremen — 2Karlsruhe Inst. of Techn., D-76131 Karlsruhe — 3CEA-LETI, F-38054 Grenoble — 4Univ. Marburg, D-35032 Marburg
A 3-beam TEM image formed by 000, 200, and 220 is used for simultaneous atomic-scale measurement of In and N in an In0.28Ga0.72N0.02As0.98 quantum well. In this setup, subsequent diffractogram filtering yields 200 and 220 lattice fringes that are not coupled by nonlinear imaging. Images are acquired with a FIB-fabricated, L-shaped objective aperture in a Cs-corrected Titan 80/300. Indium and nitrogen contents are determined by comparing chemically sensitive 200 fringe amplitude and 220 strain with simulated reference data., which includes bonding and static atomic displacements (SAD). It is demonstrated that bonding improves accuracy up to 30%, and that SAD cause absorption in Bragg beams due to Huang scattering, which is treated by additional absorptive form factors. For the present structure, annealing is shown to cause photoluminescence to increase by a factor of 20 and to blue-shift by 65nm. Using our 3-beam method, this can be assigned to a dissolution of In- and N-rich regions in favour of a homogenisation of layer thickness and -stoichiometry.