Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 33: III-V semiconductors II
HL 33.1: Vortrag
Mittwoch, 27. Februar 2008, 14:15–14:30, EW 201
Measurement of 002 structure factors for GaAs from electron spot diffraction patterns — Knut Müller1, •Marco Schowalter1, Andreas Rosenauer1, Jacob Jansen2, John Titantah3, and Dirk Lamoen3 — 1Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee1, 28359 Bremen — 2National Centre for HREM, Laboratory of Materials Science, Delft University of Technology, Lorentzweg 1, 2628 Delft, The Netherlands — 3Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
Accurate knowledge of chemically sensitive structure factors (SF) is essential e.g. for quantitative analysis of the composition in ternary semiconductor nanostructures, such as InGaAs, by TEM. Recent calculations also account for the electron redistribution due to bonding effects and are to be proven experimentally. A new method was developed to measure SF from Bragg intensities in TEM diffraction patterns. An appropriate microscope setup for nanodiffraction under parallel illumination has been worked out. Using the program package ELSTRU, the procedure first extracts the integrated intensities of each Bragg spot and subtracts the background. In the first of two refinements, the local thickness and orientation of the specimen as well as the Debye-Waller factors are refined by the routine MSLS. For the second refinement of one SF in question, a Bloch-wave simulation program was developed that fits experimental and calculated intensities. The method was succesfully tested on simulated images with background.