Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Poster Session
MM 15.77: Poster
Montag, 11. März 2013, 18:00–20:00, Poster E
Characterizing the origin of the collapse of the channeling circle in aberration-corrected HRTEM — •Alexander Surrey1,2, Darius Pohl1,2, Ludwig Schultz1,2, and Bernd Rellinghaus1 — 1IFW Dresden, Helmholtzstr. 20, D-01069 Dresden, Germany. — 2TU Dresden, Institut für Festkörperphysik, D-01062 Dresden, Germany
Calculations of the complex electronic exit wave functions (EWFs) of model structures utilizing multi-sclice algorithms in combination with HRTEM contrast simulations reveal that the amplitudes and phases of these reconstructed EWFs lead to a collapse of the channeling circle when "real" samples are investigated under realistic microscopy conditions. As a consequence, the reconstruction of the 3D structure of the samples by means of the acquisition of focal series of HRTEM images becomes impossible. A detailed analysis shows that this collapse is caused by the accumulation of contributions from (i) the modulation transfer function of the camera, (ii) slight misorientations of the sample, (iii) inelastic absorptions, (iv) amorphous overcoats or substrates, and (v) equilibrium as well as athermal phononic excitations. The collapse becomes most easily evident from a significant lack in the phase signal derived from the EWFs. Whereas the phase shift associated with moving along the channeling circle in the Gaussian plane should successively grow to the full range of 2π, the phases determined from the EWFs frequently amount to only fractions of π. This limited phase range is confirmed by the EWF recontructions determined from experimental through focus series of thin Au nanostructures acquired with an aberration-corrected FEI Titan3 80-300 microscope.