Regensburg 2013 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 2: Topical Session: TEM-Symposium - Joint Session with MI I
MM 2.3: Talk
Monday, March 11, 2013, 11:15–11:30, H4
Effect of lens aberrations on strain measurements from Convergent Beam Electron Diffraction patterns — •Christoph Mahr1, Knut Müller1, Andreas Rosenauer1, Marco Schowalter1, Daniel Erben1, Josef Zweck2, and Pavel Potapov3 — 1Universität Bremen — 2Universität Regensburg — 3GlobalFoundries, Dresden
This presentation deals with the effect of lens aberrations in a transmission electron microscope (TEM) on strain measurements in semiconductor heterostructures using Strain Analysis by Nano-Beam Electron Diffraction (SANBED). As this method is based on the analysis of disc positions in a series of Convergent Beam Electron Diffraction (CBED) patterns, strain measurements could be inexact e.g. due to lens aberrations of the projection system. The distortion field is detected by comparing the disc positions in an experimental CBED pattern obtained from a substrate region of the specimen with theoretical ones. Based on this field, we show how the distortions in all CBED patterns of a series can be corrected. Subsequently the effect of the correction on the strain measurements is investigated. It is found that the averaged difference between strain from uncorrected patterns and strain from corrected patterns is in the order of 10−3%. This difference is one order less than the precisions of contemporary strain measurement techniques, such as SANBED, which has a precision of (7−9) · 10−2%. Consequently, the effect of distortions in a diffraction pattern can be neglected at the moment. The effect could become more evident, when the precision of strain measurements is improved.