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MM: Fachverband Metall- und Materialphysik

MM 14: Topical Session TEM IV

MM 14.6: Talk

Tuesday, March 15, 2011, 12:45–13:00, IFW A

Quantitative scanning transmission electron microscopy at low energies — •Erich Müller, Marina Pfaff, Holger Blank, Tobias Volkenandt, Felix Bleimund, and Dagmar Gerthsen — Laboratorium für Elektronenmikroskopie, Karlsruher Institut für Technologie (KIT), Karlsruhe, Germany

Sensitive material (Z-)contrast is obtained by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) at low electron energies (< 30 keV). Even for small atom-number differences, quantitative analysis of composition is possible (e.g. in ternary semiconductors) and the TEM sample thickness can be determined. Moreover, knock-on damage is negligible at low electron energies, which is favorable for the examination of radiation-sensitive materials like semiconductors, organics or biological samples. The electron transmission is measured with a standard annular semiconductor detector in a state-of-art scanning electron microscope. This allows rapid change of instrumental alignments and parameters like electron energy or collection angles, which is essential for the determination of the characteristic dependence of the image intensity on these parameters. In combination with a focused-ion-beam system, samples with defined geometry and thickness can be prepared from materials with known composition which is essential to test the procedure for the extraction of quantitative image information. The presented method is based on HAADF STEM images and the comparison of the measured intensities with semi-empirical calculations or Monte-Carlo simulations. Examples of radiation-sensitive materials are shown to illustrate the method.