Berlin 2012 – wissenschaftliches Programm
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MI: Fachverband Mikrosonden
MI 2: TEM- and SEM-based material analysis
MI 2.1: Hauptvortrag
Montag, 26. März 2012, 09:30–10:15, EMH 225
Chemical mapping at the atomic level using energy dispersive X-ray spectroscopy — Peter Schlossmacher1, •Bert Freitag1, Dmitri Klenov1, Adrian D Alfonso2, and Les Allen2 — 1FEI Company, Building AAE, Achtseweg Noord 5, Eindhoven, The Netherlands — 2School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia
We demonstrate chemical mapping at the atomic level using energy dispersive X-ray spectroscopy (EDS) in Cs-corrected scanning transmission electron microscopy (STEM). The combination of the increase in current in an atomic sized probe by probe Cs-correction and the increase in sensitivity of the Super-X detector allows acquisition of such results fast and reliable. Atomic chemical maps of the strontium and titanium sub lattice in SrTiO3 are obtained in minutes with a high sampling (256*256 pixels). The signal strength is much higher when compared to previously reported results using conventional EDS detectors. Even the GaAs dumbbell of 141 pm distance can be resolved in the chemical EDS map using the Ga and As L and K-edges. Examples on interfaces and complex oxide materials are discussed.
Theoretical Bloch wave simulations are compared with the experimental GaAs results.The simulations for EDS mapping assume that the cross section for X-ray emission is proportional to the total cross section for K or L shell ionization for a detector which samples the full solid angle and all possible energy losses above the ionization threshold.