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E057-02 - Fachbereich Universitäre Serviceeinrichtung für Transmissions- Elektronenmikroskopie E138-03 - Forschungsbereich Functional and Magnetic Materials
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Journal:
Ultramicroscopy
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ISSN:
0304-3991
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Date (published):
2006
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Number of Pages:
5
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Peer reviewed:
Yes
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Keywords:
ELNES; Anisotropy; Magic angle
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Abstract:
ELNES at magic angle conditions
C. Hébert b, P. Schattschneider a, b, H. Franco b and B. Jouffrey a
a LMSS-Mat, CNRS-URA 850, École Centrale Paris, Gde Voie des Vignes, F-92295 Châtenay-Malabry, France
b Institut für Festkörperphysik, Technische Universität Wien, A-1040 Wien, Austria
Received 19 July 2005; revised 12 January 2006; accepted 5 April 2006. Available online 30 June 2006.
...
ELNES at magic angle conditions
C. Hébert b, P. Schattschneider a, b, H. Franco b and B. Jouffrey a
a LMSS-Mat, CNRS-URA 850, École Centrale Paris, Gde Voie des Vignes, F-92295 Châtenay-Malabry, France
b Institut für Festkörperphysik, Technische Universität Wien, A-1040 Wien, Austria
Received 19 July 2005; revised 12 January 2006; accepted 5 April 2006. Available online 30 June 2006.
Abstract
If one needs to cancel the effects of the anisotropy of the sample in a EELS experiment in the TEM, a particular couple of values for the collection and convergence angle must be used, called magic angle conditions (MAC). Recent developments in the theory have shown that a full relativistic treatment is mandatory to correctly describe this effect and that the MAC are strongly dependent on the acceleration voltage. We show how the analytical formula can be derived and give the exact analytical solution for the MAC which can then be easily applied to every practical case. We show the consequences of the energy dependence of the magic angle and that the parallelity of the beam will be the limiting factor for high acceleration voltages while for low acceleration voltages the contribution coming from Bragg spots may make it impossible to reach MAC.
Keywords: ELNES; Magic angle; Anisotropy
