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Recent advances in STEM spectroscopies

Speaker: 
Odile Stéphan (LPS, Universityé Paris-Sud)
Date: 
Thu, 21/04/2016 - 2:00pm to 3:00pm
Location: 
CA2DM Theory Common (S16-06)
Host: 
Alexandra Carvalho and Centre for Advanced 2D Materials
Event Type: 
Seminars

Abstract

The field of electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) has recently achieved a succession of impressive successes linked with the development of aberration correctors, enabling atomically-resolved spectroscopy, which are now spreading worldwide. A new generation of monochromators is emerging, providing improvements in energy resolution of at least one order of magnitude and giving unprecedented access to low energy-loss ranges. Similarly, recent progress in the collection of visible-range photons emitted by a sample illuminated by a focused beam has enabled novel cathodo-luminescence (CL) experiments in STEM. In addition, new ways of exploiting fast electron beams, including combining them with beams of photons, have opened up the field of nano-optics, providing a high-spatial resolution alternative to more conventional optical techniques.

Some of these new possibilities will be illustrated. Various strategies will be described for the acquisition of spatially-resolved core-level excitations signals for the mapping of functional molecular groups in graphene oxide (GO) and reduced GO [1]. Recent combined developments in EELS and CL for reaching plasmon signatures in the visible and down to the IR spectral range will be described, allowing the mapping of eigen modes in plasmonic nanostructures and a deep understanding of the physics of these excitation [2]. Finally, new possibilities for exploring the intimate link between a crystal structure (h-BN), its defects and its optical properties as revealed by nano-CL [3] will be discussed, together with some perspectives for entering the field of quantum nano-optics [4].

[1] A. Tararan, A. Zobelli, A. M. Benito, W. K. Maser, and O. Stephan, “Revisiting Graphene Oxide Chemistry via Spatially-Resolved Electron Energy Loss Spectroscopy”, unpublished
[2] A. Losquin, L. F. Zagonel, V. Myroshnychenko, B. Rodríguez-González, M. Tencé, L. Scarabelli, J. Förstner, L. M. Liz-Marzán, F. Javier García de Abajo, O. Stéphan, and M. Kociak, "Unveiling Nanometer Scale Extinction and Scattering Phenomena through Combined Electron Energy Loss Spectroscopy and Cathodoluminescence Measurements", Nano Lett., 2015, 15 (2), pp 1229–1237 DOI: 10.1021/nl5043775
[3] R. Bourrellier, M. Amato, L. H. Galvão Tizei, C. Giorgetti, A. Gloter, M. I. Heggie, K. March, O. Stéphan, L. Reining, M. Kociak, and A. Zobelli, "Nanometric Resolved Luminescence in h-BN Flakes: Excitons and Stacking Order", ACS Photonics, 2014, 1 (9), pp 857–862 DOI: 10.1021/ph500141j
[4] R. Bourrelier et al, unpublished

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