CPM Seminar

Energy Loss Spectroscopy at High Resolution:
Probing the local electronic structure and the plasmonic response of materials

Gianluigi Botton

Department of aterials Science and Engineering & Canadian Centre for Electron Microscopy
McMaster University

Electron energy loss spectroscopy (EELS) is an invaluable technique to study the detailed structure and the chemical state of materials at unprecedented spatial resolution. Today, this technique is used to characterize nanoscale materials used in a myriad of applications from energy storage and conversion, to solid-state devices and biomaterials interfaces. This technique also has the potential to provide insight into much more fundamental problems where the extracting information on local unoccupied states (at atomic sites) and site occupancy are of fundamental importance.

In this presentation, I describe recent developments in electron energy loss spectroscopy to probe the changes in bonding and coordination of atoms using quantitative measurements of the energy loss spectra [1,2]. I will show that, with atomic resolved EELS, it is possible to determine ordering of cations in oxides [3] and changes in bonding at interfaces, consistent with modifications in the coordination of interface atoms. I will highlight how atomic resolved experiments with EELS near edge fine structures (the equivalent of XANES) can be used to systematically study the local valence in high-T superconductors [4], extract the localized hole concentration in superconducting chain-ladder compounds [5] and even probe the local electronic structure of energy storage materials [6].

Finally, I will show how EELS can provide exquisite details on the plasmonic response of simple and very complex metallic nanostructures [7] and discuss the prospects for localized phonon spectroscopy measurements, down to the sub-nm scale, with new instrumentation coming to McMaster University.

[1] G.Z. Zhu, et al. Nature, 490, 384, (2012)
[2] M. Bugnet, et al., Phys. Rev. B 88, 201107(R) (2013), and Phys Rev. B, 93, 020102 (2016)
[3] S.  Turner, et al., Chem. Mater. 24, 1904-1909 (2012)
[4] N. Gauquelin, et al., Nature Communications 5, 4275 (2014)
[5] M.  Bugnet, et al., Science Advances 2016; 2:e1501652 (2016).
[6] H. S. Liu et al. Physical Chemistry Chemical Physics 18, 29064-29075. (2016) and H. Liu et al, ACS Nano, 12 (3), pp 2708-2718 (2018) DOI: 10.1021/acsnano.7b08945
[7] D. Rossouw, et al., Nano Letters 11, 1499-1504 (2011); D. Rossouw, G.A. Botton, Phys. Rev. Letters 110, 066801 (2013); S. J. Barrow et al, Nano Letters 14, 3799-3808. (2014); EP Bellido, et al., ACS Photonics, 3, 428-433 (2016), and ACS Photonics, 4, 1558-1565 (2017); E.P. Bellido, et al., Self-similarity of plasmon edge modes on Koch fractal antennas, ACS Nano, DOI: 10.1021/acsnano.7b05554), (2017).