Lee Hsun Lecture Series

Topic: Probing the Structure of Nanoscale Materials with Electron Energy Loss Spectroscopy in the Transmission Electron Microscope

Speaker: G.A. Botton
         Canadian Centre for Electron Microscopy,
         Dept of Materials Science and Engineering,
         McMaster University， Canada

Abstract：

Electron energy loss spectroscopy (EELS) is an invaluable technique to study the detailed structure and the chemical state of materials at unprecedented spatial resolution. In today’s modern electron microscopes, it is possible to tackle problems requiring the highest energy resolution to detect losses down to 70meV, and highest spatial resolution, down to the angstrom level, so that atomic resolved spectroscopy with high spectroscopic sensitivity and resolution can be obtained. This leads to the potential of covering excitation phenomena from the mid-infrared, soft-X-rays and even hard-X-ray regime.

In this presentation, various examples of applications of electron microscopy will be given. First of all, the detection of low-loss features in plasmonic nanostructures and nanoantennas, down to the mid-infrared part of the electron energy loss spectrum will be given, and this by directly imaging resonances down to 0.17eV, the lowest plasmonic features detected with EELS [1,2] and hybridization effects demonstrating strong field enhancements between nanostructures. I will then demonstrate examples of detailed structural and analytical work in a number of alloy nanoparticles systems ranging from fundamentals of phase stability and surface segregation to catalysts used for fuel cells. I will present test cases where monolayer segregation is observed and confirmed from EELS. Examples will cover various alloy catalysts [3,4] and battery materials [5,6]. I will show an example of in-situ electrochemistry studies showing the evolution of individual nanocatalysts during cyclic voltammetry and identical location high-resolution imaging whereby it is possible to clearly show the dissolution of Pt from catalyst nanoparticles [7]. I will also show how to detect bonding state changes on surfaces [8]. This powerful technique can also be used to study of the structure and substitutional effects from single atom dopants in phosphors [9], Mg alloys [10] and high-temperature superconductors [11] and to study the hole carriers distribution in highly correlated oxides [12].

[1] D. Rossouw, et al., Nano Letters 11, 1499-1504 (2011),
[2] D. Rossouw, G.A. Botton, Phys. Rev. Letters 110, 066801 (2013), and S. J. Barrow et al, , Nano Letters 14, 3799-3808.  (2014); Y. Liang; Rossouw, D.; et al, Journal of the American Chemical Society 135, 9616-9619.  (2013), E. P. Bellido et al. ACS Photonics 3, 428-433.  (2016), E.P. Bellido et al. DOI: 10.1021/acsphotonics.7b00348.
[3] S. Prabhudev et al., ACS Nano 7, 6103-6110,  (2013), and ChemCatChem 2015.
[4] S. Stambula et al., Journal of Physical Chemistry C, 118, 3890-3900.  (2014)
[5] H. S. Liu; et al, Physical Chemistry Chemical Physics 18, 29064-29075.  (2016).
[6] H.S. Liu et al, submitted
[7] G.-Z. Zhu et al, Journal of Physical Chemistry C, 118, 22111-22119. (2014), L. Chinchilla et al, Journal of Power Sources 356 (2017) 140-152
[8] G.-Z. Zhu, G. Radtke, G.A. Botton, Nature, 490, 384, (2012) 51. 
[9] G. -Z. Zhu, et al. Phys. Chem. Chem. Phys. 15, 11420-11426.  (2013);
[10] M. Bugnet, A. Kula, M. Niewczas, Botton, G. A., Acta Materialia 79, 66-73.  (2014)
[11] N. Gauquelin, et al, Nature Communications 5,  4275.  (2014)
[12] M. Bugnet et al, Sci. Adv.2 : e1501652 (2016)