New types
of Electron Spectroscopy

Work-Package 22

Why Electron spectroscopy?
The properties of nanomaterials (like for example metallic nanoparticles) or nanostructured materials (like, for example, multiferroic interfaces) are mostly determined by their nanometer morphology or environment, and atomic surface structure. For example, the size and shape of metallic nanoparticles will determine their optical properties when used e.g. in stained glassed or photovoltaic applications. The quality and chemical abruptness of the interface between two magnetic materials will govern the efficiency of so-called spin valves which can be used as improved sensors for magnetic fields.
It is therefore of prime importance to know the type of atoms constituting these materials down to the atomic scale as well as their optical and electronic properties in order to understand the behaviour of a nanoscale material in connection to its structure.

What do electron spectroscopies provide?
In order to achieve the above goal, electron-based spectroscopies in Transmission Electron Microscopes (TEM) are relevant tools. Indeed, it is now possible to produce electron probes that are of atomic size and allow the combination of structural information with Electron Energy Loss Spectroscopy (EELS). EELS is a unique tool that can unravel the chemical composition of a material down to the atomic scale as well as giving insights in the electronic (Fig 1) or optical properties of nanoparticles (see Fig 2).

JRA3 - image 1 Figure 1: Map of the Mn oxidation states in Mn3O4 along the [100] zone axis orientation. (a) Shows the spectral weight of component A (Mn3þ) and component B (Mn2þ) obtained from spectrum fitting. A color map is displayed at the bottom (Red 1⁄4 Mn3þ, Green 1⁄4 Mn2þ). (b) Maps after low-pass filtering. (c) Simulated maps of the Mn3þ and Mn2þ signals.

 JRA3 - image 2

Figure 2: Optical properties of Nanometer-scale silver disk. Left: Typical experimental (1) and theoretical (2) EELS spectra of a silver disk, clearly showing strong absorption in the visible range. Filtered maps are given on the right.

 

WP22 goals
The aim of WP22 is to further develop EELS along several directions as well as developing new spectroscopies adapted to new problems. One can cite the development of new types of electron probes (vortex beams for example) as well as holographic techniques to study magnetism at the atomic scale. We can use atomically resolved EELS to study interfaces in functional materials and the use of cathodoluminescence (another type of electron spectroscopy) to address the optical properties of quantum confined structures at the nanometer scale. In all cases, the unbeaten spatial resolution offered by the electron beam is required to answer these specific questions.

 

Deliverable: Progress report on atomic scale measurement of magnetic states

Partners involved:

CNRS/LPS Orsay (Work-Package leader)
Universiteit Antwerpen (WP co-leader)
CNRS/CEMES Toulouse
University of Cambridge
MPG Stuttgart; TU Graz 
Universidad de Zaragoza 
Jozef Stefan Institute Ljubljana
TU Dresden

Contacts:

Mathieu Kociak (CNRS/LPS Orsay)
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Jo Verbeeck (Universiteit Antwerpen)
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