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ERC

VORTEX Report Summary

Project ID: 278510
Funded under: FP7-IDEAS-ERC
Country: Belgium

Final Report Summary - VORTEX (Exploring electron vortex beams)

The VORTEX project started January 2012 and set out to explore the properties and applications of electron vortex beams (EVB). Such vortex beams were experimentally realised for the first time in 2010 by the current VORTEX team. EVB's resemble their optical vortex counterparts by the way a so-called orbital angular momentum is encoded in the phase of the waves. The charged nature of the electron however leads to the existence of a quantised magnetic moment as well.
These properties have inspired the team to think about applications in directions as diverse as nanoparticle manipulation and magnetic mapping of materials at the atomic scale.
The major goals of the project are:
• Obtain magnetic mapping on the atomic scale through inelastic electron scattering of vortex beams.
• Study elastic scattering of EVB's with (magnetic) materials.
• Transfer the angular momentum of EVB's to manipulate nanoparticles.
The project team consisted of the principal investigator, two post docs and two PhD. students. Significant progress has been made towards all goals of the project and many different properties, techniques and directions were explored, sometimes leading to unexpected results.
The highlights and achievements at the end of the project are:
• Created EVB's of atomic size (<1Å diameter), thereby reaching an important milestone of the project.
• Obtained atomic resolution images with atomic size EVB's, an important step towards atomic scale mapping of magnetic states in materials.
• Created monochromated electron vortex beams with an energy resolution up to 120 meV. This achievement is especially important to be able to study inelastic scattering of EVB's to surface plasmon excitations.
• Explored many different ways to obtain EVB's, using aberration correctors, holographic reconstruction, spiral phase plates, magnetic fields and electrostatic fields.
• Demonstrated the production of EVB's with a topological charge up to 27.
• Successfully demonstrated manipulation of nanoparticles with EVB's. This result was published in Advanced Materials.
• Developed a ground-breaking technique to create pure, single mode EVB's of high current by exploiting the magnetic field at the extremity of a magnetized needle. This result was published in Nature Physics and revolutionises the way how EVB's are made.
• Preliminary proof of atomic resolution magnetic signal in the Fe L23 edge of a ferrimagnetic material and insight in the detrimental effect of source size broadening.
• Deepened theoretical understanding of the inelastic and elastic interaction with fields and crystals.
• Developed a new technique to determine the local chirality in crystals via elastic scattering of EVB's.
• Patented two methods to create EVB's via a dynamically controllable current or voltage source.
• Developed a new method to map surface plasmon excitations in metallic nanoparticles. The method uses beam shaping to selectively excite plasmon modes of a given symmetry while suppressing others and is published in Nature Communications.
With the above realisations, the project has clearly established a solid exploration of the potential of electron vortex beams in the transmission electron microscope (TEM) and identified many areas of applications ranging from chiral materials, magnetism, surface plasmons and nanomanipulation. The insights obtained in this successful project show an emerging vision towards the wider goal of realising adaptive optics in the TEM which we expect to bring a disruptive change to the field of TEM and characterization methods in general.
Read more on the outcome of the project on http://vortex.emat.ua.ac.be.

Reported by

UNIVERSITEIT ANTWERPEN
Belgium
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