Vortex beams for atomic resolution dichroism

Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Journal of electron microscopy (Impact Factor: 1.63). 09/2011; 60(5):295-300. DOI: 10.1093/jmicro/dfr069
Source: PubMed


Vortex beams carrying orbital angular momentum have been produced recently with electron microscopy by interfering an incident
electron beam with a grid containing dislocations. Here, we present an analytical derivation of vortex wave functions in reciprocal
and real space. We outline their mathematical and physical properties and describe the conditions under which vortex beams
can be used in scanning transmission microscopy to measure magnetic properties of materials at the atomic scale.

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    ABSTRACT: We report the production of electron vortex beams carrying large orbital angular momentum (OAM) using micro-fabricated spiral zone plates. A series of the spherical waves, focussing onto different positions along the propagating direction of the electron beam, were observed. The nth order vortex beam has an OAM n times larger than that of the first-order vortex beam. We observed an electron vortex with an OAM up to in a high-order diffracted wave. A linear dependence of the diameter of the vortex beam on the OAM was observed, being consistent to numerical simulations.
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