Large electron vortex beams produced by MEMS-based device
Large electron vortex beams produced by MEMS-based device lead image
The experimental realization of electron vortex beams with helical wavefronts that carry orbital angular momentum (OAM) first occurred in 2010. Since then, scientists have realized the value in measuring and controlling the OAM of the electron beam as a novel degree of freedom in electron-matter interaction and the characterization of matter, such as probing magnetic properties.
Tavabi et al. reported the use of an electrostatic microelectromechanical systems (MEMS)-based device to produce the largest isolated electron vortex beams created to date. The generated beams have more than 1000 quanta of OAM. In addition, the diameter of the vortex in the diffraction plane increases linearly with OAM, meaning the device can tune the vortex at will.
“The device joins together two properties, large OAM and the complete tuneability of OAM, by a simple electronic control,” said co-author Vincenzo Grillo. “Having new tunable electron optics means that soon we will be able to measure new quantities inside an electron microscope at the nanoscale.”
The MEMS-based device, referred to as “MINEON” (MINiaturised Electron Optics for Nanobeams), was fabricated using silicon-on-insulator technology with trench insulation. The key component is a set of parallel electrodes with a micron separation that produces the vortex. Grillo and his colleagues developed a special holder for the device in collaboration with Thermo Fisher Scientific, maker of the transmission electron microscope employed in the study.
“We think we can measure the vertical component of the magnetic field better than in our previous studies based on fixed holographic elements,” said Grillo. “In particular, we will study vertical magnetization but also spin-orbit effects that are a very evanescent effects.”
Source: “Generation of electron vortex beams with over 1000 orbital angular momentum quanta using a tuneable electrostatic spiral phase plate,” by A. H. Tavabi, P. Rosi, A. Roncaglia, E. Rotunno, M. Beleggia, P.-H. Lu, L. Belsito, G. Pozzi, S. Frabboni, P. Tiemeijer, R. E. Dunin-Borkowski, and V. Grillo, Applied Physics Letters (2022). The article can be accessed at http://doi.org/10.1063/5.0093411 .
