Electron energy spread measurements in an ultrafast scanning electron microscope
Magdalena Solà-Garcia a, Matthias Liebtrau a, Kelly W. Mauser a, Erik Kieft b, Sophie Meuret c, Albert Polman a
a Center for Nanophotonics, AMOLF, The Netherlands, Science Park, 104, Amsterdam, Netherlands
b Thermo Fisher Scientific
c CEMES-CNRS Université de Toulouse UPS 29 rue Jeanne Marvig BP 94347 Toulouse, Cedex 04, France
Proceedings of Electron Beam Spectroscopy for Nanooptics 2021 (EBSN2021)
Online, Spain, 2021 June 14th - 15th
Organizers: Mathieu Kociak and Nahid Talebi
Poster, Magdalena Solà-Garcia, 040
Publication date: 8th June 2021

Ultrafast electron microscopy, based on either a transmission or a scanning electron microscope, is a promising technique to study material dynamics at the nanoscale. While ultrafast TEMs have been widely discussed and characterized in literature, work on ultrafast SEMs (USEMs) is still limited and is mostly focused on the analysis of spatial and temporal resolution. In this poster we show measurements of the energy spread of continuous and pulsed 5 keV electron beams. In the case of a continuous electron beam, we show that the energy spread is strongly affected by the electron current and temperature of the cathode, reaching a value down to 0.6 eV. For pulsed electron beams, we analyze two operating regimes which allow us to obtain either a high brightness or high electron current. In the case of pulses containing an average of 0.77 electrons per pulse, we extract an energy spread of 0.86 eV, which corresponds to an estimated electron pulse duration of 414 fs. Instead, highly dense pulses, containing up to 1000 electrons, exhibit an energy spread of 14.4 eV (6.4 ps) due to Coulomb repulsion between electrons from the same pulse. Overall, this poster provides a characterization of the energy distribution of low-energy (5 keV) electron beams, which is critical for optimum operation of USEMs.

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