Electron Optical Optimisation of an Imaging Energy Analyser: Real Model Field- and Trajectory Simulations Applied to k-Space Visualisation of Electronic States

Abstract

In this report we present a new numerical approach and complex analysis of electron beam propagation based on a realistic model of an optimised imaging spherical deflector analyser. Electron beam trajectory simulations, carried out for real experimental boundaries, enabled us to reveal and explain the unique optical properties which were employed in the instrumental optimisation followed by empirical, spectromicroscopic applications. In terms of numerical treatment, it was possible to verify the low-aberration imaging in reciprocal and real spaces at π and 2π, respectively, and the advantage of energy-selective visualisation of the k-space. Furthermore, this unique feature has been proven and confirmed experimentally by implementing the HeI/HeII monochromatic photon source into our improved spectromicroscopic system and by the energy-selective visualisation of an electronic state projection in the reciprocal plane. A clear correlation between a numerically simulated electronic projection and an experimentally-obtained k-space imaging has been demonstrated.