Design and Simulations of an Electron-Optical Column Using Finite-Difference and Finite-Element Methods Combination

Abstract

Computer-simulated design of electron microscopes and related optical-probe systems is an area of growing importance, because of the actual innovative advances in material science, in particular at the nano and micro structure scales. The numerical methods can accurately and rapidly predict lens-system performance from variables such as electrode geometry, electrode potential, and magnet-coil excitation. This deepened understanding leads naturally to well-reasoned optimizations of the probe parameters. Reported herein is design and simulation of an electron optical column of scanning electron microscope type, using a new hybrid method of combining the SIMION and COMSOL charged-particle optics package codes. It relies on the use of the COMSOL output as an input of SIMION code. Both the finite-element and the finite-difference methods are used in a complementary combination to accurately model the magnetic lenses and determine the electron-steering and focusing magnetic-field distributions along the optical axis. The effects of the design parameters, such as the excitation current and their arrangement, are investigated. This works also presents guidelines on the beneficial use of such method, to workout efficient charged-particle optics-based design.