Electron Energy Spectrometers for the Scanning Electron Microscope

Abstract

This thesis aims to develop energy spectrometers for the Scanning Electron Microscope (SEM). By integrating energy spectrometers into SEM design, the energy spectrum of its scatted electrons can be obtained, enhancing the kind of information that SEMs can acquire on the nano-scale, making them more powerful material science instruments. The first spectrometer is based upon the use of a circular magnetic sector beam separator, suitable for SEMs that use electric/magnetic field objective lenses. These kinds of SEMs are able to obtain high image resolution at low primary beam voltages (1 kV or less). The magnetic beam spectrometer is designed to capture the whole energy range of scattered electrons in parallel. The second spectrometer is a toroidal geometry spectrometer that can be incorporated into the specimen chamber of a conventional SEM as an add-on attachment. This spectrometer goes beyond previous toroidal spectrometer designs by achieving second-order focusing, effectively improving the energy resolution of toroidal spectrometers by over a factor of seven (for the same transmittance). The third spectrometer is a radial mirror analyzer, functioning as an add-on attachment inside conventional SEM specimen chambers. The predicted energy resolution for this spectrometer is around one order of magnitude better (for the same transmittance) than previous rotationally symmetric electric energy spectrometers. The spectrometer designs developed in this work have applications beyond electron microscopy, to other areas in applied physics such as surface science.