Toroidal spectrometer for signal detection in scanning ion/electron microscopes

Abstract

This article presents a second-order focusing toroidal spectrometer/detection system for scanning ion/electron microscopes. The spectrometer, combined with a prefocusing electrostatic lens, is predicted to have relative energy resolutions of 0.02% and 0.088% for emission angular spreads of Ϯ6°and Ϯ10°, respectively, corresponding to transmittances of around 20% and 34%. Initial experimental backscattered electron ͑BSE͒ spectra were recorded with a prototype toroidal spectrometer functioning as an attachment unit inside a conventional scanning electron microscope ͑SEM͒. These results were used to quantify SEM BSE material contrast.

Energy Analyzer Attachments for the Scanning Electron Microscope

“…This was experimentally confirmed and expressed in previous voltage contrast literature for retarding field analyzers by the wellknown Gopinath signal-to-noise formula [10]. Figure 3a shows a toroidal band-pass SE analyzer designed by Khursheed and Hoang [11,12]. In this case, only secondary electrons within a narrow energy range are able to reach the detector, and the output signal is formed by ramping the analyzer deflector plate voltage (pass energy) in time, as shown in Figure 3b.…”