Energy Analyzers of Electrically Charged Particles

Authored by: Igor Bello

Vacuum and Ultravacuum

Print publication date:  November  2017
Online publication date:  November  2017

Print ISBN: 9781498782043
eBook ISBN: 9781315155364
Adobe ISBN:

10.1201/9781315155364-27

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Abstract

Energy analyzers of electrically charged particles are instruments that employ electric fields or magnetic fields or both to resolve electrically charged particles in accordance with their kinetic energies. In this respect, the vital parameters of these devices are the detection range of energy and energy resolution. Energy resolution is the ability to differentiate ions with small differences in their energies. Energy resolution is defined as the full width at half maximum (FWHM) of an energy peak divided by the energy corresponding to the peak maximum (Δε/ε). In some cases, the width at the base of an energy peak can be taken instead of the FWHM. However, energy resolution is also defined as the FWHM, Δε, of the measured energy peak. For instance, the FWHM definition of energy resolution is used in X-ray photoelectron spectroscopy (XPS). Since the energy resolution of instruments depends on the pass energy of the particles passing via the analyzer, the resolution is evaluated at a low pass energy and for the core levels of atoms with inherently narrow electron energy distribution. In XPS, we use the signal of silicon Si 2p orbital induced by a monochromatic X-ray, for example, KAlα. At pass energies below 20 eV, we can clearly resolve the Si spin orbital splitting (2p3/2 and 2p1/2), which is 0.4 eV. The commercial XPS instruments (for instance, by Vacuum Generator and Kratos) usually claim the resolution of their instrument to be 0.4 eV, but indeed their instruments have a slightly better resolution than that.

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