Dielectric Materials for Electrical Engineering

Chapter 7

Dielectric Materials under Electron Irradiation in a Scanning Electron Microscope 1

7.1. Introduction

The study of electron irradiation of dielectric materials is of considerable interest from a fundamental point of view as well as from the point of view of applications. Research has covered a wide domain of applied physics, from the behavior of satellites subject to cosmic radiation in space research, to electrets used in radiobiology; we try to avoid the charging up of dielectric materials on board satellites in space and subject to solar winds, while we use charging up of dielectric materials to produce electrets. Dielectric material irradiation by energetic electrons is accompanied by numerous complex phenomena, notably secondary electron emission, photon emission, trapping of charges, luminescence, etc. In the case of conductors, secondary electron emission is a source of issues for particle accelerators, while it is the base of the contrast observed in electron microscopy and exploited in the manufacture of electron multipliers. In the case of irradiated insulators, the situation is different: their secondary electron emission contributes to strange effects, commonly called charging effects, which are irregular and hard to predict.

Although these complex effects are qualitatively well understood and have been described in a proliferation of articles (the complete list of which is impossible to detail here but which is previewed in this special issue [JES 92]), the ...