Field - free and field - stimulated electron emission from solids

Abstract

Electron irradiation of solids produces a backemission of secondary electrons energies between 0 and 50 eV and re ected primaries energies between 50 eV and that of the incident beam. For insulators, it is shown that an externally applied positive electric eld penetrating into the solid material, energizes electrons generated by the primary irradiation and enables them to travel back to the surface of incidence and be emitted stimulated secondary emission. I IntroductionSurfaces of solid materials irradiated by an electron beam become the source of electron emission in a direction opposite to that of the incoming beam. The energy of the emitted electrons extends from zero to the maximum of the irradiating beam. Electrons with energies between 0 and 50 eV are classi ed as secondary electrons while those with higher energies are backscattered primaries. The application of an accelerating positive eld enhances the emission of secondary electrons from the bulk of isolating materials. These additional electrons constitute a eld -stimulated emission. Here we shall discuss the mechanism of the secondary emission and show some characteristic emission curves and energy distributions for conducting and for insulating materials. We emphasize the fact that the former do not exhibit eld stimulated emission since the necessary electric eld collapses in the material. For basic information on secondary emission we refer to the papers of Sternglass 1 , Dekker 2 , Seiler 3 and von Seggern 4 . II Measurement methodMaterials discussed here as representatives of the whole eld are Te on FEP and Platinum. Data on other materials are found in the Thesis of C.A.F.Pinto 5 . Targets were circular disks with an area of 7.1 cm 2 and thickness of 25 to 40 micron for insulators; thickness of metals was higher. Insulating targets had a nonmetallized surface of incidence and a metallized backside resting on a metal disk used as the rear electrode.In front of the sample surface, Fig.1, at a distance of 2 to 3mm, was mounted a stainless steel grid transparency 80 and on top of the measuring arrangement, still within the vacuum, was mounted a metal plate with 2 circular openings for passage of the ini-

Mylar secondary emission-energy distribution and yields

“…The curves in Figures 5 and 6 represent the spectra or energy distribution functions of the secondary, g(E'). The curve obtained in this work is very similar to that obtained by Gross et al [28] for Teflon irradiated with electrons at 300eV. By increasing the intensity of irradiation energy the curve peak decreases in intensity.…”

Energy distribution of secondary electrons from gold on teflon-FEP

“…For insulating samples, it is still less common to find data about the energy distribution of the secondary electrons [19]. In the case of insulation, there is an additional experimental difficulty that involves the charges created during the emission process, which may be the reason that this type of measure is less common; however, more recently, some studies have presented research on the energy spectrum of the secondary electrons for metals and polymers [20][21][22][23][24][25].…”