Two contributions to the ratio of the mean secondary electron generation of backscattered electrons to primary electrons at high electron energy

Abstract

Based on the main physical processes of secondary electron emission, experimental results and the characteristics of backscattered electrons (BE), the formula was derived for describing the ratio (βangle) of the number of secondary electrons excited by the larger average angle of emission BE to the number of secondary electrons excited by the primary electrons of normal incidence. This ratio was compared to the similar ratio β obtained in the case of high energy primary electrons. According to the derived formula for βangleand the two reasons why β > 1, the formula describing the ratio βenergyof β to βangle, reflecting the effect that the mean energy of the BE WAV p0is smaller than the energy of the primary electrons at the surface, was derived. βangleand βenergycomputed using the experimental results and the deduced formulae for βangleand βenergywere analyzed. It is concluded that βangleis not dependent on atomic number z, and that βenergydecreases slowly with z. On the basis of the two reasons why β > 1, the definitions of β and βenergyand the number of secondary electrons released per primary electron, the formula for βE-energy(the estimated βenergy) was deduced. The βE-energycomputed using WAV p0, energy exponent and the formula for βE-energyis in a good agreement with βenergycomputed using the experimental results and the deduced formula for βenergy. Finally, it is concluded that the deduced formulae for βangleand βenergycan be used to estimate βangleand βenergy, and that the factor that WAV p0increases slowly with atomic number z leads to the results that βenergydecreases slowly with z and β decreases slowly with z.