MAXIMUM SECONDARY ELECTRON YIELD AND PARAMETERS OF SECONDARY ELECTRON YIELD OF METALS

On the basis of the free-electron model, the energy range of internal secondary electrons, the energy band of a metal, the formula for inelastic mean escape depth, the processes and characteristics of secondary electron emission, the probability of internal secondary electrons reaching surface and passing over the surface barrier into vacuum B as a function of original work function Phi and the distance from Fermi energy to the bottom of the conduction band E-F was deduced. According to the characteristics of creation of an excited electron, the definition of average energy required to produce an internal secondary electron epsilon, the energy range of excited electrons and internal secondary electrons and the energy band of a metal, the formula for expressing epsilon using the number of valence electron of the atom V, Phi, E-F and atomic number Z was obtained. Based on the processes and characteristics of secondary electron emission, several relationships among the parameters of the secondary electron emission and the deduced formulae for B and epsilon, the formula for expressing maximum secondary electron yield of metals delta(m) using Z, V, back-scattering coefficient r, incident energy of primary electron at which secondary electron yield reaches delta(m), Phi and E-F was deduced and demonstrated to be true. According to the deduced formula for delta(m) and the relationships among delta(m) and several parameters of secondary electron emitter, it can be concluded that high delta(m) values are linked to high V, Z and Phi values, and vice versa. Based on the processes and characteristics of secondary electron emission and the deduced formulae for the B, epsilon and delta(m), the influences of surface properties on delta(m) were discussed.