Formulae for secondary electron yield and the ratio of the average number of secondary electrons generated by a single backscattered electron to that generated by a single primary electron

Abstract

On the basis of the characteristic of secondary electron emission, the number of secondary electrons (δ_PEθ) released per primary electron entering metals in the incident energy (W_p0) range 10-102 keV and the incident angle (θ) range 0-89° was deduced. In addition, the number of secondary electrons released per primary electron entering metals at θ=0 (δ_PE0) was obtained. Based on the deduced δ_PEθ, the characteristic of the emission angle distribution of the backscattered electrons and the definition of β_θ, the relationships among β_θ, cosθ and the parameter x were given, where β_θ is the ratio of the average number of secondary electrons generated by a single backscattered electron to that generated by a single primary electron entering the emitter at θ. Considering the relationship between δ_PEθ and δ_PE0 and the relationship between the secondary electron yields at W_p0=10-102 keV and θ=0-89° (δ_θ) and the secondary electron yields at θ=0(δ₀), a universal formula for expressing δ_θ through δ₀, the backscattered coefficient at θ (η_θ), the backscattered coefficient at θ=0(η₀), cosθ and the parameter x were deduced. Further, the parameters x related to beryllium, uranium, aluminium and copper were computed with the deduced formula and experimental results; then, the formulae for expressing δ_θ from the four metals through δ₀, η_θ, η₀ and cosθ were obtained; and the relationships between β_θ of the four metals and cosθ were found. The δ_θ calculated with the formulae and the yields measured experimentally were compared. Finally, it is concluded that the formulae for δ_θ and β_θ from the four metals at W_p0=10-102 keV and θ=0-89° have been established, respectively.