Relationship Between Secondary-Electron Yield and Structure of Polycrystalline Diamond Prepared Under Different Methane Concentrations

To understand the mechanism of electron transport and escape to vacuum of polycrystalline chemical-vapor-deposited diamond films prepared under different methane (CH₄) concentrations, the secondary electron yield (SEY) δ as a function of primary electron (PE) energy E_p has been investigated. The δ–E_p curves exhibited different features for films synthesized under different CH₄ concentrations, and the highest SEY was obtained when the CH₄ concentration was 2%. A physical model was used to compute the key parameters of escape depth λ_s and surface factor f₀·A_s. The results indicated that λ_s is closely related to the crystal quality of the diamond film, with diamond of high quality having larger λ_s, while the surface factor f₀·A_s is mainly determined by the surface morphology, which is associated with the surface roughness of the film. Using the above model, the SEY as a function of varying λ_s and f₀·A_s was also calculated; the results suggested that f₀·A_s plays a key role in determining SEY for low-energy PEs, especially for energies < 500 eV, while the SEY is affected by both λ_s and f₀·A_s for high-energy PEs.