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 Ep has been investigated. The δ–Ep 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 λs and surface factor f0·As. The results indicated that λs is closely related to the crystal quality of the diamond film, with diamond of high quality having larger λs, while the surface factor f0·As 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 λs and f0·As was also calculated; the results suggested that f0·As plays a key role in determining SEY for low-energy PEs, especially for energies < 500 eV, while the SEY is affected by both λs and f0·As for high-energy PEs.