Effect of material properties on low-energy electron transmission in thin CVD diamond films

The electron transport process in CVD diamond was investigated using electron transmission spectroscopy. Electrons were injected into thin diamond films using a 0-20 keV electron gun, and then the secondary electrons that were transmitted through the films were detected and analyzed. In particular, the intensity and energy distribution of the transmitted electrons were measured as a function of the incident beam parameters (E₀, I₀) and analyzed using Monte Carlo simulations. Electron transmission data is measured from three CVD diamond films having similar thickness (∼ 2 μm) but different bulk properties (i.e. B concentration, amorphic C content). Measurements are also taken from two CVD diamond films of different thickness (∼ 0.15 and 4 μm). In the conduction-band transport regime, the escape depth (D_esc) was determined. In general, D_esc was sensitive to the amorphic C content and grain boundary density, but not to the B concentration. The B concentration more strongly affected the transmission yield. The transmission yield was also affected by the surface properties of the film. It can be concluded that the film should be as thin as possible to achieve the highest yield.