Transmission of low-energy electrons in boron-doped nanocrystalline diamond films

Abstract

Transmission electron spectroscopy is used to examine the low-energy electron transport and emission properties of nanocrystalline chemical-vapor-deposited diamond films. In particular, the intensity and energy distribution of transmitted electrons are measured as a function of film thickness and incident-beam parameters. Low-energy transmission is detected in measurements from two films of thickness 0.15 and 2.5 μm with similar boron concentrations. The transmitted energy distributions are very similar for the two samples and are nearly identical to those obtained in reflection measurements. The full width at half maximum of the transmitted distribution is slightly broader for the thinner film (∼0.8−0.9 eV) than for the thicker film (∼0.6−0.7 eV), and the maximum transmission yields are similar (∼3−5 emitted electrons per incident electron). However, different beam energies are required to produce the low-energy transmission. The energy-dependent data is interpreted using Monte Carlo simulations along with a qualitative model of the diamond nanostructure. From this analysis, the low-energy-electron escape depth is confirmed to be as long as ∼1 μm in the 2.5-μm-thick sample.