Electron transmission studies of diamond films

Diamond is an attractive cold emitter candidate because of specific negative-electron-affinity (NEA) surfaces and good electron transport properties. In this study, transmission electron spectroscopy is used to examine the low-energy electron transport and emission properties of thin CVD diamond films. After injecting electrons into diamond films using an external electron gun, the transmission of low-energy secondary electrons is examined. In particular, the intensity and energy distribution of the transmitted electrons are measured as a function of the film properties (thickness, doping concentration) and incident beam properties (energy, intensity). Electron transmission through a heavily-doped, 5 μm thick film exhibits a larger energy spread and lower intensity than electron transmission through a medium-doped, 2 μm thick film. However, the transmission yields are relatively low for both films compared to the reflected yield measurements. Furthermore, the incident beam parameters influence the transmitted electron distribution in ways that cannot be explained by our secondary emission model. On the other hand, the results of the study concerning the transmission of high-energy electrons confirm the theoretical predictions of electron penetration depths in diamond. These initial electron transmission measurements from thin diamond films indicate that the transport process is quite complex, and the study reveals several issues that need to be examined further before the cold emission capabilities of diamond can be assessed.