High-current electron emission characteristics of cathodes based on diamond films

Using different gas source, four types of diamond thin films were prepared on silicon substrate by microwave plasma chemical vapor deposition (MPCVD) technology, and characterized in detail through scanning electron microscopy (SEM), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. High-current pulsed emission characteristics, tested with a 2 MeV line-inducing injector, showed that all of CVD diamond films had high emission current density (> 70 A/cm2) and [100] textured B-doped microcrystalline diamond film possessed the largest emission current density of 115.1 A/cm2. No obvious bright light and luminescent zones from side view CCD images indicated a possible pure field-emission mechanism of these diamond cathodes. Simultaneously, large decrease in the electron emission capability, above 15%, could be observed after several pulsed measurements, but this decrease could be completely recovered through the treatment of surface re-hydrogenation for emitted diamond cathodes, suggesting that emission performance of CVD diamond cathodes was closely relevant to hydrogen coverage ratio. The present data indicated that as-deposited CVD diamond films could be a potential candidate as cold cathode for the application in high-current electron emission field.

Research Highlights
► CVD diamond films with different structure and composition showed high emission current density (> 70 A/cm2).
► [100] textured B-doped micro-crystalline diamond film possessed the largest emission current density of 115.1 A/cm2.
► No obvious bright light and luminescent zones of cathode surface could be observerd, suggesting a possible pure field-emission mechanism.
► After rehydrogenating cathode surface, large decrease in electron emission current with increasing emitted numbers could be fully recovered.