Comparison of S-band radio-frequency field emission performance of nitrogen-doped nanocrystalline diamond before and after O2/Ar plasma etching

The effect of surface nanostructuring via reactive O2/Ar plasma etching on the S-band radio-frequency (RF) field emission performance for nitrogen-doped nanocrystalline diamond (N-NCD) films was preliminarily investigated. A transition in terms of surface morphology, from dense flower-like aggregated shape having low roughness (∼41 nm) to uniform porous structure with increased surface roughness (∼104 nm), was observed after plasma etching. Raman spectra revealed there was no obvious change in the bonding characteristics between the pristine and nanostructured N-NCD films. At surface RF gradient of 72.1 MV/m, maximum current density of 80.2 mA/cm2 was reached for the nanostructured N-NCD cathode, increasing about 41% compared to that of the pristine N-NCD cathode. Furthermore, the mechanism in the enhanced RF field emission was tentatively discussed through the measured Fowler-Nordheim (F-N) features.