The effect of surface nanostructuring via reactive O-2/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 (similar to 41 nm) to uniform porous structure with increased surface roughness (similar to 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/cm(2) was reached for the nano structured 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. (C) 2015 Elsevier B.V. All rights reserved.