Electron field emission from vacuum-are discharge activated chemical vapor deposition diamond films has been investigated by measuring the current-voltage characteristics and the field emitted electron energy distribution. The crater region created by the discharge has been investigated by atomic force microscopy with simultaneous conductivity mapping. Comparison of the morphology and local conductivity in the activated zone with that of a good emitting, nonactivated chemical vapor deposition diamond film, shows common features. Specifically these are a large surface roughness in the submicrometer range and a drastically enhanced local conductivity. Both the activated and nonactivated diamond emitters are characterized by strong "G" and "D" lines centered at 1590 and 1350cm(-1) wave numbers in the Raman spectrum. By the combined measurement of the field emission energy distribution and of the current-voltage characteristics we determined the field enhancement factor and the work function of the emitters independently. For the nonactivated diamond emitter we found a work function of 5.6 eV and for the activated diamond emitter 5.3 eV. These values correspond well with the 5 eV work function measured for nanotubes around.