3 keV nitrogen ions are implanted into UNCD/Si from our 30 kV ion accelerator. Field emission property is enhanced upon nitrogen implantation in comparision to as-prepared UNCD. STM shows that there is agglomeration of diamond grains. CITS measurements show that diamond grains are the prominent electron emitters while grain boundaries were the prominent emitters for 75 keV N+ implantation. When N atoms are at the surface, electron emission by transfer-doping process appears to be the physical mechanism involved. When they are buried deeper as in the case of 75 keV ions, grain boundary conduction-channel process is valid.
