The effects of B and N ion implantation on structural and electron field emission (EFE) properties of ultra-nanocrystalline diamond (UNCD) films are reported. Low-dose (1012 ions/cm2) B ion implantation & annealing processes insignificantly changed the EFE properties, high-dose (1015 ions/cm2) ion implantation & annealing processes resulted in surface graphitization for UNCD films. While the field emission property of UNCD films was greatly improved due to the N ion implantation & annealing processes, they were degraded due to B ion implantations & annealing processes. Such a phenomenon is accounted for by the fact that N ions residing in grain boundaries can convert the UNCD grains into semi-conducting by charge-transfer process, whereas B ions react with carbon forming covalent bonds and are not transferring the charges with UNCD grains.
