A significant reduction of electron field emission thresholds resulting from ArF laser irradiation of nanocrystalline diamond films in borazine and ammonia atmospheres is reported for the first time. The change of emission characteristics is not connected with either laser surface graphitization or formation of bulk defects. XPS surface analysis and Raman spectroscopy data form these samples shows that laser irradiation results in the synthesis of ultra thin layers of boron-carbon-nitrogen and in B and N atoms intergrain penetration into the film to a depth above 100 angstrom. The synthesis of the B-C-N ternary and existence of sp2 bonded C-N compounds is demonstrated.