One of the promising applications of diamond is to fabricate cold cathodes utilizing negative electron affinity. In this report, the authors focus on finding a new dopant that enables them to obtain heavily nitrogen-doped diamond with much higher reproducibility. Nitrogen-doped diamond films were grown using dimethylurea as a dopant. The field emission properties of these films were measured and from the analysis using voltage-distance plots, they confirm that the electron emission from nitrogen/carbon=10 000 ppm film originates from the metal-insulator-vacuum-type emission due to its high resistance. The rest of the emitted electrons originate from the valence-band maximum, as is often observed in field emissions from chemical-vapor-deposited diamond. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3385784]