In this article, we report aspects of the growth of nanocrystalline diamond films using, microwave-assisted plasma chemical vapor deposition and their relation to electron. field emission. Nanodiamond films with grain size as small as 5-10 nm by CH4/H-2/N-2 microwave plasma enhanced chemical vapor deposition (MPECVD) and 10-20 nm by CH4/H-2 MPECVD have been achieved. An effective means to grow nanodiamond films is to increase the nucleation rate and decrease the growth rate by adjusting the CVD process parameters. With its relation to field emission, we infer that the combination of high dopant concentration resulting in lower electrical resistance of the diamond film and increased sp(2) bonded nondiamond carbon content contributes effectively to the enhancement of field emission characteristics, while the reduction in grain size of the nanodiamond film has no similar effect. (c) 2005 American Vacuum Society.