Nano-diamond/carbon (NDC) films were fabricated by the microwave plasma-enhanced chemical-vapor-deposition method. It is found that such NDC films exhibit much better electron emission properties. The turn-on field is only approximate to 2.5 V/mum, which is smaller by a factor of eight than that of the conventional microcrystalline diamond films. Raman spectroscopy and curve fitting technique were employed to investigate the bonding structure of the NDC films. The films are confirmed to consist of sp(2)-sp(3) bonded amorphous matrix in which the high-density diamond crystallites are embedded. Transmission electron microscopy observation indicates that the average size of the diamond crystallites is less than 5 nm. The good field emission properties of NDC films are discussed relating to film microstructure and electrical conductivity. (C) 2002 Elsevier Science B.V. All rights reserved.