Field emission characteristics of microcrystalline diamond film,;, deposited on p-type silicon (100) substrates by hot filament chemical vapor deposition, were studied as a function of deposition time. Scanning electron microscope (SEM) studies revealed that films deposited for short durations were discontinuous. With increasing deposition time nucleation density and crystallite size were found to increase leading to continuous films. Field emission studies showed strong dependence of the emission threshold voltage on both nucleation density and film thickness. It was lowest in discontinuous films (7.7 V/mu m) and increased with increasing thickness in continuous films. Correlation of cross-sectional SEM micrographs of these films and field emission characteristics suggested that silicon-diamond interface did affect threshold voltages. At high film thicknesses (approximate to 10 mu m), a free Si-diamond interface was observed in selected regions that further enhanced the threshold voltage to 55.5 V/mu m. (c) 2006 Elsevier B.V. All rights reserved.