Diamond films are grown on Si substrate by microwave plasma CVD using CH4 + H-2 (for undoped) and additive N-2 (for nitrogen-incorporated) with/without O-2 as precursors. Crystal structures for grown films, such as micro- and nano-crystalline and surface morphologies are characterized in terms of growth condition by Raman and field-emission SEM, respectively. Cathodoluminescence (CL) spectra are monitored to identify the nitrogen-incorporation in grown diamond films. Relative intensity ratios of nitrogen-related band to band-A (denoted by I-N/I-A) are also estimated from the CL characteristics and the influence of additive N-2 and O-2 precursors on the I-N/I-A ratio is analyzed. For all-grown films, electron-emission characteristics are measured, from which threshold fields for the emission are also estimated. Observed emission properties are correlated with crystal structures and morphologies obtained from grown films by considering the structural transformation from micro- to nano-crystalline as well as the nitrogen-induced defect states. (C) 2003 Elsevier B.V. All rights reserved.