High-pressure synthetic diamond particles (DPs) were first seeded over a high-conductive n-type Si(0 0 1) wafer and non-doped diamond layers were then grown onto the DP surfaces by chemical vapor deposition. This sample had good field emission (FE) characteristics. For comparison, a poor FE sample was made from the DP-seeded substrate. We have characterized several important factors of these samples using secondary-electron spectroscopy (SES), field emission spectroscopy (FES) and field emission microscopy (FEM). SES measurements showed that the surface electron affinity of the samples with good FE characteristics is negative but that with poor FE characteristics is positive. FES measurements for a good FE sample showed that a FES peak starts at the substrate Fermi level and moves downward in kinetic energy together with increase of the full-width at half-maximum of peak as the electric field is increased. FEM measurements showed that there are "hot spots" that strongly field-emit electrons. A plausible model of FE for isolated DPs on conducting substrate is proposed under which a key factor of FE is a resistive interface between DPs and the substrate.
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