Microscopic study of field emission from diamond particles

Abstract

The field emission properties and microscopic characteristics of diamond particles (DPs) are studied by scanning electron microscopy (SEM), secondary electron spectroscopy (SES), scanning tunneling microscopy/spectroscopy (STM/STS), scanning field emission microscopy (SFEM) and field emission electron microscopy (FEEM). DPs with an average size of 1 μm were spin-coated onto a tungsten substrate. After the spin-coat process, an undoped thin diamond layer was grown on the DP surfaces by the conventional microwave plasma-assisted CVD method. Consequently, the total emission current measured on the DP-seeded substrate (1×1 cm 2) was approximately 1 mA under an electric field of 3.5 kV/mm. The DPs with the CVD diamond overcoat have facet edges of diamond, which are sometimes covered with small crystallites. The SES spectrum for these samples showed that the surface of DPs with a CVD diamond overcoat has essentially a NEA surface. The SFEM was able to image the distribution of field emission sites by scanning the STM tip with fixed tip height. The SFEM and FEEM images suggest that some particular DPs contribute to field emission and the emission occurs from the top site of the DP. The modification of surface property and electric field at the top site or edge of the DP affects the effective field emission.