Scanning Probe Microscopy of Carbon-Nanoparticle-Based Emitters

The techniques of scanning tunneling microscopy/spectroscopy (STM/STS) and atomic force microscopy/ spectroscopy (AFM/AFS) with conductive cantilevers are applied to study electronic properties of the emission sites in field electron emitters based on carbon nanoparticles (nanodiamonds, carbon nanotubes). The emitters are produced by (i) electrochemical codeposition of metals with nanodiamond, (ii) electrophoretic deposition of single-wall carbon nanotubes, and (iii) shock-wave compacting/implantation of carbon nanoparticles into metal layers. STM analysis of the emitter surface allows to get mapping of the surface relief, field emission, surface electron potential, and local electroconductivity. It is generally found that the position of the emission sites is coincident with high-conducting regions where the surface electron potential is lowered. In addition, the STS/AFS data showed different character of local conductivity in nm-sized surface regions of the nanodiamond- and nanotube-based emitters. The obtained data provide further support for the field emission model based on the analysis of the field-enhanced emissivity of low-dimensional regions due to the quantum well effect, which has been previously proposed to account for the low-field electron emission from nanocrystalline diamond and nitride films.