Application of scanning tunneling-field emission microscopy for investigations of field electron emission from nanoscale diamond films

A special scanning tunneling-field emission microscope (STFEM) has been used for studying field electron emission from thin nanocrystalline diamond films grown by a DC plasma CVD. These are characterized by turn-on electric fields as low as 3.5 V/μm and by long-term stability of the emission current. Comparing different surface properties (topography, field electron emission intensity, surface potential and local electroconductivity distributions) on a large surface area it was found that, in most cases, emission centre position is not coincident with peaks of the surface profile. It has been noted that the diamond films studied are composed from nano-grained phases distinguished by their physical properties. These are thought to be diamond and graphitic phases. The low-field electron emission from the samples studied is considered to be associated with the presence of these phases. The results of the STFEM mapping have been compared with data on macroscopic current/field field emission characterization. The mechanisms governing low-field electron emission from nanoscale diamond films are discussed.