Cold cathode electron emission properties of nanocrystalline diamond thin films

We have developed several methods for producing nanocrystalline diamond thin films with electron emission thresholds in the 2-5 volt/micron range. The films are grown in Ar-C/sub 60/-H/sub 2/, Ar-CH/sub 4/, Ar-CH/sub 4/-H/sub 2/, Ar-CH/sub 4/-N/sub 2/, and N/sub 2/-CH/sub 4/ microwave plasmas. Although they are all nanocrystalline, with grain sizes ranging from /spl sim/5 to 100 nm, they differ in details of their morphology and electronic properties. Photoemission yields and STM images indicate that topographically enhanced electric fields may play a role in the low thresholds observed for some of these films; however, for other films, the required field enhancement is much too large to be explained in terms of local surface topography on a diamond surface, but the observed low emission thresholds appear to be associated with enhanced interband state density.