Similarity in field electron emission from nanocrystalline diamond and related materials

Results on a complex study of macroscopic and microscopic electronic properties of nanocrystalline diamond and related material (BN, GaN, CN) films are presented. It was found that all the samples studied showed similar dependencies of macroscopic emission parameters (the Fowler-Nordheim work function, the effective emitting area) on the film emissivity. Also, some microscopic properties were found to be common for all the films tested. It was generally observed that field electron emission occurred at nanosized regions on the boundary of high and low resistivity areas, and peaks of the emission intensity were associated with a lowered surface electron potential. Based on the experimental data, a mechanism of field electron emission from the surface of nanocrystalline films is proposed. We suppose that electrons are transported from narrow conducting channels into vacuum through specific low-dimensional regions, the electronic properties of which, due to the quantum size effect, are different from the bulk material. In this case the base material grains play a role of the conductive channel-containing matrix as well as a heat sink. Details of the new low-field emission mechanism including the filling of discrete energy states, and the decrease in the work function under the action of electric field are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.