Electron field emission from carbon-based materials

Carbon-based materials have long been identified as a suitable thin film cathode for use in electron emitting structures. This is in part due to the relative ease in the extraction of electrons at low applied electric fields, but also due to their enviable material properties that include chemical and high thermal stability, excellent electrical integrity and mechanical robustness. These thin film cathodes can also be deposited over large areas at low temperatures. It has been reported for a number of years that thin carbon films with low threshold fields can give emission current densities sufficient for flat panel displays, but further commercial development has been hindered due to poor uniformity of emission. A suitable solution to this problem has failed to be found, partly due there being no single accepted model which explains the electron emission process from these films. We have first attempted to categorise the amorphous carbon films found in the literature and two generic models emerge which can be used to explain the emission process. One is based on space charge-induced band bending for films with low defect densities and the second model for films with high defect densities is based on nanoscale dielectric inhomogeneities. Backed by experimental data, we will show computer simulation results that confirm our findings from a qualitative point of view and propose a model to explain the low threshold electron field emission from a majority of defective diamond-like carbon (DLC) thin films. Integrated structures that can be fabricated with gates suitable for a planar device structure will also be introduced.