On the mechanism of improvement of field emission properties of carbon coated field emitters

To clarify the origin of the superior field emission characteristics of carbon coated emitters, we investigated the field enhancement at a triple junction and work functions as calculated by ab initio simulations. The electric field near the triple junction is one order of magnitude higher than at other places. Based on ab initio calculation, we found that (1) the work functions of diamond and graphite dramatically decrease to 3 - 3.6 eV upon hydrogen termination, and (2) the effective work functions of some models decrease to 2 eV by applying an external electric field. We also estimated the field emission current from the potential distribution and local density of states under the external electric field applied.