Theoretical analysis of the field enhancement in a two-dimensional triple junction

The field enhancement at a triple junction is theoretically investigated. For a long metal-dielectric-vacuum junction, the field behavior in the three media is described as a function of the geometry and the dielectric constant. It is found that the key factor determining the field enhancement is the ratio of the angles subtended by the dielectric and vacuum portions. This phenomenon can account for the field emission enhancement and the vacuum breakdown observed in experiments. The current result implies that the triple junction can be a new type of field emission source.