Configuration-dependent enhancements of electric fields near the quadruple and the triple junction

The authors investigated the behavior of an electric field near a junction composed of metal, dielectric, and vacuum. By using the two-dimensional model of the junction, the authors calculated the electric field near the junction as a function of configuration. For the triple junction of metal-vacuum-dielectric, the electric field is found to be enhanced and reduced according to the ratio of the contact angles. The use of the same model also leads to the result that the quadruple junction of metal-vacuum-dielectric-vacuum yields a much larger field enhancement than the triple junction. It is noted that the total enhancement of the electric field at the junction is the product of the two enhancements due to the dielectric and the shape of the metallic emission site.