Fermi-Surface Structure and Field Ionization

Abstract

The process of field ionization at a metal surface is considered in this theoretical analysis as a rearrangement collision. The energy-band structure of the metal is included to determine how it influences the tunneling probabilities at surface planes of various crystallographic orientations. In particular, tunneling to states with the Fermi energy is studied, since these are the most probable final states for the tunneling electron. The specific system considered is hydrogen imaging a face-centered cubic metal whose work function and Fermi energy are assumed to be 5.5 eV and 4.5 eV, respectively. The externally applied electric field is assumed to have a value of 2.3 V/\AA{} at the surface of the metal. The results show that the topology of the Fermi surface does definitely influence the tunneling probability. Consequently, some surface planes are more favorable to tunneling than others. It is concluded that the anisotropy of the Fermi surface does produce anisotropic tunneling probabilities.