Photon assisted field ionization

Abstract
An enhancement of the field ionization current was observed when the tungsten tip was illuminated by an external light source. Enhanced ionization occurs for photon energies of lower value than the work function of tungsten. Results indicated that holes are created below the Fermi level by the interaction of photons with the tungsten tip. Hence, the critical distance for which field ionization can occur is reduced. This study provides a method which is complementary to photon assisted field emission to study the electronic states at a metal surface.