Electroluminescence produced by high electric fields at the surface of copper cathodes

Spots of light have been observed on the surface of OFHC copper cathodes following the application of high electric fields. The spectrum of the radiation shows a sharp peak at about 640 nm and its intensity obeys the Alfrey-Taylor relationship for electroluminescence. Within the light-emitting regions, discharges have been seen which it is believed are caused by the breakdown of dielectric inclusions trapped at defects in the crystal structure. Observations are consistent with the inclusions having semiconducting properties and emitting light by recombination of conduction electrons with holes produced by impact ionization within their crystal lattice structure.