Field emission spectroscopy of gold on the (110) and (211) planes of tungsten

Adsorption of Au up to monolayer amounts on the (110) plane of a tungsten field emitter leads to a decrease in work function, and also to a decrease in effective emitting area. Energy distributions of field emitted electrons show no structure attributable to Au. These results can be explained by postulating that there is no tunneling from Au atoms or from beneath Au atoms. The most probable reason for this is that in (110) tunneling matrix elements from outward normal tungsten d-orbitals are stronger than the tunneling matrix element from the non-directional 6s Au orbital. Experiments on the (211) plane show behavior similar to that previously found on (111), i.e. a work function increase but strong emission from Au atoms.