Unified Theory of Field Emission and Thermionic Emission

There are two well-known kinds of electron emissions from metal surfaces: field emission and thermionic emission. For thermionic emission electrons are emitted when they have sufficient thermal energy to overcome the work function and for field emission,as Fowler-Nordheim tunneling, they are emitted by tunneling, aided by a strong repulsive electric field.Ê We considered the most general case of both process together, using a free electron gas model.Ê This can be important in the case of a field emission current ohmically heating the emission tip. The total emission current density is compared to field emission for different temperatures and to thermionic emission for different electric fields.