Thermionic Emission in a Planar Diode
Application ID: 42551
When electrons are emitted from a heated cathode in a plane parallel vacuum diode, they contribute to the space charge density in the diode, which in turn affects the electric potential distribution. If the potential difference between the cathode and the anode is not sufficiently large, a potential minimum forms between them, repelling electrons of insufficient energy back toward the cathode. Such a diode is said to be operating in the space charge limited regime.
In this benchmark model, the dedicated Thermionic Emission feature is used to release thermal electrons from a cathode of a specified temperature and work function. The electron trajectories are bidirectionally coupled to the electric potential calculation in the diode using the specialized Electric Particle Field Interaction multiphysics coupling and Bidirectionally Coupled Particle Tracing study step. The electric potential distribution and the anode current compare favorably to the results of the analytical Langmuir-Fry model.
This model example illustrates applications of this type that would nominally be built using the following products:Particle Tracing Module
however, additional products may be required to completely define and model it. Furthermore, this example may also be defined and modeled using components from the following product combinations:
The combination of COMSOL® products required to model your application depends on several factors and may include boundary conditions, material properties, physics interfaces, and part libraries. Particular functionality may be common to several products. To determine the right combination of products for your modeling needs, review the Specification Chart and make use of a free evaluation license. The COMSOL Sales and Support teams are available for answering any questions you may have regarding this.