Field EmissionPublished on 24/2/2012 & updated on 26/7/2018
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Due to this electrostatic alteration force on a free electron, it has to aquire sufficient kinetic energy to overcome this free for escaping from the surface of the emitter. In other words, there will be a potential barrier for that electron created on the surface of the emitter. This potential barrier is also known as the surface barrier. A free electron has to overcome this surface barrier for getting emitted.
But when a sufficiently high positive charge is placed in front of the emitter surface, due to the strong electrostatic force of the created electric field, the free electron can get sufficient energy to overcome the surface barrier and can get emitted from the surface of the emitter body. As this type of electron emission is caused by the electric field present in the space, it is called field emission.
Definition of Field Emission
Description of Field EmissionWhen we place a metal surface in front of a conductor of high positive potential, with respect to the potential of metal surface, the strong electric field exerts a force on the free electrons. As the force applied to the free electrons is strong enough, the free electrons overcome the restraining force (i.e. surface barrier) and come out from the metal surface.
In emission process, a very intense electric field needs to be created in the space. A million volts per centimetre would be the voltage gradient of the field. In field emission process, the emitter may not need any extra heating for the field emission and that is why the process is also referred to as cold cathode emission.
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