Schottky effect
The
Schottky effect is a phenomenon found in physics. In electron emission devices, especially electron guns, the thermionic electron emitter will be biased negative relative to its surroundings. This creates an electric field of magnitude
F at the emitter surface. Without the field, the surface barrier seen by an escaping Fermi-level electron has height
W equal to the local work-function. The electric field lowers the surface barrier by an amount Δ
W, and increases the emission current. This is known as the
Schottky effect or field enhanced thermionic emission. It can be modeled by a simple modification of the Richardson equation, by replacing
W by. This gives the equation where
ε0 is the electric constant. Electron emission that takes place in the field-and-temperature-regime where this modified equation applies is often called
Schottky emission. This equation is relatively accurate for electric field strengths lower than about 108 V m−1. For electric field strengths higher than 108 V m−1, so-called Fowler-Nordheim tunneling begins to contribute significant emission current.