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Vacuum emission from metals tends to become significant only for temperatures over 1,000 K (730 °C; 1,340 °F). Charge flow increases dramatically with temperature. The term thermionic emission is now also used to refer to any thermally-excited charge emission process, even when the charge is emitted from one solid-state region into another.
The Schottky effect or field enhanced thermionic emission is a phenomenon in condensed matter physics named after Walter H. Schottky. In electron emission devices, especially electron guns , the thermionic electron emitter will be biased negative relative to its surroundings.
Energy level diagrams for thermionic diode in retarding potential configuration. The barrier is the vacuum near collector surface. The barrier is the vacuum near collector surface. The same setup can be used to instead measure the work function in the collector, simply by adjusting the applied voltage.
In condensed matter physics, the Nottingham effect is a surface cooling and heating mechanism that occurs during field and thermionic electron emission. The effect is named after physicist Wayne B. Nottingham who explained it in a commentary to 1940 experiments by Gertrude M. Fleming and Joseph E. Henderson. [1] [2] [3]
The scientific aspects of thermionic energy conversion primarily concern the fields of surface physics and plasma physics. The electrode surface properties determine the magnitude of electron emission current and electric potential at the electrode surfaces, and the plasma properties determine the transport of electron current from the emitter ...
Walter Hans Schottky (German: [ˈvaltɐ ˈʃɔtki]; 23 July 1886 – 4 March 1976) was a German physicist who played a major early role in developing the theory of electron and ion emission phenomena, [2] invented the screen-grid vacuum tube in 1915 while working at Siemens, [3] co-invented the ribbon microphone and ribbon loudspeaker along with Dr. Erwin Gerlach in 1924 [4] and later made ...
This gives the barrier a high resistance when small voltage biases are applied to it. Under large voltage bias, the electric current flowing through the barrier is essentially governed by the laws of thermionic emission, combined with the fact that the Schottky barrier is fixed relative to the metal's Fermi level. [6]
Schottky–Nordheim barrier for Fowler–Nordheim field emission (and enhanced thermionic emission) The Schottky–Nordheim barrier, which is the barrier model used in deriving the standard Fowler–Nordheim-type equation, [69] is a special case.