Extracting electrons from a substance placed at a particular distance from a positively biased electrode.

Source

The emission of electrons from the surface of a metallic conductor into a vacuum (or into an insulator) under influence of a strong electric field. In field emission, electrons penetrate through the potential surface barrier by virtue of the quantum-mechanical tunnel effect. Also known as cold emission. See also electron tunneling.

Source

The emission of electrons from the surface of a metallic conductor into a vacuum (or into an insulator) under influence of a strong electric field. In field emission, electrons penetrate through the potential surface barrier by virtue of the quantum-mechanical tunnel effect. Also known as cold emission. See also electron tunneling.

Source