Patent ID: 7057333
Filing Date: 2006-06-06
Classification: H01J

Abstract:
1. A method of extracting in a vacuum electrons emitted from a cathode situated in spaced-apart relationship with an anode which is placed at a given potential relative to the cathode by means of a bias source, the method comprising: making a cathode presenting at least one junction between a metal serving as a reservoir of electrons and an n-type semiconductor, the junction possessing a surface potential barrier with a height in a range of 0.05 to 0.5 eV, the n-type semiconductor presenting an emission surface for electrons and having a thickness lying in a range of 1 nm to 20 nm, defined by the value of the lowering desired for the surface potential barrier; injecting electrons through the metal/semiconductor junction to create a space charge in the semiconductor sufficient to lower the surface potential barrier of the semiconductor to a value that is less than or equal to 1 eV relative to the Fermi level of the metal; and using the bias source that creates an electric field in the vacuum to control the height of the surface potential barrier of the n-type semiconductor, so as to modify in reversible manner the electron affinity of the n-type semiconductor surface in order to control the emission of an electron flux towards the anode.