The diamond-vacuum interface: II. Electron extraction from n-type diamond: evidence for superconduction at room temperature

摘要

It is shown experimentally that n-type diamond is a negative electron affinity material from which electrons can be extracted at room temperature. This is achieved by generating an 'ohmic' tunnelling contact to the vacuum. It is found that the extracted electrons within the gap between the diamond surface and the anode are able to form a stable, highly conducting phase. Band theory, combined with the equations that describe electron transport in a vacuum diode, unequivocally show that the distances between these electrons, as well as their speeds, must keep on decreasing as long as there is an electric field between the diamond surface and the anode. This implies that steady-state current flow, as experimentally observed, can only occur if this field becomes zero while still allowing a current to flow from the diamond to the anode. The only way to achieve such a situation is for the extracted electrons within the gap to form a superconducting phase. Because electrons are fermions, an unabated decrease in their nearest-neighbour distances as well as their speeds should eventually force them to violate the Heisenberg uncertainty relationship. At this limit, they become restricted, as pairs, within volumes or 'orbitals' which in turn fill the whole space between the diamond and the anode. Because these 'orbitals' have zero spin, they are boson-like charge carriers, and because they are as near to each other as is physically possible, they automatically constitute a Bose-Einstein condensate; i.e. they constitute a superconducting phase.