Editing Quantum tunnelling (section)

==== Cold emission ====
{{Main|Field electron emission}}

Cold emission of [[electrons]] is relevant to [[semiconductor]]s and [[superconductor]] physics. It is similar to [[thermionic emission]], where electrons randomly jump from the surface of a metal to follow a voltage bias because they statistically end up with more energy than the barrier, through random collisions with other particles. When the electric field is very large, the barrier becomes thin enough for electrons to tunnel out of the atomic state, leading to a current that varies approximately exponentially with the electric field.<ref name="Taylor">{{cite book|last=Taylor|first=J.|title=Modern Physics for Scientists and Engineers|publisher=Prentice Hall|year=2004|isbn=978-0-13-805715-2|page=479}}</ref> These materials are important for flash memory, vacuum tubes, and some electron microscopes.