A tunnel junction consists of two conducting electrodes separated by a thin region through which electrons can undergo quantum tunnelling. The separating region may be an insulating layer or a narrow vacuum gap. A difference in electrochemical potential supplies occupied incident states on one side and accessible states on the other.
For a simple barrier, the transmission probability decreases approximately exponentially with thickness, making the junction very sensitive to separation. This is the basis of scanning tunneling microscopy. The measured electric current also depends on the electronic density of states and the applied voltage. When a junction connects a sufficiently small conducting island, its capacitance can make individual charging energies large enough to produce Coulomb blockade.
A tunnel junction is a type of electronic junction that allows for quantum tunneling of charge carriers, typically electrons, between two conductive regions. It is characterized by the presence of a thin insulating barrier (often just a few nanometers thick) that separates two superconductors or a superconductor and a normal conductor.
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