Tunneling microscope
Local Probe Microscopy

As a consequence of wave-particle duality, the tunnel effect occurs when a particle must pass through a region of space where its total energy is less than its potential energy. Such a region constitutes a potential barrier that the particle cannot pass through. However, if the wave associated with the particle extends over dimensions comparable to the extent of this barrier, quantum mechanics predicts that the particle can tunnel through this potential barrier, which is forbidden in classical mechanics. Since the predictions of quantum mechanics, numerous manifestations of the tunnel effect have been observed in atomic and nuclear physics.

It was at the end of the 1920s that the electron tunneling effect through the potential barrier formed...