Quantum Tunneling

Quantum tunneling is the passing of electrons through an insulating barrier which is thin compared to the de Broglie electron wavelength. If the “electron wave” is large compared to the barrier, there is a possibility that the wave appears on both sides of the barrier.

Figure 3472: Classical view of an electron surmounting a barrier, or not. Quantum mechanical view allows an electron to tunnel through a barrier. The probability (green) is related to the barrier thickness. After .

In clasical physics, an electron must have sufficient energy to surmount a barrier. Otherwise, it recoils from the barrier (Figure 3472). Quantum mechanics allows for a probability of the electron being on the other side of the barrier. If treated as a wave, the electron may look quite large compared to the thickness of the barrier. Even when treated as a wave, there is only a small probability that it will be found on the other side of a thick barrier. See green portion of curve, Figure 3472. Thinning the barrier increases the probability that the electron is found on the other side of the barrier.