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Similarly, when a metal is deposited onto a semiconductor (by thermal evaporation, for example), the wavefunction of an electron in the semiconductor must match that of an electron in the metal at the interface. Since the Fermi levels of the two materials must match at the interface, there exists gap states that decay deeper into the semiconductor.
The oligodynamic effect (from Greek oligos, "few", and dynamis, "force") is a biocidal effect of metals, especially heavy metals, that occurs even in low concentrations. This effect is attributed to the antibacterial behavior of metal ions, which are absorbed by bacteria upon contact and damage their cell membranes. [1]
The nature of these metal-induced gap states and their occupation by electrons tends to pin the center of the band gap to the Fermi level, an effect known as Fermi level pinning. Thus the heights of the Schottky barriers in metal–semiconductor contacts often show little dependence on the value of the semiconductor or metal work functions, in ...
The common anion rule guesses that, since the valence band is related to anionic states, materials with the same anions should have very small valence band offsets. [citation needed] Tersoff [5] proposed the presence of a dipole layer due to induced gap states, by analogy to the metal-induced gap states in a metal–semiconductor junction.
Metals are also toxic so a balance must be acquired to regulate where the metals are in an organism as well as in what quantities. Many organisms have flexible systems in which they can exchange one metal for another if one is scarce. Metals in this discussion are naturally occurring elements that have a tendency to undergo oxidation. Vanadium ...
This model includes a dipole layer at the interface between the two semiconductors which arises from electron tunneling from the conduction band of one material into the gap of the other (analogous to metal-induced gap states). This model agrees well with systems where both materials are closely lattice matched [11] such as GaAs/AlGaAs.
In Shockley-Read-Hall recombination (SRH), also called trap-assisted recombination, the electron in transition between bands passes through a new energy state (localized state) created within the band gap by a dopant or a defect in the crystal lattice; such energy states are called traps. Non-radiative recombination occurs primarily at such sites.
If DNA replication takes place in this state, the base pairing rule for DNA may be jeopardised, causing a mutation. [35] Per-Olov Lowdin was the first to develop this theory of spontaneous mutation within the double helix. Other instances of quantum tunnelling-induced mutations in biology are believed to be a cause of ageing and cancer. [36]