Donor atom

Donor atom

An impurity atom in a semiconductor which can contribute or donate one or more conduction electrons to the crystal by becoming ionized and positively charged. For example, an atom of column 5 of the periodic table substituting for a regular atom of a germanium or silicon crystal is a donor because it has one or more valence electrons which can be detached and added to the conduction band of the crystal. Donor atoms thus tend to increase the number of conduction electrons in the semiconductor. The ionization energy of a donor atom is the energy required to dissociate the electron from the atom and put it in the conduction band of the crystal. See Acceptor atom, Semiconductor

References in periodicals archive ?
For all depicted level is coincident if the donor atom is placed at one of the QD borders the effect of the electron-impurity attraction is weaker and therefore the energy levels tend to go up (this is due to the an infinite barrier effect).
Furthermore, the Hd signal appears to be more affected in comparison to H[[delta].sub.2], giving evidences of its closer distance to the paramagnetic centre, thus suggesting coordination to the metal ion through the N[[delta].sub.1] donor atom, as already found in other similar cases [30-32].
These 16-electron M[(CO).sub.5] fragments react quickly with any available donor atom to yield a M[(CO).sub.5]L species; and where L is a chelating bidentate ligand, rapid continuation to the chelating M[(CO).sub.4]L or bridging [M.sub.2][(CO).sub.10] ([micro]-L) products may occur [7-10].
These 16-electron M(CO)5 fragments react quicklywith any available donor atom to form a M[(CO).sub.5]L species.
Sousa, Electrochemical synthesis of metallic complexes of bidentate thiolates containing nitrogen as an additional donor atom, Coord.
a) The s-block metals (Na, K, Mg and Ca) are among the ten most abundant elements, b) these frameworks could provide gravimetric advantages for gas adsorption due to their low-atomic weights, c) higher charge density of these metal ions leads to strong bonding interactions with donor atoms, d) they are cheap and non-toxic.
There is mounting evidence that the molecules that are best at this contain soft donor atoms to the metals.
For example kryptofix 222 having nitrogen and oxygen donor atoms has drawn interest due to % its ability to selectively bind ions especially alkali and alkaline earth metal cations [8-10].
A large amount of data has been published on macrocyclic ligands containing only nitrogen, only sulphur, or both as donor atoms, namely, tetraaza [12], thiadiaza [13], thiatriaza [14], dithiadiaza [15,16], or dithiatriaza [17].
The presence of both hard nitrogen and soft sulphur donor atoms permits coordination with a wide range of transition and non-transition metal ions yielding stable and extremely coloured metal complexes, some of which have exhibited interesting physico-chemical [2-4] and potentially beneficial chemotherapeutic properties [5-8].