The term from semiconductor physics refers to the introduction of impurity atoms into the crystal lattice of a semiconductor. Though the proportion of the impurity atoms is minimal (0.1 to 100 ppm), doping determines the electrical properties of the semiconductor. For doping, elements are used whose atoms have either one electron less or one electron more on their outer shell than the atoms of the semiconductor. As a result, there is either a supernumerary electron (n-doped) or a missing electron (p-doped) at the place of the impurity atom in the crystal lattice. Several technologies are available for semiconductor doping, for example ⇒ ion implantation.