Interstitial atom

from Wikipedia, the free encyclopedia
Point defects in a two-dimensional crystal lattice and the like a. with a self-interstitial atom (top left)

As interstitial atoms ( English interstitials are) atoms or ions referred to in the atomic lattice of a crystal structure not on a regular lattice site. They sit between the grid positions and thus represent zero-dimensional grid defects ( point defects ).

The introduction of atoms in interstitial spaces usually causes strong distortions of the crystal lattice, i.e. the surrounding lattice atoms shift slightly. The energy required for the displacement represents the largest proportion of the energy required for the generation of interstitial atoms and is dependent on the size of the introduced atom. Depending on whether the interstitial atom is an atom of the same element or another element, a distinction is made between:

  1. Self-interstitial atoms : Here, atoms of the same element that the crystal is made of are located in interstitial positions. It is therefore an intrinsic defect in the atomic lattice.
  2. Foreign interstitial atoms : This is an extrinsic atomic defect in which foreign atoms are located on interstitial positions, one speaks of an interstitial or interstitial foreign atom.

Interstitial atoms can arise when lattice atoms jump or are shifted into neighboring lattice gaps, whereby so-called Frenkel defects arise. Another way of creating interstitial atoms is bombardment with high-energy particles. The particles are slowed down by collisions with the lattice atoms. Atoms can be knocked out of their lattice positions and the braked particles as well as the original lattice atoms can be placed in interstitial spaces. This is used, among other things, in semiconductor technology , where foreign atoms are introduced into a crystal with the help of ion implantation . However, in order to be able to use this to change the electrical properties (cf. doping ), the atoms and ions introduced must sit on regular grid positions. The implantation is therefore usually followed by a heating step in which the diffusion of the interstitial atoms is increased and they are inserted into the lattice.

literature

  • Siegfried Hunklinger: Solid State Physics . Oldenbourg Wissenschaftsverlag, 2009, ISBN 978-3-486-59045-6 , p. 132-134 .