Overlayer
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An overlayer is a layer of adatoms adsorbed onto a surface, for instance onto the surface of a single crystal.
Overlayers on single crystals
Adsorbed species on single crystal surfaces are frequently found to exhibit long-range ordering; that is to say that the adsorbed species form a well-defined overlayer structure. Each particular structure may only exist over a limited coverage range of the adsorbate, and in some adsorbate/substrate systems a whole progression of adsorbate structure are formed as the surface coverage is gradually increased.[1]
The periodicity of the overlayer (which often is larger than that of the substrate unit cell) can be calculated by low-energy electron diffraction, because there will be additional diffraction beams associated with the overlayer.[2]
Types of overlayers
There are two types of overlayers: commensurate and incommensurate. In the former the substrate-adsorbate interaction tends to dominate over any lateral adsorbate-adsorbate interaction, while in the latter the adsorbate-adsorbate interactions are of similar magnitude to those between adsorbate and substrate.[3]
See also
References
- ^ "6.1: Classification of Overlayer Structures". chem.libretexts.org. Retrieved 2019-03-12.
- ^ Attard, Gary; Barnes, Colin. Surfaces. Oxford Chemistry Primers. p. 53. ISBN 978-0-19-855686-2.
- ^ Attard, Gary; Barnes, Colin. Surfaces. Oxford Chemistry Primers. p. 33. ISBN 978-0-19-855686-2.
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