Artificially layered structures

Article By:

Schuller, Ivan K. Physics Department, University of California, La Jolla, California.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.053450

Manufactured, reproducibly layered structures having layer thicknesses approaching interatomic distances. Modern thin-film techniques are at a stage at which it is possible to fabricate these structures, also known as artificial crystals or superlattices, opening up the possibility of engineering new desirable properties into materials. In addition, a variety of problems in solid-state physics can be studied which are otherwise inaccessible. The various possibilities include the application of negative pressure, that is, stretching of the crystalline lattice; the study of dimensional crossover, that is, the transition from a situation in which the layers are isolated and two-dimensional in character to a situation in which the layers couple together to form a three-dimensional material; the study of collective behavior, that is, properties that depend on the cooperative behavior of the whole superlattice; and the effect and physics of multiple interfaces and surfaces. These structures serve as model systems and as a testing ground for theoretical models and for other naturally occurring materials that have similar structures. For instance, ceramic superconductors consist of a variable number of conducting copper oxide (CuO₂) layers intercalated by various other oxide layers, and therefore artificially layered structures may be used to study predictions of the behavior of suitably manufactured materials of this class. A variety of applications have also been proposed or discovered. Of course, one of the most exciting prospects is the discovery of new, as yet unpredicted phenomena. For a discussion of semiconductor superlattices See also: Crystal structure; Semiconductor heterostructures

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