Multilayers, as considered in the following articles, are manmade thin-film materials periodic in one dimension in composition or in composition and structure. This composition/structure variation is generated during synthesis, which is typically accomplished using atom-by-atom technologies. Individual component layers in a multilayer may vary in thickness from one atomic layer (~2 Å) to hundreds of atomic layers (~1,000 Å) of a given material.

An example of these synthetic micro-structures, a lattice image transmission electron micrograph of a cross section of a hundred period titanium (63 Å)/titanium-nickel (40 Å) multilayer microstructure fabricated using magnetron sputtering, is shown on the cover of this issue of the MRS BULLETIN. The titanium-nickel layers are amorphous as a result of the low substrate temperature (<75°C) and the very large atomic quench rates characteristic of vapor deposition (>1012 K/s). The elemental titanium layers are fiber textured with the basal plane of this hexagonal close-pack structure element in the plane of the layers. These (00.1) planes are the ones lattice imaged in this electron micrograph.

The general concept of a multilayer structure, as illustrated above, is now well accepted because the ability to synthesize such materials for scientific study and technological application has been demonstrated at many nationally and internationally based laboratories.