Metallic Superlattices: The Study of Materials at Length Scales From a Few to Hundreds of Angstroms
- PDF / 2,791,272 Bytes
- 6 Pages / 604.8 x 806.4 pts Page_size
- 87 Downloads / 184 Views
We present the possibilities that metallic superlattices offer for the study of materials at length scales ranging from a few to hundreds of angstroms. The materials problems being studied span practically all interesting solid-state phenomena, including superconductivity, magnetism, elastic behavior, development of novel materials, diffusion, ion beam mixing, crystallization, and amorphization. Several applications are also being pursued. We present a few examples of problems that can be studied at different length scales. Emphasis is made that for a proper study of materials properties, extensive structural characterization is imperative. Introduction
In recent years there has been a Virtual explosion in studies related to the physics of layered and thin films.1"3 Multilayers in which one of the elements is a metal have been used in basic studies of the nature of a large variety of physical phenomena. 1 The main reason for the versatility of multilayers is that layer thicknesses can be changed in order to study physical phenomena at length scales ranging from a few hundred angstroms (as for superconducting studies) to a few angstroms (as for rwo-dimensional magnetic studies). In addition, many potential applications are envisioned and some have already been implemented. Although periodic metallic multilayers were first studied over 40 years ago,4 the large increase in the work in this area has occurred only recently. Because the field is still developing, it is impossible to give a completely comprehensive, up-to-date review. We will use examples mostly from our own work to illustrate the type of physics that can be done at different length scales. Those interested in a more extensive and comprehensive review are referred to several recent books on the subject.1'3
has been claimed that the structures of the samples are similar. The structural properties of importance for the multilayers are the composition profile in the direction perpendicular to the layers, the roughness, and the crystallinity. As a first structural tool, electron microscopy can be valuable in enabling one to observe the presence of the layered structure (especially for complex structures) and to make some Statements regarding the Substrate and interfacial roughness. For electron microscopy studies, a multilayered sample is cut in the form of a wedge, perpendicular to the layers (like a slice of birthday cake). Consequently, the electron beam is aimed parallel to the interfaces and a direct image of the layers can be obtained, as illustrated for a W/C Fabry-Perot structure in Figure l. 7 The figure shows extremely wellformed layers at a superlattice periodicity of —32.5 Ä. An averaging phenomenon occurs along the electron path, however, and the roughness might appear to be less than in reality. To date, these techniques7 have not been applied to all types of samples; in particular, metal/metal multilayers have not been extensively imaged this way. More sophisticated electron microscopy
techniques, such as dark field imaging, have received ev
Data Loading...
