This review paper presents the applications of x-ray diffraction to routine measurements and the procedures for extending its capabilities of analysis to undertake a detailed structural investigation of low-dimensional structures. The uses and limitations of the familiar double-crystal diffractometer are discussed as are the advantages of 'reciprocal space mapping' with a multiple-crystal diffractometer. In general x-ray diffraction has been used for composition and thickness measurement in low-dimensional structures (us) and these aspects are covered, as well as the avoidance of the piifalls associated with their determination. The possibilities for the use of x-ray diffraction methods to determine interface quality, the evolution of lattice relaxation, the detailed microstructure, etc, are discussed, with an indication of the limits of the techniques. P F Fewster Aspects to considerThis section discusses some very general points that should be considered before any analysis using x-ray diffraction techniques.

The absolute lattice parameters of single‐ and polycrystalline materials have been measured to within a few parts per million with a high‐resolution diffractometer. The problems associated with 'zero errors' and sample centring on the goniometer are eliminated and high precision is achieved by virtue of the exceedingly high angular resolution of the instrument. The high‐resolution multiple‐crystal multiple‐reflection diffractometer is used to determine the lattice parameter with a single quick measurement on a range of 'perfect' semiconductor‐substrate materials, layer structures and inhomogeneous samples. The various corrections and alignment procedures associated with this method are discussed.

X-ray diffraction is sensitive to thin films of atomic dimensions to thicknesses of many tens of microns, by virtue of the x-ray wavelengths employed and the very high diffractionspace resolutions attainable. X-ray methods are generally non-destructive, in that sample preparation is not required, and they can provide a very appropriate route to obtain structural information on thin films and multilayers. Analysis can be performed across the whole spectrum of material types from perfect single crystals to amorphous materials. The choice of the x-ray diffraction analysis procedure depends on the quality of the structural form and therefore this review has been organized to reflect this. Following a description of the various material types, some typically important material parameters have been given arising from the application areas. These material parameters relating to the structure are then categorized into macroscopic and microscopic properties which can then be further subdivided and correlated to the most appropriate analysis method. It is clear from this that x-ray analysis covers the whole range and from this the recent developments will become clear. It is intended therefore that the reader is not compelled to read from beginning to end, but rather be able to find the structural parameter of interest to him/her in a simple way and from that discover the various approaches to its determination.

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