An introduction to surface diffractometry

For most solids, the surface constitutes the main defect, equivalent to a sudden break in the periodic arrangement of atoms. From a stractural point of view, the surface of a sohd is the layer of atoms that ends this solid. Some authors have shown that it is possible, in specific conditions, to study the stmcture of these surfaces, that is, the nature of the atoms that comprise the solid s hmit and how they are arranged. The experimental techniques used rely on X-ray diffraction, but these methods are very specific and the structural study of surfaces, even though it started about 20 years ago, remains a field reserved to a few specialists. Most studies involve the surface of semiconductors or metals. We should point out, however, that over the past few years, the surface stmcture of a few simple oxides have been studied [REN 98]. 

The underlying idea behind these measurements is to irradiate the single ciystal we wish to stndy at a very low angle, below the critical angle of total reflection. As 

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