Characterization of nanometer‐scale epitaxial structures by grazing‐incidence x‐ray diffraction and specular reflectivity

X‐ray rocking curve analysis is a powerful and nondestructive technique for the characterization of heteroepitaxial structures. Conventionally, measurements are performed in symmetrical scattering geometry using a double‐crystal x‐ray diffractometer but the technique can be extended to the study of very thin layers (<200 Å) by the use of glancing‐incidence scattering geometry and a triple‐crystal diffractometer. These structures can also be studied by the technique of total external x‐ray reflectivity. This is sensitive to the electron‐density profile of the heterostructure as a function of depth. By combining the above techniques we have found it possible to obtain structural information on layers as thin as 20 Å. Such measurements permit accurate measurement of individual layer thicknesses and interface roughnesses on the angstrom level. The lattice parameter strain can be obtained by modeling of the intensity distribution of the crystal truncation rod.