DETERMINATION OF THE LATTICE-CONSTANTS OF EPITAXIAL LAYERS

When a thin layer is grown coherently on a single crystal substrate th e lattice constants of the film in its relaxed state, which are indica tive of its chemical composition, cannot be measured directly due to e lastic strain. They can be calculated, however, if the anisotropic ela sticity is taken into account when interpreting X-ray diffraction data . This calculation is performed for the most general case: a triclinic epilayer on a triclinic substrate of arbitrary orientation, thereby i ncluding all seven crystal classes. The correction term is given expli citly for the high symmetry orientations of the individual crystal cla sses, and implicitly for all other orientations.