Abstract
A new X-ray topographic technique of measuring the lattice mismatches between epitaxial films and substrates is reported. The X-ray beams diffracted from the epitaxial film and the substrate at each point of the specimen are recorded on a photographic film at four incident azimuths making 90° to each other by a double-crystal arrangement of non-parallel (+, -) setting, and the local variations in the spacing and the crystallographic orientation of the net planes are separately analyzed. In the present study, for the first crystal were employed various reflections of nearly perfect Si (111) and (100) slices which are usually used for solid state devices. The present technique is simple in mechanism and allows us to study any reflection of various kinds of crystals, in which the fractional variation of spacing Δd/d is of the order of 10-410-5. This technique is applied to study the lattice mismatches between epitaxial garnet films and gadolinium gallium garnet substrates. The apparent symmetry of the epitaxial garnet film was found to be rhombohedral on account of an elastic deformation induced by the lattice mismatch between film and substrate.
