Modulation of Renninger scan intensity: A new x-ray technique to characterize epitaxial structures

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Abstract
We have demonstrated a new x-ray diffraction technique to characterize epitaxial structures. It makes use of Renninger scans [Z. Phys. 106, 141–176 (1937)] in which a crystal is rotated about the normal to a set of diffracting planes while diffraction from those planes is measured. To obtain these scans an x-ray beam passes through, and is modulated by, the epitaxial layer on the way into and/or out from a substrate reflection. The scans show multiple diffraction features from the substrate and new features which are due to the epitaxial layer. These modulations of Renniger scan intensity data, which we call MORSI, yield information about the orientation, lattice dimensions, and structural perfection of the sample in a variety of directions. In addition to the new features, changes are observed in the shape of a given multiple beam interaction from sample to sample. These appear to be due to differences in the perfection of substrate material. In this letter we report a MORSI study of a 1.4-μm-thick ZnSe layer grown by molecular beam epitaxy on a (001) oriented GaAs substrate using the GaAs (004) for the Renninger scan.