X-ray scattering from multiple-layer structures forming Bragg-case interferometers

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Abstract
The sensitivity of the Bragg-case interferometer, formed from a thin highly mismatched epitaxial layer of composition A sandwiched between material of composition B, to changes in the spacer (A) layer thickness is discussed. It is shown that for thick cladding (B) layers, the interference fringes can modulate the double-axis X-ray rocking curves sufficiently to cause distinct splitting of layer peaks. Such large intensity changes can form the basis of Bragg-case moire topography, which in principle has a resolution capable of detecting monolayer changes in spacer layer thickness across a large area. The effect of relaxation is examined and it is demonstrated that this may result in an additional Bragg peak associated with the changed strain in the capping layer.