Kramers-Kronig constrained modeling of soft x-ray reflectivity spectra: Obtaining depth resolution of electronic and chemical structure

• Published in: Physical review. B, Condensed matter and materials physics Vol. 86; no. 2
• Main Authors: Stone, Kevin H., Valvidares, S. Manuel, Kortright, Jeffrey B.
• Format: Journal Article
• Language: English
• Published: United States American Physical Society 10-07-2012
• Subjects: Condensed matter; Electronic structure; Electronics; Optical properties; Reflectivity; Scattering; Strontium titanates; X-rays
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.86.024102

Resonant x-ray scattering is a powerful technique for the study of electronic structure at the nanoscale. In common practice, the optical properties of the constituent components of a material must be known prior to modeling of the scattered intensity. We present a means of refining electronic structure, in the form of optical properties, simultaneously with physical structure, in a Kramers-Kronig consistent manner. This approach constitutes a sensitive and powerful extension of resonant x-ray scattering to materials where the optical properties are not sufficiently well known. The application of this approach to specular reflectivity from a single crystal of SrTiO sub(3) is presented as an example case, wherein we find evidence for both a nonresonant surface contaminant layer and a modified SrTiO sub(3) surface region. Extrapolating from this study we comment on the potential utility of this approach to resonant scattering studies in general.