Development of ReflEXAFS data analysis for deeper surface structure studies

An analytical approach to the analysis of ReflEXAFS data collected from complex multilayer samples, at a range of angles above and below the critical angle is presented. The aim of the technique is to generate a structural model of the investigated system that is consistent with the variable depth sensitivity of the experimental data. The procedure follows three main steps (i) the determination of the free atom reflectivity background for the multilayer system, (ii) the estimation of the depth dependent EXAFS signals and (iii) the calculation of the corresponding ReflEXAFS components. By iterating between steps (ii) and (iii), and varying the estimates of the EXAFS signals, a consistent set of structural parameters is extracted that reflects the bulk structure of the multilayer system through the basic reflectivity signals, and the depth dependent local atomic structure through the estimated EXAFS components. An example of the depth dependent structure of copper in a copper-chromium multilayer stack is presented to illustrate the capabilities of the method.