Using Anomalous Dispersion Effect for Maximum Entropy Method Analysis of X-ray Reflectivity from Thin-Film Stacks

We used the anomalous dispersion effect and the maximum entropy method (MEM) to analyze X-ray reflectivity had been used, a theoretical layer models were not necessary. We measured the reflectivity of a layer stack at two x-ray wavelengths, the near Ru-K edge and pre Ru-K edge, for a sample with a 0.8 nm thick Ru layer at the stack top. We calculated the differential reflectivity between the two wavelengths by subtracting the near Ru-K edge curve from the pre Ru-K edge curve. We analyzed the differential curves using the Fourier transform (FT) method and MEM. The results showed the interface depths of the samples from the surface to the interfaces. The peak width produced by MEM analysis was narrower than the peak width produced by the FT analysis. Furthermore, using MEM analysis, it is possible to analyze the interface of the thin film in the vicinity of the surface. This result suggests the promising candidate for analyzing the layer structure of a sample by using the anomalous dispersion effect and MEM analysis