Simultaneous analysis of multiple extended x-ray-absorption fine-structure spectra: Application to studies of buried Ge-Si interfaces

Ge <i>K</i>-edge extended x-ray-absorption fine-structure (EXAFS) spectra of a series of strained-layer [(Si)<i>_m</i>/(Ge)<i>_n</i>]<i>_p</i> superlattices grown by molecular-beam epitaxy on the〈100〉face of single-crystal Si have provided a determination of the degree of intermixing and the extent of relaxation as a function of the thickness of the Ge layer. The results are obtained with use of constrained simultaneous nonlinear least-squares curve fits to multiple data files from different samples. This procedure, along with associated analysis of the fit surface, has improved the reliability of the analysis. We discuss the general applicability of simultaneous analysis procedures to EXAFS analysis of a series of related samples, such as those spanning compositional variation or thermal processing.