Two-wave X-ray optical diagnostics of GexSi1−x/Si modulation-doped heterostructures

New X-ray optical methods—two-wave reflecto- and refractometry—have been used for the first time for the determination of GexSi1−x/Si composition and exact measurements of multilayer heterostructure thicknesses. Both techniques are based on simultaneous measurements of two intense characteristic X-ray lines separated from the polychromatic X-ray probe by semitransparent monochromators. X-ray reflectometry of multilayer structures completely eliminates intensity drift influence and geometrical errors at small grazing angles. The refractometry technique provides direct determination of refractive index decrement and the respective value of x in a solid solution with ∼1% accuracy. Refractometry data are not influenced by mechanical strain and by presence of overlaying thin film structure.