Structure at the Yb/GaAs Interface Studied by Anomalous X-Ray Scattering
Two kinds of 4×1 superstructures are found for Yb/GaAs(001) contacts with different Yb thicknesses. Different Schottky-barrier height values are also found for these samples. To clarify the role of Yb atoms in the 4×1 structure, an X-ray anomalous dispersion effect has been used in the grazing-incidence X-ray diffraction geometry. Diffraction intensities measured in the X-ray energy range near the Yb L III absorption edge show a characteristic variation, which reflects the energy dependence of the real part of the anomalous scattering factor (f ’ ) for Yb atoms. As a result, for all the samples, Yb atoms are found to order in 4×1 structures. By comparison of the calculated diffraction intensities with observed intensities, two (4×1) structural models are found for the thin and thick Yb-layer samples, respectively.
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