(Color online) Picture of the whole experimental HAXPES and XRD setup. The x-ray detector arm can be seen at the left side while the HAXPES electron analyzer can be seen at the right side.
(Color online) (a) Small angle x-ray reflectivity using photon energy of 14.5 keV. The experimental data are represented by the open circles while the solid line represents the corresponding fit. The thickness and roughness of each layer forming the stack are obtained from the fit to the Kiessig fringes. An error function has been used for the roughness determination. The obtained values are summarized in Table I . (b) Wide angle XRR using photon energy of 14.5 keV.
(Color online) Representative HAXPES spectra. (a), (b), (c) Ge 1 s and 2 s spectra taken at a photon energy between 11 and 17 keV, which corresponds to an electron kinetic energy range between 3.5 and 11.5 keV. The large penetration depth of high kinetic energy electrons enables the analysis of the Ge substrate buried by 10 nm thick layers. No trace of Ge oxide is present on the spectra. (d) Si 1 s spectra taken at photon energy of 11 keV, which corresponds to an electron kinetic energy of 9 keV. The extremely high sensitivity of HAXPES enables the discrimination between Si and SiO2 from a monolayer thick layer buried by 8 nm of material.
(Color online) Intensities vs electron kinetic energy for the Ge 1 s and 2 s photoelectron peaks normalized to the corresponding Ge-bulk signals. The best fit (lower solid line) to the experimental data is obtained for a depth profile model characterized by the presence of a sharp interface between Si and Ge without the formation of Ge oxide. The upper line represents the intensity behavior as a function of the electron kinetic energy for an abrupt interface with the existence of a 0.5 nm oxide between the Si and Ge. An exponential diffusion profile with 1 nm diffusion width is represented by the middle line.
(Color online) Chemical state resolved depth profile on Hf 2p3/2 for a photon energy of 11 keV (a), 13 keV (b), and 15 keV (c). The dashed line marks the binding energy of 9561. The Hf2p3/2 spectra obtained with photon energy of 15 keV clearly show a chemical shift and a new component. (d) Compositional depth profile.
(Color online) In-plane reciprocal space maps RSM of a 2,4 nm La0.7Ca0.3MnO3 thin film grown on SrTiO3(001). (a) (1 1 0.8) and (b) (−0.5 1.5 0.5) reflections. The notation is referred to the reciprocal lattice units of the substrate. The diffraction peaks are clearly elongated, pointing to the (0,0) evidencing a strain relaxation. The elongation is about 1% that corresponds to the lattice mismatch between the substrate and the overlayer.
(Color online) (a) Nondestructive compositional depth profile obtained by HAXPES on the 2.4 nm film. The experimental data can be adjusted by a nonuniform compositional model in which the La is diffused to the interface with the substrate and the Ca is segregated to the surface as depicted in (b).
Summary of the layer thickness and diffusion width at each interface obtained from the fit to the XRR curve. An error function has been used for the interface diffusion profile.
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