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Anomalous x‐ray diffuse scattering is used to study the short‐range order (SRO) and lattice distortions in the electron‐type superconductor, Nd1.85Ce0.15CuO4−y. The intensity measurements were made at two energies below the Ce LIII absorption edge; the difference data greatly simplified the analysis to involve only atom pairs including Ce. The data sets were analyzed using a kinematic diffraction equation expanded up to the second order in atomic displacements. The fitted SRO parameters indicate the formation of Ce‐Ce atom pairs along the 〈001〉 directions. For superconductivity to occur in this and other doped cuprate compounds, the size of the dopant free regions in the basal plane may have to exceed the superconducting coherence length.

The structural and optical properties of high temperature-annealed superlattices of GaN quantum dots embedded in AlN barrier have been studied by a combination of X-ray techniques (reciprocal space mapping, multiwavelength anomalous diffraction, and diffraction anomalous fine structure), high resolution transmission electron microscopy, and photoluminescence spectroscopy. Taking advantage of the disentangling of the chemical and structural information provided by the simultaneous use of X-ray absorption and diffraction data obtained in a synchrotron environment, we provide quantitative determination of strain and composition for each different region of the nanostructures. Eventually, it is shown that strain driven dot/barrier intermixing is present, mostly on top of the dots. These observations have been confirmed by high resolution electron microscopy. A blue shift of photoluminescence peak has been furthermore observed and assigned to GaN/AlN intermixing suggesting a new path for engineering the emission wavelength of such heterostructures.

The strain state of the [11¯00] GaN quantum dots and quantum wires has been studied by a combination of multiwavelength anomalous diffraction and diffraction anomalous fine structure under grazing incidence. The three components of the anisotropic deformation have been independently determined. On one hand, a weak residual strain state along the c-axis, similar for quantum dots and quantum wires, is found. On the other hand, along the [112¯0] direction, quantum wires appear to be more relaxed than quantum dots. Based on high resolution transmission electron microscopy, this is assigned to elastic strain relaxation of GaN governed by either misfit dislocation formation or three-dimensional islanding, depending on the anisotropic strain state of the [11¯00] AlN buffer layer.

Reflection high-energy electron diffraction (RHEED) was used to monitor the strain of GaN/AlN quantum dots (QDs) grown by molecular beam epitaxy. Quantitative and absolute values of the in- and out-of-plane strains of the QDs were determined and compared to reference values, obtained by x-ray diffraction measurements. A very good agreement was found between RHEED and x-ray measurements. The growth and thermal ripening of the dots were analyzed. A progressive strain relaxation was observed during the ripening stage, suggesting a morphology evolution of the dots.

Grazing incidence anomalous x-ray scattering was used to monitor in situ the molecular beam epitaxy growth of GaN∕AlN quantum dots (QDs). The strain state was studied by means of grazing incidence multiwavelength anomalous diffraction (MAD) in both the QDs and the AlN during the progressive coverage of QDs by AlN monolayers. Vertical correlation in the position of the GaN QDs was also studied by both grazing incidence MAD and anomalous grazing incidence small angle scattering as a function of the number of GaN planes and of the AlN spacer thickness. In a regime where the GaN QDs and the AlN capping are mutually strain influenced, a vertical correlation in the position of QDs is found with as a side effect an average increase in the QD width.