The microstructural evolution and thermal properties of nanocrystalline ͑nc͒ Cu during mechanical attrition were investigated by using quantitative x-ray-diffraction and thermal analysis techniques. Upon milling of the Cu powders with coarse grains, the grain sizes are found to decrease gradually with the milling time, and remain unchanged at a steady-state value ͑about 11 nm͒ with continued milling. The microstrain and the stored enthalpy increase to maximum values during the grain refinement, and decrease then increase to the second maxima and decrease again within the milling stage of steady-state grain size, while the lattice parameter remains unchanged during the entire milling process. The grain boundary ͑GB͒ enthalpy of the nc Cu was estimated, showing a GB softening-hardening-softening cyclic variation within the steady-state milling. The present work indicated with clear experimental evidence that even within the milling stage of steady-state grain size, the microstructure ͑both the GB's and the crystallites͒ of nc materials is still changing, which may result from the GB sliding.
Quantitative grazing-incidence small-angle x-ray scattering experiments have been performed on self-assembled InAs quantum dots ͑QDs͒ grown by molecular-beam epitaxy. We find pronounced nonspecular diffuse scattering satellite peaks with high diffraction orders, indicating a lateral ordering in the spatial positions of the InAs QDs. The mean-dot-dot distance and correlation lengths of the dot lateral distribution are found to be anisotropic. We observe the sharpest dot distribution in the ͓110͔ direction. Additional broad diffraction peaks are observed and associated with dot facet crystal truncation rods of the ͕111͖ and ͕101͖ facet families. This suggests an octagonal-based dot shape.
Grazing incidence small angle X-ray scattering (GISAXS) and atomic force microscopy (AFM) experiments are employed to study self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) on GaAs (001). The GISAXS spectra show pronounced non-specular diffuse scattering satellite peaks with high diffraction orders up to
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