1,005 research outputs found
Amorphous interface layer in thin graphite films grown on the carbon face of SiC
Cross-sectional transmission electron microscopy (TEM) is used to
characterize an amorphous layer observed at the interface in graphite and
graphene films grown via thermal decomposition of C-face 4H-SiC. The amorphous
layer does not to cover the entire interface, but uniform contiguous regions
span microns of cross-sectional interface. Annular dark field scanning
transmission electron microscopy (ADF-STEM) images and electron energy loss
spectroscopy (EELS) demonstrate that the amorphous layer is a carbon-rich
composition of Si/C. The amorphous layer is clearly observed in samples grown
at 1600{\deg}C for a range of growth pressures in argon, but not at
1500{\deg}C, suggesting a temperature-dependent formation mechanism
Fabrication of conductive interconnects by Ag migration in Cu-Ag core-shell nanoparticles
Fabrication of conductive nanoparticle films is observed in Cu-Ag core-shell nanoparticles by fast diffusion of Ag at 220 degrees C from particle surfaces, leading to the formation of sintered necks of Ag at the initial particle-particle contacts. Transmission electron microscopy showed that the necks were pure Ag and that particle surfaces away from the contacts were nearly Ag-free. The extent of neck formation is controllable by the choice of initial Ag thickness. Analysis of the thermodynamics of the Ag-Cu system and the relative diffusivities of Ag and Cu provide criteria for fabrication of other core-shell two-phase systems by the same mechanism
Nanometer-scale sharpness in corner-overgrown heterostructures
A corner-overgrown GaAs/AlGaAs heterostructure is investigated with
transmission and scanning transmission electron microscopy, demonstrating
self-limiting growth of an extremely sharp corner profile of 3.5 nm width. In
the AlGaAs layers we observe self-ordered diagonal stripes, precipitating
exactly at the corner, which are regions of increased Al content measured by an
XEDS analysis. A quantitative model for self-limited growth is adapted to the
present case of faceted MBE growth, and the corner sharpness is discussed in
relation to quantum confined structures. We note that MBE corner overgrowth
maintains nm-sharpness even after microns of growth, allowing the realization
of corner-shaped nanostructures.Comment: 4 pages, 3 figure
Vacancies, twins, and the thermal stability of ultrafine-grained copper
Ultrafine-grained metals have impressive strength but lack the thermal stability necessary for most applications. Nano-scale, deformation twinned copper microstructures exhibit a rare combination of strength and stability. While storing less energy in their interfaces than other nanostructured metals, they also exhibit lower vacancy supersaturations, reducing the driving force and mobility for microstructure evolution. From a thermal stability perspective, the nano-twinned microstructure may thus be preferred over the more commonly produced nano-scale equiaxed microstructures
Structured-light 3D scanner in use to access the human body posture in physical therapy : a pilot study
A numerical test of differential equations for one- and two-loop sunrise diagrams using configuration space techniques
We use configuration space methods to write down one-dimensional integral
representations for one- and two-loop sunrise diagrams (also called Bessel
moments) which we use to numerically check on the correctness of the second
order differential equations for one- and two-loop sunrise diagrams that have
recently been discussed in the literature.Comment: 11 pages, no figures, published versio
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