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Using hemisphere-shaped patterned r-plane sapphire substrates, high quality nonpolar (1120) a-plane gallium nitride (GaN) films have been obtained with superior structural characteristics to films grown on conventional (unpatterned) r-plane sapphire. This is evidenced by reduced x-ray rocking curve widths, smaller in-plane crystallographic anisotropy, and smoother surface morphology. Observations by transmission electron microscopy and cathodoluminescence reveal that the defect density is remarkably reduced in regions above the patterned hemispheres. The growth of a-plane GaN on the patterned substrates proceeds first by a relatively fast growth of the film on the flat surface region, and then a gradual lateral overgrowth over the protruding hemispheres, where the direct epitaxial growth is severely retarded. [ABSTRACT FROM AUTHOR]

We have investigated the structural properties and relaxation phenomenon of InGaN multiple quantum wells (QWs) on [formula] semipolar GaN templates grown on patterned (001) silicon substrates by selective area growth technique. Our studies by transmission electron microscopy and x-ray diffraction reciprocal space mapping reveal that QWs emitting light at 540 nm experience significant strain relaxation along the in-plane [formula] direction by the generation of an array of basal stacking faults (BSF). The generation of BSFs in 540 nm QWs could be an important factor limiting its luminescence efficiency. [ABSTRACT FROM AUTHOR]

In contrast to the commonly observed dynamic roughening in film growth we have observed dynamic smoothing in the growth of diamondlike-carbon nanocomposite (TiC/a-C) films up to 1.5 μm thickness. Analytical and numerical simulations, based on the Edwards–Wilkinson model and the Mullins model, visualize the effect of the diffusivity parameters and the noise strength on the interface evolution of dynamic smoothing. The prediction is in a good agreement with the measured roughness evolution. High-resolution transmission electron microscopy shows that the formation of an amorphous front layer 2 nm thick excludes possible influence of nanocrystallites on the dynamic growth behavior of the nanocomposite film. [ABSTRACT FROM AUTHOR]

In this letter we report the controlled growth and microstructural evolution of self-assembled nanocomposite multilayers that are induced by surface ion-impingement. The nanoscale structures together with chemical composition, especially at the growing front, have been investigated with high-resolution transmission electron microscopy. Concurrent ion impingement of growing films produces an amorphous capping layer 3 nm in thickness where spatially modulated phase separation is initiated. It is shown that the modulation of multilayers as controlled by the self-organization of nanocrystallites below the capping layer, can be tuned through the entire film. [ABSTRACT FROM AUTHOR]

Nanoscale deformation in TiC/a-C nanocomposite coatings is revealed by combined nanoindentation and high resolution cross-sectional transmission electron microscopy. A process characterized by rearrangement of TiC nanocrystallites and the displacement of a-C matrix is found to dominate the deformation mechanism at length scales ranging from tens of nanometers down to 1 nm and contributes to toughening of the nanocomposite coatings by delocalizing local plastic deformations. [ABSTRACT FROM AUTHOR]

A direct correlation has been established between stacking faults in a-plane GaN epilayers and luminescence peaks in the 3.29–3.41 eV range. The structural features of the stacking faults were determined by diffraction-contrast transmission electron microscopy, while the optical emission characteristics were observed by highly spatially resolved monochromatic cathodoluminescence. The studies were performed in the exact same regions of thinned foils. We find that stacking faults on the basal plane are responsible for the strong emission at ∼3.14 eV. Luminescence peaks at ∼3.33 and ∼3.29 eV are associated with the presence of stacking faults on prismatic a planes and partial dislocations at the stacking fault boundaries, respectively. [ABSTRACT FROM AUTHOR]