Detailed surface analysis of V-defects in GaN films on patterned silicon(111) substrates by metal–organic chemical vapour deposition

The growth mechanism of V-defects in GaN films was investigated. It was observed that the crystal faces of both the sidewall of a V-defect and the sidewall of the GaN film boundary belong to the same plane family of \{ {{{10\bar 11}}} \}, which suggests that the formation of the V-defect is a direct consequence of spontaneous growth like that of the boundary facet. However, the growth rate of the V-defect sidewall is much faster than that of the boundary facet when the V-defect is filling up, implying that lateral growth of \{ {{{10\bar 11}}} \} planes is not the direct cause of the change in size of V-defects. Since V-defects originate from dislocations, an idea was proposed to correlate the growth of V-defects with the presence of dislocations. Specifically, the change in size of the V-defect is determined by the growth rate around dislocations and the growth rate around dislocations is determined by the growth conditions.

Direct imaging of segregation layers in Bi-doped Cu grain boundaries

Upon aging of a quenched-in super-saturated alloy at lower temperatures, the Bi segregates to the grain boundaries and ebritt1ement and faceting occur. Recent data suggest that the distribution of facet orientations for Σ = 3 misorientation grains evolves with aging at 600 C with a preference for the eventual formation of (-111)|(1-11) facets. Whereas the concentration of Bi on the facets and the macroscopic orientation of the facets has been established, little is known about the structure of these facets on the atomistic scale. In this abstract, the summarized results from a detailed analysis of the internal structure of a Σ = 3 (-111)|(1-11) grain boundary facet is presented and contrasted with the structure of a Σ = 3 (111) twin.