Stacking mismatch boundarie

A7.2 Planar defects in GaN basal plane faults, prismatic faults, stacking mismatch boundaries and inversion domain boundaries... 

FIGURE 4 Schematic representation of a possible structure for a (1010) stacking mismatch boundary in GaN. The Ga and N atoms at the boundary (indicated by the dashed line) are threefold coordinated man sp2 configuration. The N 2p-orbitals give rise to a two-dimensional band of dangling bond states inside the bandgap [14]. This planar fault may also be specified by a displacement... 

The 0.5 pm thick area above the GaN/PSC boundary contains mainly threading defects, which most likely are stacking mismatch boundaries (SMBs). Such defects are known to originate from three-dimensional growth mode of GaN on a foreign substrate and terminate within GaN rather than extend to the free surface [57,58]. 

The structural solution computes the full 3D elastic-plastic deformation and stress fields for the solid components of the stack. The primary stress-generation mechanism in the SOFC is thermal strain, which is calculated using the coefficient of thermal expansion (CTE) and the local temperature difference from the material s stress-free temperature. These thermal strains and mismatches in thermal strains between different joined materials cause the components to deform and generate stresses. In addition to the thermal load, the stack will have boundary conditions simulating the mechanical constraints from the rest of the system and may also have external mechanical preloading. The stress solution is obtained based on the imposed mechanical constraints and the predicted thermal field. Figure 26.6 shows... 

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