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Stacking faults can arise during crystal growth or from plastic deformation. In addition, dislocations in low stacking-fault energy materials typically dissociate into an extended dislocation, which is a stacking fault bounded by partial dislocations. Stacking Faults
The stacking-fault energy (SFE) is a materials property on a very small scale. It is noted as γ SFE in units of energy per area. A stacking fault is an interruption of the normal stacking sequence of atomic planes in a close-packed crystal structure. These interruptions carry a certain stacking-fault energy.
Stacking faults occur in a number of crystal structures, but the common example is in close-packed structures. They are formed by a local deviation of the stacking sequence of layers in a crystal. An example would be the ABABCABAB stacking sequence. A twin boundary is a defect that introduces a plane of mirror symmetry in the ordering of a crystal.
In stacking faults, the region of stacking mismatch is bounded by two partial dislocations, and an extended dislocation is formed. For anti-phase domains which only exhibit chemical disorder, the region is bounded by two complex stacking faults, which exhibit both stacking and chemical disorder. [1]
When forming stacking faults, the partial dislocations reach an equilibrium when the repulsive energy between partial dislocations matches the attractive energy of the stacking fault. This means that higher stacking fault energy materials, i.e. those with high shear modulus and large Burgers vectors, will have smaller distance between partial ...
The width of this stacking-fault region is proportional to the stacking-fault energy of the material. The combined effect is known as an extended dislocation and is able to glide as a unit. However, dissociated screw dislocations must recombine before they can cross slip , making it difficult for these dislocations to move around barriers.
Conventional epitaxial growth techniques of GaN on SiC, sapphire and Si substrate are known to produce high density of structural defects, [15] [16] [17] mainly edge and screw dislocations and stacking faults, in the order of 10 9-10 10 cm-2. PE and LEO, the latter also referred to epitaxial lateral overgrowth (ELO), are known to enable two to ...
A linear variation has been observed between twin thickness, stacking fault energy and grain size, [47] and to a lesser degree, the stress state of the twinning grain (Schmid Factor). [48] The twin thickness saturated once a critical residual dislocations’ density reached the coherent twin-parent crystal boundary. [33] [49]