Prismatic stacking faults

FIGURE 3 Ball and stick model of the (1210) prismatic stacking fault in GaN. Each atom is fourfold coordinated and there are no wrong bonds [13]. 

SiC terraces separated by a step. Unlike the case for sapphire, the polarity of the SiC 0001 surfaces and the bonding at the film/substrate interface prevents die formation of inversion domain boundaries (IDBs) in GaN grown on SiC 0001 [11,12,19]. Vermaut et al [10] identified the SMBs in GaN and AIN grown on SiC as prismatic stacking faults with three possible Burgers vectors / <2023>, V3 <10l0> and V2 <0001>. 

Figure 10.10 Bright-field image (g = 1010) of inclined prismatic stacking faults, each bounded by two basal stacking faults.

HVPE <3-plane GaN film grown on r-plane prismatic stacking faults as well as sapphire taken along the [1120] zone axis, rectangular voids (b) enlarged view of the slightly tilted away from the zone axis area indicated by a white rectangle in (a). 

Figure n.17 A HRTEM image of a prismatic stacking fault. The arrows assign a BSF crossing the PrSF being shifted in c direction. 

There are two questions that needed to be answered here. (1) How can the ligand access the interiors of big prismatic particles to lead to the smaller particles and (2) Why do the ligands lead to smaller particles at all While it is difficult to conclusively find answers to both the questions, the first step in the digestive ripening procedure offers some leads. (1) The big prismatic particles obtained by the reverse micelle-based synthesis are loaded with defects such as twinning boundaries and stacking faults. 

Only poorly diffracting crystals of the monoclinic polymorph of Au 3 (MeN = COMe)3 could be obtained [41]. These appear to contain a stacking fault and may have been twinned. The arrangement of these gold atoms within the unit cell is shown in Fig. 20. There are two crystallographically different prismatic stacks each contains just three of the trinuclear molecules. The average out-of plane Au Au distance in these stacks is 3.28(3) A. While there is stacking of the trimeric molecules in this polymorph, these stacks are... 

Most wurtzite GaN films have been grown on either 6H-SiC(0001) (see Datareview A7.8) or sapphire (A1203) substrates. The orientation of sapphire most frequently used is C-plane (0001) although there have been some structural characterisation studies made for growth on A-plane (1120) [1-4] and R-plane (0112) [1,2,5-7] substrates. Other defects found in the a-phase include inversion domain boundaries, prismatic faults, nanopipes, pits, voids and cracks. The limited structural information available on bulk single crystals of a-GaN shows that they contain a low density of line dislocations and stacking faults near inclusions [12] (see Datareview A7.5). 

The process of stacking fault folding involves stair-rod dislocations to mediate between the different prismatic and pyramidal crystal planes because the displacement vectors of the stacking faults on the (1100) and (1102 planes are not the same. An HRTEM plan-view image of the tip of a prismatic/pyramidal stacking fault domain found in an HVPE film is shown in Figure 11.16. The arrows indicate the position of stair-rod dislocations. It is noteworthy that the tip involves the interaction of an fr-type BSF, representative for all such domains found in the film. The tip position coincides with a terminated BSF and consists of two PyS F, each of them subsequently folding onto the m plane. 

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

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