Lattice defects stacking faults 324 twin boundarie

The lattice defects are classified as (i) point defects, such as vacancies, interstitial atoms, substitutional impurity atoms, and interstitial impurity atoms, (ii) line defects, such as edge, screw, and mixed dislocations, and (iii) planar defects, such as stacking faults, twin planes, and grain boundaries. 

Despite continuing progress in the crystal growth, 3C-SiC films still contain many lattice defects. In particular, twins, stacking faults and antiphase boundaries (APBs) have been reported [64,65]. APBs occur as a common defect when a polar film, SiC in this case, is heteroepitaxially grown on a non-planar substrate. To eliminate this particular defect in 3C-SiC films, Si substrates misoriented from the (100) plane have been used, as stated above [39,53],... 

Another contribution to variations of intrinsic activity is the different number of defects and amount of disorder in the metallic Cu phase. This disorder can manifest itself in the form of lattice strain detectable, for example, by line profile analysis of X-ray diffraction (XRD) peaks [73], 63Cu nuclear magnetic resonance lines [74], or as an increased disorder parameter (Debye-Waller factor) derived from extended X-ray absorption fine structure spectroscopy [75], Strained copper has been shown theoretically [76] and experimentally [77] to have different adsorptive properties compared to unstrained surfaces. Strain (i.e. local variation in the lattice parameter) is known to shift the center of the d-band and alter the interactions of metal surface and absorbate [78]. The origin of strain and defects in Cu/ZnO is probably related to the crystallization of kinetically trapped nonideal Cu in close interfacial contact to the oxide during catalyst activation at mild conditions. A correlation of the concentration of planar defects in the Cu particles with the catalytic activity in methanol synthesis was observed in a series of industrial Cu/Zn0/Al203 catalysts by Kasatkin et al. [57]. Planar defects like stacking faults and twin boundaries can also be observed by HRTEM and are marked with arrows in Figure 5.3.8C [58],... 

Stacking faults are a-boundaries for which a = 2xg R. (0gi-0g2) is zero for all g. In some structures, stacking faults and twins are closely related, and different regular sequences of these defects produce various polytypes. Wollastonite is a relatively simple example of such a structure, for which the stacking faults have been studied in some detail by TEM, both by their a-fringe contrast and in two-dimensional high-resolution lattice images. 

---