Etch pits dislocation

Dislocations, Etch Pits and the Effect of Cold Work on Corrosion... 

We describe here an experiment which indicates that the dislocation etch pit theory is a useful tool in interpreting formation of... 

THE FORMATION OF dislocation etch pits and in particular the nucleation of steps at dislocations and the motion of steps are briefly discussed. The role of dislocations in oxidation processes is summarized. 

While a knowledge of surface mobility is of great interest in physical adsorption, it becomes essential in chemisorption phenomena. For instance in calorimetric work a curve of differential heats of adsorption versus surface coverage will be horizontal if adsorption is localized but shows the customary slope from high to low values of the heat of adsorption if the adsorbed layer is mobile Furthermore if a chemisorbed intermediate takes part in a surface reaction (crystal growth, corrosion, catalysis), it is essential to know whether, after adsorption anywhere on the surface, it can migrate to a locus of reaction (dislocation, etch pit, active center). Yet here again, while Innumerable adsorption data have been scrutinized for their heat values, very few calculations have been made of the entropies of chemisorbed layers. A few can be found in the review of Kemball (4) and in the book of Trapnell (11). 

Brantley S. L., Crane S. R., Crerar D., Hellmann R., and Stallard R. (1986) Dissolution at dislocation etch pits in quartz. Geochim. Cosmochim. Acta 50, 2349-2361. 

Archer 1-3 min, a dilute Schinunel etch, enhances visibility of dislocation etch pits in very thin layer of lightly doped epitaxy on heavily doped substrate 375... 

The etch pattern of dislocations is determined by the inclination of dislocations to the surface. For dislocations lying nearly parallel to the surface, dislocation lines are observed. For dislocations lying at a steep inclination to the surface, etch pits result. The basic unit of an etch pit is generally bounded by the (111) planes intersecting the surface. The shape of a dislocation etch pit, which can be viewed as a superposition of the basic units etched at different intervals along a dislocation, is uniquely determined by the orientation of wafer surfaces and dislocation lines. Figure 7.61 schematically illustrates the shapes of etch pits developed on the three major surfaces. 

FIGURE 7.61. Schematic drawing of dislocation etch pit on (A, left) (111) surfaces, (B, center) (100) surfaces, and (C, right) (110) surfaces. D refers to the emergence of a dislocation to the surface. Solid line refers to the shape of an etch pit. Dashed line refers to the basic unit of an etch pit. After Yang. (Reproduced by permission of The Electrochemical Society, Inc.)... 

Fig. 45. Intersecting arrays of dislocation etch pits in graphite. 62)...

Fig. 55. Typical alignments of dislocation etch pits on the rhombohedral 100 faces of (a) untreated calcite, and (b) samples...

Alignments of Decomposition Centers and Dislocation Etch Pits on 100 Faces of Calcite< ... 

Alignment direction on 100 Presence of dislocation etch pits Presence of decomposition centers Slip plane of dislocation at which reaction is preferred... 

Figure 5. Dense swarms of dislocation etch pits in two apatite grains from the Early Cretaceous sandstones of the Otway Basin of southeastern Australia. Grains containing such high dislocation densities are most often observed in volcanic apatites and are best completely avoided for fission track counting. Typical dislocation features such as sub-parallel arrays, branching and extremely long etch channels can be seen. Fortunately, even in such samples, many grains are free of such features enabling reliable track counting.

Dissolution at dislocation etch pits in quartz. Geochimica et Cosmochimica Acta, 50, 2349-2361. 

Dislocation etch pits in quartz. In Geochemical Processes at Mineral Surfaces, eds. Davis, J.A., Hayes, K.F. American Chemical Society, Washington D.C., pp. 635-649. 

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