Epitaxial alignment

The X-ray diffraction pattern shown in Figure 4 indicates that nearly phase-pure Hg-1212 films can be obtained after the annealing step. The films are epitaxially aligned with the c axis normal to the substrate plane. The c-axis lattice parameter varies to some extent with the annealing treatment and has been obtained in the range of 12.48-12.6 A, which is somewhat smaller than the value observed in the bulk (12.71 A). 

Many different etchants have been developed for the evaluation of different types of crystal defects such as flow-pattern defects [115], stacking faults [74, 192, 193], dislocations [69, 72-74, 194], dislocation network [72, 193, 195], oxide precipitates [196], swirl patterns [74, 75, 148], striations [74, 197], hillock defects [198], epitaxial defects [192], epitaxial alignment [199], grain boundary [69, 72, 200], twin band [69], diamond saw damage [201], pn junction [202-204], metallic precipitates [205], and damaged layer of mechanically polished surface [206],... 

The formation of passive oxide films on the (111) surfaces of Cu and Ni has also been studied in detail by SXS [94, 95]. Measurements of Cu(lll) in 0.1 M NaCl04 (at pH 4.5) showed that the oxide exhibited a crystalline cuprite structure (CU2O) that was epitaxially aligned with the underlying Cu substrate [94]. Although a similar oxide structure was observed for oxidation in air, there were some key differences in the structure of the aqueous oxide. In particular it was found that a preferred reversed orientation of the oxide film was formed, and this indicated that oxide growth occurs at the interface between the oxide and the Cu(lll) surface... 

Figure 6. Scheme for the epitaxial alignment of Poly(4BCMU) on buffed PBT substartes. 

Figure Bl.24.11. The backscattering yield from an Si sample tiiat has been implanted with Si atoms to fonn an amorphous layer. Upon annealing this amorphous layer reerystallizes epitaxially leading to a shift in the amorphous/single-erystal interfaee towards the surfaee. The aligned speetra have a step between the amorphous and erystal substrate whieh shifts towards the surfaee as the amorphous layer epitaxially reerystallizes on the Si.

The structure of metallic deposits is determined primarily by the size, shape (faceting), type of arrangement, and mutual orientation of the crystallites. Two factors may influence the orientation and spatial alignment of the microcrystals in electrocrystallization the field direction (or direction of the electric current) and the nature of the substrate. The deposits are said to have texture when the crystallites are highly oriented in certain directions. Epitaxy implies that the lattice is altered under the influence of the substrate. 

The pathway and kinetics of the C to S transition have been studied on shear-aligned cylinders of the commercial diblock copolymer of PS and poly(ethylene-co-butylene) (KRATON G 1657 Shell Chemical Company) [143, 144], A complete dissolution of the cylindrical structure before the epitaxial... 

Two diacetylenes have been epitaxially polymerized as thin films in contact with alkali halide substrates. These films in contact with alkali halide substrates. These films consisted of highly oriented single crystals aligned along both <110> directions of the substrate. The structures of both poly(TCDU) and poly(DMDA) were modified by this technique and, in all cases, highly crystalline near-perfect films were achieved. 

It will be obvious that the cluster mechanism of deposition is unlikely to lead to an oriented film, since the clusters would have to align themselves with the substrate lattice, either on adsorption or subsequently. Therefore an epitaxial film is highly suggestive of an ion-by-ion growth, which is more likely to be directed by the substrate. 

When reading the literature, in many (probably most) cases it is not clear whether the deposition proceeds by an ion-by-ion process. The reason is that, unless another mechanism is specifically discussed, it is often assumed that the deposition proceeds via the ion-by-ion mechanism. If the exact deposition parameters are known, which mechanism is operative can, in most cases, be calculated. Two criteria have often been cited in the literature as proof of deposition via the ion-by-ion mechanism. One is epitaxial deposition of the CD film. (Epitaxy refers to growth of one material on another in such a way as to result in coherence between the lattice of the substrate and the deposit. Often—although not necessarily—the lattice of the deposit is aligned in the same direction as that of the substrate.) This is based on the expectation that a cluster mechanism will not result in an epitaxial film for this to occur, clusters of maybe thousands of atoms would need to be able to rearrange themselves on the substrate. Some examples of epitaxial growth are given in Sections 3.4.2 and 4.I.5.2. 

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