Lattice decoration

The SEM can also be used to provide crystallographic information. Surfaces that to exhibit grain structure (fracture surfaces, etched, or decorated surfaces) can obviously be characterized as to grain size and shape. Electrons also can be channeled through a crystal lattice and when channeling occurs, fewer backscattered electrons can exit the surface. The channeling patterns so generated can be used to determine lattice parameters and strain. 

Figure 8.42. ID structural models with inherent loss of long-range order, (a) Paracrystalline lattice after HOSEMANN. The lattice constants (white rods) are decorated by centered placement of crystalline domains (black rods), (b) Lattice model with left-justified decoration, (c) Stacking model with formal equivalence of both phases (no decoration principle)... 

Inconsistency of all Lattice Models. The decoration principle of all lattice models coupled to polydispersity leads to a fundamental inconsistency of all lattice... 

A decision on the decoration of the lattice has not yet been made. Two variants are depicted in Fig. 8.42a and Fig. 8.42b, respectively. Thus there are different variants of lattice models. 

Let us demonstrate the centrally-decorated lattice model115. The corresponding geometrical consideration for the deduction of the higher thickness distributions is somewhat involved. Figure 8.46 presents a geometrical construction scheme that helps to link both the observable distribution of long periods, hi (x), and the observ-... 

IR Studies of Lattice Defects Decorated with Hydrogen. 158... 

The implantation of hydrogen into silicon or crystal growth in a hydrogen atmosphere introduces vibrational bands that have been ascribed to lattice defects decorated with hydrogen. While IR experiments were begun —10 years before similar studies of passivated shallow impurities, the structures of the complexes that result from H+ implantation are not well understood. This subject has been reviewed previously by Pearton et al. (1987, 1989). Here, the central experimental results will be summarized. A recent uniaxial stress study (Bech Nielsen etal., 1989) of several of the vibrational features will be discussed in Section IV.3. 

To make further progress in the assignment of the hydrogen decorated lattice defects, additional structural or chemical information is required. 

Uniaxial stress results have been reported for several of the IR bands associated with H decorated lattice damage (Bech Nielsen et al., 1989). For these experiments H+ was implanted into Si at room temperature. The resulting spectral features correspond to those observed previously by Stein (1975) and others (see Section III.3). Uniaxial stress splitting patterns were measured for infrared absorption spectra taken at 9 K. The... 

Irrespective of the exact configuration around the promoter atom, we have a detailed picture of the Co-Mo-S phase on the atomic scale. Figure 9.23 summarizes schematically what a working Co-Mo/A1203 hydrodesulfurization catalyst looks like. It contains MoS2 particles with dimensions of a few nanometers, decorated with cobalt to form the catalytically highly active Co-Mo-S phase. It also contains cobalt ions firmly bound to the lattice of the alumina support, and it may contain crystallites of the stable bulk sulfide Co9S8, which has a low activity for the HDS reaction [49]. 

The combination of the point lattices constructed on the basis of the crystallographic systems with the possible centring translation results in the 14 so-called Bravais lattice type, illustrated in Fig. 3.4. Substituting (decorating) each lattice... 

Figure 3-4. Dislocation decoration in an AgBr-NaCl interdiffusion zone. Dislocations formed by self-stress due to lattice parameter changes. The decoration density indicates the dislocation density [after H. Haefke, H. Stenzel (1989)].

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