Bulk crystals

Because the electrons do not penetrate into the crystal bulk far enough to experience its three-dimensional periodicity, the diffraction pattern is determined by the two-dimensional surface periodicity described by the lattice vectors ai and ai, which are parallel to the surface plane. A general lattice point within the surface is an integer multiple of these lattice vectors ... 

As with solid phase decompositions (Sect. 1), the kinetic characteristics of solid—solid interactions are controlled by the properties of lattice imperfections, though here many systems of interest involve the migration, in a crystal bulk of a mobile participant, from one interface to another. Kinetic measurements have been determined for reactions in a number of favourable systems, but there remain many possibilities for development in a field that is at present so largely unexplored. 

The surface after the reaction was found, using AES, to be clean with the exception of the presence of strongly adsorbed nitrogen and some small amounts of sulfur that segregated from the crystal bulk during the course of the reaction. Exposure of this surface to reaction conditions resulted in a reaction rate similar to that over the clean surface. A layer of PeN was prepared by exposing the surface to 5x10 Torr of ammonia at 673 K for 10 hrs. ( ). ... 

A very different model of tubules with tilt variations was developed by Selinger et al.132,186 Instead of thermal fluctuations, these authors consider the possibility of systematic modulations in the molecular tilt direction. The concept of systematic modulations in tubules is motivated by modulated structures in chiral liquid crystals. Bulk chiral liquid crystals form cholesteric phases, with a helical twist in the molecular director, and thin films of chiral smectic-C liquid crystals form striped phases, with periodic arrays of defect lines.176 To determine whether tubules can form analogous structures, these authors generalize the free-energy of Eq. (5) to consider the expression... 

Fig. 32. The relationship between the reduction potential 0TTiI) /D- of the excited singlet state of rhodamine and the ionisation energies Ic at the surface of the organic crystals as derived from the yield for hole generation at the different crystals (Fig. 31). As an example at anthracene the potential curve (valence band) is shown for the hole moving into the crystal bulk at two different external field strengths 3 x 105 V/cm (solid curve) and 1 X 105 V/cm (dashed curve)...

By a change of temperature or pressure, it is often possible to cross the phase limits of a homogeneous crystal. It supersaturates with respect to one or several of its components, and the supersaturated components eventually precipitate. This is an additive reaction. It occurs either externally at the surfaces, or in the crystal bulk by nucleation and growth. Reactions of this kind from initially homogeneous and supersaturated solid solutions will be discussed in Chapter 12 on phase transformations. Internal reactions in the sense of the present chapter occur after crystal A has been brought into contact with reactant B, and the product AB forms isothermally in the interior of A or B. Point defect fluxes are responsible for the matter transport during internal reactions, and local equilibrium is often established throughout. 

In many non-equilibrium situations, this local equilibrium assumption holds for the crystal bulk. However, its verification at the phase boundaries and interfaces (internal and external surfaces) is often difficult. This urges us to pay particular attention to the appropriate kinetic modeling of interfaces, an endeavour which is still in its infancy. 

Section 14.1.1 treated the smoothing of a sinusoidally roughened surface by means of surface diffusion to obtain Eq. 14.13. Show that the corresponding expression for smoothing by means of crystal bulk diffusion, as in Fig. 3.7, is... 

This additional contribution was first noted by Lee et al. [24] for polycrystalline silver and examined in more detail later by several groups on polycrystalline silver [44, 54, 58-60], single crystal bulk silver electrodes [7, 42, 43, 56, 127], and on thin silver films [55, 57, 101, 128]. For the early single crystal work [42, 43, 56] the studies were performed at a fixed electrode geometry with the crystal axis direction unknown relative to the incident beam. 

In this section we show that photo-induced light scattering is a powerful tool, especially to obtain information about the polar structure in the crystal bulk. The polar structure in SBN Ce can be considered as the composition of different periodical and/or quasi-periodical assemblies of ferroelectric 180°-domains distributed in the bulk aligned along the c-axis. The existence of... 

Wurtzite-structure ZnO thin films grown by a variety of deposition techniques, as well as commercially available single crystal bulk samples are discussed. Furthermore, data for ZnO thin films intermixed with numerous elements are reviewed. Most of the results are obtained by SE, which is a precise and reliable tool for measurements of the DFs. The SE results are supplemented by Raman scattering and electrical Hall-effect measurement data, as well as data reported in the literature by similar or alternative techniques (reflection, transmission, and luminescence excitation spectroscopy). 

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