Binary materials

It is extremely difficult to know values for all of these parameters precisely. Therefore, absolute quantitation is almost never attempted. The determination of relative atomic ratios is an inherently more tractable approach, however. This method is best illustrated by consideration of a binary material composed exclusively of atoms A and B that is perfectiy homogeneous up to the surface. In this case, independent equations can be developed relating the number of atoms sampled to the xps intensity for each atom as follows ... 

In many cases, this binary material will not be homogeneous all the way up to the surface, because it is covered with a thin ovedayer of contamination. Therefore, for most real samples, the photoelectrons of interest from atoms A and B are coming from a depth equal to the thickness of the ovedayer, d. In this case. 

The in-V compounds combine the elements of Group HI (aluminum, gallium, indium) with those of Group V (phosphorus, arsenic, antimony, bismuth). As can be imagined, a wide variety of compounds can be produced which, in addition to the binary materials, also include ternary and even quaternary materials. 

Later on, this concept was extended to precursors containing both elements of the desired material already connected by a chemical bond in a single molecule. Such precursors are mainly referred to as single source precursors. Their potential application for the deposition of thin films of the corresponding binary materials by MOCVD processes could be demonstrated. In particular Lewis acid-base adducts R3M—ER3 and four- and six-membered heterocycles [R2MER x (Fig- 1) have been in the focus of research groups both in industry and university. Consequently, the development of powerful synthetic pathways for the preparation of such precursors has been forced. 

Davies DA, Vecht A, Silver J, Marsh PJ, Rose JA (2000) A novel method for the preparation of inorganic sulfides and selenides 1. Binary materials and Group 11-Vl phosphors. J Electrochem Soc 147 765-771... 

On the assumption that the background bremsstrahlung has been removed, and that the data are in the form of the measured intensities at full width half maximum (FWHF), equation (1) can be used to calculate the ratio of the number of atoms of A to the number of atoms of B, i.e. the concentrations in the binary material. 

In the last decade, numerous compounds of these types have been the subject of detailed CVD studies, demonstrating their potential for the deposition of the corresponding binary materials. Most of the work has concentrated on binary nitrides and phosphides, while the deposition of binary MSb films has been studied to a far lesser extent. The lack of potential precursors has been the major problem for the deposition of group 13-antimonide films for many years. Only a very few group 13-Sb compounds have been known until we and Wells established general synthetic pathways as was shown in Sections 2 and 3. Consequently, detailed investigations concerning their potential to serve for the deposition of the desired materials... 

This review has described the synthesis, structure and reactivity of important classes of group 13/15 compounds such as Lewis acid base adducts and heterocycles. In addition, their potential to serve as single source precursors for the deposition of the corresponding binary materials by MOCVD process has been demonstrated. Because of the large number of compounds containing the lighter elements of group 15, N, P and As, these... 

One of the potential strategies for the synthesis of compound semiconductors is the pyrolysis of a single-molecule precursor that incorporates the elements of a compound into a single molecule. For a number of binary materials, predominantly metal oxides but also compound semiconductors, such as GaAs [101] or metal alloys [102-104], it has been demonstrated that the use of single-molecule precursors (SMPs), which contain both components for the respective material in one molecule rather than applying two independent... 

Although irreversible thermodynamics neatly defines the driving forces behind associated flows, so far it has not told us about the relationship between these two properties. Such relations have been obtained from experiment, and famous empirical laws have been established like those of Fourier for heat conduction, Fick for simple binary material diffusion, and Ohm for electrical conductance. These laws are linear relations between force and associated flow rates that, close to equilibrium, seem to be valid. The heat conductivity, diffusion coefficient, and electrical conductivity, or reciprocal resistance, are well-known proportionality constants and as they have been obtained from experiment, they are called phenomenological coefficients Li /... 

Figure 1 Structures of some common crystal lattices (a) NaCl, (b) Si, (c) GaAs, (d) ZnO wurtzite, (e) T102 rutile, (f) Ti02 anatase, (g) M0S2. For the binary materials, the shaded circles represent the more electronegative elements (i.e. Cl, As, O, and S) and the empty circles represent the less electronegative elements (i.e. Na, Ga, Zn, Ti, and Mo)...

Here is the atomic fraction of species u. For a binary material the intensity is given by a linear combination of three partial structure factors weighted by the atomic scattering factors. Keating " has proposed that three independent intensities be collected by modifying the atomic scattering factors. A set of three independent equations is produced which can then be solved for the partial structure factors. Explicitely, these equations can be written (for a specific value of h) as ... 

In recent years a number of groups have developed compounds that serve as single precursors for specific binary materials 133, 134, 135,136,137,138,139,140,141,142). In this approach, the objective is to synthesize precursor molecules that are easy to handle with low toxicity and that intrinsically contain not only the desired stoichiometry of the material but also a low energy decomposition pathway. When successful these rational precursors have the desired properties of convenience and safety but, as important, create opportunities for preparing films of presently known stoichiometry with new properties as well as for exploring systems of unknown stoichiometry and properties. 

Stabilize such particles and explains the observation that only amorphous binary materials are produced in these reactions [58, 59]. What has proven to be remarkably effective, however, is the combination of both PR3 ligands in conjunction with surface tellurolate groups, RTe. Thus the 4 8 1 2 combination of AgCl,... 

Chemistry. We shall assume rather simple chemistry. In some of the discussion, the material will be as simple as ice, that is to say of a single, fixed composition and at other times we shall consider binary mixtures such as the sulfide (Zn, Fe)S—which can be thought of as a mixture of ZnS and FeS—or a polymer mixture of trifluorethylene and tetrafluorethylene. With such a binary material, there is the possibility of variation in composition within a sample. One might say that the purpose of the book is to learn to understand how nonhydrostatic stress can affect such variations in composition. 

Figure 15.1 Three representations of a nonuniform binary material of formula (A, B)X. (a) Filled circles show atoms of component A and open circles show component B component X is not shown, (b) Atoms of A are conceived as atoms of B to which an additive has been attached, (c) The material is conceived as a uniform substrate of BX, on which a non-uniform distribution of the additive is imposed.

The conclusion is that even for a simple binary material, we should not look for a single factor K constructed from and K as in eqn. (14.9). 

The distinction now being emphasized between a-terms and star-terms was shown diagrammatically in Figure 15.3b with black and white arrows. It is a distinction easy to make in (A, B)X compounds and less easy to make in simple binary materials. One purpose of this review chapter is to identify aspects that are not yet fully worked out, that are currently fuzzy, and binary materials such as alloys are one such aspect. Clearly, to some extent binary alloy behavior can be described as joint behavior with some interdiffusive... 

This chapter has two purposes, one limited and one more extensive. The limited purpose is to reconsider simply binary materials like ideal alloys, where two components A and B or copper and tin mix with each other in any proportion without being encased in a matrix of a third species X. 

The conclusion is that for simple binary materials, to work with K and with a joint velocity field and an exchange velocity field, is the preferred approach, as it is for materials of type (A, B)X. It seems that even when no stoichiometry constraint operates, to use an atom-for-atom scheme for describing changes of composition is an efficient way to work. 

A binary material s behavior can be described by giving a velocity field for the joint behavior of both components plus a velocity field for the exchange of one for the other. In many circumstances this effectively separates questions of mechanics from questions of chemistry in particular, nonhydrostatic stress affects only the joint field, while gradients of composition through space affect only the exchange process. In such circumstances, boxes (i) and (ii) in Figure 19.1 are empty and eqn. (12.8) relating the strain rate to the potential is exactly equivalent to eqn. (12.7) in terms of the stress 0. 

Monolithic zirconia networks can also be formed using a similar procedure giving porous 2xQ>2 structures [9]. As the titania and zirconia precursors are miscible, binary inorganic networks of various Ti Zr ratios could be produced [9]. The crystallinity and photocatalytic properties of the mixed material were studied X-ray amorphous materials were produced for Ti Zr ratios of 2 8 to 7 3, and the binary material containing 10% zirconia (the presence of which inhibited crystal transformation to the rutile phase) showed the highest photocatalytic activity for the photodecomposition of sahcylic acid and 2-chlorophenol [9]. 

TABLE 11.3-3 Summary of Binary Material Balance Equations... 

Ozin and coworkers recently extended the supra-molecular I S+ assembly into the synthesis of binary mesoporous yttrium oxide-stabilized-zirconium oxide materials.These materials were synthesized by a modified sol-gel method under basic conditions, where zirconium ethoxide and yttrium acetate were used as the precursors for the transition metal oxides, and CTAB was used to form the supramolecular templates. The use of ethylene glycol with coordinating capability as a cosolvent may play a role in controlling the hydrolysis rate and solubility of zirconium(IV) and yttrium(III). This synthesis strategy is similar to that of so-called polymerizable-complex method, which was widely used to prepare multicomponent single-phase oxides. The yttrium content in these binary materials can be tuned from 12-56 wt%, and no phase segregation of yttrium and zirconium oxides was observed. These materials could be applied in designing new solid oxide fuel-cell electrode materials. 

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