Kink site position alloys

SURFACE SELECTIVITY IN ALLOY DEPOSITION 8.5.1 Kink site positions of alloys... 

In Chapter 7, the outstanding role of a kink site position in the process of formation of a crystalline phase was shown. Kink site positions are of similar importance in alloy deposition. But for alloys several kink site positions must be defined depending on the lattice neighbors of the kink site position. In the following the situation of a bi-component alloy AB of stoichiometric lattice structure will be described. In this case one must consider two different kink site positions A and B (Figure 8.4). 

Figure Different kink site positions A and B in alloy deposition (surrounded areas). Atoms in kink site positions can react with ions A " or of the electrolyte to form one of the four kink site positions AA, AB, BA, or BB. ...

The concept of kink site positions can be extended to alloys of variable stoichiometry and of irregular composition (solid solutions). Atoms of different chemical nature A or B surround each atom in a kink site position. Restricting the discussion to first neighbors in the case of a cubic close packed or hexagonal close packed lattice, the following different situations are possible ... 

The probability can be expressed by the equilibrium constants and ion concentrations in the electrolyte bath by insertion of the relations (8.32) for the active atoms in the kink site positions in Eq. (8.33a-d). The relation between the alloy composition and electrolyte concentration is derived by the procedure described in Section 8.6.1. 

It was approximated that in the treatment of a binary alloy, the character of a kink site position is determined by the previously deposited atom and not so much by the environment of the atom. If this is extended to a ternary alloy one can describe the processes on the surface by nine main reactions... 

The following mechanism is based on an alloy of two comp)onents A and B. In an approximate description on the surface four different kinds of kink site positions exist, AA, AB, BA, and BB. Three steps for each component describe the dissolution via ad-atoms. 

Surface density of kink site positions Frequency shift Complex frequency shift Gibbs energy of alloy A j ... 

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