Technique of the Atomic Metal Evaporation

As a rule, deposition results in the formation of mini-clusters. Their size depends on the process conditions and the nature of the metal. Transition metals are used in most cases. Cr clusters contain 2-3 metal atoms, those of Mo contain 2-5 metal atoms, and clusters of other metals include not more than 10 atoms.  

In principle, the kinetics of metal vapor condensation is analogous to the coagulation kinetics of an ideal suspension. There are unstable states, which can be described by the Smoluchowski equation for fast coagulation. 

Spectral techniques have been used for the identification of polymer-immobilized clusters. For example, monomers, dimers, and trimers of molybdemun immobilized on poly(methylphenylsiloxane), absorb at X, = 318, 418, and 502 nm, respectively, whereas the tettanuclear and pentanuclear clusters absorb at = 598 and 640 nm, respectively. This makes it possible to follow the growth of cluster particles. According to scheme 5, this process comprises a munber of consecutive irreversible bimolecular reactions  

The formation of clusters may be regarded as a continuous deposition of metal atoms on a polymeric film over the time t at the rate W then the corresponding rate equations are 

The concentration of cluster nuclei M L2 of various nuclearities on the polymer may be expressed in general form as 

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