Multilayer growth multinuclear

At higher overpotentials the nucleation rate increases faster than the step (Chapter 3) propagation rate, and the deposition of each layer proceeds with the formation of a large number of nuclei. This is the multinuclear multilayer growth. Armstrong and Harrison (13) have shown that initially, the theoretical current-time transient for the two-dimensional nucleation (Fig. 7.7) has a rising section, then passes through several damped oscillations, and finally, levels out to a steady state. 

Figure 5.24 Oscillogram of a current transient at multinuclear multilayer growth in the standard system Ag (100)/AgNO3 15.45). Overvoltage / = - 14 mV current scale 2 (tA div" time scale 5 ms divV...

The kinetics of metal deposition on crystal faces free from screw dislocations is determined by the rate of nucleation /, nuclei cm sec of new lattice nets and their rate of propagation v, cm sec over the face. Almost simultaneously Nielsen/ Chernov/ and Hillig " showed that, depending on the values of these two parameters, two different mechanisms can be distinguished, whereby the extension of the surface plays a significant role (i) a layer by layer growth and (ii) a multinuclear multilayer growth. 

Figure 13. (a) Theoretical and experimental current-time transients for multinuclear multilayer growth. Drawn line, Ref. 46 dashed line. Ref. 45 circles Monte Carlo simulation. Ref. 49 dash-dot-dash line first monolayer formation. The hatched area represents the range of variation of the experimental i vs. t curves obtained at different overpotentials on dislocation-free Ag (100) faces. " All transients normalized to the I max and max at the first layer formation, (b) Experimental current transient for multinuclear multilayer growth, rj = 14 mV. Vertical sensitivity, 2 ptA/div time base, 5 msec/div. 

In this Chapter we consider the mononuclear-monolayer growth, the growth of step trains and the spiral growth mechanisms. The multinuclear-monolayer and the multinuclear-multilayer growth mechanisms will be considered in Chapter 5. 

Figure 5.5. Circular two-dimensional clusters formed and growing on a plane substrate according to the multinuclear-multilayer mechanism of growth (a schematic representation).

Figure 5.6. Experimental current transient illustrating the multinuclear-multilayer mechanism of growth in the case of electrodeposition of silver on the cubic fhce of a single silver crystal [5.44] (With permission from Elsevier Science and courtesy of V.Bostanov).

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