Evolution of Film Morphology

Structural measures of these patterns in Fig. 4.5. The characteristic wavelength of the patterns was determined by taking the two-dimensional Fourier transform of the pictures. The resulting ring-shaped pattern indicated isotropy (no lateral direction is preferred), as expected from theory. Radially averaging the data resulted in a clear peak with the position of its maximum (= qmax) determining 

While the lateral regularity of the structure is maintained during this initial period, the amplification is nonhomogeneous with different depressions thinning at different rates as indicated by 

It can be noted that most of the amplification has occurred in the last 30 seconds of this stage, which is only about 10% of the total duration of the stage. This also confirms the theoretical predictions that the amplification is slow in the beginning, whereby the surface fluctuations get arranged on a dominant wavelength, but later enters a nonlinear explosive phase of growth, consistent with an exponential increase of the amplitude. 

This amplification of surface fluctuations is followed by the process of pseudo dewetting initiated by the touchdown of the depressions at the minimum thickness (determined by the grafted layer) to form isolated circular holes (white portions), with the relatively deeper depressions touching earlier (images B1 and B2 in Fig. 4.4) and others following later (image B3 in Fig. 4.4). The variation of the number of holes with time (n(t)) is also presented in Fig. 4.5 to highlight the existence of a finite time window for the formation of holes. 

Ht is not true dewetting because the iayer of grafted moiecuies always remains and thus cannot dewet 

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