These highlight the pathway for the transition - it appears
that it occurs with the streaks gradually losing intensity
over time until they are more spot-like (seen in cluster 6).
Beyond t = 120 s, four clusters characterize the remaining
t = 100 s of growth, and these are outlined with olive dash
lines in the upper panel. Interestingly, there is little difference
between these clusters (compared with the clusters
in the layer-by-layer growth segment), and moreover, the
similarity suggests little roughening effects in the grown
film. We can therefore assign, unambiguously, that the
layer-by-layer growth transitions to the step-flow mode
when cluster 1 is active, i.e., at t = 120 s. Thus, the kmeans
clustering allows identification of growth mode
transitions as well as the pathway through which this occurs
in k-space, and furthermore allows identification of
existence or absence of surface roughening. The method