  Despite extensive study, fundamental understanding of self-organized
patterning by broad-beam ion bombardment is still incomplete and controversial.
Understanding the nanopatterning of elemental semiconductors, particularly
silicon, is both foundational for the broader field and of intrinsic scientific
and technological interest itself. This is the second component of a two-part
investigation of the kinetics and fluctuation dynamics of self-organized
nanoscale ripple development on silicon during 1 keV Ar$^+$ (Part I) and Kr$^+$
bombardment. Here, it's found that the ion-enhanced viscous flow relaxation is
essentially equal for Kr$^+$-induced patterning as previously found for Ar$^+$
patterning. The magnitude of the surface curvature dependent roughening rate in
the early stage kinetics is larger for Kr$^+$ than for Ar$^+$, qualitatively
consistent with expectations for erosive and mass redistributive contributions
to the initial surface instability. As with the Ar$^+$ case, fluctuation
dynamics in the late stage show a peak in correlation time at the length scale
corresponding to the dominant structural feature on the surface -- the ripples.
Analogy is made to the phenomenon of de Gennes narrowing in liquids, but
significant differences are also pointed out. Finally, it's shown that speckle
motion during the surface evolution can be analyzed to determine spatial
inhomogeneities in erosion rate and ripple velocity on the surface. This allows
the direction and speed of ripple motion to be measured in real time, a unique
capability for measuring these fundamental parameters outside the specialized
environment of FIB/SEM systems.
