  Topography evolution of Si(100) surface due to oblique incidence low energy
ion beam sputtering (IBS) is investigated. Experiments were carried out at
different elevated temperatures from 20$^{\circ}$C to 450$^{\circ}$C and at
each temperature, the ion fluence is systematically varied in a wide range from
$\sim$ 1$\times$10$^{18}$cm$^{-2}$ to 1$\times$10$^{20}$cm$^{-2}$. The ion
sputtered surface morphologies are characterized by atomic force microscopy and
high-resolution cross-sectional transmission electron microscopy. At room
temperature, the ion sputtered surfaces show periodic ripple nanopatterns and
their wave-vector remains parallel to ion beam projection for entire fluence
range. With increase of substrate temperature, these patterns tend to demolish
and reduce into randomly ordered mound-like structures around 350$^{\circ}$C.
Further rise in temperature above 400$^{\circ}$C leads, surprisingly,
orthogonally rotated ripples beyond fluence 5$\times$10$^{19}$cm$^{-2}$. All
the results are discussed combining the theoretical framework of linear,
non-linear and recently developed mass redistribution continuum models of
pattern formation by IBS. These results have technological importance regarding
the control over ion induced pattern formation as well as it provides useful
information for further progress in theoretical field.
