Medium energy Ar+-ion induced ripple formation: Role of ion energy in pattern formation

We show that the energy scaling of the ion beam induced depth of amorphization and ripple wavelength in the medium energy regime can be understood in terms of dominant nuclear energy loss in this energy regime. Specifically, thickness of amorphous layer developed under 60 keV Ar+-ion bombardment of Si at an incidence angle of 60° as determined by micro-Raman Spectrometry and cross-sectional transmission electron microscopy is shown to be consistent with the assumption of only nuclear energy loss mediated evolution. Further, the variation of ripple wavelength with ion energy is estimated using SRIM. Estimated variation of ripple wavelength with ion energy under this assumption is found to be in qualitative agreement with experimental observations in the medium energy range.