Formation and evolution of ripples on ion-irradiated semiconductor surfaces

We have examined the formation and evolution of ripples on focused-ion-beam (FIB) irradiated compound semiconductor surfaces. Using initially normal-incidence Ga+ FIB irradiation of InSb, we tuned the local beam incidence angle (theta(eff)) by varying the pitch and/or dwell time. For single-pass FIB irradiation, increasing theta(eff) induces morphological evolution from pits and islands to ripples to featureless surfaces. Multiple-pass FIB irradiation of the rippled surfaces at a fixed theta(eff) leads to island formation on the ripple crests, followed by nanorod (NR) growth. This ripple-NR transition provides an alternative approach for achieving dense arrays of NRs. (C) 2014 AIP Publishing LLC.