Plan view SEM images of Si nanostructures after different etch durations with the NIL masks removed. (a) 30-, (b) 60-, and (c) 180-s etch durations. The top surfaces of the nanostructures remain smooth after the process due to a good degree of protection offered by the NIL masking layer. This contrasts with the rougher sidewalls. Slight narrowing in the lateral dimensions of the Si nanostructures from approximately 180 nm to approximately 160 nm occurs when the etching duration is increased from 30 to 180 s. The fine lines or streaks observed in (b) and to a greater degree in (c) between the Si nanostructures are attributable to non-uniform gold coating of low-relief surfaces between higher structures prior to FESEM to reduce charging effects.
Ho et al. Nanoscale Research Letters 2013 8:506 doi:10.1186/1556-276X-8-506