Graphite and silicon nanoneedles are fabricated by different etching processes on highly oriented pyrolitic graphite (HOPG) and SiO2/Si. The masks used to engrave such substrates are needle-shaped ferrite nanocrystals. We are able to control the height of these nanoneedles by manipulating the plasma etching parameters such as gas selectivity and etching time. The morphology of the engraved structures is characterized by scanning electron microscopy and atomic force microscopy. We show that the limiting dimension in the transfer using nanocrystals as masks is not that of the mask objects themselves but that of the distance separating them. We demonstrate that nanocrystals achieve the role of colloidal masks leading to resolutions down to 10 nm in distance between objects when the etched substrate is SiOx and less than 3 nm when the substrate is HOPG. This resolution is better than that reported in the literature. The difference in lateral resolution is discussed.
Source : High resolution patterned transfer using needle-shaped ferrite nanocrystals. D.Ingert and M.P.Pileni, J.Phys.Chem.C., 2008,112, 19329-19335.