Tuning the surface morphology in self-organized ion beam nanopatterning of Si(001) via metal incorporation: from holes to dots.

We report on the selective production of self-organized nanohole and nanodot patterns on Si(001) surfaces by ion beam sputtering (IBS) under normal-incidence of 1 keV Ar(+) ions extracted with a cold cathode ion source. For a fixed ion fluence, nanohole patterns are induced for relatively low ion current densities (50-110 µA cm(-2)), evolving towards nanodot patterns for current densities above 190 µA cm(-2). Both patterns display similar characteristics in terms of wavelength, short-range hexagonal order and roughness. Rutherford backscattering spectrometry measurements show that the surface morphology is tuned by the incorporation of metals coming from the ion source and sample surroundings during the IBS process. The metal content measured in nanohole patterns is almost twice that found in nanodot morphologies. Thus, the pattern morphology results from the balance between the dependences of the erosion rate on the ion flux, the local surface topography and composition. These nanostructures have promising applications as growth templates for preferential growth on either hillocks or cavities.