Production of nanohole/nanodot patterns on Si(001) by ion beam sputtering with simultaneous metal incorporation

We have established the conditions for which nanohole and nanodot patterns are produced on Si(001) surfaces by 1 keV Ar+ ion beam sputtering (IBS) at normal incidence with an alternating cold cathode ion source (ACC-IS). Nanohole patterns are produced within a narrow IBS window for low ion fluxes (<100 μA cm-2) and relatively low ion fluences (<1018 ions cm-2) whereas nanodot morphologies are produced above this window. The nanohole pattern is not stable after prolonged irradiation since it evolves to a nanodot morphology. Rutherford backscattering spectrometry (RBS) measurements show that nanohole patterns are produced when the metal content on the irradiated surfaces is higher (within (2.5-3.5 x 1015) atoms cm-2) than in the case of nanodots (<2.5 x 1015 atoms cm-2). The different metal content is related to the ACC-IS operation, since the set-up provides simultaneous incorporation of Fe and Mo on the target surface from the erosion of the cathodes and sample holder, respectively. The role of metal incorporation on pattern selectivity has been corroborated qualitatively by extending the results obtained with the ACC-IS to a standard Kaufman-type source. In order to gain further information on the metal effects, chemical analysis of the surface has been performed to complement the compositional RBS results, showing for the first time the relevant participation of metal silicides. Further outlook and a discussion regarding the role of metal incorporation are also given.