In recent years, the study of the possible influence of metal incorporation and substrate heterogeneity during ion beam sputtering (IBS) on the induced target surface nanopatterning is being increasingly addressed both experimentally and theoretically . Here, we describe our findings on the correlation between the surface metal content and the type of nanopattern produced on Si(001) surfaces when they are irradiated by 1 keV Ar IBS at normal incidence with an alternating cold cathode ion source (ACC-IS). In our case, metal sources during IBS are related to the ACC-IS operation, since this set-up leads to the simultaneous Fe and Mo incorporation on the target surface from the erosion of the cathodes and sample holder, respectively. The morphologies were routinely characterized by Atomic Force Microscopy and compositionally by Rutherford Backscattering Spectrometry. When nanodot patterns were produced the residual metal content was relatively low whereas, in contrast, when the metal content was higher nanohole patterns were induced. Interestingly, the nanohole patterns can display similar characteristics to nanodot patterns in terms of roughness, wavelength and order. We have performed further experiments with a standard Kaufman-type source (where metal contribution from the plasma discharge is suppressed) in order to determine whether this pattern selectivity is specific to the ACC-IS system or, rather, be controlled with the metal incorporation rate. These experiments confirm the role of metals on the pattern selectivity. In addition, chemical analysis of the surface has been performed showing, for the first time, the relevant formation of metal silicides. We have also studied the dynamics of nanodot formation at different ion fluxes and contrasted it with predictions from a two-field continuum model of IBS nanopatterning that does not take into account any compositional heterogeneity on the target material. Somehow surprisingly, the quantitative agreement between the experimental and theoretical morphological observables is quite satisfactory. We have performed additional experiments on Si(001) surfaces immersed in a magnetically confined plasma, for which cellular patterns appear, that we have analyzed using tools from the study of froths and foam patterns.
2009 Materials Research Society Fall Meeting
Publication date: November 2009.
L. Vázquez, R. Gago, J.A. Sánchez-García, J. Munoz-Garcia, R. Cuerno, A. Redondo-Cubero, M.M. García-Hernández, M. Castro, Hole, dot and cellular nanopatterns induced on silicon surfaces by ion bombardment, 2009 Materials Research Society Fall Meeting. Boston, United States of America, 30 November - 04 December 2009