Ion-beam sputtering (IBS) is known to produce surface nanopatterns over macroscopic areas on a wide range of materials. In Refs [Castro and Cuerno, 2010; Cuerno et al 2011] we introduced a hydrodynamical approach to ion beam sputtering in which pattern formation can be understood as the effect of ion induced solid flow due to the stress produce by irradiation and consequent viscous relaxation of defects. In particular, in Ref [Castro and Cuerno 2012] we presented two alternative ways to account for the stress produced by the ion: through an effective angle-dependent body force (acting on the bulk) and through a constant applied stress (whose effect manifests exclusively on the surface). We have performed detailed experiments of IBS on Si substrates that validate dynamical and morphological predictions from that theory [Castro et al 2012]. Moreover, we introduce a systematic approach to perform the experiments under conditions that guarantee the applicability of a linear description, helping to clarify the experimental framework in which theories should be tested. Among our results, the pattern wavelength is experimentally seen to depend almost linearly on ion energy, in agreement with existing results for other targets that are amorphous or become so under irradiation. Our work substantiates flow of a nanoscopically thin and highly viscous surface layer, driven by the stress created by the ion beam, as an accurate description of this class of systems.
International Symposium on Nanoscale Pattern Formation at Surfaces
Publication date: May 2013.
M. Castro, A. Moreno Barrado, R. Cuerno, J. Munoz-Garcia, R. Gago, L. Vázquez, Stress-induced solid flow drives surface nanopatterning of silicon by ion-beam irradiation, International Symposium on Nanoscale Pattern Formation at Surfaces. Copenhague, Denmark, 26-30 May 2013