Tunable ion-swelling for nanopatterning of macroscopic surfaces: The role of proximity effects

Ordered surface nanopatterns with different spatial periods and various characters were prepared on silicon surfaces by masked ion irradiation utilizing the local ion-swelling effect. Langmuir–Blodgett (LB) monolayers of hexagonally arranged Stöber silica particles as nanomasks were applied on large area Si substrates during Ar+ or Xe2+ exposure with different fluences. We show that the height and curvature of surface swelling patterns can be tuned by appropriate selection of the particle diameter, ion energy, and ion fluence. It is also revealed that the ion beam-induced anisotropic deformation of the silica mask can be exploited to tailor the surface geometry. We point that, having knowledge on the diameters and average spacing between the silica particles as extrinsic beam spreading factors, and considering the lateral straggling of the bombarding ions in the mask and in the substrate material as intrinsic beam spreading factors, a simple model of the radial fluence distribution can be applied to predict the main features of irradiation-induced surface patterns. The role of proximity effects in the potential use of this easy, fast, wafer-scale nanofabrication method is discussed.