Ion beam induced sintering of colloidal polystyrene nano-masks

Nano-masks of polystyrene formed by self-organized arrangement of colloidal nano-spheres in a hexagonally close-packed monolayer on Si(100) surfaces were irradiated with 15 and 75 keV C+ ions at room temperature. At fluences above 10(15) C/cm(2) the polystyrene nano-spheres are observed to form necks at the contact points. This neck formation is thought to result from the near surface reduction of polymer viscosity due to molecular chain scission, which in turn allows to minimize the enormous surface tensions caused by the small radii of surface curvatures at the sphere contact points. This nano-scale effect was observed earlier in colloidal nano-masks of silica and called Ion Beam induced SIntering (IBSI). In polystyrene it is superimposed by the strong volume shrinkage of spheres resulting from polystyrene damage. Both effects cooperate to form novel nano-net structures on the silicon surface. (c) 2007 Published by Elsevier B.V.