Surface stress influences on nanopatterns formed in polystyrene films using a force-modulated nanohammer

Two-dimensional lattices of nanodots can be reproducibly produced on polymer surfaces by a biaxial stress field generated using a force-modulated atomic force microscope tip as a nanohammer. Molecular sized super-lattice nanostructures were previously formed by a combination of fundamental and harmonic modulation of surface stress waves in different scanning directions. We find that similar super-lattice structures can be formed in polystyrene films using only fundamental force modulation by taking advantage of elastic interactions between nearby nanoridges. Influences of the initial nanoridge size and the molecular weight of polystyrene on the formation of simple lattice patterns and complex nanometer-scale super-lattice patterns were studied.