Fabrication of discrete polystyrene nanoparticle arrays with controllable their structural parameters.

We have demonstrated the fabrication of two-dimensionally periodic non-close packed arrays of spherical polystyrene nanoparticles with controllable their structural parameters including diameter and interpartcile distance. The principle of this procedure relies on stepwise integration of spin-coat-assisted colloidal self-assembly of the single layer of close-packed polystyrene nanoparticle on a substrate, and subsequent etching of the particle under atmospheric pressure helium plasma. The plasma process converted the close-packed nanoparticle array into non-close-packed arrangement remaining with unchanged their original spherical shape and periodicity. Owing to the etching process underwent isotropically, the structural parameters could be controlled with nanometric accuracy by the treatment time. The etching rate strongly depended on the working pressure conditions, and the etching rate under 250 Torr was ca. 3 times faster than that of the 760 Torr. The effects of the working pressure indicated the neutral helium radicals and photons diffused from the plasma might be primarily responsible for the etching.