A method for large-area monolayer coverage of micro- and nanospheres on surfaces with low wettability using a cold atmospheric plasma and spin-coating

Self-assembled monolayers of micro- or nanospheres deposited from a colloid on material surfaces can serve as a stencil mask for an easy fabrication of reticular or ordered nanopatterns without costly lithographic equipment. However, in the case of hydrophobic surfaces the colloidal solutions often require special chemical treatment, e.g. by various surfactants, to allow for preparation of continuous monolayers with sufficient coverage on large areas. We demonstrate here a cost effective and fast method of fabrication of large-area continuous monolayers of polystyrene (PS) spheres with diameter of 500 nm on the surface of a Pt film deposited on a Si substrate. We have employed a combination of initial surface treatment using a cold atmospheric pressure plasma (CAPP) in ambient air and subsequent spin-coating of water based colloid solution of the PS nano-spheres without any chemical treatment (e.g. by surfactants) of the solution. The plasma treatment by CAPP in ambient air provides suitable Pt surface activation and significant increase of its wettability. For demonstration of possible applications of this method we present a porous Pt mesh and an ordered array of Pt nanodots prepared by using the PS nanosphere monolayer deposited by this method as a lithographic mask.