Bottom-up nanofabrication of materials for organic electronics

Abstract

Self-organising functional systems and devices are the ultimate aim of bottom-up fabrication. Here, we show how spontaneous organisation can be exploited for patterning a variety of materials, relevant to organic electronics, into arrays of lines or dots by means of a stamp-assisted deposition method, termed lithographically controlled wetting (LCW). LCW is a versatile bottom-up method, able to exploit the spontaneous properties of materials; a stamp is gently placed on a solution layer cast on a substrate. Capillary forces pin the layer to the stamp protrusions, and the hydrodynamic flow during solvent evaporation moves the solution under the protrusions. As the critical concentration is achieved, the solute precipitates only in the regions where the solution is confined by the menisci, and the pattern exhibits the motif of the stamp. By changing concentration or stamp-substrate distance, it is possible to downscale the feature size down to sub-100 nm length scale. Spatially organised nanodots or crystallites can be fabricated by exploiting dewetting, ripening and crystallization.