Selecting adhesive molecular layers with matched surface free energy and chemisorption for shape-fixed UV-cured thin films fabricated by laser-drilled screen printing and UV nanoimprinting

Abstract

This study investigates the importance of surface free energy and chemisorption of substrates for the formation of a UV-cured thin film corresponding to a residual layer in UV nanoimprint lithography. Silicon substrate surfaces were modified with binary molecular layers which were prepared through photo-oxidation of a monomer-repelling monolayer and implantation of a reactive surface modifier with an acrylate polymerizable group. Laser-drilled screen printing enabled the placement of droplets of high-viscosity dimethacrylate UV-curable liquid on the modified substrates. UV nanoimprinting with a modified flat mold surface allowed the formation of UV-cured films with a square shape and a sub-100 nm thickness. The thickness of the UV-cured film was tuned precisely in the case of the substrate showing almost the same surface free energy value as the mold surface. The comparison with and without the reactive surface modifier revealed that the chemisorption was essential for the film formation on the substrates.