Nanodimple Arrays Fabricated on SiO2 Surfaces by Wet Etching through Block Copolymer Thin Films

Abstract

Block copolymer thin films are promising nanotemplates because highly ordered periodic structures are spontaneously formed through microphase separation on a deca-nanometer scale and over a large area. An amphiphilic block copolymer, which consists of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) with azobenzene mesogens and is denoted by PEOm-b-PMA(Az)n, indicates a strong chemical contrast between the corresponding microdomains, which offer structurally reliable nanotemplates for fabricating nanostructured materials. Thermally annealing a PEOm-b-PMA(Az)n thin film provides hexagonally arranged, perpendicularly oriented PEO cylinders, which perform as ion-conductive nanochannels. In this study, a SiO2 layer on a silicon wafer substrate is etched by NH4F through a PEO114-b-PMA(Az)54 thin film as a nanomask. The SiO2 layer is patterned with a 24-nm-periodic hexagonally arranged nanodimple array. Atomic force microscope (AFM), field emission scanning electron microscope (FESEM), and cross-sectional transmission electron microscope (TEM) observations reveal that the nanodimple array has a 2-nm depth and is spread over the entire SiO2 surface on centimeter scale.