Lithography-Free Route to Hierarchical Structuring of High-χ Block Copolymers on a Gradient Patterned Surface

• Main Authors: Ha Ryeong Cho, Ayoung Choe, Woon Ik Park, Hyunhyub Ko, Myunghwan Byun
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Materials
• Subjects: high <i>χ</i> di-block copolymer; wedge-on-si geometry; controlled evaporative self-assembly; hierarchically ordered nanostructures; gradient patterned surface; oxide nanogroove
• Online Access: https://www.mdpi.com/1996-1944/13/2/304

A chemically defined patterned surface was created via a combined process of controlled evaporative self-assembly of concentric polymer stripes and the selective surface modification of polymer brush. The former process involved physical adsorption of poly (methyl methacrylate) (PMMA) segments into silicon oxide surface, thus forming ultrathin PMMA stripes, whereas the latter process was based on the brush treatment of silicon native oxide surface using a hydroxyl-terminated polystyrene (PS-OH). The resulting alternating PMMA- and PS-rich stripes provided energetically favorable regions for self-assembly of high <inline-formula> <math display="inline"> <semantics> <mi>&#967;</mi> </semantics> </math> </inline-formula> polystyrene-<i>block</i>-polydimethylsiloxane (PS-<i>b</i>-PDMS) in a simple and facile manner, dispensing the need for conventional lithography techniques. Subsequently, deep reactive ion etching and oxygen plasma treatment enabled the transition of the PDMS blocks into oxidized groove-shaped nanostructures.