Vertical Orientation of Nanodomains on Versatile Substrates through Self‐Neutralization Induced by Star‐Shaped Block Copolymers

Abstract

wileyonlinelibrary.comspeed, and simplicity of the process. [1][2][3][4][5] Although vertical orientation of lamellar and cylindrical nanodomains of block copolymers on a substrate is desirable, parallel orientation is usually obtained in a thin fi lm because of different affi nity between two block segments in a block copolymer toward the substrate and/or air. To induce vertical orientation, diverse preor post-treatments to neutralize the preferential affi nity have been introduced in the literature, for instance, solvent vapor annealing, [6][7][8][9] surface neutralization by random copolymer brush treatment, [10][11][12] blend system, [ 13 ] graphoepitaxy, [ 14,15 ] temperature gradient, [ 16,17 ] electric fi eld [ 18,19 ] or top coating. [20][21][22] Among them, solvent vapor annealing is one of the most powerful post-treatment methods for developing vertical orientation of block copolymer nanodomains. However, this method is diffi cult to apply for industrial applications owing to the use of solvents and the dewetting problem. To avoid using solvent, thermal annealing of block copolymer thin fi lms would be the most promising platform for commercialization of DSA due to easy and large scale process. However, to induce vertically oriented nanodomains, neutralization of a substrate by various surface modifi cations, for instance, functionalization with random copolymers, introducing rough substrates, employing graphene fi lms or nanoparticle monolayers, [ 11,13,[23][24][25] is still needed to tune interfacial interactions between a substrate and each block of the block copolymer. Therefore, a simple and cost-effective DSA process that does not require above-mentioned neutralization methods and solvent vapor annealing is demanded for the fabrication of vertically oriented nanodomains to compete with conventional top-down lithography.Kramer and co-workers [ 26 ] investigated the effect of block copolymer chain architecture on the orientation of nanodomains in relatively thick fi lms (600-800 nm) using poly(cyclohexylethylene)-block -poly(ethylene) (PCHE-b -PE) block copolymers. They found that PCHE-b -PE-b -PCHE triblock copolymer showed perpendicularly oriented nanodomains by introducing lower surface energy block as the midblock, whereas PCHE-b -PE diblock copolymer exhibited parallel Vertical Orientation of Nanodomains on Versatile Substrates through Self-Neutralization Induced by Star-Shaped Block CopolymersSangshin Jang , Kyuseong Lee , Hong Chul Moon , Jongheon Kwak , Jicheol Park , Gumhye Jeon , Won Bo Lee , and

Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

“…Introduction of more intricate BCP architectures leads to more dramatic effect in thin films. Jang et al . demonstrated an entropy‐dominated ordering phenomenon using a star BCP with 18 PS‐ b ‐PMMA arms, the PMMA block making up the inner block.…”

“…Chain arrangement of cylindrical nanodomains of star‐shaped block copolymer on a substrate for e) parallel and f) vertical orientations. Reproduced with permission . Copyright 2015, Wiley‐VCH.…”

Perpendicularly aligned nanodomains on versatile substrates via rapid thermal annealing assisted by liquid crystalline ordering in block copolymer films

“…Flexible substrates, such as transparent polyethylene terephthalate (PET) sheets and conductive aluminum foils, have been rarely reported to date, even though they are highly desired for the increasingly developing elds of exible and wearable electronic devices. 31 Poly(styrene-b-methyl methacrylate) (PS-b-PMMA) is by far the most widely studied block copolymer and most favorable for industrial applications due to its easy synthetic accessibility, high quality and good etching selectivity. Perpendicular orientation of microdomains can be obtained via thermal annealing at relatively high temperatures (180-250 C) on a neutralized substrate.…”

Directional Self‐Assembly of Fluorinated Star Block Polymer Thin Films Using Mixed Solvent Vapor Annealing

“…Though, there have been some notable advances reported in the star BP literature, the directional alignment of self‐assembled star BP thin films is under‐explored with respect to its feasibility for nanolithography. For practical applications of such BP thin films, the phase‐separated domains (especially lamellae) should be perpendicularly oriented on a substrate .…”