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Title: Combinatorial Block Copolymer Ordering on Tunable Rough Substrates

Abstract

Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, amore » high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} {approx} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period of several months. These results also highlight importantly that BCP orientation control for nanotechnology is possible not only on specially prepared patterned substrates but also on industrially viable sol-gel substrates.« less

Authors:
; ; ;  [1];  [2];  [2]
  1. (IIT-India)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCES
OSTI Identifier:
1048554
Resource Type:
Journal Article
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 45; Journal Issue: (10) ; 05, 2012
Country of Publication:
United States
Language:
ENGLISH
Subject:
14 SOLAR ENERGY; AGING; AMPLITUDES; CATALYSTS; CHEMICAL PROPERTIES; COPOLYMERS; DIMENSIONS; FRACTALS; LAMELLAE; MICROSTRUCTURE; MORPHOLOGY; NEUTRONS; ORIENTATION; ROUGHNESS; SCATTERING; SILICA; SOLAR CELLS; SOLS; STORAGE; SUBSTRATES; SURFACE ENERGY; THIN FILMS

Citation Formats

Kulkarni, Manish M., Yager, Kevin G., Sharma, Ashutosh, Karim, Alamgir, Akron), and BNL). Combinatorial Block Copolymer Ordering on Tunable Rough Substrates. United States: N. p., 2012. Web. doi:10.1021/ma300169a.
Kulkarni, Manish M., Yager, Kevin G., Sharma, Ashutosh, Karim, Alamgir, Akron), & BNL). Combinatorial Block Copolymer Ordering on Tunable Rough Substrates. United States. doi:10.1021/ma300169a.
Kulkarni, Manish M., Yager, Kevin G., Sharma, Ashutosh, Karim, Alamgir, Akron), and BNL). Thu . "Combinatorial Block Copolymer Ordering on Tunable Rough Substrates". United States. doi:10.1021/ma300169a.
@article{osti_1048554,
title = {Combinatorial Block Copolymer Ordering on Tunable Rough Substrates},
author = {Kulkarni, Manish M. and Yager, Kevin G. and Sharma, Ashutosh and Karim, Alamgir and Akron) and BNL)},
abstractNote = {Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, a high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} {approx} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period of several months. These results also highlight importantly that BCP orientation control for nanotechnology is possible not only on specially prepared patterned substrates but also on industrially viable sol-gel substrates.},
doi = {10.1021/ma300169a},
journal = {Macromolecules},
number = (10) ; 05, 2012,
volume = 45,
place = {United States},
year = {2012},
month = {10}
}