Thin Poly(styrene-<i>block</i>-4-hydroxystyrene) Block Copolymer Films Spin-Coated Directly on Topographic Prepattern Substrates

Lee, Geuntak; Jo, Pil Sung; Yoon, Bokyung; Kim, Tae Hee; Acharya, H. N.; Itô, Hiroshi; Kim, Ho Cheol; Huh, June; Park, Cheolmin

doi:10.1021/ma801631y

Cited by 10 publications

(10 citation statements)

References 25 publications

(19 reference statements)

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“…Size and pitch of these structures were varied in the range of 100 nm to 6 μm. PS thin films were directly spin-coated on patterned substrates, which results in slight thickness variation around the protruded features. − Spin-coating on topographically patterned substrates largely produced uniform coating on the flat, bottom parts of the substrates, whereas the top portions of the channel walls and pillars received much thinner coatings that were even largely absent in the shorter channels and pillars of widths less than about 1 μm. For example, the AFM images of bare EBL patterned substrate in Figure a shows the height of pillars ∼115 nm.…”

Section: Resultsmentioning

confidence: 99%

Submicrometer Pattern Fabrication by Intensification of Instability in Ultrathin Polymer Films under a Water–Solvent Mix

Verma

Sharma

2011

Macromolecules

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Dewetting of ultrathin (< 100 nm) polymer films, by heating above the glass transition, produces droplets of sizes of the order of microns and mean separations between droplets of the order of tens of microns. These relatively large length scales are because of the weak destabilizing van der Waals forces and the high surface energy penalty required for deformations on small scales. We show a simple, one-step versatile method to fabricate sub-micron (>~100 nm) droplets and their ordered arrays by room temperature dewetting of ultrathin polystyrene (PS) films by minimizing these limitations. This is achieved by controlled room temperature dewetting under an optimal mixture of water, acetone and methyl-ethyl ketone (MEK). Diffusion of organic solvents in the film greatly reduces its glass transition temperature and the interfacial tension, but enhances the destabilizing field by introduction of electrostatic force. The latter is reflected in a change in the exponent, n of the instability length scale, λ ~hn , where h is the film thickness and n = 1.510.06 in the case of water-solvent mix, as opposed to its value of 2.190.07 for dewetting in air. The net outcome is more than one order of magnitude reduction in the droplet size as well as their mean separation and also a much faster dynamics of dewetting. We also demonstrate the use of this technique for controlled dewetting on topographically patterned substrates with submicrometer features where dewetting in air is either arrested, incomplete or unable to produce ordered patterns.

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Section: Resultsmentioning

confidence: 99%

Submicrometer Pattern Fabrication by Intensification of Instability in Ultrathin Polymer Films under a Water–Solvent Mix

Verma

Sharma

2011

Macromolecules

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“…At the same time the film thickness appears to be modulated so that the film in trench regions is thicker than on top of the crests/mesas due to capillary forces during film formation. The dimensions of the gratings periodicity as well as vapor conditions during spin-coating or annealing may affect the dewetting stability of a thin film during preparation. , The initial surface roughness tends to annihilate upon annealing to a (quasi)equilibrium topography of the film . The extent of the coupling between the substrate roughness and the final corrugations at the film surface was systematically studied for polystyrene films as a function of the film thickness and interactions with the substrate to compare the behavior of simple liquids and polymeric fluids .…”

Section: Introductionmentioning

confidence: 99%

Surface Roughness-Mediated Ordering in Block Copolymer Films toward Spatially Controlled Patterns

Park

2017

Macromolecules

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We studied structure development in block copolymer films with a regular surface roughness induced by the deposition on corrugated supports. Upon thermal annealing, the residual surface roughness in thin films of cylinder-forming polystyrene-b-polybutadiene (PS-b-PB) diblock copolymer was found to be independent both on the averaged starting film thickness h 0 and on the initial thickness gradient induced by spin-coating. Surface patterns in PS-b-PB films on linear and squared wave gratings appear in a form of spatially registered cylinder and nonbulk lamella phases with the morphological sequences coupled to the topography of the substrate. The observed complex phase behavior is independent of the h 0 in up to three layers thick films. At the same time, the initial surface roughness was shown to be essential for the flow-field-induced sequenced ordering of the microdomains. We identify a number of specific features of complex confinement on corrugated substrates as compared to flat space, such as extreme deviations from the bulk cylinder morphology to nonbulk lamella structures in thick films, as well as the violation of the surface-tension-driven segregation of the soft PB component to the free surface. Differences in the flow behavior of PS-b-PB films and of PS homopolymer films under strong confinement, reported earlier, confirm the decoupling of the dynamics of the chains at the free surface from the underlying layers and suggest novel insights into the distribution of the surface fields through the film.

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“…The dewetting is initiated at the sharp edge of topographic patterns due to localized polymer flow at the pattern edges in order to spontaneously reduce the excess chemical potential induced by high curvature at the pattern edge, which causes draining of fluid from the mesas to the trenches . Similar dewetting patterns have been observed in spin-coated polymer on the topographic pattern. , The capillary-driven flow will rapidly tend to raise the thickness of the solution in the trenches, thus reducing the curvature difference and the capillary pressure. This planarization of the film on a topographic surface renders the film on mesa regions thinner than on trenches.…”

Section: Resultsmentioning

confidence: 70%

Micropatterns of Hierarchical Self-Assembled Block Copolymer Droplets with Solvent-Assisted Wetting of Brush Monolayers

2010

Self Cite

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We present a method to fabricate micropatterns of a self-assembled block copolymer droplets with hierarchically ordered nanostructures by controlling solvent-assisted wetting of the droplets. This method is based on transfer-printing the micropatterned dewetted droplets formed onto a topographic poly(dimethylsiloxane) prepattern to a silicon wafer, followed by wetting triggered by solvent annealing. Solvent vapor provides sufficient mobility of block copolymer molecules in convex-shaped micropatterns and allows for controlling the 2D circular spread of the ∼7 nm thick brush monolayer, resulting in a novel structure hierarchically terraced with ordered spherical microdomains in the individual block copolymer droplets. Our micropatterning technique capable of controlling both shape and microstructure of individual droplets also enables us to produce a novel polarity tunable surface since contact angle of a water droplet is easily tailored as a function of solvent annealing time on micropatterns.

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Thin Poly(styrene-block-4-hydroxystyrene) Block Copolymer Films Spin-Coated Directly on Topographic Prepattern Substrates

Cited by 10 publications

References 25 publications

Submicrometer Pattern Fabrication by Intensification of Instability in Ultrathin Polymer Films under a Water–Solvent Mix

Submicrometer Pattern Fabrication by Intensification of Instability in Ultrathin Polymer Films under a Water–Solvent Mix

Surface Roughness-Mediated Ordering in Block Copolymer Films toward Spatially Controlled Patterns

Micropatterns of Hierarchical Self-Assembled Block Copolymer Droplets with Solvent-Assisted Wetting of Brush Monolayers

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