Orientation-Controlled Self-Assembled Nanolithography Using a Polystyrene−Polydimethylsiloxane Block Copolymer

Jung, Yeon Sik; Ross, Caroline A.

doi:10.1021/nl070924l

Cited by 426 publications

(633 citation statements)

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“…The higher resolution silicon imprint templates were patterned using block-copolymer self-assembly followed with plasma etching. 20,21 Figure 2a shows the tilted scanning electron micrograph (SEM) of a nanoimprint template bearing hexagonally arranged posts with a diameter of 20 nm and singlecrystal domain size of hundreds of nanometers. The template surface was treated with a mold-release agent (MRA) for easy template removal without material peel-off.…”

Section: Methodsmentioning

confidence: 99%

Formation of Bandgap and Subbands in Graphene Nanomeshes with Sub-10 nm Ribbon Width Fabricated via Nanoimprint Lithography

et al. 2010

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O rganic-based photovoltaic cells (OPVs) are of great interest owing to their potential for low-cost solar energy conversion. 1 An important breakthrough for OPVs was the use of a heterojunction (HJ) structure, in which the difference of the energy levels of two materials (donor and acceptor) can lead to efficient dissociation of photogenerated excitons at the HJ interfaces. 1 Since then, tremendous efforts have been taken to optimize the carrier donor/acceptor (DA) interface morphology to improve the photogenerated exciton dissociation and consequently the overall power conversion efficiency. 2 One successful approach is to use a bulk heterojunction (BHJ) structure that can create dissociation centers everywhere within the active layer. 2 Typically, the formation of a BHJ structure can be achieved via self-assembly of nanostructured soft materials by spontaneous phase separation in a number of solution processed polymer/ fullerene systems, yet efficiency in these structures might be significantly reduced through unpredicted shunt paths and isolated islands of materials. 3 Nanoimprint lithography (NIL) offers a potential solution for producing well-defined interpenetrating networks at the DA interface and is compatible with roll-to-roll manufacturing for lowcost and high-throughput nanopatterning. 4,5 To efficiently harvest photogenerated excitons, densely packed nanoimprinted OPV structures with halfpitch smaller than 2 times that of the exciton diffusion length are needed (typically sub-20 nm regime). 6 Recent efforts in this field have been mainly focusing on polymeric PV materials. However, OPVs with small-molecular weight materials could also benefit from similar morphologies. In addition, small-molecular weight OPV materials provide additional advantages over polymers, such as higher chemical/thermal stability and higher material purity. 7 Previous work has shown relatively poor stability of imprinted nanostructures in smallmolecular compounds. 8Ϫ10 Problems arise due to pronounced surface diffusion and self-faceting and are exacerbated when features head toward the sub-20 nm regime. 11,12 These instabilities must be understood and overcome to achieve efficient nanostructured OPVs.Boron subphthalocyanines (SubPcs) are a class of photoactive small-molecularweight materials with unique physical properties. 13 A typical SubPc has a nonplanar pyramid-shaped structure, in which the boron atom is surrounded by three coupled

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Section: Methodsmentioning

confidence: 99%

Formation of Bandgap and Subbands in Graphene Nanomeshes with Sub-10 nm Ribbon Width Fabricated via Nanoimprint Lithography

et al. 2010

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“…Most work on the templated self-assembly of block copolymers for nanolithography has focused on the generation of periodic patterns of parallel lines, close-packed dots or concentric rings, using shallow trenches 1,6,9,10,[12][13][14]22,24,26 , sparse post arrays 3 or chemical templates with a periodicity either similar to that of the BCP 2,7,8,15 or a factor two, three or four times larger 3-5 . Nealey and colleagues have shown that non-regular features such as lamellae with bends 2,11 or square-packed dots 15 could be formed using a chemical pattern of the same density as the desired block copolymer pattern.…”

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confidence: 99%

“…The HSQ posts and native oxide on the silicon wafers were chemically functionalized with a brush layer of PDMS to ensure that the posts had an affinity for the PDMS block of the block copolymer and to improve annealing kinetics. Thin PDMS layers formed at the air and substrate interfaces 3,[25][26][27] .…”

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A Path to Ultranarrow Patterns Using Self-Assembled Lithography

Jung¹,

Chang²,

Verploegen³

et al. 2010

Nano Lett.

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Templated self-assembly of block copolymer thin films can generate periodic arrays of microdomains within a sparse template, or complex patterns using 1:1 templates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . However, arbitrary pattern generation directed by sparse templates remains elusive. Here, we show that an array of carefully spaced and shaped posts, prepared by electron-beam patterning of an inorganic resist, can be used to template complex patterns in a cylindrical-morphology block copolymer. We use two distinct methods: making the post spacing commensurate with the equilibrium periodicity of the polymer, which controls the orientation of the linear features, and making local changes to the shape or distribution of the posts, which direct the formation of bends, junctions and other aperiodic features in specific locations. The first of these methods permits linear patterns to be directed by a sparse template that occupies only a few percent of the area of the final self-assembled pattern, while the second method can be used to selectively and locally template complex linear patterns.Microphase separation of a block copolymer thin film can generate dense arrays of microdomains with periodicity as low as $10 nm (refs 6,16-19). Such arrays have been used as lithographic masks to pattern various functional materials, and to create devices including nanocrystal flash memory, nanowire transistors, gas sensors and patterned magnetic recording media [20][21][22][23][24][25] . Block copolymer thin film self-assembly on an unpatterned substrate leads to close-packed arrays of features such as lines or dots that lack long-range order, thus limiting their utility. As a result, both chemical and topographical substrate features have been used to template or guide block copolymer self-assembly, imposing long-range order and generating microdomain geometries not observed in untemplated films [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . These templates are often defined using electronbeam lithography (EBL) [3][4][5]7,8,11 , because of its ability to pattern small features of arbitrary geometry. However, the serial nature of EBL makes it clearly advantageous to minimize the density of the EBL-written features required to template a given arrangement of block copolymer microdomains. Even in a production context in which EBL is used only to write a master pattern that is to be replicated by some higher-throughput mechanism (such as nanoimprinting), the time required just to write the master can be prohibitively long. The challenge in template design is therefore to find a set of template features of minimum complexity that will deterministically program the block copolymer to form a desired final pattern, such as an interconnect level in an integrated circuit, which may contain both periodic and aperiodic features.We describe an approach to this problem that uses a sparse array of chemically functionalized topographical posts to control the self-assembly of dense linear block copolymer (BCP) stru...

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“…As shown in Figure 2, the self-assembled PS-PDMS block copolymer patterns show an excellent degree of ordering within the trenches, with quality similar to that obtained previously in trenches etched into silicon and coated with a thin PDMS brush. 25 Although the cylinders adjacent to the trench edges show some edge roughness, correlated to roughness in the trench walls, the cylinders closer to the center of the groove are very straight with an edge roughness of 3.6 nm.…”

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confidence: 99%

Nanowire Conductive Polymer Gas Sensor Patterned Using Self-Assembled Block Copolymer Lithography

et al. 2008

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Nanostructured conjugated organic thin films are essential building blocks for highly integrated organic devices. We demonstrate the largearea fabrication of an array of well-ordered 15 nm wide conducting polymer nanowires by using an etch mask consisting of self-assembled patterns of cylinder-forming poly(styrene-b-dimethylsiloxane) diblock copolymer confined in topographic templates. The poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) nanowires operated as an ethanol vapor sensor, suggesting that the electronic properties of the organic film were preserved during the patterning processes. The higher sensitivity to ethanol vapor, compared to an unpatterned film with the same thickness, was attributed to the enhanced surface-to-volume ratio of the nanowire array.A molecular rectifier, theoretically proposed by Ratner and Aviram in 1974, was the starting point for a boom in molecular electronics research that has persisted for the last three decades. 1 Later, single-molecule field-effect transistors and logic gates were also conceptually proposed, 2 and Reed et al. first reported single-molecule conductance measurements through benzene-1,4-dithiol. 3 The development of conductive polymers has continued to attract interest for many different applications including optoelectronic devices, 4-6 field effect transistors, 7,8 and chemical or biological sensors. 8,9 In these applications, device performance has been improved by miniaturizing the feature sizes down to the nanoscale regime, 10,11 and there is considerable interest in methods that enable the patterning of electronically active polymers on the nanoscale.Various fabrication techniques have been developed for generating conducting polymer nanowires. Chemical or electrochemical growth without templates usually produces entangled nanowires with a large distribution in diameter and length, which is undesirable in terms of performance and reproducibility, despite the convenience of fabrication. 12-17 For better-organized structures, scanning-probe and electronbeam patterning have been employed to direct the growth of conducting polymer nanowires. 11,18,19 Recently, spontaneous ordering of polymer nanowires was induced within a submicron gap between electrodes fabricated using a focused ion beam. 20 However, the throughput and manufacturability of these methods are limited by the serial nature of the patterning techniques. Well-ordered conducting polymer nanopatterns have also been produced by nanoimprint lithography, 21 but this technique requires fabrication of master molds.In this communication, we report fabrication of well-ordered arrays of 15 nm wide, 35 nm period poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conducting polymer nanowires, made over areas of several square centimeters using a self-assembled block copolymer mask, and we demonstrate the capability of the patterned structures to act as an ethanol vapor sensor, confirming the preservation of the electronic properties of the PEDOT:PSS during patterning. Bloc...

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Orientation-Controlled Self-Assembled Nanolithography Using a Polystyrene−Polydimethylsiloxane Block Copolymer

Cited by 426 publications

References 30 publications

Formation of Bandgap and Subbands in Graphene Nanomeshes with Sub-10 nm Ribbon Width Fabricated via Nanoimprint Lithography

Formation of Bandgap and Subbands in Graphene Nanomeshes with Sub-10 nm Ribbon Width Fabricated via Nanoimprint Lithography

A Path to Ultranarrow Patterns Using Self-Assembled Lithography

Nanowire Conductive Polymer Gas Sensor Patterned Using Self-Assembled Block Copolymer Lithography

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