Printing meets lithography: Soft approaches to high-resolution patterning

Michel, Bruno; Bernard, André; Bietsch, Alexander; Delamarche, Emmanuel; Geißler, Matthias; Juncker, David; Kind, Hannes; Renault, Jean Philippe; Rothuizen, H.; Schmid, Heinz; Schmidt‐Winkel, Patrick; Stutz, R.; Wolf, Heiko

doi:10.1147/rd.455.0697

Cited by 463 publications

(353 citation statements)

References 91 publications

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“…We attribute the postimprint feature relaxation to surface diffusion, driven by a reduction in surface energy; surface diffusion is pronounced in such smallmolecular-weight organic compounds. 8,9 The improvement in feature stability between 80Ϫ90°C is related to a change in the crystallinity as demonstrated by X-ray diffraction (XRD) data ( Figure 5). XRD spectra of SubPc-A samples imprinted at various temperatures were measured and are plotted in Figure 5a.…”

Section: Resultsmentioning

confidence: 98%

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: Resultsmentioning

confidence: 98%

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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“…SEM images of the resulting surfaces demonstrate the accuracy and precision of the transfer of small densely populated structures, as well as large deprotected areas and micrometer size features, a task that remains one of the most challenging for traditional µCP ( Figure 5). 6 The transferred pattern contains 3000 × 600 nm rods separated by 2000 nm and were produced from stamp structures with 0.042 aspect ratio; these features were accurately and uniformly reproduced over the entire stamped region, indicating the absence of gas diffusion and suggesting an exceptionally low deformation in the patterned acidic stamp. In traditional µCP diffusive wetting results in at least 50 nm ink spreading, even under optimal conditions.…”

Section: Icrocontact Printing (µCp) Was First Introduced Bymentioning

confidence: 91%

Inkless Microcontact Printing on SAMs of Boc- and TBS-Protected Thiols

2009

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We report a new inkless catalytic µCP technique that achieves accurate, fast, and complete pattern reproduction on SAMs of Boc-and TBS-protected thiols immobilized on gold using a polyurethane-acrylate stamp functionalized with covalently bound sulfonic acids. Pattern transfer is complete at room temperature just after one minute of contact and renders sub-200 nm size structures of chemically differentiated SAMs.KEYWORDS Microcontact printing, soft lithography, catalytic lithography M icrocontact printing (µCP) was first introduced by Whitesides and co-workers in 1993 as a new flexographic technique for patterning self-assembled monolayers (SAMs) on metal surfaces. 1-9 It represents the prototypical embodiment of a family of related patterning techniques, collectively termed soft lithography, that make use of conformal contact between a substrate and a flexible stamp as a means of pattern reproduction. 5,8,10 Since its inception, µCP has become a highly successful lowcost printing method that efficiently reproduces high-resolution patterns over large surface areas. During the past 20 years µCP has been successfully utilized to pattern small organic compounds, inorganic substances, biomolecules, and even living cells on a variety of hard materials. Recently, µCP has been used for the fabrication of organic thin film transistors, where it is utilized as an inkjet printing alternative to pattern conductive organic polymers on both hard and flexible substrates. [11][12][13] Although traditional µCP is capable of reproducing features with reasonably high spatial resolution, structures smaller than 300 nm significantly limit the number of possible ink-substrate systems and demand precise control over stamping time, the amount of ink applied, the printing force, and the shape and definition of the stamp pattern. 6,14 In routine applications, several shortcomings of traditional µCP, especially distortion and deformation of the elastomeric stamp, 15,16 and more importantly, spreading of molecular inks by both gas diffusion and diffusive wetting, 17 preclude accurate replication of submicrometer features. Several approaches to minimize ink spreading have recently been developed, through substitution of liquid inks by various solid analogues, such as polymers and metal thin films, [18][19][20][21][22] or by avoiding the use of chemical inks completely and utilizing instead a catalytic reaction between the elastomeric stamp and substrate. [23][24][25][26] The first example of catalytic microcontact printing was reported in 2003 by Reinhoudt et al., who used an oxidized PDMS stamp to deprotect TMS-and TBS-modified SAMs on gold. The method clearly demonstrated the ability of an acidic stamp to deprotect immobilized silyl ethers and reproduce micrometersize features with sub-100 nm edge resolution, although the approach achieved only partial cleavage and required a new stamp for each pattern transfer. 23 Recently, we reported two inkless µCP methods that employ catalysts bound to polymeric stamps to reproduce patterns...

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“…A dvances in nanoscience and technology increasingly rely on unconventional techniques for fabricating structures with nanometer dimensions (1)(2)(3). Patterning methods that have emerged from the microelectronics industry (photolithography, electron beam lithography, and others) are well suited for patterning 2D structures on ultraflat glass or semiconductor surfaces.…”

mentioning

confidence: 99%

Fabricating complex three-dimensional nanostructures with high-resolution conformable phase masks

Jeon

Park

Cirelli

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

285

311

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High-resolution, conformable phase masks provide a means to fabricate, in an experimentally simple manner, classes of 3D nanostructures that are technologically important but difficult to generate in other ways. In this approach, light passing through a phase mask that has features of relief comparable in dimension to the wavelength generates a 3D distribution of intensity that exposes a photopolymer film throughout its thickness. Developing this polymer yields a structure in the geometry of the intensity distribution, with feature sizes as small as 50 nm. Rigorous coupledwave analysis reveals the fundamental aspects of the optics associated with this method; a broad-range 3D nanostructures patterned with it demonstrates its technical capabilities. A nanoporous filter element built inside a microfluidic channel represents one example of the many types of functional devices that can be constructed.

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Printing meets lithography: Soft approaches to high-resolution patterning

Cited by 463 publications

References 91 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

Inkless Microcontact Printing on SAMs of Boc- and TBS-Protected Thiols

Fabricating complex three-dimensional nanostructures with high-resolution conformable phase masks

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