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Thermochemical nanopatterning of organic semiconductors

Abstract

Patterning of semiconducting polymers on surfaces is important for various applications in nanoelectronics and nanophotonics. However, many of the approaches to nanolithography that are used to pattern inorganic materials are too harsh for organic semiconductors, so research has focused on optical patterning1,2,3 and various soft lithographies4. Surprisingly little attention has been paid to thermal5, thermomechanical6,7 and thermochemical8,9,10,11,12,13 patterning. Here, we demonstrate thermochemical nanopatterning of poly(p-phenylene vinylene), a widely used electroluminescent polymer14, by a scanning probe. We produce patterned structures with dimensions below 28 nm, although the tip of the probe has a diameter of 5 µm, and achieve write speeds of 100 µm s−1. Experiments show that a resolution of 28 nm is possible when the tip–sample contact region has dimensions of 100 nm and, on the basis of finite-element modelling, we predict that the resolution could be improved by using a thinner resist layer and an optimized probe. Thermochemical lithography offers a versatile, reliable and general nanopatterning technique because a large number of optical materials, including many commercial crosslinker additives and photoresists, rely on chemical mechanisms that can also be thermally activated8,15,16.

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Figure 1: Thermochemical nanopatterning.
Figure 2: Nanopatterning of organic semiconductors.
Figure 3: Thermal analysis and cross-sections.
Figure 4: Finite-element simulation of thermal profiles and ultimate resolutions.

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Acknowledgements

The authors dedicate this paper to Dr Azzedine Hammiche, who passed away in May 2008, after contributing to this work. L.B. was funded from a Wellcome Trust Programme grant to M.A. Horton (UCL). This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) and the EU Sixth Framework Programme (ERAS-CT-2003-980409) as part of the European Science Foundation EUROCORES Programme on Self-Organized NanoStructures (SONS). Thanks also go to the EPSRC (DTA studentship to D.C.) and the Royal Society for financial support. The authors thank S. Nesbitt for assistance with the fluorescence imaging and M. Stoneham for useful discussions.

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Contributions

F.C. conceived the lithographic experiments, which were performed by O.F., L.B., D.C. and A.H. Atomic force microscopy of lithographic structures and micro-thermal analysis of the precursor material were conducted by O.F., and the confocal microscopy was performed jointly between Y.S. and O.F. O.F. and G.M.L. built the finite element model. The paper was written by O.F. and F.C. in consultation with all authors.

Corresponding author

Correspondence to Franco Cacialli.

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Fenwick, O., Bozec, L., Credgington, D. et al. Thermochemical nanopatterning of organic semiconductors. Nature Nanotech 4, 664–668 (2009). https://doi.org/10.1038/nnano.2009.254

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