High-Resolution Scanning Near-Field Optical Lithography of Conjugated Polymers

 

Nanopatterning techniques are crucial to realising the potential of nanoscience and nanotechnology in areas spanning from nanomedicine to photonics, electronics, and quantum computing.

At the London Centre for Nanotechnology the group of Franco Cacialli has produced complex patterns of conjugated polymers, of at least 65,000 dots, via Scanning Near-field Optical Lithography (SNOL) over areas of several 100ths of square microns. In this technique light from a tiny tip is used to produce a local chemical modification as it is scanned across the surface.

They have demonstrated the possibility of patterning films of conjugated polymers down to ~55 nm lateral resolutions for thicknesses of ~ 15 nm. These results are obtained on non-metallic substrates, thereby offering greater versatility of application.
The method can be applied to a wide range of conjugated polymers. For example, the molecules might have attached to them chemical groups which form bridges between them when exposed to light (Winroth et al APL 2008). The present work demonstrates the versatility of the method by patterning polyfluorenes that have been functionalised with an oxetane side chain. Work on the nanostructural properties of "soft matter" is of increasingly wider relevance in connection with biopolymers. Indeed the techniques reported here also have potential for biopolymer nanopatterning.

D. Credgington, O. Fenwick, A. Charas, J. Morgado, K. Suhling and F. Cacialli.
Adv. Funct. Mat. (2010). http://dx.doi.org/10.1002/adfm.201000202

a) AFM image of our institution's logo (~65000 pixels). Precursor film thickness ~15 nm and exposure through a 50 nm probe aperture (λ = 325 nm). (b) AFM scan of the area highlighted in (a). (c) AFM image zoomed-in to highlight the smallest features of the design, with 2 representative cross-sections defined. (d,e) cross sections, showing typical feature size ~ 60 nm

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