11 September 2007 Fabrication of sub-diffraction-limit molecular structures by scanning near-field photolithography
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Using a scanning near-field optical microscope coupled to a UV laser, an approach we term scanning near-field photolithography (SNP), structures as small as 9 nm (ca. λ/30) may be fabricated in self-assembled monolayers of alkanethiols on gold surfaces. Selective exposure of the adsorbate molecules in the near field leads to photoconversion of the alkylthiolate to a weakly bound alkylsulfonate which may be displaced readily be a contrasting thiol, leading to a chemical pattern, or used as a resist for the selective etching of the underlying metal. A novel ultra-mild etch for gold is reported, and used to etch structures as small as 9 nm. Photopatterning of oligo(ethylene glycol) (OEG) terminated selfassembled monolayers facilitates the fabrication of biomolecular nanostructures. Selective removal of the protein-resistant OEG terminated adsorbates created regions that may be functionalized with a second thiol and derivatized with a biomolecule. Finally, the application of SNP to nanopatterning on oxide surfaces is demonstrated. Selective exposure of monolayers of phosphonic acids adsorbed onto aluminum oxide leads to cleavage of the P-C bond and desorption of the adsorbate molecule. Subsequent etching, using aqueous based, yields structures as small as 100 nm.
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Robert E. Ducker, Robert E. Ducker, Matthew T. Montague, Matthew T. Montague, Shuqing Sun, Shuqing Sun, Graham J. Leggett, Graham J. Leggett, "Fabrication of sub-diffraction-limit molecular structures by scanning near-field photolithography", Proc. SPIE 6645, Nanoengineering: Fabrication, Properties, Optics, and Devices IV, 664513 (11 September 2007); doi: 10.1117/12.735801; https://doi.org/10.1117/12.735801

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