Gap Size Reduction and Increased SERS Enhancement in Lithographically Patterned Nanoparticle Arrays by Templated Growth

Authors

  • Virginia Merk,

    Corresponding author
    1. Humboldt-Universität zu Berlin, Department of Chemistry, Berlin, Germany
    2. BAM Federal Institute for Materials Research and Testing, Berlin, Germany
    • Science Institute, University of Iceland, Reykjavik, Iceland
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  • Janina Kneipp,

    1. Humboldt-Universität zu Berlin, Department of Chemistry, Berlin, Germany
    2. BAM Federal Institute for Materials Research and Testing, Berlin, Germany
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  • Kristjan Leosson

    1. Science Institute, University of Iceland, Reykjavik, Iceland
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E-mail: virginia@hi.is

Abstract

A general method for reducing interparticle gap size in lithographically patterned metal particle arrays is introduced. Dense gold nanoparticle arrays are fabricated by electron beam lithography and the patterned structure is subsequently covered with thin layers of gold and annealed at a high temperature. This results in ripening of the initially patterned particles and in reduced interparticle distances, as well as in an improvement in the optical properties through gold recrystallization and grain growth. At intermediate processing steps, a distinctly bimodal particle distribution can be realized for effective nanofocusing of incident radiation into a high density of hotspots. 3D finite-difference time domain simulations and surface-enhanced Raman scattering experiments confirm that high local electric fields arise in such structures, resulting in enhancement of the Raman signals on the order of 106. This combination of lithographic patterning and self-assembly can be used to obtain novel plasmonic nanostructures that cannot be directly fabricated by other means.

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