Understanding the plasmonics of nanostructured atomic force microscopy tips


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Authors
Sanders, A 
Bowman, RW 
Zhang, L 
Turek, V 
Sigle, DO 
Abstract

Structured metallic tips are increasingly important for optical spectroscopies such as tip-enhanced Raman spectroscopy, with plasmonic resonances frequently cited as a mechanism for electric field enhancement. We probe the local optical response of sharp and spherical-tipped atomic force microscopy (AFM) tips using a scanning hyperspectral imaging technique to identify the plasmonic behaviour. Localised surface plasmon resonances which radiatively couple with far-field light are found only for spherical AFM tips, with little response for sharp AFM tips, in agreement with numerical simulations of the near-field response. The precise tip geometry is thus crucial for plasmon-enhanced spectroscopies, and the typical sharp cones are not preferred.

Description
Keywords
physics.optics, physics.optics
Journal Title
Applied Physics Letters
Conference Name
Journal ISSN
0003-6951
1077-3118
Volume Title
109
Publisher
American Institute of Physics
Sponsorship
Engineering and Physical Sciences Research Council (EP/G060649/1)
Engineering and Physical Sciences Research Council (EP/L027151/1)
European Research Council (320503)
Engineering and Physical Sciences Research Council (EP/K028510/1)
The authors thank EPSRC Grant Nos. EP/G060649/1, EP/K028510/1, and EP/L027151/1, and ERC Grant No. LINASS 320503 for funding and NanoTools for their services providing Au-coated spherical AFM tips. R.W.B. thanks Queens' College and the Royal Commission for the Exhibition of 1851 for financial support.
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