Optimization of the particle density to maximize the SERS enhancement factor of periodic plasmonic nanostructure array

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Abstract
Low-cost surface-enhanced Raman scattering (SERS) substrate with the largest possible enhancement factor is highly desirable for SERS-based sensing applications. In this work, we systematically investigated how the density of plasmonic nanostructures affects the intensity of SERS signal. By directly depositing of metallic layer on electron-beam-lithography defined dielectric nanoposts, plasmonic structures array with different densities were reliably fabricated for SERS measurements. Two main experimental phenomena were obtained: (1) the SERS intensity did not increase monotonically when increasing the density of plasmonic structures, and (2) these ultra-dense plasmonic structures resulted in the maximal SERS intensity. These results could be well explained based on finite-difference time domain (FDTD) simulations and provide robust experimental evidences to guide the design of the best possible SERS substrate.
Funding Information
  • Foundation for the Author of National Excellent Doctoral Dissertation of the People's Republic of China (FANEDD) (201318)
  • National Natural Science Foundation of China (NSFC) (61504001)
  • Natural Science Foundation of Hunan Province (2015JJ1008, 2015RS4024)
  • the Beijing Municipal Natural Science Foundation (4162023)

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