Abstract
We present computational studies of quasi three-dimensional nanowell (NW) and nanopost (NP) plasmonic crystals for applications in surface enhanced Raman spectroscopy (SERS). The NW and NP plasmonic crystals are metal coated arrays of cylindrical voids or posts, respectively, in a dielectric substrate characterized by a well/post diameter (D), relief depth (), periodicity (P), and metal thickness (). Each plasmonic crystal is modeled using the three-dimensional finite-difference time-domain (FDTD) method with periodic boundary conditions in the x- and y-directions applied to a computational unit cell to simulate the effect of a periodic array. Relative SERS responses are calculated from time-averaged electric field intensity enhancements at and or at via or , respectively, where . Comparisons of and are made to previously reported experimental SERS measurements for NW and NP geometries. Optimized NW and NP configurations based on variations of D, P, , and using are presented, with 6× and 2× predicted increases in SERS, respectively. A novel plasmonic crystal based on square NP geometries are considered with an additional 3× increase over the optimized cylindrical NP geometry. NW geometries with imbedded spherical gold nanoparticles are considered, with 10× to 10 increases in SERS responses over the NW geometry alone. The results promote the use of FDTD as a viable in silico route to the design and optimization of SERS active devices.
Highlights
Surface enhanced Raman spectroscopy (SERS) employing metallic nanostructures is a well studied phenomenon that arises predominantly from large electric field intensity enhancements when light is incident on a metal that supports surface plasmons (SPs) [1,2,3]
A novel plasmonic crystal based on square NP geometries are considered with an additional 3× increase over the optimized cylindrical NP geometry
Time-averaged electric field intensity enhancements were calculated for λ = 785, 821, and 857 nm using the finite-difference time-domain (FDTD) method for a series of nanowell (NW, Figure 1a) and cylindrical nanopost (NP, Figure 1b) geometries
Summary
Surface enhanced Raman spectroscopy (SERS) employing metallic nanostructures is a well studied phenomenon that arises predominantly from large electric field intensity enhancements when light is incident on a metal that supports surface plasmons (SPs) [1,2,3]. Incident light resonant with the plasmon frequency can excite the SP within the metal, giving rise to sub-wavelength field confinement and intensity enhancements, defined hereafter as g2 =|E|2 /|E0 |2 , where |E| and |E0 |are the magnitudes of the total and incident electric field, respectively. Molecules that traverse the SP field experience enhanced absorption of light proportional to the enhancement factor at the excitation frequency,. And enhanced Raman scattering proportional to the enhancement factor at the Raman scattered gexc.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
