Figure 7.

Behavior of the film-coupled nanosphere, assuming a local model and a nonlocal model with various values of β (nonlocal parameter), as a function of the separation distance. Calculations refer to a gold nanosphere of radius r = 30 nm on a 300 nm-thick film. (A) Position of the peak scattering intensity as a function of gap size. (B) Corresponding field enhancement ratio. Notably, in the absence of nonlocal effects, the peak scattering wavelength is extreme, and the field enhancement grows to enormous values; thus, nonlocality places a limit on the ultimate enhancement. Reproduced with permission from ref (108). Copyright 2012 American Association for the Advancement of Science.