Table 1.

Approximate maximum values for the electromagnetic enhancement ($G_{SERS}^{Em}$) and for the chemical enhancement ($G_{SERS}^{Chem}$). Reproduced with permission from Pilot et al. [81]. Copyright (2018), Springer International Publishing AG.

${\mathit{G}}_{\mathit{S}\mathit{E}\mathit{R}\mathit{S}}$	Approx. Max. Value	Note	Ref.
$G_{SERS}^{Em}$	${10}^8$	Averaged over the substrate	[16,115]
$G_{SERS}^{Em}$	${10}^{10}$	In a hot spot	[116]
$G_{SERS}^{Chem}$	${10}^2$	Atomic scale roughness	[5,10,115,117]
$G_{SERS}^{Chem}$	${10}^4$	Charge transfer resonance	[9]