Fig. 3: Gap-dependence of PL.
From: Non-thermal emission in gap-mode plasmon photoluminescence
a Tuning and matching of gap-mode plasmon resonances among various SiO2 spacer gap thicknesses. The resonant energies are equal to the laser energy for maximum absorption. b Photoluminescence (PL) power-law exponents (PLE) vs emitted photon energy, for the labeled values of \({d}_{{{{{{{{{\rm{SiO}}}}}}}}}_{{{{{{{{\rm{2}}}}}}}}}}\). Smooth curves are fits, as described in the text. c, d PLE dependence on emitted photon energy for \({d}_{{{{{{{{{\rm{SiO}}}}}}}}}_{{{{{{{{\rm{2}}}}}}}}}}=3\) nm. Smooth curves in (c) are dependences expected for different nonlinear PL (NPL) emission mechanisms: “hot” Raman emission (blue), intraband “hot” electron emission (red), two-photon interband PL (2PPL) emission (yellow), and non-thermal emission (purple). Smooth curves in (d) are dependences expected for hybrid “hot” electron NPL emission mechanisms: “hot” electron/"hot” Raman scattering (blue), “hot” electron/2PPL (yellow), “hot” electron/non-thermal (purple). e Fitting parameters obtained from hybrid “hot” electron/non-thermal fitting of gap PLE in (b). f Extracted ratios of the relative contributions of thermal to non-thermal (thermal:non-thermal) electronic distributions from the emitted light as a function of gap size.
