Fig. 4

Spectral measurements and analysis of electroluminescence from SC Au plasmonic nanogap devices and Schematics of physical mechanism underlying the observed large enhancement in hot carrier tunneling current. a Measured light emission spectra at different bias. Inset shows the extracted surface plasmon modes through a normalization analysis. b Normalized spectra plotted on logarithmic scale versus the photon energy. Extracted effective temperatures of the hot carriers are shown in the legends. c Extracted effective temperatures vs. applied voltage bias for three different materials. d Photon yield comparison between SC Au (points) and PC Au and PC Au/Cr (density plots). e SC Au showing defect-free nanostructures that suppress electron-phonon scattering and increase the mean free path (L_SC) of hot carriers. f PC Au showing reduced hot carrier mean free path (L_PC) due to enhanced electron-phonon scattering