Fig. 2

Spectral shift response of the cavity-plasmon resonance for varying the nanowire-film distance. a Typical dark-field scattering spectra of individual 0.5-nm-thick CTAB-covered Au-NWOM systems separated by an Al₂O₃ film with thickness ranging from 5 to 0.5 nm (inset of (b) shows its schematic). The insets show the corresponding dark-field images. b Measured average resonant peak (plasmon resonance energy) of the cavity plasmon of the Au-NWOMs versus the Al₂O₃ thickness. The error bars represent the standard deviation from about ten Au-NWOMs with the nanowire diameters in the range of 45 ± 2 nm