Fig. 1. (a) Schematic of Au nanosphere dimer-on-film nanocavity (DoFN) composed of the Au nanosphere dimer and Au film spaced by the monolayer MoS2 and Al2O3. (b) Bright- and (c) dark-field images of the Au dimer DoFNs. The white boxes denote the Au dimer measured in the optical setups. (d) SEM image of the DoFN. (e) Raman spectrum of the monolayer MoS2 taken nearby the dimer.

Fig. 2. (a)–(d) Scattering spectra of Au nanosphere DoFNs illuminated with two typical wave vectors and polarizations shown in the insets of left panels. Here, the left and right panels are for the experiment and simulation results, respectively.

Fig. 3. (a)–(f) Charge distributions (upper panels) and electric field enhancement maps (lower panels) of modes I–VI shown in Fig. 2.

Fig. 4. (a) Photoluminescence (PL) spectra of MoS2 around the DoFNs (red and blue curves for polarization along and perpendicular to dimer axis, respectively) and on bare Au film (black curve with 8× magnification). (b) Polarization dependence of the PL peak intensity. Insets in (a) and (b) are the quantum yield enhancement at 685 nm and PL excitation configuration, respectively.