The increased LFE and hot-spot areas are associated with the increased tips in the multilayer structure and the intra-particle coupling among the Au crescents. Results also show that further intensified LFE can be achieved using semiconductor materials instead of dielectrics, due to the charge transport at the metal-semiconductor interface.

Advantages of cylinder-based tuning

Compared with changing the size of the independent metallic crescent, the unique cylinder-based tuning technique has several advantages. First, the plasmon band can be tuned over a wider range. For example, the plasmon peak can be tuned into the NIR regime for in vivo detection, and even into the MIR regime for catching some specific targets. Second, the band tuning is more precise since the cylinder can be fabricated by photolithography, which is suitable for preparing reproducible devices with well controlled parameters. Finally, tuning by changing the cylinder material rather than the size resolves the conflict between the red-shift of the resonance peak and a decrease in LFE, as an increase in radiation loss can be fully avoided when the size of the crescent is fixed.

All of these benefits suggest that the multilayer Au/dielectric/Au nanocrescent structure has valuable potential in a variety of applications such as diagnostics and in vivo nanoscale spectroscopy.

Having performed the numerical study, the team is now working on the fabrication of the multilayer Au/dielectric/Au nanocrescent structure.

More details can be found in the journal Nanotechnology.