文摘
As a newly discovered surface plasmon resonance system, the nanoparticle dimer–film structure provides a novel approach to enhance light power on a plane film due to the redistribution of the electromagnetic field. This structure has been widely applied in surface enhanced Raman scattering (SERS), solar cells, photocatalysis, etc., especially for the homodimer–film case. However, the properties of heterodimers on film still remain unclear. In this work, the effect of particle size on electromagnetic field redistribution for a Ag nanoparticle dimer on Au film system is investigated first. The results obtained from the finite element method indicate that a smaller nanoparticle has much greater ability to focus light energy on Au film, and the corresponding energy can be 5 times stronger than that of the larger nanoparticle case. Further research indicates that this energy focusing ability has a strong relationship to the wavelength and the diameter ratio of the dimer. A similar focusing phenomenon has been found in the system of thick nanowire–small nanoparticle on film. Then the SERS spectra collected in the small nanoparticle–large nanowire system provide experimental evidence for this theoretical predication. Our results strengthen the understanding of surface plasmon on plane film and have potential applications in surface plasmon related fields.
