Abstract:
The spatial distribution of the electric field of a light wave in ensembles of silicon nanowires (SiNWs) coated with gold nanoparticles (AuNPs) is calculated. It is found that, compared to the case of nanowires without nanoparticles, the electric field of a light wave in a SiNW/AuNP composite structure significantly increases, which is explained by the combined contribution of the enhancement of the local electric fields due to Mie scattering on silicon nanowires and the fields of localized surface plasmons in gold nanoparticles. It is shown that the local field enhancement is nonmonotonic and strongly dependent on the excitation wavelength in the 600 – 800 nm range, which is due to the manifestation of spectral maxima of elastic scattering of the excitation light in the silicon nanowire array. Enhancement also depends on the type of nanoparticle size distribution (monodisperse or lognormal) and is maximal at a nanowire space filling factor of approximately 50%. The obtained results explain the experimental data on giant Raman scattering in SiNW/AuNP structures excited by 633 nm light and point to further opportunities for improving the parameters of semiconductor–metal structures for use in optical molecular sensing methods.
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