Study of Surface plasmon resonance of Au nanoparticles coated with dielectric layers

In this work, atomic layer deposition (ALD) was used to deposit different thickness layers of Al2O3 on Au nanoparticles fabricated by thermal annealing of Au thin films. The effects of the Au-coated Al2O3 layer thickness variation to local surface plasmon resonance (LSPR) in gold (Au) nanoparticles was investigated using transmission surface plasmon resonance (T-SPR) spectroscopy. Thermal annealing of ultrathin films of Au sputtered on transparent substrates can get a dispersed metal particles system which exhibit transmission spectra showing an extinction band attributed to localized surface plasmon resonance (LSPR). The particles prepared by thermal annealing are much more like elliptical rather than sphere. The dielectric medium layer Al2O3 was deposited on these Au particles with the thickness from few nanometers to tens of nanometers by ALD. We found that All the LSPR peak positions of particles on different substrates red shifted as the thickness of deposition layer increase, but the LSPR red-shift effect of particles on alumina substrate was much more remarkable than particles on glass substrate. The results in this paper show that it is a very continent method to manipulate LSPR position which is a profound useful effect in solar cell application by controlling the deposition layer thickness on particles prepared by thermal annealing on suitable substrate.