Abstract
In situ real-time spectroscopic ellipsometry is used to monitorthe growth of magnetron sputtered silver nanoparticles onSiO2 substrates, through the percolation threshold and into the bulk film regime. Theplasmon polariton resonances in the nanoparticulate regime are effectively modelledby a Lorentz oscillator. The resonance energy of the oscillator is observed toreduce to zero shortly after the percolation threshold, whereby the oscillation isdescribed by Drude free electron theory. From the Drude theory, the electronic meanfree path is observed to increase dramatically at the percolation threshold, toa value of 16 nm in the bulk regime, in good agreement with x-ray diffractionand transmission electron microscope measurements of the crystallite size in thefilms. Shortly before the percolation threshold the data is better modelled by twoLorentz oscillators, attributed to coupling between the plasmon polaritons. Theonset of the coupling is determined to occur at a surface area coverage of 52%.
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