We demonstrate an effective method for depositing smooth silver (Ag) films on SiO(2)/Si(100) substrates using a thin seed layer of evaporated germanium (Ge). The deposited Ag films exhibit smaller root-mean-square surface roughness, narrower peak-to-valley surface topological height distribution, smaller grain-size distribution, and smaller sheet resistance in comparison to those of Ag films directly deposited on SiO(2)/Si(100) substrates. Optically thin ( approximately 10-20 nm) Ag films deposited with approximately 1-2 nm Ge nucleation layers show more than an order of magnitude improvement in the surface roughness. The presence of the thin layer of Ge changes the growth kinetics (nucleation and evolution) of the electron-beam-evaporated Ag, leading to Ag films with smooth surface morphology and high electrical conductivity. The demonstrated Ag thin films are very promising for large-scale applications as molecular anchors, optical metamaterials, plasmonic devices, and several areas of nanophotonics.

Cathodoluminescence spectroscopy has been performed on silver nanoparticles in a scanning electron microscopy setup. Peaks appearing in the visible range for particles fabricated on silicon substrate are shown to arrive from excitation of out of plane eigenmodes by the electron beam. Monochromatic emission maps have been shown to resolve spatial field variation of resonant plasmon mode on length scale smaller than 25nm. Finite-difference time-domain numerical simulations are performed for both the cases of light excitation and electron excitation. The results of radiative emission under electron excitation show an excellent agreement with experiments. A complete vectorial description of induced field is given, which complements the information obtained from experiments.

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We show by pump-probe spectroscopy that the optical response of a fishnet metamaterial can be modulated on the femtosecond time scale. The modulation dynamics is dominated by pump-induced changes in the constituting dielectric medium, but the strength of modulation is dramatically enhanced through the plasmon resonance. The pump-induced spectral responses of the metamaterial provide understanding on how the resonance is modified by pump excitation. Our study suggests that metamaterials can be used as high-speed amplitude/phase modulators with terahertz-bandwidth.