Nanoporous plasmonic coatings
- The International Society for Optical Engineering
- Publication Type:
- Maaroof Abbas et al. 2007, 'Nanoporous plasmonic coatings', The International Society for Optical Engineering, USA, pp. 6647OD-1-6647OD-10.
- Issue Date:
The electrical and optical properties of mesoporous gold are compared to those of thin porous gold films and a simulated thin film made by randomly distributing voids in gold, until the voids fill 76% of film volume. All layers are electrically conducting but in some cases the critical percolation thresholds are close to zero, so conduction is possible at very high void content. Significant qualitative differences are apparent between the properties of mesoporous gold, and very thin sputtered gold containing voids, in plasmonic responses at optical frequencies and in dc resistance, both as a function of fill factor. The mesoporous films have an effective plasma frequency determined by void fill factor and structure, but do not support surface plasmons. In contrast thin porous gold layers display optical features associated with localized and de-localized surface plasmons. Sputtered porous gold is 2-dimensional and its percolation threshold requires a "Swiss-cheese" rather than particle cluster model. Thicker mesoporous layers have critical parameters consistent with very high connectivity, or equivalently large hyper-dimensionality. Our meso-gold samples display various hyper-dimensionalities from 3 to above 10.
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