Metal island films

The first SERS experiments were performed with electrochemically roughened electrodes and metal colloids, and many other types of suitable SERS substrates are known - e.g. metal island films, metal films over nanoparticles (see Fig. 4.58, below) or rough substrates, gratings, and sputter-deposited metal particles. 

Metal island films form spontaneously during slow evaporation of the metal on to supports with low adhesion. The metal islands can produce the surface-enhancement required for Raman characterization of the surface of the support. 

Figure 3. Various type of SERS active metallic nanostructures (a) metal-island films (b) metal-coated nanospheres (semi-nanoshells) (c) metal-coated random nanostructures and (d) polymer coatings embedded with metal nanoparticles. Inset An SEM image of silver-coated polystyrene spheres.

In order to investigate molecules adsorbed at the solid-liquid interface roughened electrode surfaces or metal colloids in solution (sols) are prepared. For investigations of the solid-gas or solid-vapour interface several methods are available to produce metal island films on SERS-active substrates. 

Furthermore, it is possible to increase the sensitivity of the IR technique, and thus the probability of detecting transient surface species characterized by (very) low absorption coefficients (such as the intermediate species present during the first steps of the polymerization reaction on the Phillips catalyst) by exploiting the surface-enhanced infrared absorption (SEIRA) effect. It is known that molecules adsorbed on metal island films or particles exhibit 10-1000 times more intense infrared absorption than would be expected from conventional measurements without the metal (253-256). The possibility of performing SEIRA spectroscopy should therefore be expected to provide an opportunity to better investigate the nature of the intermediate species, not only for ethene polymerization on Cr(II)/ Si02, but for other reactions on solid catalysts. 

Although the connection between SERS and SPPs is established in (1.2), how to effectively produce desirable SERS on a given metallic structure remains challenging. To address this issue, different plasmonic systems at different dimensionalities have been proposed, fabricated, and characterized with the same intention to maximize the local field strength at cOexc and cors [13-16]. A variety of structures have been found to support SERS well, including roughened metal electrodes, metal nanoparticles colloids, metal island films, metal nanorods, etc., or more specifically, substrates that contain nanoscale gaps or hotspots are particularly... 

SIERA Surface-enhanced infrared absorption As in the case of surface-enhanced Raman scattering (SERS), molecules adsorbed on metal island films or particles exhibit intense infrared absorption several folds higher than what one would expect from conventional measurements without the metal. This effect is referred to as surface-enhanced infrared absorption (SEIRA). 

Kovacs, G.J., Loutfy, R.O., Vincett, P.S., Jennings, C., and Aroca, R. (1986) Distance dependence of SERS enhancement factor from Langmuir-Blodgett monolayers on metal island films evidence for the electromagnetic mechanism. Langmuir, 2, 689-694. 

Jensen TR, Van Duyne RP, Johnson SA, Maroni VA (2000) Surface-enhanced infrared spectroscopy a comparison of metal island films with discrete and nondiscrete surface plasmons. Appl Spectrosc 54 371-377... 

Specific substrates like, e.g., metallic island films or metallic wires, may show a SEIRA effect. In combination with a device, this effect can enhance the detection sensitivity. 

Metal island films of controlled mass thickness are deposited in a commercial vacuum system evaporator using a glow discharge evaporation unit. The metal island films are in general fabricated onto preheated glass substrates. The film thickness is monitored using a commercial quartz crystal microbalance. 

Jennings, C.A., J. Kovac, and R. Aroca (1992). Near-infrared surface-enhanced Raman scattering from metal island films. J. Phys. Chem. 96, 1340. 

T Nakano, K Baba, M Miyagi. Coupler-type waveguide polarizer using metal island films its mechanism and design Electronics Letters, vol.29, no.6, pp.536-8,1993. 

A. Leitner, Z. Zhao, H. Brunner, F. Aussenegg and A. Wokaun Optical properties of a metal island film close to a smooth metal surface". Applied Optics 32,102 (1993). 

C. Y. Chen and E. Burstein, Giant Raman Scattering by Molecules at Metal-Island Films, Phys. Rev. Lett. 

R. Aroca and F. Martin, Tuning Metal Island Films for Maximum Surface Enhanced Raman Scattering., /... 

Photochemistry and luminescence of adsorbates near metal-island films, J. Chem Phys. 81, 5189-5200(1984). 

Aussenegg, F., Leitner, A., and Gold, H. (1995). Optical second-harmonic generation of metal-island films. Appl. Phys. A, 60 97 -101. 

A., Liao, P., and Olson, D. (1981). Surface second-harmonic generation fi om metal island films and microlithographic structures. Phys. Rev. B, 24 849 - 856. 

Orfanides, P., Buckner, T.F., Bundck, M.C., Meriaudeau, F. and Ferrell, T.L (2000) Demonstration of surface plasmons in metal island films and the effect of the surrounding medium an undergraduate experiment American Journal of Physics, 68, 936—42. 

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