Aluminum surface plasmons

In transmission studies of small aluminum spheres, Batson (22) has shown details of the generation of surface plasmons in the aluminum and in the thin coating oxide layer. Marks (23) and Cowley (24) have examined the surface plasmons and surface state excitations of small MgO smoke crystals. It is clearly evident that these excitations may be produced by electron beams passing the crystal in the vacuum, 3 nm or more away from the surface. 

This condition predicts that N.A. = 1.4 would capture the surface plasmon peak from an aluminum film surface but not from a silver-film surface. Therefore, since objectives with aperture higher than 1.4 are rather rare, an aluminum film is a better choice. 

As an example of extinction by spherical particles in the surface plasmon region, Fig. 12.3 shows calculated results for aluminum spheres using optical constants from the Drude model taking into account the variation of the mean free path with radius by means of (12.23). Figure 9.11 and the attendant discussion have shown that the free-electron model accurately represents the bulk dielectric function of aluminum in the ultraviolet. In contrast with the Qext plot for SiC (Fig. 12.1), we now plot volume-normalized extinction. Because this measure of extinction is independent of radius in the small size... 

Differences in surface plasmon absorption among various metals are clearly revealed by imagining the trajectories to be superposed onto the contour plot . Spherical silver and aluminum particles have intense surface plasmon absorption peaks because t" is small at the frequency where c is - 2, whereas gold... 

Extinction calculations for aluminum spheres and a continuous distribution of ellipsoids (CDE) are compared in Fig. 12.6 the dielectric function was approximated by the Drude formula. The sum rule (12.32) implies that integrated absorption by an aluminum particle in air is nearly independent of its shape a change of shape merely shifts the resonance to another frequency between 0 and 15 eV, the region over which e for aluminum is negative. Thus, a distribution of shapes causes the surface plasmon band to be broadened, the... 

The doped and intrinsic silicon layers (p, i, n) are packed between a TCO front contact and a highly reflective back contact. The back contact is usually either a metal like silver (Ag) or aluminum (Al), or a TCO/metal double layer structure. The latter has been shown to reduce absorption losses due to a better grain growth of Ag layers onto ZnO. Additionally, absorption losses due to surface plasmons in the metal film have to be considered [33]. Both effects result in a higher reflectivity of the TCO/Ag back reflector. In module production, magnetron sputtered ZnO is usually applied as TCO-material for the back reflector in combination with either Ag (highest reflectivity) or Al (low cost). Depending on the deposition sequence of the doped and intrinsic silicon layers, one speaks of so-called superstrate (p-i-n) or substrate (n-i-p) cell structure (see Fig. 8.4). 

Surface plasmons (SPs) are surface electromagnetic waves that propagate parallel along a metal/dielectric interface. For this phenomenon to occur, the real part of the dielectric constant of the metal must be negative, and its magnitude must be greater than that of the dielectric. Thus, only certain metals such as gold, silver, and aluminum are usually used for SPR measurements. The dispersion relation for surface plasmons on a metal surface is ... 

There are three major components of the MAMEF technique 1) plasmonic nanoparticles (i.e., silver, gold, copper, nickel, aluminum, zinc, etc.), 2) microwaves and 3) an aqueous assay medium. TTie plasmonic nanoparticles serve as (i) a platform for the attachment of one of the biorecognition partners (anchor probes) (ii) as an enhancer of the close-proximity fluorescence signatures via surface plasmons (i.e., MEF effect) [2] and (iii) a material not heated by microwaves for the selective heating of the aqueous media with microwave energy. 

Figure 15.18 (Top Left) shows the surface plasmon-coupled chemiluminescence (SPCC) and the fiee-space emission from a blue chemiluminescent dye on a 20 nm aluminum ftiin-film layer. It can be seen that the free-space emission is of much higher magnitude than the SPCC signal. This is...

Spectral dependencies of the effective index, attenuation, and propagation length of a surface plasmon supported by gold, silver and aluminum are shown in Fig. 4. 

Molecule 11 forms amphiphilic Pockels-Langmuir monolayers at the air-water interface, with a collapse pressure of 34 mN m and collapse areas of 50 A at 20 °C these monolayers transfer on the upstroke only, with transfer ratios around 100% onto hydrophilic glass, quartz, or aluminum,or onto fresh hydrophilic Au, but transfer poorly on the downstroke onto graphite, with a transfer ratio of only abont 50%. The LB monolayer thickness of 11 was 23-25 A by X-ray diffraction, spectroscopic ellip-sometry, surface plasmon resonance, and XPS. With... 

Earlier observations by Cesario et al. [60] of a decay in fluorescence for arrays of Au nanoparticles spaced above a Ag film by a Si02 layer of increasing thickness, were interpreted as due to the finite vertical extent of the evanescent fields associated with a surface plasmon. In this model the coupling results in an enhanced interaction between individual localized plasmons at individual nanostructures [61] and thus an enhancement in the radiative efficiency increasing the spacer layer thickness moves the nanowires out of the evanescent field of the surface plasmon. A possible physical mechanism for the experimentally observed decay involves nonradiative decay of the excited states. The aluminum oxide deposited in these experiments was likely to be nonstoichio-metric, and defects in the oxide could act as recombination centers. Thicker oxides would result in higher areal densities of defects, and decay in fluorescence. A definitive assignment of the mechanism for the observed fall off of fluorescence would require determination of the complex dielectric function of our oxides (as deposited onto an Ag film), and inclusion in the field-square calculations. Finally it should be noted that at very small thicknesses quenching of the fluorescence is expected [38,62] consistent with observations of an optimum nanowire-substrate spacer thickness. 

Keywords Deep-UV Surface-enhanced Raman scattering (SERS) Resonance Raman scattering Surface plasmon Aluminum... 

---