Optical properties of thin semicontinuous gold films over a wavelength range of 2.5 to 500 μm

Percolation in nanoporous gold and the principle of universality for two-dimensional to hyperdimensional networks

“…Resistivity is also measured in the plane of the films. Thus we will put the possible complexities of anisotropy aside for thus study, assume in plane anisotropy and use the f and L values predicted by equation (4). An additional check on this approach comes from the ability to also optically fit effective layer thickness t using this basic model, since t has been measured independently on some samples using SEM cross-sections as shown in figure 1b.…”

“…The application of percolation theory to experimental materials has been predominantly for dc and ac electrical data on composites made from powders [17][18][19], while natural structures such as porous rocks [20] and sea ice [21] have also been studied. Optical studies of metal percolation exist [2,4,[22][23][24], but since the farfield spectral transition is more gradual, have received much less attention. Nevertheless percolation has a unique optical signature.…”

“…At shorter deposition times these films consist of islands of metal, and at longer times connected labyrinths of metal envelop remaining voids, which gradually close up with further deposition. The thickness ranges in these studies for metals such as gold and silver are typically below 8 to 14 nm for deposition onto room temperature glass substrates, with some variations in critical mass and thickness according to the energetics of the deposition process [1][2][3][4][5]. These percolating granular films are random networks and their voids traverse the film from one side to the other.…”

“…Nevertheless percolation has a unique optical signature. Thin metal films in the early stages of growth [2][3][4] and nanostructured cermets [23,24] have been the main focus for the influence of percolation on optical response. Recent interest in nano-plasmonics has included fascinating data on near-field optical response in 2-dimensional thin metal films close to percolation [25,26].…”

Electromagnetic field fluctuations and optical nonlinearities in metal-dielectric composites

“…[38]). Note that for semicontinuous metallic "lms at p"p A the transmittance "¹" +0.25 in a wide spectral range from the visible to the far infrared spectral range [85]. The average surface current 1 j2 is related to the average electric "eld 1E2 through the Ohm's law; in thin "lms it takes the following form 1 j2"a 1E2"a ¹E , where "!i / (4 ) is the e!ective conductivity, and thickness of the "lm is approximated by the size a of a metal grain.…”