The incorporation of metal clusters into thin organic dye layers as a method for producing strongly absorbing composite layers: an oscillator model approach to resonant metal cluster absorption

Abstract

We present data on the NIWVIS/UV optical constants of thin composite layers. built up from a copper phthalocyanine matrix with embedded metal clusters.The metal clusters (copper, gold and silver) have diameters on a nanometre scale and act as strong absorption centres. In particular, local plasmon resonances and metal interband transitions could be obselved from a fit of the experimentally determined dielectric functions by means of a Lorentzian multi-oscillator model Average dipole transition matrix elements with respect to a single metal cluster have been estimated from the oscillator parameters.

Metal-dielectric composite optical coatings: underlying physics, main models, characterization, design and application aspects

“…Concerning film characterization, metal island films turn out to be accessible to both spectrophotometric and spectroellipsometric measurements, as shown by relevant studies [17,18] . In this regard, full compatibility to conventional coating characterization technology is also guaranteed.…”

Comparison of two techniques for reliable characterization of thin metal–dielectric films

“…The reason is that in random metaldielectric composites, particles present a size and shape distribution and one may expect that the absorption is due to a distribution of resonances rather than to a single resonance. Assuming a Gaussian distribution of resonances and that the width of this distribution is large enough, the imaginary part of the dielectric function may present a Gaussian line shape [23,37]. In this case the dielectric function is written in the following way:…”

“…The most popular technique is based on a well-known oscillator model [23][24][25]. However, wavelength dependencies of the optical constants of thin metal-dielectric films in the visible and infrared spectral ranges are quite complicated [1,[7][8][9]13,[26][27][28], and multiple oscillator models have to be used.…”

“…However, wavelength dependencies of the optical constants of thin metal-dielectric films in the visible and infrared spectral ranges are quite complicated [1,[7][8][9]13,[26][27][28], and multiple oscillator models have to be used. Because each oscillator is defined by several parameters, a large number of parameters has to be determined in the course of the characterization process using a multiple oscillator model [23][24][25]29].…”

“…The use of the multiple oscillator model requires knowledge on the material structure, as the optical constants' dispersion is strongly dependent on the composite arrangement: composites consisting of isolated metal clusters are characterized by large absorption within some limited spectral range due to the surface plasmon resonance phenomena [23,25], while composites with a percolated metal phase show metal-like behavior [25,29]. Thus, in a general case, the choice of the number of required oscillators and an initial guess for parameter values are not straightforward tasks.…”