In this work is studied the influence of annealing on metal island and compact Au films formed on the substrates with and without Ge seed layer. Samples with different thicknesses of Au were annealed at different temperatures. Optical characterization of the samples was performed based on ellipsometric measurements. The obtained results demonstrate that, even in the conditions of moderately elevated temperature, Ge seed layer promotes the percolation of metal islands.
Dark plasmon modes in metal nanoparticle systems are usually excited by non-optical means. We show that strongly focused illumination can lead to excitation of dark modes. We first use rigorous vectorial diffraction theory to compute the distribution of light at the focus and then numerically calculate the response of single particles and particle dimers. Controlling the distribution of light arriving at the focusing lens by pupil filters enables enhancing the excitation of dark modes. Overall, these results present guidelines for the excitation of dark plasmon modes using standard optical instrumentation.
Thin metal island films exhibit unique optical properties and possess a high potential in design and fabrication of
multilayer coatings with sophisticated spectral performances over wide wavelength and angular ranges. Optical
properties of these films are dependent on film thickness. In the present study we consider and solve a problem
of designing multilayers which reflect different colors from their front and back sides and have specified average
transmittance values. Additionally, in many cases the reflected colors are stable to variations of the incidence
angle. In the design process we use optical constants of Ag metal island films, that were carefully determined
based on recently proposed characterization approach.
The influence of the substrate temperature on the effective optical behavior of Ag-SiO2 composites obtained by electron beam evaporation was studied. Optical characterization of the composites was performed by means of spectroscopic ellipsometry measurements. The effective dielectric function of the composites, modeled using a multiple oscillator approach, could be widely tuned by controlling the deposition temperature. The spectral dependence of the composite absorption appeared to be better described with a Gaussian line shape than with the classical Lorentz oscillator model. The description of the effective dielectric function using standard effective medium theories failed and the experimental results could be explained only in the general framework of the Bergman spectral density theory.
Metal island films show unique optical properties owing to the local surface plasmon resonance of islands free electrons.
In the present study, the electric field assisted dissolution of clusters in metal island films is reported. Island films of Au,
Ag, and Cu are deposited under different conditions by thermal evaporation and coated with thin dielectric layers. The
samples are treated with the simultaneous application of an intense electric field and temperature, leading to the sample
partial or total bleaching due to the dissolution of metal clusters in the films. Owing the facility of production of metal
island films and the inexpensive technical requirements of the dissolution process, this approach suggests a novel path
for the production of low-cost photonic structures.
During the last few years, refractive index profiles are being studied more intensively. Several papers have been written about the use of optical methods, spectrophotometry, ellipsometry, together with reverse engineering, these have yielded interesting results. Here we study the differences of a ZrO2 film grown on an amorphous substrate and that of a pre-evaporated layer of another material, Y2O3. In the first run, two glass substrates have been coated with an Y2O3 layer. In the second run a bare glass substrate and the pre-coated Y2O3 have been coated with a ZrO2 layer. Each of the materials used had exactly the same growth conditions for all layers. The only difference was the nature of the substrates. The spectra of R and T of both samples have been used for the optical characterisation. Multisample analysis with gradual introduction of new parameters has been carried out. It was found that for the appropriate modelling of the layer, grown on the pre-coated substrate, introduction of an interface layer between the two materials was necessary. The refractive index profiles of both ZrO2 layers have been determined and discussed.
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