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In this paper, the results of studies on sub-micrometer planar structures used for aimed frequency-dependent electromagnetic radiation dissipation are presented. The proposed specific geometry of periodic parts of surface structures should enable the occurrence of phenomena related to selective reflectance and interference. The inner porous structure should lead to the formation of destructive interference of electromagnetic radiation and its dissipation. The investigated structures were irradiated by a Gaussian-type radiation source. The propagation was analyzed using the MEEP software package for electromagnetic simulation via the finite-difference time-domain method. The reflectance spectra were obtained by the Fourier transform of the response to the short pulse. The obtained results showed that the surface structures are mainly responsible for reflected electromagnetic spectrum composition, while the porous parts were responsible for thermal radiation dissipation. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of systematic studies on optical wave propagation thru a dielectric, perforated waveguide with a variable radius of hole-type defect. Such structures represent photonic crystals-like behaviour due to a finite number of periodic perforations, and their properties are strongly dependent on the geometrical shape of the central irregularity. By changing the radius of this defect, we can show that the resonant mode is trapped and localized at the defect position, while if there is continuity preserved in the perforations, no resonant mode is observed. All calculations were made using finite difference time-domain method. [ABSTRACT FROM AUTHOR]

The results of our studies on the structure and optical properties of In2O3 films deposited by DC magnetron sputtering onto Al2O3 (012) substrates are summarized. The films differ in terms of deposition time and substrate temperature. X-ray diffraction shows that the position and half-width of the peak related to the (222) plane of the cubic modification of In2O3 depends on the deposition time. Ellipsometric and optical transmission measurements show that the refractive index of films deposited on substrates at room temperature increases in the direction from the substrate to the external interface. The refractive index of the films deposited at a substrate temperature of more than 300°C is uniform, except for a rough layer on the surface. Annealing eliminates inhomogeneity of the refractive index and decreases the observed band gap for direct transitions. The latter results from a decrease in lattice defects concentration that causes a change in the Burstein-Moss shift. The true value of the band gap is insensitive to annealing. [ABSTRACT FROM AUTHOR]

The effect of annealing on the optical properties of zinc oxide nanostructures grown by atmospheric pressure metalorganic chemical vapor deposition on silicon substrates covered with a thin film of silver is investigated. It is shown that annealing at temperatures above 600 ℃ significantly reduces the concentration of oxygen vacancies, and as a result, the ratio of the integrated intensity of ultraviolet emission to visible is improved 4.3 times. As a result of further high-temperature annealing at 900 ℃, the excitonic emission peak at 378 nm in the photoluminescence spectra is observed to shift towards larger wavelengths to 380 nm. Simultaneously, a decrease in its half-width from 140 to 100 nm is observed, which indicates an improvement in the structural perfection of ZnO/Ag/Si nanostructures. At the same time, an additional band in the region of 475 nm appeared, which, as we suggest, is due to optical transitions from the levels of shallow donors to the acceptor level created by the diffusion of silver in the lattice of zinc oxide. Annealing of ZnO nanostructures grown on silicon substrates as well as Ag-coated Si substrates improves their structure and optical properties, but unfortunately, this leads to a reduction in the photocatalytic activity of prepared ZnO nanostructures. [ABSTRACT FROM AUTHOR]

In this work, we study the physical properties of hybrid organic/inorganic mixture semiconducting layers. Materials selected for the research were poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4- b0]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] and nanostructured cadmium sulfide (CdS) powder. These materials have been chosen due to their narrow optical band gap combined with high chargecarrier mobility, which makes them interesting for application as components of active layers in bulk p-n heterojunctions. In particular, we present the results of studies on the influence of CdS content on the physical properties of thin hybrid films. The ellipsometric measurements showed that the composition of the base layers influenced their optical properties without significantly influencing their thermal stability. [ABSTRACT FROM AUTHOR]

Structural, optical and rheological properties of pulp and seed extracts of three different avocado cultivars were analyzed using spectroscopy and rheology techniques at room temperature. Ultraviolet spectra and Fourier transform infrared spectroscopy signals for the pulp and avocado seed extracts were recorded in the wavelength range 190-600 nm and the wave number range 4200-400 cm-1, respectively. The flow behaviours for all avocado pulp and seed samples were also analysed in the shear rate range of 10-2-10² s-1 and in the frequency range of 10-1-10³ rad/s, respectively. The ultraviolet spectra of all the samples were observed as two peaks around 210 and 290 nm. The optical energy band gaps for all samples were found to be consistent with Planck's radiation approach. [ABSTRACT FROM AUTHOR]

Ba-doped TiO2 thin films were deposited onto glass substrates by sol-gel spin-coating method and annealed at 550°C for 2 h. The effect of barium doping on the structural, morphological, optical, and photocatalytic properties of TiO2 thin films was investigated. X-ray diffraction analysis revealed that all films crystallize in the anatase phase with the plane (101) as preferential orientation. As a result of the Ba doping, the crystallite size decreased from 19 to 9 nm. The surface morphology and roughness of TiO2 were shown to be affected by Ba doping content using atomic force microscopy. As Ba content increased, the optical transmittance of the films increased to over 85% in the visible region and the gap energy increased from 3.42 to 3.77 eV. Doping by barium enhances the photocatalytic activity of TiO2 film for degradation of rhodamine B under UV light irradiation, and the best performance was found for 3% of Ba:TiO2 film. [ABSTRACT FROM AUTHOR]