Wyniki wyszukiwania - BazTech

1

Investigations of optical and thermal properties of surface layers of Cd1-xBexTe samples by the photoacoustic method

Bychto Leszek, Maliński Mirosław, Chrobak Łukasz, Zakrzewski Jacek, Boumhamdi Mohammed

Opto-Electronics Review

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2024

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Vol. 32, No. 2

art. no. e150186

EN

The work presents the results of a research on the photoacoustic spectra of thin surface layers of Cd₁-xBexTe crystals formed by grinding and polishing their surfaces. As a result of matching the theoretical and experimental photoacoustic spectra, thermal and optical parameters of these layers were determined. Thermal parameters of the surface layers, such as thermal conductivity and thermal diffusivity, turned out to be much worse than the analogous parameters of the substrate. The increase in the optical absorption of surface layers for photon energies below Eg was also determined.

2

Estimation of optical parameters of silicon single crystals with different orientations

El-Nahass M. M., Ali H. A. M.

Materials Science Poland

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2019

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Vol. 37, No. 1

65--70

EN

Optical properties of Si single crystals with different orientations (1 0 0) and (1 1 1) were investigated using spectrophotometric measurements in a spectral range of 200 nm to 2500 nm. The data of optical absorption revealed an indirect allowed transition with energy gap of 1.1 ± 0.025 eV. An anomalous dispersion in addition to a normal dispersion was observed in the spectra of refractive index. The normal dispersion of the refractive index was discussed according to Wemple-DiDomenico single oscillator model. The oscillator energy Eo, dispersion energy Ed, high frequency dielectric constant ϵ∞, lattice dielectric constant ϵL and electronic polarizability αe were estimated. The real ϵ1 and imaginary ϵ2 parts of dielectric constant were also determined.

3

Determination of the efficiency factors of the absorption and scattering of nickel nanoparticles

Machulianskyi O., Babych B., Machulianskyi V.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2018

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T. 8, nr 1

4--7

EN

In the dipole approximation for the spherical nickel nanoparticle with a diameter D0 = 2.5 ÷ 7 nm in the spectral range from 0.2 to 1.1 μm at T = 300 K, efficiency factors of the absorption Κa and scattering Κs were determined with the help of the experimental values of the complex specific electrical polarizability. Numerical calculations of the Κa and Κs of the nickel nanoparticles were carried out in accordance with the theories of classical and quantum dimensional effects. It was shown that it is impossible to explain the photoabsorption of nickel nanoparticles by the intraband (Drude) type of absorption even taking into account classical or quantum dimensional effects.

PL

Na podstawie wartości eksperymentalnych zespolonej właściwej polaryzacji elektrycznej zostały wyznaczone współczynniki efektywności absorpcji Κa i rozpraszania Κs w przybliżeniu dipolowym dla sferycznej nanocząstki niklu o średnicy D0 = 2,5 ÷ 7 nm w zakresie spektralnym od 0,2 do 1,1 μm przy T = 300 K. Wykonano obliczenia numeryczne Κa i Κs nanocząstek niklu na podstawie teorii efektów klasycznego i kwantowego. Wykazano, że fotoabsorpcji nanocząstek niklu nie można wyjaśnić absorpcją wewnątrzstrefową (Drudowską), nawet biorąc pod uwagę efekty klasyczne lub kwantowe.

4

Optical and structural properties of nanostructured copper oxide thin films as solar selective coating prepared by spray pyrolysis method

Asadi M., Rozati S. M.

Materials Science Poland

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2017

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Vol. 35, No. 2

355--361

EN

Copper (II) oxide thin films were prepared by spray pyrolysis method on soda-lime glass substrates using copper acetate precursor solution. Influence of substrate temperature on structural and optical properties was investigated. Structural analysis of these layers were carried out by X-ray diffraction (XRD). Single phase nature and high crystallinity of CuO nanostructures were observed on XRD patterns. The general appearance of the films was uniform and black in color. FT-IR transmittance spectra confirmed the results from the XRD study. Selective solar absorber coatings of copper oxide (CuO) on stainless steel substrates was prepared by spray pyrolysis method. Effect of deposition temperature on optical properties of thin films was investigated. Optical parameters, absorbance (α) and emittance (α) were evaluated from reflectance data. It can be deduced that the porous structure, such as a light traps, can greatly enhance absorbance, while the composition, thickness and roughness of thin films can greatly influence the emissivity. Single phase nature and high crystallinity of CuO nanostructures were observed by XRD patterns. Solar absorbance of thin films were in the range of 85 % to 92 %.

5

Influence of annealing temperature on the structural and optical properties of As30Te70 thin films

Abd-Elnaiem A. M., Mohamed M., Hassan R. M., Abu-Sehly A. A., Abdel-Rahim M. A, Hafiz M. M.

Materials Science Poland

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2017

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Vol. 35, No. 2

335--345

EN

Chalcogenide glasses have attracted much attention largely due to their interesting physical and chemical properties. Though few published articles exist on the As-Te system, little is known about the optical properties of eutectic or near eutectic composition of As-Te system upon heat treatment. Therefore, this paper reports the effects of annealing temperature on the structural and optical parameters of As30Te70 thin films. The bulk and thin films of 150 nm thick As30Te70 chalcogenide glasses were prepared by melt-quenching and thermal evaporation techniques, respectively. The glass transition and crystallization reactions of the bulk samples were investigated using differential scanning calorimetry (DSC). The influence of annealing temperature on the transformation of the crystal structure was studied by X-ray diffraction (XRD), while the surface morphology of the annealed samples was examined using scanning electron microscope (SEM). The optical band gap, refractive index and extinction coefficient were also calculated. The DSC scans showed that the melting temperature remains constant at 636.56 K. In addition, other characteristic temperatures such as the glass transition temperature, the onset crystallization temperature, and the crystallization peak temperature increase with increasing the heating rate. The crystalline phases for the as-prepared and annealed films consist of orthorhombic As, hexagonal Te, and monoclinic As2Te3 phases. Furthermore, the average crystallite size, strain, and dislocation density depend on the annealing temperature. The optical absorption results revealed that the investigated films have a direct transition, and their optical energy gap decreases from 1.82 eV to 1.49 eV as the annealing temperature increases up to 433 K. However, the refractive index, extinction coefficient, dielectric constant and the ratio of free carrier concentration to its effective mass, increase with increasing the annealing temperature.

6

Badanie wpływu sposobu zasilania na wybrane parametry optyczne zestawu diod elektroluminescencyjnych

Błaszczak U., Gilewski M., Gryko Ł., Zając A.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 9

150--153

PL

Dobierając sposób zasilania można w ograniczonym zakresie sterować parametrami optycznymi źródeł światła zawierających diody elektroluminescencyjne. W referacie przedstawiono wyniki pomiarów zmiany tych parametrów dla zestawu diod. Dotyczyły one zmian: mocy optycznej, długości fali dla której występuje maksimum emisji oraz szerokości połówkowej. Zamieszczono również przykładowe wyniki pomiarów widmowych charakterystyk badanego układu z zastosowaniem kamery smugowej.

EN

By proper design of the power supply it is possible to control, in limited extent, optical parameters of light sources consisting of lightemitting diodes. The paper presents results of measurements of selected optical parameters changes for the set of LEDs. These changes concerned: optical power, wavelength of maximum emissions, and half-width. Sample results of measurements of the spectral characteristics tested system using streak camera were also presented.

7

The influence of the mounting manner on thermal and optical parameters of power LEDs

Górecki K., Ptak P.

International Journal of Microelectronics and Computer Science

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2015

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Vol. 6, nr 1

23--28

EN

The paper refers to the investigation results concerning thermal and optical properties of power LEDs. The measuring-set to measure thermal and optical parameters of the considered semiconductor devices is described and some results of measurements of transient thermal impedance and illuminance emitted by power LEDs operating at different cooling conditions are presented. Investigations were performed both for LEDs operating solely and sets of such diodes situated on the common heat-sink.

8

Impact of optical indices on particle size distribution of activated sludge measured by laser diffraction method

Sochan A., Polakowski C., Łagód G.

Ecological Chemistry and Engineering. S

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2014

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Vol. 21, nr 1

137--145

EN

The important factors that strongly influence the particle size distributions measured by the laser diffraction method are the optical parameters of the suspension (refractive index and absorption coefficient). Knowledge of the values of these parameters is necessary for Mie theory. Mie theory is applied for conversion of the intensity of light recorded on detectors into particle size distribution (PSD) of tested material. Both wastewater and activated sludge are mixtures of a variety of elements (mineral or organic, including living organisms). In practice, it is not possible to define clearly the values of the optical parameters, as the composition of the suspension changes over time. The aim of the study was to estimate the impact of assumed values of the optical parameters on particle size distributions obtained. The PSDs of suspensions sampled in different stages of wastewater treatment are the most reproducible when the following optical parameters are defined: absorption coefficients - 1.0 and the refractive index - 1.52.

PL

Czynnikami, które w istotny sposób wpływają na rozkłady granulometryczne wyznaczane za pomocą dyfrakcji laserowej, są parametry optyczne mierzonej zawiesiny (współczynnik załamania światła oraz współczynnik absorpcji). Znajomość wartości tych parametrów jest niezbędna przy zastosowaniu teorii Mie. Teoria Mie jest wykorzystywana do przeliczenia intensywności światła zmierzonego na detektorach na rozkład granulometryczny (PSD) badanego materiału. Zarówno ścieki, jak i osad czynny są mieszaninami bardzo różnych składników (mineralnych i organicznych, w tym żywych organizmów). W praktyce nie ma możliwości określenia rzeczywistych wartości parametrów optycznych mieszanin, tym bardziej, że ich skład zmienia się w czasie. Celem niniejszej pracy było określenie wpływu założonych wartości parametrów optycznych na uzyskiwane rozkłady granulometryczne. Rozkłady granulometryczne zawiesin pobranych na różnych etapach oczyszczania ścieków są najbardziej powtarzalne dla następujących wartości współczynników optycznych: współczynnika absorpcji - 1,0 i współczynnika załamania światła - 1,52.

9

Ellipsometric investigation of CdTe films

Evmenova A., Odarych V., Vuichyk M.

Optica Applicata

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2012

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Vol. 42, nr 3

667-675

EN

Ellipsometric parameters of CdTe films prepared by "hot-wall" vacuum-epitaxy method on single crystal Si substrates were measured at the wavelength of 632.8 nm. Refractive index, extinction coefficient and thickness of the films were determined. Based on the Maxwell-Garnett approximation of inhomogeneous material containing inclusions of different components (cavities, oxides) the refractive indices and extinction coefficients of effective media were calculated. Optical parameters of the film were found to depend on its thickness, which could be explained by different volume concentration of the substance in the film depth.

10

Zastosowania metody fotoakustycznej w badaniach parametrów optycznych i rekombinacyjnych materiałów półprzewodnikowych

Maliński M.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2009

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Nr 1

11--22

PL

W pracy przedstawiono przykładowe wyniki badań fotoakustycznych, wykonanych w Katedrze Podstaw Elektroniki, szeregu materiałów półprzewodnikowych w okresie ostatnich 5 lat. Z założenia jest to przegląd przeprowadzonych badań w tym okresie czasu ilustrujący obszar poszukiwań naukowych w dziedzinie fotoakustyki i jej zastosowań do charakteryzacji optycznej, termicznej i rekombinacyjnej ciał stałych. Jest to też okazja do podsumowania uzyskanych w tym czasie wyników badań i wskazanie kierunków dalszych poszukiwań.

11

Mathematical model of light propagation through liquid crystal display working under real conditions

Olifierczuk M.

Opto-Electronics Review

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2008

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Vol. 16, No. 3

287-296

EN

The main aim of our work is to present a theory of light propagation through a liquid crystal display worked out in our University. This theory takes into account real conditions of a display operation such as temporal coherence of light source, interference phenomena, spectral characteristics of refractive coefficients of individual layers and their complex forms, real directions of ordinary and extraordinary wavevectors into each layer, real directions of light polarization into anisotropic or dichroic layers etc. Therefore, our theory can be used to determine optical parameters of a liquid crystal display operating under real or at least quasi-real conditions. Contrary to other theories (e.g., Beremann or geometric optics approximation), this model is characterized by a small number of simplifications. Thus, it can be used to analyse a display operating in special conditions, such as military or out-door applications. In these cases, very high optical parameters (luminance and contrast ratio) are needed. Application of even small simplifications conducts to significant changes of calculated parameters.