Optical Properties Of Thin Films Research Articles

Formation of composite coatings by ion-beam spraying of targets based on pyrogenic silica micro-powders containing copper compounds

In the introduction, the object of research is indicated – thin films obtained by ion-beam spraying of targets based on pyrogenic silica micro-powders containing copper compounds. The aim of the research is to study the behavior of copper ions during the formation of thin films by ion beam sputtering of a SiO2:CuO target in an Ar/O2 mixture of gases. The main part presents the results of a study of the structural and optical properties of thin films (~ 100 nm thick) formed by ion beam spraying of targets based on pyrogenic silica micro-powders containing copper compounds. The morphology of the film surface as a whole shows integral homogeneity and in fact does not depend on the composition of the gas medium, while there is some ‘‘granularity’’ of the coating surface, which is typical for spraying porous targets consisting of agglomerates or domain structures. The obtained frequency dependences of the dielectric constant of SiO2:CuO films showed a decrease in the dielectric constant in the range of 10 kHz – 1 MHz. It was found that when the SiO2:CuO film thickness is less than 100 nm, a thin-film capacitor is not always formed. Based on the analysis of the optical parameters of film accumulation depending on the sputtering medium, it was suggested that in an inert medium a large absorption of globular spheroidal CuO is formed in the film, and copper oxide can also be reduced to Cu+ and possibly to Cuº. It is indicated by the change in ε and tgδ, as well as an increase in the optical prohibited gap of SiO2:CuO thin films from 3.91 to 3.97 eV with an increase in the oxygen content in the Ar/O2 gas mixture. The resulting films can be used as active media in solar cells, sensors and other devices.

Structural, Morphological, Optical Properties and Modelling of Ag Doped CuO/ZnO/AZO Solar Cell

Copper (II) oxide (CuO) has attained significant attention from researchers because of its unique chemical and physical properties. Ag-doped CuO thin films have been produced on the soda glass substrate (SLG) by spin coating technique at different doping ratios. Structural, morphological, and optical properties of thin films produced depending on altered silver ratios have been examined through X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), and UV-vis absorption spectroscopy, respectively. Band gaps of prepared undoped and 1% Ag-doped CuO thin films have been measured as 1.90eV and 1.63eV, respectively. Ag/undoped CuO and Ag-doped CuO/ZnO/AZO solar cells have been modelled, and their photovoltaic parameters have also been calculated using the SCAPS-1D simulation program. This work aims to investigate the photovoltaic parameters that would improve the efficiency of a solar cell. The effect of Ag atoms on the efficiency of CuO solar cells has been investigated depending on the acceptor density (Na), the interface defect density (Nt), and the operating temperature. Ag-doped CuO solar cells have shown the highest efficiency for Nt=1010 cm-3 and Na=6, 5x1016 cm-3 values. It has been well observed that as the operating temperature increases, the solar cells’ power conversion efficiency decreases. The highest charge generation rates in the undoped and Ag-doped solar cells have been determined as 1.49×1022 1/cm3.s and 1.51×1025 1/cm3.s, respectively. All the results, either theoretical or experimental, have been presented in this work and have been compared for a conclusion that has been made in detail.

Optical, structural and composition properties of silicon nitride films deposited by reactive radio-frequency sputtering, low pressure and plasma-enhanced chemical vapor deposition

We present a comparative study of optical properties of silicon nitride thin films deposited by reactive radio-frequency (R-RF) sputtering, low pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD). For LPCVD process, two different proportions of mixed gases were used (LPCVD (A) and LPCVD (B) processes) and PECVD deposition were conducted in three regimes: low frequency (LF), mixed frequency and high frequency. Dielectric functions were extracted from ellipsometric measurements for the wavelength range from ultraviolet to near-infrared wavelengths, spanning from 210 nm to 1690 nm. To understand how different deposition parameters affect the optical properties of thin films, additional structures and composite analysis was done by using X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, X-ray reflectometry, atomic force microscopy, reflection electron energy loss spectroscopy, Fourier-transform infrared spectroscopy and stress measurements. The series of analysis show that the influence of deposition method on optical properties is significant especially for in the range of 200 nm–400 nm. For these UV wavelengths, LPCVD (A)-deposited films give a transparency window at the shortest wavelength up to 275 nm, while R-RF-sputtering and PECVD (LF) lead to transparency windows starting up to 320 nm wavelengths. Hence, appropriate techniques and recipes should be selected to account for various peculiarities in optical and structural properties of silicon nitride films towards their potential applications in photonic and nanostructured systems.

Optical and morphological properties of ZnO and Alq3 incorporated polymeric thin layers fabricated by the dip-coating method

In this report, we present the influence of polymer matrix on morphological and optical properties of thin films containing zinc oxide (ZnO), tris(8-hydroxyquinolinato)aluminium (Alq3) and ZnO:Alq3. Polyvinylpyrrolidone (PVP) and poly(methyl methacrylate) (PMMA) dissolved in isopropanol and tetrahydrofuran, respectively, were used as polymeric matrices of fabricated composites. The analysed thin layers were deposited on Si substrates using a dip-coating method and characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Spectroscopic Ellipsometry (SE) and photoluminescence (PL). It was found that adding the polymer to Alq3 causes a blueshift in absorption compared to pure Alq3 layers. We also observed photoluminescence in the region of 2.2–2.8 eV for ZnO:Alq3:PMMA and ZnO:Alq3:PVP, as well as for Alq3:PMMA at room temperature. PL measurements showed that adding ZnO to Alq3:polymer matrix did not result in any shift in PL spectra compared to the results of Alq3:polymer layer. AFM and SEM measurements show that relatively smooth films were obtained in the case of composites based on PVP and PMMA. Moreover, a change in the size of ZnO agglomerates depending on polymer used is observed for the three-component layers. We also noticed that the values of the refractive index are higher for the samples in the PVP matrix. However, the opposite behaviour was observed in the case of the extinction coefficient.

Electronic structure, magnetic, transport, and optical properties of bulk and film Fe2CrGa Heusler alloy. Effect of structural disorder

Magnetic, transport, and optical properties of thin film and bulk Fe2CrGa alloy samples with different types of atomic order were experimentally investigated. The obtained data were discussed in terms of first-principle calculation results made for the stoichiometric Fe2CrGa alloy with different types of atomic order and disorder. An ultimate atomic disorder in Fe2CrGa alloy films was obtained by employing vapor quenching deposition onto substrates cooled by liquid nitrogen. Annealing of as-quenched Fe2CrGa alloy films causes their crystallization at Tann=750 K with the formation of the disordered A2-type structure, which is accompanied by the rapid growth of alloy resistivity in a narrow temperature range, formation of multi-phase magnetic structure and changes in the optical properties. Crystalline bulk and film Fe2CrGa alloy samples show the dome-like temperature dependence of the resistivity with maximums near their Curie temperatures and explained in terms of competition between negative with temperature contribution from highly resistive media and positive from the electron–magnon scattering. The big resemblance between calculated for Hg2CuTi type of atomic order and experimental optical conductivity spectra for annealed Fe2CrGa alloy films proves that Hg2CuTi type of atomic order is more probable for this alloy.

Polarization eigenstates analysis of helically structured thin films.

The optical properties of thin films are generally determined by direct photometric quantities. We show that additional insight into the properties of anisotropic thin films can be obtained by computing the polarization eigenstates and eigenvalues of their Jones matrices. We consider helically structured thin films, which display intriguing optical response, such as the circular Bragg resonance. Using numerical simulations and actual measurements, we show that the eigenvectors are mutually orthogonal in most regions of the wavevector space, except near the circular Bragg and the oblique resonances. Special wavevector values, called exceptional points, are found where the Jones matrix becomes defective and its eigenvectors coalesce. Exceptional points are also found in pairs of wavevector values differing only by a sample rotation by π around the direction normal to the sample; this property is shown to arise from Saxton - de Hoop's reciprocity principle, which applies to lossy materials and contains time reversal symmetry, which only applies to lossless materials, as a special case.

Effect of PbS on ZnS nanostructure deposited using thermal evaporation: growth, morphological and structural study

ZnS film has been deposited on PbS buffer layer using thermal evaporation, the ZnS film has nanostructure (nanowires) due to effect of PbS which play role of catalyst. This growth for non doped films have dense structure (for PbS and ZnS films). SEM morphology of ZnS/PbS, ZnS and PbS have been studied in details (surface and cross section). Atomic force microscopy (AFM) used to characterized the thins films (ZnS and PbS). X-ray photoelectron spectroscopy (XPS) and EDX techniques have utilized to know the chemical and stoichiometry of deposited films. The crystallographic properties have been studied using XRD patterns, it found that the results in Raman and XRD characterization have a good agreement. UV-Vis spectroscopy is used to acquire an idea about optical properties of thin films deposited on glass substrate. The deposited ZnS nanowires and thin film have hexagonal phase, which indicate to the buffer layer, which does not affects the structural but changes the growth mechanism. High Resolution Transmission Electron Microscope (HRTEM) images have confirmed the formation of ZnS nanowires.

Structural, chemical, morphological and optical properties of thin films based on potassium bis(2-methyllactato) borate hemihydrate doped by iodine

Structural, chemical, morphological and optical properties of thin films based on potassium bis(2-methyllactato) borate hemihydrate doped by iodine

Optical properties of Au-Hf thin films

The optical properties of thin films of intermetallic Au$_{3}$Hf were experimentally investigated for the first time, which display clear plasmonic properties in the optical and near infrared region with negative permittivity. In contrast to similar alloys, such as films of Au$_{3}$Zr, the films express more negative $\epsilon'$ values and lower $\epsilon''$ values across most of the wavelengths (370-1570 nm) investigated. The Au$_{3}$Hf films were fabricated by DC magnetron sputtering at a range of deposition temperatures, from room temperature to 415$^{o}$C, and annealed at different vacuum levels. The films mostly formed as a combination of Au$_{3}$Hf, Au$_{2}$Hf and Au$_{4}$Hf phases when deposited below 400$^{o}$C, and exclusively Au$_{3}$Hf phase at above 400$^{o}$C, indicating key conditions for isolating this phase. The films were stable when annealed at 10$^{-8}$ Torr, but when annealed again at 10$^{-6}$ Torr the films oxidised and changed into a mix of Au- Hf phases, suggesting resistance to oxidization may be an issue for un-encapsulated applications at elevated temperatures.

Cu2O thin films prepared by chemical bath deposition: An improved method

ABSTRACT Cuprous oxide (Cu2O) thin films were prepared for the different weights (0.08, 0.09, 0.10, 0.13, and 0.14 g) on glass substrates by the chemical bath deposition (CBD) method. The effects of weight on the structural, morphological, and optical properties of thin films were investigated. The XRD pattern shows cubic structured Cu2O thin films and the crystallinity is increased with an increase in weight. The average crystallite size is also increased from 10 to 17 nm. The FESEM images picturized cubic and irregular-shaped non-homogeneous particles. The transmittance is found to be decreased with an increase in weight. The direct energy bandgap decreased from 2.26 eV to 2.17 eV as the weight increased. Also, the extinction coefficient, refractive index, and dielectric coefficients have been affected by the variation of weight.

Characteristics of Al & Ti oxide-thin films for thermal solar energy selective absorption applications

Controlled oxidation of sputtered layers of Ti and Al results oxide layers with nano-sized thickness comparable to thermal solar selective absorber layers. In this work, RF magnetron sputtering was used to obtain thin layers of Al and Ti on substrates of stainless steels (St. St). Deposited thin films were oxidized at 400 °C and 800 °C for 4 hours and 1 hour, respectively. The as-deposited Ti, and Al layers were air–oxidized and their optical absorbance and emittance were studied. Microstructure, surface topography, structure and new phases formed after oxidation were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD). Thin films optical properties were investigated by spectrophotometer & Fourier Transform Infrared (FTIR) Spectroscopy. The new microstructures exhibited a dual metallic and oxide nature. Deposited thin film of Ti had maximum absorbance and lowest emittance about 90% and 1.8% respectively; while after oxidation, the deposited layers changed their selective absorbance pattern. The absorbance values increased, and the emittance values decreased for all wave lengths in the infrared (IR) range. The effect of the oxidation process of both Ti thin film and Al thin film was compared. The Al thin film showed lower absorbance in as-deposited and oxidized states.

Spectroscopic ellipsometry study of dielectric functions of Ag films and chemically deposited layers of Ag nanoparticles on silicon

The optical properties of thin films and layers of Ag nanoparticles on a c-Si substrate are modeled by calculating the complex pseudo-dielectric function <ε>. The evolution of the imaginary part <ε2> with an increase in the thickness of continuous layers from the dielectric function ε of the substrate to ε of bulk silver is studied, which demonstrates the appearance of optical characteristics of Ag and the suppression of c-Si features in the form of critical points. The data measured on the spectroscopic ellipsometer for Ag films produced by magnetron sputtering for several nominal thicknesses from 10 to 300 nm, and layers of Ag nanoparticles chemically deposited on a c-Si substrate, were interpreted using a pseudo-dielect ric function and by calculating the complex dielectric functions ε using the Drude-Lorentz model. Morphological parameters obtained by atomic force microscopy and scanning electron microscopy were also used in the calculations. Since the Ag layers and films were deposited on the c-Si substrate without any additional layers (except for the native layer), the determined pseudo-dielectric functions for thicknesses in the range of 7−50 nm turned out to be close to the calculations of the dielectric functions using the Drude-Lorentz model. It was found that in the calculated and experimental spectra in the imaginary part of ε2 and <ε2> a peak appears at E ∼ 3.9 eV, which is interpreted as a plasmon resonance in the longitudinal mode at oblique incidence of light. In the ε2 spectrum of a layer of disordered Ag nanoparticles produced by chemical deposition, there is a broader localized surface plasmon resonance peak at E ∼ 2.5 eV, in contrast to thin films. Whereas, in a layer of larger nanoparticles, the peak is absent, and its ε dependence is close to ε for bulk Ag.

Structural, Optical and Electrical Properties of Nebulizer Spray-Deposited Tin Disulphide Thin Films with Different Substrate Temperatures

The Nebulizer spray pyrolysis technique is used to make tin disulphide thin films at various substrate temperatures. SnS2 thin films structural, electrical and optical properties are investigated. The polycrystalline nature was confirmed by X-ray diffraction (XRD) analysis, which revealed a hexagonal structure with a preferred orientation along the (0 0 2) plane. The full width half maximum value of the Bragg peak is used to calculate the size of SnS2 crystallization. Scanning Electron Microscope (SEM) is used to examine the composition and surface morphology of SnS2 thin films. The wavelength range of 400-1110 nm is used to determine the transmittance and absorption spectra of these films. With increasing substrate temperature, the optical band gap of tin disulphide thin films decreases from 3.17 eV to 2.61 eV. With regard to substrate temperature, the absorption coefficient and activation energy were reduced with SnS2 deposition.

The Effect of the Number of Laser Pulses on Some Physical Properties Affecting Gas Sensitivity of CdO Thin Films Prepared by PLD Method

In this research, thin films of cadmium oxide (CdO) were manufactured using pulse laser deposition (PLD) technology on glass substrates under pressure of (0.001 mbar) at room temperature by a laser power effect (800mj/cm) with a number of different laser pulses (N= (150-200-250 and 300)). The optical and synthetic properties of thin cadmium oxide films were studied, as well as their gas sensitivity. The optical properties of thin films were analyzed and studied using absorption spectra (UV-VIS) UV-Visible measurements show that CdO films of different thicknesses have a direct permissible transition with the band gap between (2.51) and (2.22) eV before annealing and after annealing the band gap decreases to become between (2.44) and (2.06). As for synthetic properties, they were analyzed and studied through X-ray diffraction patterns which showed the thin films are multicrystalline the grain size increase with the increase in the number of pulses from (100) pulse to (300) pulse gradually as for the effect of annealing, it also led to an increase in the size of the particles. While gas sensor properties were studied using static gas sensor system. The results of gas sensor showed that the increase in operating temperature improves film sensitivity. the maximum sensitivity of the pure CdO film to gas (NO2) was found to be 46.16% at 200°C and the number of pulses was (150). After annealing, the gas sensitivity decreased to was (34.25%) for (150) pulses.

Effect of Films Thickness on Structural and Optical Properties of Gold (Au) Thin Films Prepared by DC Magnetron Sputtering

In this paper, the effect of films thickness on the structural and optical properties of gold (Au) thin films prepared by the DC sputtering method was studied. At three different deposition times, three samples of gold thin films of three different thicknesses (200,400, and 600 nm) were prepared. X-ray diffraction patterns, scanning electron microscopy (SEM), and atomic force microscopy (AFM) images, as well as optical spectroscopy, were used to characterize thin films. The crystalline structure of gold thin films was determined by the XRD pattern which showed to be cubic phase and polycrystalline in nature. The preferred orientation was (111) at 2Ѳ equal 37.4. The effect of deposition time on the morphology of the deposited films was visualized with a scanning electron microscope (SEM) which showed a homogenous surface with nanoparticles with a diameter size of 50-100 nm. Changes in deposition time caused variations in roughness, thickness, and surface quality, as shown by AFM results. UV-Vis reflection spectroscopy was also used to investigate the optical properties of thin films.

Optical Characterization of Boron-doped ZnO nanostructures

Zinc oxide and Boron-doped zinc oxide (B-ZnO) thin films have been dip coated on glass substrates using Sol-Gel technique. The ZnO solution was prepared by using zinc acetate dihydrate (ZAD) as starting material. Ethanol and citric acid are used in the Sol-Gel process as solvent and solution stabilizer, respectively. Doping of boron is achieved by adding a proper molar ratio of Boric acid (H3BO3) solution to the final ZnO solvent. The optical properties of thin films were investigated using UV-vis spectrophotometer measurements. Transmittance of undoped ZnO films exhibits high values that are decreasing upon increasing the Boron concentration. We found that the index of refraction of undoped ZnO films demonstrates values ranging between 1.6 and 2.2 and increase as B concentration is increased and approximately match those of bulk ZnO. In addition, structural properties were investigated using XRD, SEM and EDAX techniques. Upon annealing, we found that the films exhibit a hexagonal structure and as B concentration increases the grain size increases and the strain decreases. Our results indicate that (B-ZnO) films could be used as seeded platforms for growing nanostructures using hydrothermal method.

Elaboration, characterization and applications of SnO2, 2 %Gd-SnO2 and 2 %Gd-9 %F-SnO2 thin films for the photocatalytic degradation of MB by USP method

• An investigation on SnO 2 , 2 %Gd-SnO 2 and 2 %Gd-9 %F-SnO 2 thin films have been synthesized by USP method. • Effect of doping and co-doping on the structrales, microdtructurales, optical and electrical properties of SnO 2 thin films. • The development of the parameters: lattice parameters, average crystalline sizes, Seeback coefficient and energy gap with doping and co-doping are discussif. • The photocatalytic degradation of methylene blue was studied using 2 %Gd-SnO 2 and 2 %Gd-9 %F-SnO 2 thin films. In this study, SnO 2 , 2 %Gd-SnO 2 , and 2 %Gd-9 %F-SnO 2 films were grown from tin chloride solutions by the ultrasonic spray technique on ordinary microscope glass substrates heated to a fixed temperature of 450 °C for photocatalytic application. The microstructural characterization of the thin films obtained was performed using X-ray diffraction (XRD), SEM, EDAX, and Infrared Spectroscopy (IR). The optical properties of thin films were studied by UV–Visible spectroscopy. To examine the electrical properties, we use the four-point method, the Seebeck effect and the Mott Shottky analysis. X-ray difraction reveals the formation of the routile phase of SnO 2 in all thin films with average crystallite size estimated in the range of 24–62 nm. The co-doping in (Gd-F) permitted an improvement of the thermoelectric properties of SnO 2 . Moreover, we have demonstrated that an increase in grain size allows toimprove the Seebeck coefficient, to increase the electrical conductivity, on the other hand the doping in (Gd), presents a decrease in the size of the crystallites, which improves the degradation of methyl blue. The UV–Visible spectra of optical transmission of the layers show that the pure, doped and co-doped SnO2 films are of good quality with a transmittance of 73–83% in the visible and have an optical gap evaluated between 3.89, 3.98 and 3.99 eV respectively.

A Simple Method to Obtain Protective Film against Acid Rain

Acid rain is a major problem for animals, plants, buildings, and also for the top glass of photovoltaic (PV) solar panels and greenhouses. Air pollutants such as NOx, NH3, and H2S can mix with water in the atmosphere to form acid rain. It was discovered that atmospheric water vapor adsorbed on the surface of glass can also lead to corrosion of the glass surface. The purpose of this work is to obtain a protective film for glasses used in different domains such as solar cells, windows, stained glass windows from historical buildings, etc. Thin film deposited on glass must be protective against acid rain, transparent in the visible domain with a band gap up to 3.2 eV, and have a vitreous structure (glass). Electron beam (e-gun) technology is a deposition technique for producing high-purity and dense coatings in a short time. It is well known that Ta2O5 is an oxide with anticorrosive properties, but it is expensive and cannot form glass by itself. ZnO is an oxide known as a glass former, exhibiting good optical properties. In this paper, a thin film obtained by the deposition of ZnO and Ta2O5 on a glass substrate using e-gun technology are studied. The simulated acid rain effect on the structure, morphology, and optical properties of thin films are studied after a 65% nitric acid attack on the surface. The X-ray diffraction (XRD) pattern shows the vitreous state of the thin film with a composition 50%ZnO 50%Ta2O5 before and after the acid attack. The morphology, composition, and thickness of the film are investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and profilometry.

Fabrication and Characterization of the Broccoli-like Structured CuO Thin Films Synthesized by a Facile Hydrothermal Method and Its Photoelectrochemical Water Splitting Application

CuO thin films with broccoli-like structure were prepared using a facile hydrothermal method to construct photocathodes for water-splitting application. The morphological, structural, and optical properties of thin films were characterized and measured using several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and ultraviolet-visible spectroscopy (UV-Vis). The thickness, structure, and morphology of CuO thin films can be controlled by varying the precursor concentration (Cp) and reaction temperature (Tr), which are also discussed. Moreover, the electrical properties of CuO thin films were also measured in the three-electrode system. The photocurrent density of photocathodes, when synthesized by a 0.5 M solution at 150 °C for 12 h, was 0.5 mA/cm2 at −0.6 V vs. Ag/AgCl, which is 1.8 times higher than that of photocathodes synthesized in a 0.1 M solution at 100 °C with the same reaction time. In addition, increasing the reaction temperature and precursor concentration aided in the enhancement of the IPCE and APCE values, which peaked at a wavelength range of 330–400 nm.

MBE grown preferentially oriented CdMgO alloy on m- and c-plane sapphire substrates

Unlike other II-VI semiconductors, CdO-based transparent oxide has great potential application for the fabrication of many optoelectronic devices. In this work, we study the growth of CdxMg1-xO alloys on m- and on c-plane sapphire substrates in Cd-rich to Mg-rich conditions using the plasma-assisted molecular beam epitaxy method. A structural and morphological study of CdMgO random alloys was carried out using X-ray diffraction and Atomic Force Microscope (AFM) techniques whereas composition analysis was done by Energy-dispersive X-ray (EDX) spectroscopy method. The optical properties of thin films were investigated by UV–Vis spectroscopy at room temperature. X-ray analysis confirmed the presence of cubic rock salt structure with <111> CdMgO crystallographic orientation on c-plane sapphire and <110> CdMgO preferential orientation on m-plane sapphire. The surface roughness was measured by the AFM. From the absorption curve, the optical bandgaps were determined using Tauc relation and it was found that the bandgap of films is influenced by the incorporation of Mg2+ ions into the CdO lattice. Bowing parameter was calculated for both samples on m- and c-sapphires.