thin film

CdS and Ni-CdS thin films were synthesized using the chemical bath deposition technique. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), and energy-dispersive X-ray spectroscopy (EDS). The average crystallite size of both thin films ranged between 1.5 to 4.26 nm, analyzed by the XRD as well as the Williamson-Hall method. The SEM results reveal the nanoflakes-like morphology uniformly distributed over the surface of thin films. The optical band gap was decreased from 2.29 to 2.03 eV when Ni2+ was incorporated into the CdS crystal lattice. The potential valence and conduction band position of CdS and Ni-CdS thin films was found to be 9.5, 7.7 eV, and 7.2, 5.6 eV, respectively. The synthesized films were used to degrade methylene blue (MB) dye under 160 W mercury vapor lamp irradiation. The degradation rate of MB dye was found to be significantly enhanced when Ni-CdS was used instead of pure CdS in visible light photocatalysis experiments. Degradation efficiency for the CdS thin films was 64% after 120 minutes, while for the Ni-CdS films, it was an impressive 84% after the same amount of time. Incorporating nickel ions into the CdS matrix improved the photocatalytic efficacy by increasing light absorption and decreasing electron-hole recombination. Films doped with Ni showed better photocatalytic activity, as the rate constant (k) for MB degradation rose from 0.028 min−1 (CdS) to 0.038 min−1 (Ni-CdS).

In this research, pure nickel chloride films (NiCl2 )  and doped with aluminum oxide (Al2O3 ) in proportions of (1,2,3)% . Using the method of thermal chemical spraying, where pure (NiCl2) was prepared and sprayed on glass slides, then the smearing process was carried out at the above-mentioned proportions using a technique with a heating degree of the base (150)⁰C , a thin film of a certain thickness was obtained Then the films were annealed in degree (350)⁰C  for one hour for each degree, and by making optical measurements ( UV visible spectrophotometer ) and studying the surface on the prepared films ( Atomic Force Microscope ) and matching them. With what was prepared in advance, fine Results have been obtained.

In this study, crystalline nanoparticles of ferrite compound with the formula of Ni0.5Zn0.5Fe2O4 have been synthesized and deposited on the Si substrate by a physical method known as Pulsed Laser Deposition (PLD) method. The physicochemical properties and microstructure of the resultant Zn/Ni ferrite-deposited thin films were investigated using different characterization techniques including XRD, SEM, AFM and FTIR techniques. Uniform and evenly distributed nanoparticles on the Si surface were observed in SEM and AFM analysis. Moreover, the morphological studies revealed that the deposited-nanoparticles grains are clear with well-defined grain boundaries. Some droplet and cluster aggregates were also observed in morphological analysis, which are related to the sample ablation during PLD process due to incomplete elimination of target splashing. The FTIR spectra showed the characteristic chemical bands of the materials used for the fabrication of nanoparticles and thin films. The single-phase cubic spinel structure of samples has been confirmed from X-ray diffraction analysis.

The next generation of photonics and nano-optical devices may be based on two-dimensional(2D) transition metal dichalcogenides (TMDs). In this research, molybdenum diselenide (MoSe2) nanosheets, as one important member of TMDs, have been synthesized by the solvothermal method and characterized through XRD patterns, SEM, and TEM images. Nanosheets were found to have a hexagonal phase based on XRD patterns and the crystallinity percentage is 24.8 %.  The lattice constants of the hexagonal phase of MoSe2 are calculated as a= 3.08 ͦ A, c= 13.72 ͦ A. The calculated average value of the crystallite size, dislocation density, and micro strain are 21.935 nm, 2.138   nm-2 and 9.070 , respectively. A few layers of nanosheets without wrinkles were observed on TEM and SEM. Next, the synthesized nanosheets were employed to prepare thin films with three different thicknesses using the spin coating method.  By employing a continuous wave (CW) Nd : YAG laser at 532 nm via a Z-scan approach, this study investigates how thin film thickness affects the thermal nonlinear optical (NLO) responses of MoSe2 nanosheets. The magnitude of NLO coefficients of the prepared thin films decreased with increasing film thickness. It is observed that the prepared thin films possess saturable absorption (SA) as well as the self-focusing effect. Saturable absorbers and mode-locking devices can be developed with MoSe2 thin films because of their improved NLO properties.

In this article, cobalt thin films with 250, 500, and 1000 nm thicknesses were grown on the copper substrate by electrodeposition method. The crystal structure of the cobalt thin film was studied using X-ray diffraction (XRD) and found that the layer and substrate both have orientation (111) and (200). The roughness of the layers was investigated using an atomic force microscope (AFM) and the saturation roughness were measured 5.8, 7.9 and 10.1 nm for 250, 500 and 1000 nm thickness, respectively. Examination of the kinetic roughening of cobalt thin layers showed that they have an anomalous scaling. The magnetic properties of the thin films were checked using a vibrating sample magnetometer (VSM) and their hysteresis loops were drawn and coercivity of samples obtained about 2800 Oe.

This paper deals with the effect of adding a TiO2 thin film as a planar defect to a one-dimensional photonic crystal (PC) consisting of [Si/SiO2] stacks. Theoretical calculations were carried out based on the 2×2 transfer matrix method (TMM) using MATLAB software in order to engineer the photonic band gap (PBG). The defect was considered as a variation in the refractive index, so that its presence in the structure leads to the breaking of the symmetry, creating a transmission peak (TP) in the forbidden band. In addition, the amplitude and location of TP can be shifted by changing physical parameters such as the functional wavelength range, thickness of layers, defect layer thickness, and angle of incidence. The results demonstrate that it is possible to arbitrarily engineer the transmission spectrum by changing the aforementioned parameters. Finally, two gaps are induced in the visible and infrared wavelength bands using an innovative and relatively symmetric structure. Through simple calculations, the location of the TPs can be appropriately engineered and adjusted. Importantly, [Si/SiO2]3/TiO2/[Si/SiO2]3/Si3N4 PC structure with three adjustable TPs is designed, which can be used for band pass filter applications.

In this paper, a one-dimensional photonic crystal (PhC) composed of [SiO2/ZrO2] stacks is designed to act as an optical filter. These types of filters have been extensively used in safety glasses working in the wavelength of 355 nm. Here, theoretical calculations are carried out in MATLAB software based on the transfer matrix method (TMM). Simulations showed that the structure of Quartz/[SiO2/ZrO2]20 can block the wavelength of 355 nm, reducing the transmittance ratio to 1.29×10-5%. By forming 16 stacks, the optical density (OD) reaches 5, completely protecting the user’s eyes from laser beams with incident angles ranging from 0 to 22 degrees. For higher incident angles up to 38 degrees, 20 stacks of [SiO2/ZrO2] are needed to reach OD = 5. The visible light can pass through this filter about 70%, being sufficient for the user’s vision. Finally, the distribution of the electric field is simulated to confirm the performance of the resulting structures.

In this article, the growth kinetic and optical property of amorphous carbon (a-C) nanolayers deposited by ion beam sputtering deposition technique on glass substrates are investigated. The atomic force microscopy is used to measure the variation of surface roughness versus deposition time. According to the calculations, the roughness of thin films increases during the growth process as a fractal scaling law. The Hurst exponent (α) has a value higher than 0.5, and the growth exponent (β) changes in the range of 0.02 to 0.22. These fractal exponents predict that the growth process of amorphous carbon nanolayers obeys the rules of the Wolf-Villain model belonging to the Edwards-Wilkinson universality class, in which the relaxation and surface diffusion happen during the growth process. The results indicate that the optical band gap decreases by reducing the surface roughness, Hurst exponent and the correlation length during thin film growth which is the first observation of this trend.

In this research study, the growth of SnZnSe thin film materials was carried out using the cationic precursor, which was an aqueous solution of 0.035 mol solution of ZnSO4.7H2O while the anionic precursor was 0.1 mol solution of selenium metal powder was prepared by dissolving with 4 mL of hydrogen chloride (HCl). The XRD of the films deposited on FTO substrates at different dopant concentration 1%, 2%, 3% and 4% showed the reflection peaks at (220), (221), (300), (310), (311), (222) and (320) with the lattice constant of a=7.189 Ǻ.  The SEM results revealed the random distribution of tiny nano-grains on the substrate, the nano-grains were observed to agglomerate due to the presence of large free energy characteristics of small particles. The optical bandgap of the deposited material enhanced from 2.0-2.3 eV as the dopant concentration increased.

In this work, silver thin films were prepared using sputtering at different deposition times with the nanoscale thickness. To investigate their surface morphology, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed. The surface topography of the samples studied using the AFM. The results revealed that, the roughness of the thin films enhanced by increasing the sputtering time. The permutation entropy (PE) was introduced as an interesting parameter to characterize the surface morphology. At the best of our knowledge, it is the first time one uses the PE for characterizing the thin films. Although the roughness might always enhance by increasing the film thickness, it was not the case for PE. The PE was found to be an independent parameter for characterizing the surface of thin film.

With attention to the thin film structure of colloidal quantum dot solar cells, in this paper in order to improvement of active layer absorption of them, we have proposed the use of nanostructure pattern for enhancement of their performance. For this purpose we have presented suitable nano hemisphare patterns in colloidal quantum dot solar cells for light trapping in absorption layer. Then with simulation of the obtained nanostructure solar cells we have studied on improving the absorption spectrum and thus increasing the short circuit current density of them. In order to simulation of light propagation in nanostructures, we have used finite-difference time-domain method. According to the calculation results and with optimization of periodic nanostructure patterns, we have shown that short circuit current density has been increased up to 15.95%. Absorption spectrum, quantum efficiency density and short circuit current density have been discussed for colloidal quantum dot solar cells nanostructures with low and high thickness of absorption layer in this paper.

Light emitting diodes (OLEDs) are one the newest lighting in industrial lighting which can be a promising candidate in this area. A typical reverse OLED is made from cathode, injection/transport electron and hole layers, emissive layer (EM). Electrons and holes after injection to EM are recombined in emissive layer which is an organic material. In reverse structure, holes inject EM well while electrons cannot be easily injected to emissive layer. Here, effect of lithium doped zinc oxide (LZO) on the led performance was investigated. The results showed that lithium can be increased conductivity of injection electron layer and facile to inject electron to emissive layer.

ZnO is a promising material suitable for variety of novel electronic applications including sensors, transistors, and solar cells. Intrinsic ZnO film has inferiority in terms of electronic properties, which has prompted researches and investigations on doped ZnO films in order to improve its electronic properties. In this work, aluminum (Al) doped ZnO (AZO) with various concentrations and undoped ZnO films were coated on glass substrates by a sol–gel spin coating technique. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Uv-Vis spectrometer and four point probe technique to investigate the structural, surface morphology, optical transmittance, and electronic properties of the thin films. The optical transmittances of these samples in the visible region are in the range of 85-95% and the SEM images showed the size of nanoparticles were decrease with doping. Also 2% Al doped ZnO thin films had a lowest resistivity of all the samples that prepared in this study.

In this study, thin films of pure ZnO and doped ZnO with different percentages of gallium (0.5, 1, 2 and 4vt. %) on the glass substrates were deposited by using sol-gel method via spin coating technique at 2500 rpm, and all layers were annealed at 200°C for 1h and then Were examined their electrical, optical and structural properties. Concentration of all solution was 0.1M. The results show that the optimized layer is 0.5% GZO. By examining the transmittance spectrums we find that by doping the transparency of samples were improved and all samples in the visible areas 400-800nm are transparent. The electrical conductivity of all samples has been measured by four-point probe technique. The electrical conductivitys of pure ZnO sample and 0.5% GZO are 910-5 S/cm and 110-4 S/cm respectively. It can be a good choice for optoelectronic applications. Also X-ray diffraction results showed that diffraction peaks of 0.5% GZO sample have a small changes towards lower angles compared to the diffraction peaks of ZnO.

In this study, different samples of Niobium and Vanadium co-doped titania thin films (5-10-15 mol% Nb and 5-10-15 mol% V) were prepared via sol−gel dip coating method, using niobium chloride as niobium precursor, ammonium metavanadate as vanadium precursor, and titanium (IV) butoxide (TBT) as titanium precursor. The effects of doping amount on the structural, optical, and photo-catalytic properties of formed thin films have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis absorption and transmission electron microscopy (TEM). XRD patterns showed a decrease in peak intensities of the anatase crystalline phase by increasing the Nb/V dopant and doping inhibition effect on the grain growth, and revealed that all samples contained only anatase phase (T= 475 ºC). The photo-catalytic activity of the thin film was measured on degradation rate of methylene blue (MB) solution under UV irradiation. Highest photo-catalytic activity of doped TiO2 thin films were measured in the TiO2–5 mol% Nb-15 mol% V sample (TNV4). Small granular crystallites of 10-15 nm 2D diameter were observed in electron microscope micrographs.