جستجوی مقالات مرتبط با کلیدواژه « spray pyrolysis » در نشریات گروه « زمین شناسی »

This research investigates and amends the physical properties of pure ZnO and ZnO/ZnS, ZnO/ZnS/ZnO thin films in detail for the first time. Thin films of ZnO, ZnO/ZnS, and ZnO/ZnS/ZnO were prepared on glass and SnO2: F (FTO) substrates at 300-550℃ by spray pyrolysis technique. The initial solution was prepared using zinc chloride (ZnCl2) and thiourea (SC(NH2)2) for ZnS and Zinc acetate (ZnC₄H₆O₄) for ZnO. The optimum solution molarity ratio of Zn:S was determined to be 2:1. Also, the best volume of pure ZnO solution and pure ZnS solution was 50 mL and 25 mL, respectively. In addition, the optimum flow rate for the deposition of pure ZnO solution and deposition of pure ZnS was 1.4 mL/min and 1.2 mL/min, respectively. The best temperature for deposition of pure ZnO solution and pure ZnS solution in air ambient was 500℃ and 450℃, respectively. The physical, electrochemical, and structural properties of ZnO, ZnO/ZnS, and ZnO/ZnS/ZnO thin films prepared by the spray pyrolysis method were investigated using different analyses. The properties of ZnO, ZnO/ZnS, and ZnO/ZnS/ZnO were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), Near-infrared (NIR) Spectroscopy, Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS). The results show that the films have a nano-scale structure. In this respect, the XRD results showed the presence of cubic phase and hexagonal phase corresponding to ZnS with a preferred orientation along the ZnS (111) and (002) cubic and hexagonal direction. FESEM demonstrated a homogeneous and compact surface of the prepared thin films. The electrochemical properties of the nanostructured thin films were determined by CV, GCD and EIS analyses. The nanostructured ZnO/ZnS thin film demonstrates the highest specific capacitance compared to the other prepared thin films.

In this research, the diodes were made using a thin films of molybdenum oxide on the doped P-type silicon substrate with the aim of studying the effect of the substrate temperature on the characteristics of the diode. For this purpose, thin films of molybdenum oxide were deposited on the substrate at substrate temperatures of 350, 400, 450 and 500 ˚C by spray pyrolysis. The structural and optical properties of the thin films were characterized. They show a fairly crystalline nature with a straight structure and peaks corresponding to (020), (040) and (060) planes, with the preferred peak being (040) in all samples. The shape of the surface of the samples is without cracks and has a rectangular granulation with the size of the grains in the range of 110 to 210 nm. Also, their average surface roughness was measured in the range of 157 to 167 nm. The optical gap of the samples was estimated in the range of 2.84 to 2.95 eV. The voltage-current diagram of the samples showed their diode behavior. The diode made at 400 ˚C substrate temperature has the lowest threshold voltage.

Nickel oxide thin films were successfully percipitated at different substrate temperatures (440, 460, 480, and 500 oC), spray rates (1, 2.5, 5, and 7.5 ml/min), solution volumes (50, 100, 150, and 200 ml), and nickel concentration (5, 10, 15, and 20 at.%) glass substrates using NiCl2.6H2O as precursor and the spray pyrolysis technique. The structural and  optical properties of the thin films were characterized. They show a polycrystalline nature with a cubic structure of single-phase NiO and peaks related to (111), (200), and (220) with a preferential orientation along (111). The morphology of the NiO thin films resembles that spherical grains on the entire surface, with an average roughness ranging from 28.71 to 105.63 nm, depending on the deposition conditions. The range of the optical gap and Urbach energy were measured to be 2.55 to 3.49 eV and 0.41 to 0.55 eV, respectively.

In this research, titanium dioxide (TiO2), as a metal-oxide semiconductor that can be applied in dye-sensitized solar cells as a photoanode, was studied and synthesized. For this reason, thin films of TiO2 were grown using the spray pyrolysis method and their physical properties were studied. To prepare the FTO substrate as the conductive layer, the FTO layer was deposited on the glass substrate. The transmittance above 90% in the visible region and low electrical resistance allows the use of the synthesized FTO as a transparent electrode. Subsequently, TiO2 films were coated using spray pyrolysis at the temperature of 150°C on top of both bare glass and FTO coated glass substrates. The precursor solution for spray was made of TTIP as the main material and isopropanol as solvent. Samples were prepared by two methods of pulsed and non-pulsed spraying in two volumes of precursor solution of 200 and 350 mL. Results showed that the pulsed deposited samples cause the formation of TiO2 films with higher crystal quality. XRD pattern analysis revealed the formation of the anatase crystal phase with preferred growth along the (101) plane on the FTO substrate. Considering its physical characteristics, the TiO2 sample deposited on FTO in a precursor solution volume of 200 mL by the pulsed method was introduced as the most suitable sample for being used as a photoanode.

The In-doped vanadium pentoxide nanostructures with different doping levels including 0, 10, 20 and 30 at.% were prepared by the spray pyrolysis technique. The prepared thin films were characterized by the x-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results revealed that the films were crystalline in tetragonal phase. Increasing the In-doping level made the structure more disordered and decreased the crystallite size up to more than 50% for V2O5: In30at.% with respect to the pristine sample. The SEM results showed single phased nanorod- and nanobelt-shaped V2O5 structures with average diameters of 50-100 nm. The Hall effect measurements showed that all the involved films are n-type semiconductors whose resistance increases with In content; this also can be related to the enhanced structural disorder of the samples.

In this research, zinc oxide thin films with gallium impurity have been deposited using the spray pyrolysis technique. The structural and optical properties of these films are investigated as a function of gallium doping concentrations. The ZnO and ZnO:Ga  films grown at a substrate temperature of 350 ºC with gallium doping concentrations from 1.0 to 5.0.%. The XRD analysis indicated that ZnO films have nanocrystalline wurzite structure with (002) preferential orientation and grain size varied from 39.1 to 16.1 nm. The optical properties of the thin films have been performed using UV-Vis spectrophotometer and band gap energy values are determined. The results show that the transmittance of these films was higher than 90% in the visible region and by adding Ga up to 5.0%, band gap films have been increased.

In this research, molybdenum oxide (α-MoO3) thin films were coated on glass substrates using spray pyrolysis technique. 0.05 M ammonium heptamolybdate tetrahydrate was used as precursor and deionized water as solvent. The effects of carrier gas pressure, during the spraying of the solution, on the structural, optical, morphological and gas sensing properties of thin films were studied. X-ray diffraction (XRD) pattern analysis showed preferred growth at (020) peak direction and the formation of alpha phase of molybdenum oxide. The most intensive peaks were observed in the XRD pattern of the sample prepared under the carrier gas pressure of 2 bar, which indicates better crystallization of the sample. In addition, Raman spectrum of this sample confirmed the XRD results. UV-Vis spectroscopy results showed that the sample prepared under the carrier gas pressure of 1.8 bar has the highest optical absorption and the lowest band gap (~ 3.48 eV). Scanning electron microscope (SEM) images showed the layer structure of samples. Moreover, gas sensor devices based on the prepared samples at different carrier gas pressures, were fabricated and their sensing performances were investigated. Results showed that, the work temperature (i.e. the lowest temperature with the highest gas response at the specified ethanol vapor concentration of 200 ppm) was 200 ºC and belongs to the sample prepared under the carrier gas pressure of 1.8 bar. Also, studying the effect of ethanol vapor concentration extent for this sample showed the increasing of sensitivity percent from 1.42 to 15.62 % for 100 to 1000 ppm ethanol vapor, respectively.

In this research, ZnO thin films with Al impurity as dopant were coated onto cleaned glass substrates by the spray pyrolysis technique. Crystal structure of the thin films was studied via XRD, and UV-vis spectroscopy was carried out to investigate their optical properties. Finally, in order to study the effect of Al impurity in ZnO thin films, the band structures of both pure and doped systems were calculated and compared using ab initio calculations in the frame work of DFT. The results show that polycrystalline thin films with hexagonal wurtzite structure have been grown, and the crystal size of the (002) ones is 25.41 nm. Moreover, the transmission in the visible region is more than 80%. Furthermore, Fermi energy is shifted into the conduction band in the case of Al doped ZnO which leads to increasing the electrical conductivity and changing the optical transmission threshold.

The structural, morphological and magnetic properties of Co0.5Zn0.5Fe2O4 nanoferrite thin films on glass substrates were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM), respectively. These thin films were deposited by spray pyrolysis method and subsequently calcined at 500 and 600 ˚C. The XRD results reveal that the calcined samples have a single-phase, and their crystallite size and lattice parameter increase as the calcination temperature increases. FE-SEM images exhibit a homogeneous grain size distribution for calcined thin films, and the grains size of samples calcined at 500 and 600 ˚C are ~ 20 and 35 nm respectively. The room temperature magnetic measurements indicate that the magnetization and coercivity of the samples in both parallel and perpendicular direction to applied magnetic field increase with calcination temperature. These can be attributed to the migration of non-magnetic Zn2 ions from octahedral to tetrahedral sites.