Influence of substrate temperature on the structural and electrical properties of α-Fe2O3 films prepared by ultrasonic spray pyrolysis

Iron oxide films were prepared by ultrasonic spray pyrolysis (USP) on SiO₂ coated Si wafers using iron acetylacetonate as an iron precursor. The crystallographic properties and surface morphologies of the films were characterized by X-ray diffraction and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy (XPS) was carried out to determine the Fe oxidation states. The satellite peak associated with Fe³⁺ photoemission at a binding energy of 719 eV was detected in the XPS results for iron oxide films, which is one of the indications of the Fe₂O₃ composition. The as-deposited films exhibit a polycrystalline -Fe₂O₃ structure. In order to observe thermal stability of the films, the resistance variation with ambient temperature was measured. All the iron oxide films deposited in this experiment were found to be -Fe₂O₃ with the thermal stability lower than 2%/ °C.     

Tunable structure,morphology of Zn1−xMgxO fine powder prepared by spray pyrolysis method and its luminescence properties

In this report, the role of Magnesium on the crystal structure, morphology, and its luminescence properties of Zn_1−xMg_xO particle were investigated. The Zn_1−xMg_xO particle was prepared by spray pyrolysis method. The obtained particle was analyzed using XRD, SEM-EDS, and photoluminescence spectroscopy correspondingly for crystal structure, morphology and elemental analysis, and photoluminescence properties due to the presence of magnesium dopant. The XRD results showed that the original structure of the particle is hexagonal wurtzite and change to cubical as the increase of Mg. The a- lattice parameter increased, and c- lattice parameter decreased with increasing the concentration of Mg in wurtzite crystal. The SEM results exhibited different morphology of the resulting particle. The morphology of the sample is dense with wrinkled shape and is changing to spherical as the result of Mg incorporation into the crystal. Photoluminescence study revealed that the addition of Mg affects the existence of new energy state beside native defect of ZnO in between valence and conduction band. The widening of bandgap on Zn_1−xMg_xO is due to the blue shift of excitonic peak in the excitation spectrum that usually called Burstein-Moss effect.     

Nano-sized α and β-TCP powders prepared by high temperature flame spray pyrolysis

Nano-sized α-TCP powders with spherical shape and non-aggregation characteristics were directly prepared by high temperature flame spray pyrolysis from the mixed spray solution of water and ethyl alcohol. The α-TCP powders prepared from the aqueous spray solution without ethyl alcohol had a bimodal size distribution with nanometer and micron sizes. Nano-sized and monodisperse α-TCP powders were prepared when the volume ratio (ethyl alcohol/distilled water, V/V) in the mixed solvent was of 40/60. The mean size of the nano-sized α-TCP powders was 32 nm. The composition ratio of calcium and phosphorous components of the nano-sized α-TCP powders was 1.49. The mean size of the spherical-like powders post-treated at a temperature of 600 °C was 57 nm. The mean size of the powders increased with increasing the post-treatment temperatures. The phase of α-TCP powders prepared by flame spray pyrolysis did not change at post-treatment temperatures below 700 °C. On the other hand, the powders post-treated at temperatures of 800 and 900 °C had single β phase of TCP.     

Dependence of structural, optical and electrical properties on substrate temperature for hexagonal MgxZn1−xO films

Single hexagonal-phase Mg_xZn_1?xO films were deposited on glass substrates by pulsed laser deposition from a ZnO target mixed with MgO. The effect of substrate temperature on the structural, electrical and optical properties was investigated by X-ray diffraction and the transmittance measurements. It was observed that Mg incorporation lead to a clear shift of the (002) peak position to lower angle with reference to pure ZnO films due to the residual stress change with deposition temperature. It was also found that Mg doping increased the resistivity by 2 orders of magnitude and the maximum resistivity was 0.072 Ω·cm at 550 °C with the carrier concentration of 1.1 × 10¹⁹ cm^?3. The visible transmittance of above 80 % was obtain in the alloy films, which optical band gap was observed to increase with the substrate temperature, attaining 3.85 eV at 600 °C. The possible mechanism was discussed.     

Effect of Zn doping on structure and ferroelectric properties of PST thin films prepared by sol–gel method

(Pb _y Sr_1−y )Zn _x Ti_1−x O_3−x thin films were prepared on ITO/glass substrate by sol–gel process using dip-coating method. The phase structure, morphology and ferroelectric property of the thin film were studied. All the thin films show the typical perovskite phase structure. Both the crystallinity and c/a ratio of the perovskite phase increases initially and then decreases gradually with doping Zn in the thin film. Ferroelectric properties of the Zn-doped PST thin films, including ferroelectric hysteresis-loop, remnant polarization and coercive force, decrease gradually with increasing Zn. And the effect of Zn on ferroelectric properties is more obvious in PST thin film with high content of Pb than that with low Pb although the high lead thin film exhibits high intrinsic ferroelectric properties.     

Effects of Nb doping on microstructure and properties of Bi4Ti3?xNbxO12 thin films prepared by magnetron sputtering

Bi₄Ti_3−xNb_xO₁₂ ferroelectric thin films were fabricated on p-Si substrates by magnetron sputtering. The effects of Nb doping on microstructure and properties of Bi₄Ti_3−xNb_xO₁₂ films were investigated. Bi₄Ti_3−xNb_xO₁₂ films had the same structure as Bi₄Ti₃O₁₂ with smaller and more uniform grains. The dielectric and ferroelectric properties of Bi₄Ti_3−xNb_xO₁₂ films were improved by Nb doping. Bi₄Ti_3−xNb_xO₁₂ films have better dielectric and ferroelectric properties with P _r = 16.5 μC/cm², E _C < 100 kV/cm, ε _r > 290, low dielectric loss (<0.9%) and clockwise C–V curves with a memory window of 0.9 V when x = 0.03–0.045, while an excessive Nb doping would lead to bad dielectric and ferroelectric properties.     

Synthesis and characterization of Sn1Mg1−xO2 thin films fabricated by aero-sole assisted chemical vapor deposition

In order to achieve high conductivity and transmittance of transparent conducting oxide, Mg doped SnO₂ (Mg_xSn_1?xO₂) thin films have been fabricated and characterized to investigate their structural and optical properties. The Mg_xSn_1?xO₂ thin films have been deposited on glass substrate using aero-sole assisted chemical vapor deposition. The molar concentration of Mg contents was changed from 0 to 8 %. The confirmation of tetragonal structure and particle size (32–87 nm) of thin films was analyzed by X-ray diffraction. The surface roughness has been found to decrease with the increase of the dopant concentration as investigated by atomic force microscopy. The optical transmission increased from 54 to 78 % and the band gap of pure SnO₂ has been found to be 3.75 eV while it rises up to 3.88 eV with increasing Mg doping. The sheet resistance (R_s) of undoped SnO₂ is maximum which become lowest at 4 % Mg doped SnO₂.     

Preparation of Ni particles by ultrasonic spray pyrolysis of NiCl2·6H2O precursor containing ammonia

The preparation of nickel particles from nickel ammine complex was studied by ultrasonic spray pyrolysis in the presence and the absence of hydrogen. In the presence of H₂ (about 9 vol.%), nickel particles were formed at 500 °C, which is much lower than that reported. Metallic nickel, together with NiO, was obtained as a major phase at 400 °C. In the absence of H₂, metallic Ni was also obtained, but higher temperature (e.g. 900 °C) was needed. It is suggested that the addition of NH₃·H₂O and NH₄HCO₃ to NiCl₂·6H₂O precursor changes the reaction pathway of Ni formation. By careful control, spherical, solid and well-distributed Ni particles of about 0.5 m were obtained at a residence time of 7–9 s in the aerosol reactor.     

Effects of Mg doping on sol–gel derived nanocrystalline hydroxyapatite thin films

Abstract

Both pure and Mg doped thin films were fabricated by sol–gel dip coating. The films were sintered either at 800 or 1000°C. The average grain size of the films was significantly affected by Mg substitution in the hydroxyapatite (HA) structure and change in the sintering temperature. The grains were considerably larger in the films sintered at higher temperatures. In addition, Mg doped films contained significantly larger grains compared to undoped HA films. Mg doping also caused rodlike grains at 800°C, and led to whitlockite (β-TCP) formation at 1000°C. The ratio of the existing phases was estimated as β-TCP/HA=27 : 73. All the films had rough surfaces with high porosity. It was also observed that undoped films had higher surface roughness than Mg doped ones.     

Structural,optical, and electrical properties of NixZn1−xFe2O4 thin film prepared by spray pyrolysis route

Journal of Materials Science: Materials in Electronics - Nanocrystalline spinel NixZn1?xFe2O4 (x?=?0.0, 0.3, 0.5, 0.7) thin films have been deposited on glass substrate at...     

Influence of annealing temperature and oxygen atmosphere on the optical and photoluminescence properties of BaTiO3 amorphous thin films prepared by sol–gel method

Homogeneous and transparent BaTiO₃ thin films were prepared by sol–gel dip coating method. The prepared BaTiO₃ thin films were annealed in air and O₂ atmosphere at different temperatures. The annealed BaTiO₃ thin films were amorphous in nature. Scanning electron microscopy (SEM) revealed the nucleation and particle growth on the films. Energy-dispersive X-ray (EDX) analysis data revealed the adsorption of oxygen atoms in the BaTiO₃ film. The direct energy band gap was found to vary (3.84–3.58 eV) as functions of annealing atmosphere and temperature. Photoluminescence (PL) revealed intense emission peaks at 393 and 675 nm. Quenching of PL intensity was observed in films annealed at high temperature and in O₂ atmosphere. This is due to reduction in the oxygen vacancy by the adsorption of oxygen in the film. Luminescence spectra also have been related to the results obtained by SEM and EDX analysis. The change in luminescence intensity of BaTiO₃ thin films makes it suitable for optoelectronic temperature sensor applications.     

AC plasma induced modifications in β-In2S3 thin films prepared by spray pyrolysis

β-In₂S₃ thin films, deposited by spray pyrolysis, were treated in N₂ and air plasmas at 240 and 400 Pa. X-ray diffraction, SEM, and EDS analysis, and optical and electrical studies have been used to characterize the as-prepared and plasma treated thin films. The post-deposition plasma treatments affect the morphology and the optoelectronic properties of the In₂S₃ thin films. The In₂S₃ thin films treated with N₂ plasma at 240 Pa showed an optical band gap, E_g, of 2.16 eV and an electrical conductivity of 2 × 10^− 2 (Ω cm)^− 1.     

The growth of aligned carbon nanotubes on quartz substrate by spray pyrolysis of hexane

Vertically aligned multiwall carbon nanotubes were grown by spray pyrolysis of hexane as the carbon source in the presence of ferrocene as catalyst precursor on a quartz substrate. In recent work we used optimal experimental parameters for the feeding method, reactor conditions, reaction temperature and time, concentration of catalyst and flow rate of feed and gas. The process parameters were chosen so as to obtain multiwall carbon nanotubes and aligned multiwall carbon nanotubes. The tubes are around 15-80?nm in diameter. The morphology and structure of the samples were characterized by x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy analyses.     

Structure,morphology, photocatalytic and antibacterial activities of ZnO thin films prepared by sol–gel dip-coating method

ZnO thin films were deposited on soda lime glass substrates by the sol–gel dip-coating method with variations of the initial Zn²⁺ concentrations. Various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) were used to investigate the effects of the initial Zn²⁺ concentrations on the structure, and surface morphology and topography of the prepared films. All prepared ZnO thin films showed a high transparency of over 88% in the visible region. The particle size increased with an increased initial Zn²⁺ concentration. This also reduced the surface denseness and the energy band gap of the ZnO thin films. All the prepared films showed photocatalytic properties through photodegradation of the methylene blue (MB) dye. The ZnO thin film prepared from the 0.1 M Zn²⁺ concentration showed the greatest efficiency as it had the highest surface area because of its greatest surface roughness. Furthermore, the prepared ZnO thin film showed antibacterial activities against the Escherichia coli bacterium.     

Structural, optical, FTIR and photoluminescence studies of CdS1?xSex thin films by chemical bath deposition method

The ternary CdS_1?xSe_x alloy thin films with the nominal composition of x?=?0.2, 0.4, 0.6 and 0.8 have been synthesized on glass substrate by chemical bath deposition (CBD) method at 80°C from aqueous solution. Crystalline phases and optical absorption of the films have been studied by X-ray diffraction and UV–visible spectrophotometer. Elemental composition of the CdS_1?xSe_x films was studied by the energy dispersive X-ray (EDX) analysis. The optical absorption and transmission studies revealed that CdS_1?xSe_x films had direct allowed transition with band gap energy decreased from 2.28 to 1.92?eV as thickness varied from 762.4 to 621.2?nm. The average crystalline size was calculated from X-ray line broadening and it is increased from 12.71 to 14.67?nm for x?=?0.2–0.8 which was confirmed by SEM studies. The substitution of Se concentrations into the Cd–S and Cd–S–Se lattice is confirmed by the increase of lattice parameters, FTIR and photoluminescence studies. The broad variation in the band gap of CdS_1?xSe_x thin films have potential applications in the field of optoelectronic devices.     

Effects of Bi doping on dielectric and ferroelectric properties of PLBZT ferroelectric thin films synthesized by sol–gel processing

[Pb _0·95(La_1???y Bi _y ) _0·05][Zr_0·53Ti_0·47]O₃ (PLBZT) ferroelectric thin films have been synthesized on indium tin oxide (ITO)-coated glass by sol–gel processing. PLBZT thin films were annealed at a relatively low temperature of 550 °C in oxygen ambient. Effects of Bi doping on structure, dielectric and ferroelectric properties of PLBZT were investigated. Bi doping is useful in crystallization of PLBZT films and promoting grain growth. When the Bi-doping content ${\mathit{y}}$ is not more than 0·4, an obvious improvement in dielectric properties and leakage current of PLBZT was confirmed. However, when the Bi-doping content is more than 0·6, the pyrochlore phase appears and the remnant polarization P _r of PLBZT thin films is smaller than that of $\left({Pb}_{{1-x}} {\bf La}_{x}\right)\!\!\left({Zr}_{{1-y}} {Ti}_{y}\right){O}_{3}$ (PLZT) thin films without Bi doping. PLBZT thin films with excessive Bi-doping content are easier to fatigue than PLZT thin films.     

Structural,optical and photoluminescence properties of hybrid metal–organic halide perovskite thin films prepared by a single step solution method

We report an inexpensive single step solution method to produce hybrid organic–inorganic lead iodide perovskite thin films for their application to photovoltaic devices. Using PbI₂ and CH₃NH₃Cl (MACl) as precursors for this single step solution method, CH₃NH₃PbI₃ (MAPbI₃) mixed with a small amount of CH₃NH₃PbCl₃ (MAPbCl₃) can be obtained after an annealing process at temperatures around 100 °C for 2 h. The synthesis of the obtained hybrid halide perovskites yields uniform films with reproducible properties. The films were characterized by X-ray diffraction (XRD), Raman spectroscopy, UV–Vis spectroscopy and photoluminescence (PL). The XRD measurements confirm the presence of cubic CH₃NH₃PbCl₃ perovskite crystallites mixed with tetragonal perovskite crystallites of CH₃NH₃PbI₃ in the films with crystallite sizes for the latter around 34.8 nm. Texture analysis indicates that these crystallites have a preferential orientation at the (002) plane. Raman characterization shows the presence of PbI₂ and MAPbI₃ vibrational modes. Photoluminescence at room temperature shows an intense emission peak at 1.61 eV associated to the excitonic transition energy of the hybrid lead iodide perovskites. From optical transmittance measurements we notice that the absorption edge is around 1.61 eV, in good agreement with the photoluminescence results. This effective band gap energy is associated with a small amount of CH₃NH₃PbCl₃ (around 6%) mixed with CH₃NH₃PbI₃ crystallites. We are in the process of optimizing the photoelectronic and structural properties of the films for their application as inexpensive absorbing layers in solar cells.     

Microstructure and properties of Sip/Al–Si surface composites prepared by ultrasonic method

Primary Si particles reinforced Al–Si surface composites (Si_p/Al–Si surface composites) were prepared by means of ultrasonic equipment with a special horn crucible. The microstructure and properties of the surface composites were investigated using optical microscope, scanning electron microscopy (SEM), hardness meter and friction and wear tester. The results show that when Al–12%Si alloy was treated by ultrasonic, Si element was easy to move up because of the decrease of the viscosity of the melt, and the alloy composition at the top of the melt became hypereutectic. So, a mass of primary Si particles formed in this place. The thickness of the surface composite layer in the surface composites decreased with increasing the ultrasonic input power. The average size of the primary Si particles in the surface composite layer was larger than that of Al–Si alloy untreated by the ultrasonic and increased with increasing ultrasonic input power. The top layer hardness of Si_p/Al–Si surface composites is higher than that of Al–Si alloy without ultrasonic treatment and increased with increasing ultrasonic input power. The friction coefficients of the top layers of the surface composites are lower than that untreated by ultrasonic. The friction coefficient decreased with increasing ultrasonic input power. With the increase of the applied load, the friction coefficient of the top layer of the surface composites increased. The wear mass loss of Si_p/Al–Si surface composites is lower than that Al–Si alloy without ultrasonic treatment. The wear resistance of the surface composites was improved with increasing ultrasonic input power.     

Effect of Mg2+-Fe3+ replacement on physical and electrical properties of the system MgxZn0.3Fe2.7−xO4±δ

X-ray analysis and d.c. electrical resistivity have been studied for the system Mg _x Zn_0.3Fe_2.7–x O_4± . The apparent density, X-ray density and porosity were also studied. It was found that the lattice parameter is independent of the substitution of iron ions with magnesium ions. Density, X-ray density and porosity do depend on replacement of the iron ions by magnesium ions. Two regions of resistivity were found; one region indicates the p-type and another one the n-type. This behaviour depends on the excess or deficiency and type of valency of the iron ions in the composition.