Mohammad Mahdi Bagheri-Mohagheghi

Single-phase Ruddlesden popper of La2-xSrxCoO4 nanopowders with x = 0.7, 0.9, 1.1 and 1.3, were successfully synthesized by a modified sol-gel method. Structural stability and morphology of the prepared samples were examined using HT-XRD analysis, FE-SEM and SEM techniques. HT-XRD analysis of the samples, in the range of room temperature to 850 °C, revealed that the structure of all samples was tetragonal. The electrical conductivity measurements, in the range of room temperature to 850 °C, indicated that by increasing the temperature the electrical conductivity mechanism inverts from variable range hopping to the nearest-neighbor hopping of small polarons. In addition, it was found that by increasing Sr concentration the structure of the sintered samples becomes more stable. The electrochemical characterization was carried out using the impedance spectroscopy (EIS) measurements on symmetrical cells at three different temperatures, 650 °C, 750 °C and 850 °C. The area specific polarization resistance (ASR) of La2-xSrxCoO4-CGO-La2-xSrxCoO4 symmetrical cell, in oxygen flow, was obtained about 1.07, 0.35, 0.33 and 0.43 Ωcm2 at 850 °C for the samples with x = 0.7, 0.9, 1.1 and x = 1.3, respectively. According to our EIS results, the main rate-limiting step for La2-xSrxCoO4 cathode performance is the dissociation process of oxygen at the surface of cathode at 650 °C and the charge transfer limiting in the cathode/electrolyte at 750 °C and 850 °C. Our results showed that the samples with Sr contents of x = 0.9 and x = 1.1 can be the promising cathodes for IT-SOFC applications. © 2018 Elsevier Ltd and Techna Group S.r.l.

Ruddlesden-Popper (RP) La2−xSrxCoO4 (x = 0.7, 0.9, 1.1, 1.3) were synthesized by a modified sol-gel route. The synthesized samples were characterized by XRD, FE-SEM technique, iodometric titration, FT-FIR spectroscopy and VSM analysis. The variation of Co-O bond length obtained from Rietveld refinements and the related peak shifts in the FT-FIR spectra showed that Co3+ has both LS and IS spin states. It is found that the population of Co3+ in the LS state decreases and IS state increases with increasing Sr concentration. Jahn-Teller effect was identified in the FT-FIR absorption bands, corresponding to the vibration modes of Co bonds with the apical and equatorial oxygen atoms. The ferromagnetic characteristic of La0.7Sr1.3CoO4, obtained by VSM, revealed the increase of Co3+ IS population by Sr doping, in agreement with XRD and FT-FIR results. The shift and split of the IR absorption bands with the change in the structural parameters are proposed to be an applicable tool to probe the spin states and Jahn-Teller effect in La2−xSrxCoO4 compounds. © 2018 Elsevier B.V.

In this paper, we consider a deformed STU model in four dimensions including both electric and magnetic charges. Using the AdS/CFT correspondence, we study holographic superconductors and obtain transport properties like electrical and thermal conductivities. We obtain transport properties in terms of the magnetic charge of the black hole and interpret it as the magnetic monopole of dual field theory. We find that the presence of the magnetic charge is necessary to have maximum conductivities, and the existence of a magnetic monopole with a critical charge (137 e) to reach the maximum superconductivity is important. Also, we show that the thermal conductivity increases with increasing of the magnetic charge. It may be concluded that the origin of superconductivity is the magnetic monopole. © 2017, The Author(s).

Nanoparticles of porous MoS2 have been synthesized by polymerizing-complexing sol–gel process using MoO3 powder in two precursors: (A) ammonia and (B) ammonium persulfate [(NH4)2S2O8]. The citric acid as complexing and ethylene glycol as polymerization agents were used. The structural properties of the prepared molybdenum disulfide nano-particles annealed at different temperatures of 200, 300, 400 and 750 °C in sulfur atmosphere have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) analyses. X-ray diffraction analysis showed the formation of MoS2 single-phase with hexagonal structure at annealing temperature of 750 °C in B precursor. The SEM images of MoS2 nanoparticles synthesized with ammonia (A) have shown a Rosette-like growth and also, MoS2 nanoparticles synthesized with (NH4)2S2O8 (B) had particle-cluster type growth with porous case. The values of band gap were obtained in the range of 3.96–2.95 and 3.11–2.02 eV from solutions consist of ammonia and (NH4)2S2O8, respectively. © 2017, Springer Science+Business Media, LLC.

In this paper, a study to improve the structural properties of graphene synthesized by Arc discharge method with TiO2 and ZnO catalysts was studied. We have developed a method for synthesizing few layered graphene by arc- discharge in a mixture of graphite flake and different catalysts. In the presence of TiO2 and ZnO catalytic, growth mechanism is different from the mechanism of growth in the absence of catalysts. Two different growth mechanisms have been proposed. The catalytic growth mechanism that is a bottom to up approach and the exfoliation mechanism that is an up to bottom approach. Structural properties, morphology and functional groups of samples by transmission electron microscopy, scanning electron microscope, X-ray diffraction, FTIR, UV–Vis, and Raman were analyzed. The results show that graphene sheets have been produced in all methods. This study showed that Arc- graphene synthesis with TiO2 as catalytic has the best structural properties. The obtained graphene nano-sheets showed the in-plane crystallite size from 35.6 nm to 53.6 nm. The results show that the AC arc-discharge method can be used for few-layer graphene sheet synthesis with flake graphite as a carbon source and TiO2 or ZnO as a catalyst. © 2017, Springer Science+Business Media New York.

In this research, molybdenum disulfide (MoS2) nanoparticles were prepared by chemical reduction method using MoO3 and thiourea as a precursor. The physical properties of the synthesized MoO2–MoS2 nanoparticles annealed at different temperatures of 200, 300, 750 °C have been investigated, before and after exposure to sulfur vapor. The nanostructure of nanoparticles has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) analyses and UV–Vis spectrophotometer. The X-ray diffraction analysis showed the formation of MoS2 single phase at annealing temperature of 750 °C in the presence of sulfur vapor. The Raman spectrum of the nanoparticles revealed that the formation of MoS2 at 750 °C after annealing in sulfur vapor. The values of band gap were obtained in the range of 3.64–3.17 eV and 3.47–1.95 eV for MoS2 nanoparticles before and after exposure to sulfur vapor, respectively. According to SEM images, the grain size decreases with increasing annealing temperature up to 750 °C. Also, nanoplate–nanoparticles of MoS2 are formed at annealing temperature of 200–750 °C. The TEM images of MoS2 nanoparticles at Ta = 750 °C confirm that the nanoparticles have a homogeneous distribution with a hexagonal structure. The FTIR spectra of the MoS2 nanoparticles showed the peaks at about 467 cm−1 belong to the characteristic bands of Mo–S. © 2016, Springer-Verlag Berlin Heidelberg.

Titanium dioxide thin films have been deposited on glass substrate at various solution flow rates by spray pyrolysis technique with substrate temperatures between 350 °C–550 °C. Samples were characterized for structural, morphological and optical properties by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–visible spectrometry. The XRD analysis of deposited TiO2 films exhibited nanocrystalline nature and preferentially oriented along [101] direction. The UV–visible transmittance results show that all thin films were transparent with an average transmittance higher than 70% in the visible region. Due to nanosized grains, the optical band gaps of the TiO2 thin films (3.35–3.68 eV) were larger than the bulk TiO2 (3.2 eV). The SEM analysis revealed that thickness and morphology of TiO2 films can be adjusted by rate of solution flow and substrate temperature. It seems that the process of spray pyrolysis provides an easy way to prepare either homogeneous thin and thick films. © 2016 Elsevier B.V.

A systematic study to optimize the electrical properties of ITO–graphene composite films deposited by spray pyrolysis method was investigated. The Hummers method was used for the synthesis of graphene oxide (GO) powder. Graphene was prepared by chemical reduction method from GO. To reduce GO, the most common reducing agent hydrazine hydrate at 3 ml per 100 mg of GO was used, Then, “ITO–graphene” composite films deposited by spray pyrolysis method. Structural, electrical and optical properties of films by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, two-point probe method, Hall Effect experiment and UV–Vis were analyzed. The results show that graphene sheets and “ITO–graphene” composite have been produced. The obtained ITO–graphene composite films showed an energy band gap from 3.62 to 3.57 eV and sheet resistance from 7.5 to 1.5 KΩ/sq in comparison with undoped ITO films. This study showed that adding graphene to ITO film without causing much change in structural properties and energy gap, reduces the resistance of ITO film about 75 % and increases its transparency up to 90 %. The results of this study may lead to ITO–graphene composite films be more interested in sensing and solar cells applications and composites. © 2016, Springer Science+Business Media New York.

Transparent conducting fluorine and Sb-doped [SnO2: (F, Sb)] thin films have been deposited onto preheated glass substrates using the spray pyrolysis technique by the various dopant quantity of spray solution. The effect of antimony impurities on the structural, morphological, electrical, Thermo-electrical, optical and photoconductive properties of films has been investigated. The [F/Sn] atomic concentration ratio (x) in the spray solution is kept at value of 0.7 and the [Sb/Sn] atomic ratio (y) varied at values of 0, 0.0005, 0.001, 0.002, 0.01, 0.03, 0.05, 0.07 and 0.10. It is found that the films are polycrystalline in nature with a tetragonal crystal structure corresponding to SnO2 phase having orientation along the (110) and (200) planes. SEM images indicated that nanostructure of the films has a particle type growth. The average grain size increases with increasing spraying quantity of Sb-dopant. The compositional analysis of SnO2: (F, Sb) thin films were studied using EDAX. SEM and AFM study reveals the surface of SnO2: (F, Sb) to be made of nanocrystalline particles. The Hall Effect measurements have shown n-type conductivity in all deposited films. The lowest sheet resistance and highest the carrier concentration about 7.7 Ω/□ and 6.6 × 1022, respectively, were obtained for the film deposited with y = [Sb/Sn] = 0.001 and x = [F/Sn] = 0.7. The maximum of the Seebeck coefficient equal to 12.8 μV K−1 was obtained at 400 K for the film deposited with y = [Sb/Sn] = 0.10. The average transmittance of films varied over the range 10–80 % with change of Sb-concentration. The band gap values of samples were obtained in the range of 3.19–3.8 eV. From the photoconductive studies, the Sb-doped films exhibited sensitivity to incident light especially in y = 0.001. The electrical resistivity and carrier concentration vary in range 5.44 × 10−4 to 1.02 × 10−2Ω cm and 2.6 × 1022–6.6 × 1022 cm−3, respectively. © 2015, Springer Science+Business Media New York.

A systematic study to optimize the structural properties of graphene synthesized from modified graphene by both chemical and physical reduction methods were studied. In the chemical method, the two most common reducing agent hydrazine hydrate and sodium borohydride at different concentrations were used. In the physical method, two different samples were produced using a heat treatment at 200 °C in the presence of argon gas. Structural properties, morphology and functional groups of samples by SEM, TEM, XRD, FTIR, UV–Vis, PL and TGA were analyzed. The results show that graphene sheets have been produced in all methods. This study showed that modified graphene with hydrazine hydrate (3 ml per 100 mg of GO) has the best structural properties. The result of physical reduction method by heat treatment in argon gas showed the lowest energy gap among other samples. The PL emission spectroscopy showed the strong intensities at 500 and 600 nm due to the overlap of the second order emissions in the electron–hole recombination processes as results from different types of electronically excited states and physical reduction had minimum of intensity. The obtained graphene nano-sheets showed an energy band gap from 1.37 to 2.70 eV that is suggested as an application method in opening of the energy band gap. However, synthesized graphene by the chemical reduction method by hydrazine hydrate treatment has the better structure, but the physical reduction method is rapid and equally appropriate. © 2015, Springer Science+Business Media New York.

This paper presents a comprehensive investigation on the transparent microstrip patch antenna based on fluorine doped tin oxide (FTO). High quality FTO films have been deposited by spray pyrolysis technique and opto-electrical properties of the films were measured. Deposited films show 6.7-8.4 Ω/ surface resistance and ∼85% optical transparency. Substrate thickness effect on transparent conductor losses and theoretical transparency analysis using Drude model and thin film transfer matrix (TTM) method has been performed. Microstrip antennas with transparent patch/transparent ground plane, and copper patch/copper ground plane (as reference) for 5 GHz resonance frequency were fabricated, analyzed, and compared. The fabricated microstrip antenna with both transparent patch and ground plane shows 1.72 dBi gain at 5 GHz. © 2015 Taylor and Francis.

Transparent conducting phosphorus-fluorine co-doped tin oxide (SnO2:(P, F)) thin films have been deposited onto preheated glass substrates using the spray pyrolysis technique by the various dopant quantity of spray solution. The [F/Sn] atomic concentration ratio (x) in the spray solution is kept at value of 0.7 and the [P/Sn] atomic ratio (y) varied at values of 0, 0.001, 0.005, 0.01, 0.02, 0.04, 0.06, and 0.10. The structural, morphological, X-ray diffraction, electrical, optical and photoconductive properties of these films have been studied. It is found that the films are polycrystalline in nature with a tetragonal crystal structure corresponding to SnO2 phase having orientation along the (110) plane and polyhedrons like grains appear in the FE-SEM image. The average grain size increases with increasing P-dopant concentration. The compositional analysis of FTO:P thin films were studied using EDAX. The Hall effect measurements have shown n-type conductivity in all deposited films. The lowest sheet resistance and highest the carrier concentration about 6.4 Ω/□ and 7.4×1022, respectively, were obtained for the film deposited with y=[P/Sn]=0.01. The films deposited with y=0.04 phosphorus-doped SnO2:F shows 68% optical transparency. From the photoconductive studies, the P-doped films exhibited sensitivity to incident light especially in y=0.04. The electrical resistivity and carrier concentration vary in rang 6.2×10-4 to 21.1×10-4 Ω cm and 7.4×1022 to 1.3×1022 cm-3, respectively. © 2014 Elsevier Ltd. All rights reserved.

Transparent microstrip antenna with fluorine-doped tin oxide (FTO or SnO2:F) patch is studied here. The authors make use of spray pyrolysis technique to deposit FTO transparent patch on a Pyrex glass substrate. The deposited FTO patches show high optical transmittance (about 80-90%) and low electrical surface resistance (as low as 7 Ω/□). Two transparent microstrip patch antennas (with conventional conductor as ground plane), which are fed by proximity coupling at 2.5 and 5 GHz resonance frequencies, are fabricated and their radiation properties are presented and compared with copper patch antenna counterparts. In order to reduce the conductor loss of the antenna and ameliorate antenna efficiency, thick substrates should be used. The 2.5 GHz antenna shows low efficiency and significant loss in transparent layer but the 5 GHz one shows 3.63 dBi maximum gain and only ~0.83 dB degradation in comparison with the copper patch antenna. © The Institution of Engineering and Technology 2015.

In this study, vanadium oxide (V2O5) was doped with different percentages of fluorine (F) and deposited on glass substrates by using spray pyrolysis method. The substrate temperature during the film deposition was kept constant at 450 °C. The obtained nanostructured thin films were characterised by X-ray Diffraction (XRD), UV-visible spectroscopy, and Scanning Electron Microscopy (SEM). The XRD results showed that F doped films are polycrystalline with main phase of β-V2O5 and with preferred orientation along (200). Increasing dopant to 30% improved crystallinity, but for more doping, the structure of samples tended to be amorphous. VF2 phase was also observed when doping of F was increased to more than 10%. The incorporation of fluorine in nano-layers led to a decrease in optical absorption by 1.3 a.u. and an increase in band gap of energy from 2.23 to 2.83 eV. SEM images showed that the shape of grains was spherical with 10% doping and changed to bacilliform with 70% F concentration. The cyclic voltammetry results obtained for different samples showed expanded anodic and cathodic peaks for the undoped sample. The samples prepared with 20% and 40% F-doping level had milder anodic and cathodic peaks. However, by increasing the dopant to 70%, the peaks were expanded. The thin film with 40% F-doping showed the least resistance, but the resistance increased dramatically with 70% F dopant concentrations. © 2014 Elsevier Ltd. All rights reserved.

We have established the effect of copper dopant concentration (Cu/Sn = 0 - 30 at.%) on the structural, morphological and optical properties of SnO2 : S films grown on glass substrate using a spray pyrolysis technique. According to the experimental evidence and data analysis, we found that the polycrystalline layers in undoped condition mainly consist of mixed phases such as SnS2 and SnO2, whilst in doped ones, Cu2SnS3 and Cu4SnS4 phases are dominant. With increasing Cu concentration, a decrease in the grain size with a change in the shape of the grains is observed. Optical measurement analysis showed that these films have a direct band gap energy of about 2.98 - 3.59 eV. © Carl Hanser Verlag GmbH & Co. KG.

In this research, S-doped vanadium oxide thin films, with doping levels from 0 to 40 at.%, are prepared by spray pyrolysis technique on glass substrates. For electrochemical measurements, the films were deposited on florin-tin oxide coated glass substrates. The effect of S-doping on structural, electrical, optical and electrochemical properties of vanadium oxide thin films was studied. The x-ray diffractometer analysis indicated that most of the samples have cubic β-V2O5 phase structure with preferred orientation along [200]. With increase in the doping levels, the structure of the samples tends to be amorphous. The scanning electron microscopy images show that the structure of the samples is nanobelt-shaped and the width of the nanobelts decreases from nearly 100 to 40 nm with increase in the S concentration. With increase in the S-doping level, the sheet resistance and the optical band gap increase from 940 to 4015 kΩ/square and 2.41 to 2.7 eV, respectively. The cyclic voltammogram results obtained for different samples show that the undoped sample is expanded and the sample prepared at 20 at.% S-doping level has sharper anodic and cathodic peaks. © 2013 The Royal Swedish Academy of Sciences.

A sol-gel method based on the Pechini process was used to synthesize different phases of alumina nanoparticles using a polymeric precursor with Aluminum nitrate. The emphasis was on investigating the effect of two different complexing agents, urea and citric acid, on the structural properties, particle size, and phase transformation during the heat treatment that was studied by XRD, TEM, SEM, BET, and FT-IR spectroscopy. The obtained results showed that particles do get fused together at high temperatures, and also the size of particles increases with the increase of annealing temperature. It was concluded that the size of α-alumina synthesized by urea was 10-15 nm, whereas the sample with citric acid yielded α-powder with particle size of 200 nm. Also, the resulting powder prepared by urea exhibited larger surface area (84.2 m2/gm-1) compared to citric acid (39.92 m 2/gm-1) at 750°C. © 2013 A. Rajaeiyan and M. M. Bagheri-Mohagheghi.

Vanadium oxide thin films were prepared on glass substrates by using the spray pyrolysis technique. The effect of solution concentration (0.1 M, 0.2 M and 0.3 M) on the nanostructural, electrical, optical, and electrochromic properties of deposited films were investigated using X-ray diffraction, scanning electron microscopy, UV - vis spectroscopy, and cyclic volta-metrics. The X-ray diffraction shows that only the sample at 0.1 M has a single β-V2O5 phase and the others have mixed phases of vanadium oxide. The lowest sheet resistance was obtained for the samples prepared at 0.3 M solution. It was also found that the optical transparency of the samples changes from 70% to 35% and the optical band gap of the samples was in the range of 2.20 to 2.41 eV, depending on the morality of solution. The cycle voltammogram shows that the sample prepared at 0.3 M has one-step electerochoromic but the other samples have two-step electerochoromic. The results show a correlation between the cycle voltammogram and the physical properties of the films. © 2013 Chinese Institute of Electronics.

Vanadium oxide thin films were grown on glass substrates using spray pyrolysis technique. The effects of substrate temperature, vanadium concentration in the initial solution and the solution spray rate on the nanostructural and the electrochromic properties of deposited films are investigated. Characterization and the electrochromic measurements were carried out using X-ray diffraction, scanning electron microscopy and cyclic voltammogram. XRD patterns showed that the prepared films have polycrystalline structure and are mostly mixed phases of orthorhombic α-V 2O5 along with minor β-V2O5 and V4O9 tetragonal structures. The preferred orientation of the deposited films was found to be along [101] plane. The cyclic voltammogram results obtained for different samples showed that only the films with 0.2 M solution concentration, 5 ml/min solution spray rate and 450°C substrate temperature exhibit two-step electrochromic properties. The results show a correlation between cycle voltammogram, morphology and resistance of the films. © 2013 World Scientific Publishing Company.

Thin films of tin selenide (SnxSey) with an atomic ratio of r=[y/x] = 0.5, 1 and 1.5 were prepared on a glass substrate at T = 470°C using a spray pyrolysis technique. The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride (SnCl4· 5H2O) and selenide acide (H 2SeO3). The prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy, scanning tunneling microscopy, scanning helium ion microscopy, and UV-vis spectroscopy. The photoconductivity and thermoelectric effects of the SnxSey thin films were then studied. The SnxSey thin films had a polycrystalline structure with an almost uniform surface and cluster type growth. The increasing atomic ratio of r in the films, the optical gap, photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV, 0.01 to 0.31 and -26.2 to -42.7 mV/K (at T = 350 K), respectively. In addition, the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe2 phases. © 2013 Chinese Institute of Electronics.

In this research, Sn-doped In2S3 thin films were prepared on glass substrates by spray pyrolysis technique. The effect of tin impurity on the structural, morphological, electrical, thermo-electrical, optical and photoconductive properties of films has been investigated. The tin to indium atomic ratios (x = [Sn]/[In]) were varied from 0 to 0.15 in the spray solution. X-ray diffraction analysis showed the formation of cubic β-In2S3 phase in all deposited films. Scanning electron microscopy images indicated that nanostructure of the condensed films has a particle-cluster to rock-plate growth type. The Hall effect measurements have shown n-type conductivity in all deposited films. The lowest resistance of 1.3 MΩ/□ and the highest the carrier concentration of 3.93 × 1018 cm- 3 were obtained for the film deposited with x = 0.08. The maximum of the Seebeck coefficient equal to 132 μVK- 1 was obtained at 400 K for the film deposited with x = 0.15. The average transmittance of films varied over the range of 40-60%. The band gap values of samples were obtained in the range of 2.89-3.75 eV for direct and 2.61-3.37 eV for indirect allowed transitions. From the photoconductivity studies, the sample prepared with x = 0.05 exhibited the highest photoconductivity among the In2S3:Sn films. © 2013 Elsevier B.V. All Rights Reserved.

In this work, the structural and optical properties of titanium dioxide (TiO2) nanopowders are studied. The TiO2 nanoparticles were synthesized by complexing sol-gel process and effect of complexing agents on transition of the anatase phase to rutile phase during the heat treatment have been investigated. In addition, we have studied the grain size of TiO 2 powders and their dependence on the type of complexing agent. The analysis of the XRD patterns, FT-IR and UV-Vis spectroscopy, BET surface area and TEM images show that the synthesis of nanoparticles with acetyl acetone (AcAc) as complexing agent yielded the smallest size of nanoparticles about 22-35 nm. Our results indicate that with increasing the calcinating temperature, the size of the nanoparticles is increased and the energy gap reduced, too. Also, the optical band gap was obtained in the range of 3.4-4.1 and 3.06-3.74 eV for anatase and rutile phases, respectively. © 2012 Springer Science+Business Media New York.

The nanostructured γ and α alumina powders were synthesized by sol-gel and co-precipitation methods, and properties of the powders were studied by XRD, SEM, TEM, BET and FTIR. The results showed that both γ and α phases were formed in the lower temperature in precipitation method compared to sol-gel. The size of spherical α-alumina synthesized by sol-gel was 10-15 nm, whereas the sample prepared by co-precipitation yielded nearly spherical and hexagon α-powder with particle size of 10-50 nm. At 750 °C the resulting powder prepared by co-precipitation exhibited larger surface area (206.2 m2/g) compared to sol-gel (30.72 m2/g), hence it is recommended for catalytic and sensing applications. © 2013 Shanghai University and Springer-Verlag Berlin Heidelberg.

Vanadium oxides condensed films are prepared on glass substrates, using spray pyrolysis (SP) technique. The effects of substrate temperature, vanadium concentration in initial solution and the solution spray rate on the nano-structural, electrical, and optical properties of deposited films were investigated. Characterizations of the samples were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectroscopy methods. The type and concentration of the charge carriers were determined and measured by Hall effect experiment. XRD patterns showed that the prepared films had polycrystalline structure, mostly tetragonal β-V2O5 and V4O9 phases with the preferred orientation along (200) direction. The Hall effect experiment revealed that all samples were n-type, except the ones deposited at substrate temperatures T sub = 300 °C and T sub = 450 °C, vanadium concentration 0.1 mol/L and solution spray rate 10 mL/min. The charge carrier concentrations obtained were in the range 1016-1018 cm-3. The lowest sheet resistance (R s) was obtained for the samples prepared at T sub = 450 °C, vanadium concentration 0.05 mol/L and solution spray rate 10 mL/min. It was also found that the optical transparency of the samples changed from 20% to 75% and the optical band gap of the samples was from 2.22 eV to 2.58 eV, depending on the deposition conditions. © 2013 Shanghai University and Springer-Verlag Berlin Heidelberg.

In this study In 2O 3 and In 2O 3:S thin films were prepared on glass substrates using the spray pyrolysis technique. The effect of sulfur impurities on the structural, morphological, electrical, thermo-electrical, optical and photoconductive properties of films has been investigated. The sulfur to indium atomic ratios (x=[S]/[In]) were varied from 0 to 15 in the spray solution. From the x-ray diffraction analysis, a phase transition occurred from the cubic In 2O 3 to the cubic β-In 2S 3 phase with increasing S-doping level. SEM images indicated that the nanostructure of the films has a particle-cluster type growth. The Hall effect measurements have shown n-type conductivity in all of the deposited films. The lowest resistance of 19kΩsq 1 and the highest carrier concentration of 1.32×10 19cm -3 were obtained for the film deposited with an [S]/[In] atomic ratio of 0.6. The maximum of the Seebeck coefficient equal to 141μVK 1 was obtained at 400K for the film deposited with an [S]/[In] atomic ratio of 1. The average transmittance of films varied over the range 40-80% with S-concentration. The band gap values of samples were obtained in the range of 3.85-3.96eV. From the photoconductivity studies, the sample prepared with the [S]/[In] atomic ratio of 0.2 exhibited the highest photoconductivity among the In 2O 3:S films. © 2012 The Royal Swedish Academy of Sciences.

In this paper, the effect of S and Al concentrations on the structural, electrical, optical, thermoelectric and photoconductive properties of the films was studied. The [Al]/[Sn] and [S]/[Sn] atomic ratios in the spray solutions were varied from 10 at.% to 40 at.% and 0 to 50 at.%, respectively. X-ray diffraction analysis showed the formation of SnO 2 cassiterite phase as a main phase and the numerous sulfur phases including S, SnS, SnS 2 and Sn 2S 3 in SnO 2:Al films. Scanning electron microscopy studies showed that in the absence of S, increasing the Al content results in a smaller grain size and with the addition of S, the films appear to contain small cracks and nodules. The minimum resistance of 0.175 (kΩ/□) was obtained for S-doped SnO 2:Al (40 at.%) film with 20 at.% S-doping. From the Hall effect measurements, the majority carrier concentration was obtained in order of 10 17-10 18 cm - 3. The thermoelectric measurements showed that majority carriers change from electrons to holes for S-doping in SnO 2:Al (40 at.%) thin films. The maximum Seebeck coefficient of + 774 μV/K (at T = 370 K) was obtained for S-doped SnO 2:Al (10 at.%) film with 50 at.% S-doping. The band gap values were obtained in the range of 3.8-4.2 eV. The S-doped SnO 2:Al (40 at.%) films have shown considerably photoconductivity more than S-doped SnO 2:Al (10 at.%) with increasing S-doping. The best photoconductive property was obtained for co-doped SnO 2 thin film with 40 at.% Al and 5 at.% S concentration in solution. © 2012 Elsevier B.V. All rights reserved.

Co-doped TiO2 nanoparticles were synthesized via non hydrous complex-polymer sol-gel method. A series of Cox :Ti 1-xO 2 samples with x ≤0.01, 0.03, 0.05, 0.08 and 0.10, were prepared and subsequently annealed at 400°, 600° and 800 °C. Structural and magnetic properties of Cox :Ti 1-xO 2 have been studied by means of X-ray diffraction and DC magnetometry. All samples annealed at 400 °C show a paramagnetic behavior with an average grain size of 11 nm. With increasing annealing temperatures a complete crystallization is seen with growth of the cluster size up to 31 nm with clear evidence of a presence of CoTiO 3. For all concentrations and annealing conditions no sign of a metallic phase, even at x ≤0.10, is seen. Copyright © 2012 American Scientific Publishers.

In this work, ZnO thin films have been prepared by spray pyrolysis deposition method on the glass substrates. The effect of deposition parameters, such as deposition rate, substrate temperature and solution volume has been studied by X-ray diffraction (XRD) method, UV-Vis- NIR spectroscopy, scanning electron microscopy (SEM), and electrical measurements. The XRD patterns indicate polycrystalline wurtzite structure with preferred direction along (0 0 2) planes. Thin films have transparency around 90% in the visible range. The optical band gap was determined at 3.27 eV which did not change significantly. Evolution of electrical results containing the carriers' density, sheet resistance and resistivity are in agreement with structural results. All the results suggest the best deposition parameters are: deposition rate, R =3ml/min, substrate temperature, T s =450°C and thickness of the thin films t =110-130 nm. © Indian Academy of Sciences.

In this paper, the SnO 2-Al 2O 3 binary thin-film system has been deposited on a glass substrate by the spray pyrolysis technique. The effect of aluminum concentration on the structural, electrical, thermoelectrical, optical and photoconductivity properties of films was studied. The [Al]/[Sn] atomic ratio was in the range 0-100 at.% in solution. X-ray diffraction analysis shows that all films with different doping levels have polycrystalline SnO 2 cassiterite phase. At doping levels of 40 at.% and above, the Al 2O 3 phase was observed and the sheet resistance of the films increased with increasing Al doping in the ranges from 5 at.% to less than 40 at.% and more than 60 at.% due to the substitution of Al 3+ with Sn 4+. Minimum sheet resistance of films was found in the range 40-60 at.%. Using Hall effect measurements, the majority carriers concentration obtained was of the order of 10 18 cm -3. Hall effect and thermoelectrical measurements show that at doping levels between 10 and 20% and also higher than 60 at.%, majority carriers change from electrons (n-type conduction) to holes (p-type conduction). Also, a higher Seebeck coefficient value equal to -341 μV K -1 was obtained for the 30 at.% Al-doping level. The average transmittance of the films at low doping levels was about 75-90%. The photoconductivity properties of SnO 2-Al 2O 3 thin films increased with increasing doping level.

Tin sulfide thin films (SnxSy) with an atomic ratio of y/x = 0.5 have been deposited on a glass substrate by spray pyrolysis. The effects of deposition parameters, such as spray solution rate (R), substrate temperature (Ts) and film thickness (t), on the structural, optical, thermo-electrical and photoconductivity related properties of the films have been studied. The precursor solution was prepared by dissolving tin chloride (SnCl4, 5H2O) and thiourea in propanol, and Sn xSy thin film was prepared with a mole ratio of y/x = 0.5. The prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectroscopy. It is indicated that the XRD patterns of SnxSy films have amorphous and polycrystalline structures and the size of the grains has been changed from 7 to 16 nm. The optical gap of SnxSy thin films is determined to be about 2.41 to 3.08 eV by a plot of the variation of (αhν)2 versus hν related to the change of deposition conditions. The thermoelectric and photo-conductivity measurement results for the films show that these properties are depend considerably on the deposition parameters. © 2011 Chinese Institute of Electronics.

In this work, some structural and optical properties of the zinc oxide (ZnO) nanoparticles were studied. The highly crystalline ZnO nanoparticles were produced by the hydrothermal and sol - gel methods. The analyses of the XRD patterns, STEM images and UV spectroscopy showed that the size of the nanoparticles prepared by oxalic acid was smaller than the ones by urea. The properties of oxalic acid and urea were also investigated to determine the most effective crystallization process of ZnO nanoparticles. It has been shown that pH, decomposition temperature and activity coefficient of the complexing agent have certain effects on crystallization process. © Indian Academy of Sciences.

In this paper, thin films of tin sulfide (SnxSy) with atomic ratios of y/x=0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 have been prepared on a glass substrate at T=420°C using the spray pyrolysis technique. The initial materials for the preparation of thin films were an alcoholic solution consisting of tin chloride (SnCl4.5H2O) and thiourea (CS(NH3)2). The prepared thin films were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray analysis, scanning helium ion microscopy and UV-vis spectroscopy. The photoconductivity and thermoelectric effects of SnxSy thin films have been studied. The SnxSy thin films had a polycrystalline structure with a nearly uniform surface and cluster-type growth. With increasing the atomic ratio of (y/x) in films, the optical gap, photosensitivity, thermal activation energy and Seebeck coefficient changed from 2.72 to 2.37 eV, from 0.05 to 0.78, from 0.07 to 0.48 eV (in the high temperature range) and from +0.17 to -0.22 mV K-1 (at T=350 K), respectively. In addition, the structure of tin sulfide thin films tends to a nearly single-crystal state in (001) preferred orientation corresponding to SnS2 phase with increasing (y/x) ratio. These structure situations considerably influence the photosensitivity and thermoelectric properties of thin films. © 2011 The Royal Swedish Academy of Sciences.

ZnO:Mg thin films with different amounts of Mg were deposited on a glass substrate using the spray pyrolysis technique. The structural, optical and antibacterial properties of the films were studied as a function of the dopant concentration. The ZnO:Mg films were characterized using methods such as x-ray diffractometry, scanning electron microscopy, scanning tunneling microscopy and UV-Vis spectroscopy. The samples display hexagonal wurtzite structure, with no secondary phase. Morphological studies indicated the deposition of a uniform film, and particle size decreases with Mg doping. Optical studies revealed that the optical band gap and optical transmittance increase with Mg concentration. The antibacterial activities of the samples against Escherichia coli (gram-negative) cultures were tested by the drop test method, which shows that Mg doping increases antibacterial activities of thin films. © 2011 The Royal Swedish Academy of Sciences.

Ni-doped TiO2 nanoparticles were synthesized by the non-hydrous complex-polymer sol-gel method. Titanium isopropoxide was used as precursor and acetyl acetone (AcAc) and citric acid were used as polymer and complex agent, respectively. A series of Nix: Ti1-xO2 samples with x=0.01, 0.03, 0.05 and 0.10 were prepared and subsequently annealed at 400, 600 and 800 °C. The structural and magnetic properties of Nix: Ti1-xO2 were studied by means of x-ray diffraction (XRD) and dc magnetometery. Samples annealed at 400 °C attained a particle size of 12 nm with structural phases of anatase, rutile and cubic NiO. From the blocking temperatures of the zero-field-cooled and field-cooled measurements, similar particle sizes (as from XRD) were obtained. The presence of ferro- and antiferromagnetic (AFM) interactions further confirms that the particles have different structural compositions. At 800 °C the particles have grown to about 30 nm with either a rutile or NiTiO3-type structure. The presence of NiTiO3 is also seen in the magnetic measurements, which show the characteristic AFM peak at 23 K. © 2011 The Royal Swedish Academy of Sciences.

In this research, nickel oxide (NiO) transparent semiconducting films are prepared by spray pyrolysis technique on glass substrates. The effect of Ni concentration in initial solution and substrate temperature on the structural, electrical, thermoelectrical, optical and photoconductivity properties of NiO thin films are studied. The results of investigations show that optimum Ni concentration and suitable substrate temperature for preparation of basic undoped NiO thin films with p-type conductivity and high optical transparency is 0.1 M and 450 °C, respectively. Then, by using these optimized deposition parameters, nickel-lithium oxide ((Li:Ni)Ox) alloy films are prepared. The XRD structural analysis indicate the formation of the cubic structure of NiO and (Li:Ni)Ox alloy films. Also, in high Li doping levels, Ni2O3 and NiCl2 phases are observed. The electrical measurements show that the resistance of the films decreases with increasing Li level up to 50 at%. For these films, the optical band gap and carrier concentration are obtained to be 3.6 eV and 1015-10 18 cm-3, respectively. © 2010 Elsevier B.V. All rights reserved.

In this paper, the relative importance of effective parameters such as the activity coefficient, thermal decomposition and pH of chemical additives is investigated on the control procedure of ZnO nanoparticle growth. It is found that the activity coefficient is of greater importance compared with other parameters and should not be neglected in nanosynthesis any longer. This effect of activity coefficient of additives may also improve the fabrication and properties of other applicable nanostructures. © 2011 The Royal Swedish Academy of Sciences.

In this paper, pn and pin heterojunctions based on transparent semiconducting oxides are fabricated employing the spray pyrolysis technique. The prepared p-NiO:Li/n-SnO2:F (bi-layer) and p-NiO:Li/i-ZnO/n- SnO2:F (tri-layer) junctions are structurally, electrically and optically characterized, and the effect of insertion of the intrinsic buffer layer (i-ZnO) followed by post-annealing is investigated through IV measurements. The measurement results for the proposed p-NiO:Li/n-SnO 2:F device show that the forward threshold and the reverse breakdown voltages are about 0.4 and -2.8 V, respectively. By applying the middle layer, the forward threshold and reverse breakdown voltages reach ∼1 and -4.2 V; then by post-annealing this element at 700 °C for 30 min, the mentioned voltages reach about 1.6 and -3.1 V, respectively. © 2010 Elsevier B.V.

In this paper, we report on the structural, microstructural and optical properties of nano-crystalline indium tin oxide (ITO) particle, which has been synthesized by solgel process using a simple starting hydro-alcoholic solution consisting of In(NO3)3.5H2O, SnCl 4.5H2O, citric acid as complexing and ethylene glycol as polymerization agents. The structural properties of indium tin oxide nano-powders annealed at different temperatures (T=350650 °C) have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The XRD patterns show In2O3-cubic phase in nano-powders without any indication of crystalline SnOx as an additional phase. The TEM images show the nano-particles as nearly spherical shaped with size in the range of 1045 nm as the size of grains increases by increasing the annealing temperatures. The optical direct band gap of ITO nano-particles was calculated to be about 3.394.02 eV in the temperature range 350650 °C by optical absorption measurements. The optical band gap shifts to a higher energy with increasing annealing temperature is due to the improvement of the crystallinity, thereby increasing the carrier concentration as determined from the BursteinMoss effect. © 2010 Elsevier B.V.

The electrical, optical and structural properties of Cobalt (Co) doped SnO2 transparent semiconducting thin films, deposited by the spray pyrolysis technique, have been studied. The SnO2:Co films, with different Cocontent, were deposited on glass substrates using an aqueous-ethanol solution consisting of tin and cobalt chlorides. X-ray diffraction studies showed that the SnO2:Co films were polycrystalline only with tin oxide phases and preferential orientations along (1 1 0) and (2 11) planes and grain sizes in the range 19-82 nm. Optical transmittance spectra of the films showed high transparency ∼ 75-90% in the visible region, decreasing with increase in Co-doping. The optical absorption edge for undoped SnO2 films was found to be 3.76 eV, while for higher Co-doped films shifted toward higher energies (shorter wavelengths) in the range 3.76-4.04 eV and then slowly decreased again to 4.03 eV. A change in sign of the Hall voltage and Seebeck coefficient was observed for a specific acceptor dopant level ∼11.4at% in film and interpreted as a conversion from n-type to p-type conductivity. The thermoelectric electro-motive force (e.m.f.) of the films was measured in the temperature range 300-500 K and Seebeck coefficients were found in the range from -62 to +499 μVK-1 for various Co-doped SnO2 films. © 2010 Elsevier B.V. All rights reserved.

Nano-crystalline indium oxide (In2O3) particles have been synthesized by sol-gel and hydro-thermal techniques. A simple hydro-alcoholic solution consisting indium nitrate hydrate and citric acid (in sol-gel method) and 1, 4-butandiol (in hydro-thermal method) have been utilized. The structural properties of indium oxide nano-powders annealed at 450 °C (for both methods) have been characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and specific surface area (SSA) analysis. Structural analysis of the samples shows cubic phase in sol-gel and cubic-hexagonal phase mixture in hydro-thermally prepared particles. The nano-particles prepared by sol-gel method have nearly spherical shape, whereas hydro-thermally-made ones display wire- and needle-like shape in addition to the spherical shape. The obtained In2O3 nano-particles surface areas were 23.2 and 55.3 in sol-gel and hydro-thermal methods, respectively. The optical direct band gap of In2O3 nano-particles were determined to be ∼4.32 and ∼4.24 eV for sol-gel and hydro-thermal methods, respectively. These values exhibit ∼0.5 eV blue shift from that the bulk In2O3 (3.75 eV), which is related to the particle size reduction and approaching the quantum confinement limit of nano-particles. © 2009 Elsevier B.V. All rights reserved.

In this paper, we report structural, electrical, optical, and especially thermoelectrical characterization of iron (Fe) doped tin oxide films, which have been deposited by spray pyrolysis technique. The doping level has changed from 0 to 10 wt% in solution ([Fe]/[Sn] = 0-40 at% in solution). The thermoelectric response versus temperature difference has exhibited a nonlinear behavior, and the Seebeck coefficient has been calculated from its slope in temperature range of 300-500 K. The Hall effect and thermoelectric measurements have shown p-type conductivity in SnO2:Fe films with [Fe]/[Sn] ≥ 7.8 at%. In doping levels lower than 7.8 at%, SnO2:Fe films have been n-type with a negative thermoelectric coefficient. The Seebeck coefficient for SnO2:Fe films with 7.8 at% doping level has been obtained to be as high as +1850 μV/K. The analysis of as-deposited samples with thicknesses ∼350 nm by X-ray diffraction (XRD) and scanning electron microscopy (SEM) has shown polycrystalline structure with clear characteristic peak of SnO2 cassiterite phase in all films. The optical transparency (T%) of SnO2:Fe films in visible spectra decreases from 90% to 75% and electrical resistivity (ρ) increases from 1.2 × 10-2 to 3 × 103 Ω cm for Fe-doping in the range 0-40 at%. © 2008 Elsevier Masson SAS. All rights reserved.

Nano-crystalline SnO2 particles have been synthesized by sol-gel process using a simple starting hydro-alcoholic solution consisting of SnCl4, 5H2O and citric acid as complexing and ethylene glycol as polymerization agents. The structural properties of the prepared tin oxide nano-powders annealed at different temperatures (300-700 °C) have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The XRD patterns show SnO2-cassiterite phase in the nano-powders, and size of crystals increases by increasing the annealing temperatures. The TEM images show nano-particles as clusters with size in the range of 5-25 nm. Electron diffraction pattern of nano-powders annealed at different temperatures shows a homogeneous distribution of spherical particles due to the effect of ethylene glycol as polymerizing agent in sol-gel process. The optical direct band gap values of SnO2 nano-particles were calculated to be about 4.05-4.11 eV in the temperature range 300-700 °C by optical absorption measurements. These values exibit nearly a 0.5 eV blue shift from that of bulk SnO2 (3.6 eV), which is related to size decrease of the particles and reaching to the quantum confinement limit of nano-particles. © 2008 Elsevier B.V. All rights reserved.

In this paper, we investigate the electrical, optical and structural properties of Li-doped SnO2 transparent conducting films deposited on glass substrates by the spray pyrolysis technique. The SnO2:Li thin films were deposited at a substrate temperature of 480°C using an aqueous ethanol solution consisting of tin and lithium chloride with various doping levels from 0 to 25 wt% in solution. The effect of increasing Li concentration on the electrical, optical and structural properties of SnO2 films has been studied. The results of x-ray diffraction have shown that the deposited films are polycrystalline without any second phases with preferential orientations along the (110) and (211) planes and an average grain size of 28.7 nm. Also, the Hall effect and resistivity measurements of the films show that for a specific acceptor dopant concentration of ∼2 wt% or [Li]/[Sn] atomic ratio equal to 37 at% in solution, the majority of carriers convert from electrons to holes and for a Li concentration of ∼15 wt% in solution, p-conductivity increases sharply. The optical absorption edge for undoped SnO2 films lies at 4.11 eV, whereas for high acceptor doped films it shifts towards lower energies (longer wavelengths) in the range of 4.11 to 3.61 eV.

In this study, the influence of increasing the Al concentration on the electrical, optical and structural properties of spray-pyrolysis-deposited SnO2 films has been investigated. The SnO2 : Al films were deposited at a substrate temperature of 480°C using a hydro-alcoholic solution consisting of tin and aluminium chlorides with various Al-doping levels from 0 to 30 wt% in solution. The [Al]/[Sn] atomic ratios were from 0 to 12.1 in films. The results of x-ray diffraction have shown that the deposited films are polycrystalline without any second phases with preferential orientations along the (110), (211) and (301) planes and an average grain size of 28.7 nm. Also, the Hall effect and resistivity measurements of the films show that for a specific acceptor dopant (Al) concentration (8.0 at% in film), majority carriers convert from electrons to holes and p-conductivity dominates. The optical absorption edge for undoped SnO2 films lies at 4.105 eV, whereas for high acceptor-doped films it shifts towards lower energies (longer wavelengths) in the range of 4.105-3.604 eV.

In this paper, deposition, electrical, optical and structural characterizations of SnO2-ZnO transparent conducting binary-binary systems with various compositions have been investigated. Firstly, the n-type SnO2 thin films are deposited using a hydro-alcoholic solution by spray pyrolysis technique. Then, certain amounts of zinc chloride (anhydrous) have been added to the initial solution, in order to prepare the SnO 2-ZnO transparent conducting binary-binary system with various chemical compositions. The SnO2-ZnO polycrystalline thin films were deposited at TS = 480 °C with a Zn-content [Zn/(Sn+Zn)] atomic ratio of 0-30 at.% in films. The effect of increasing Zn-content on electrical, optical and structural properties of SnO2-ZnO films has been studied. The results of X-ray diffraction and Scanning electron microscopy analysis, Hall effect experiment and resistivity measurement of films in the high Zn-concentration indicate the association of both SnO2 and ZnO phases in thin film structure. In addition, for a given Zn-content atomic ratio (20.7 at.% in film), both electrical conductivity and carrier concentration increased sharply. © 2003 Elsevier B.V. All rights reserved.

In this paper, deposition and electrical, optical and structural characterizations of the In2O3:Zn transparent conducting thin films are investigated. At first, undoped and non-stoichiometric n-In2O3 thin films are deposited using an alcoholic solution by spray pyrolysis technique. Then, in order to prepare Zn-doped In2O3 thin films, certain amounts of zinc chloride are added to the initial solution. Finally, the effects of Zn doping on electrical, optical and structural properties of In2O3 films are studied. The results of XRD analysis, Hall effect experiment and resistivity measurement of films indicate that no phase change in In2O3 lattice occurs in high acceptor doping condition, and for a given acceptor dopant (Zn2+) concentration (∼6wt% in solution), electrical conductivity increases sharply and p-conductivity dominates.