Results 1 - 10 of 34
Results 1 - 10 of 34. Search took: 0.019 seconds
|Sort by: date | relevance|
[en] Highlights: • Nanostructured undoped and AZO thin films prepared by chemical spray pyrolysis. • Effect of Al doping on the structural, morphological and photoluminance properties. • Photocatalytic degradation of phthalic acid under UV light illumination. • Reaction kinetics and mineralization of phthalic acid. - Abstract: Undoped and Al doped ZnO (AZO) thin films are successfully prepared by spray pyrolysis technique at optimised substrate temperature of 400 °C onto amorphous and F:SnO_2 coated glass substrates. Effect of Al doping on structural, morphological and optical properties of ZnO thin films is studied. Deposited films are polycrystalline with a hexagonal (wurtzite) crystal structure having (0 0 2) preferred orientation. The PEC characterization shows that, short circuit current (I_s_c) and open circuit voltage (V_o_c) are (I_s_c = 0.38 mA and V_o_c = 421 mV) relatively higher at the 3 at.% Al doping. SEM images show deposited thin films are compact and uniform with seed like grains. All films exhibit average transmittance of about 82% in the visible region and a sharp absorption onset at 375 nm corresponding to 3.3 eV. The photocatalytic activities of the large surface area (64 cm"2) Al-doped ZnO photocatalyst samples were evaluated by photoelectrocatalytic degradation of phthalic acid under UV light irradiation. The results show that the 3 at.% AZO thin film photocatalyst exhibited degradation of phthalic acid up to about 45% within 3 h with significant reduction in COD and TOC values
[en] Transparent conducting thin films of F:SnO2 have been deposited onto preheated glass substrates by a spray pyrolysis technique by varying the concentration of SnCl4. A fine spray of the source solution using air as a carrier gas has grown films of thickness up to 1108 nm. Optical absorption, X-ray diffraction, Van der Pauw technique for measurement of a sheet resistance and Hall effect measurements at room temperature for determination of carrier density and conductivity has been used. The as deposited films are of polycrystalline SnO2 with a tetragonal crystal structure having preferentially orientation along the (2 0 0) direction with texture coefficient as high as 6.92 with average grain size of 48 nm. The maximum value of figure of merit (61.8 x 10-3 Ω-1) with 87% transmittance at 550 nm has been obtained. The surface morphology of the films has been studied with SEM and AFM techniques. SEM shows continuous periodic arrangement of the smaller grains in between two bigger grains, with pinhole free surface. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. For the optimized sample the values of lowest sheet resistance (Rs) resistivity (ρ) and mobility (μ) are 3.71 Ω, 3.7 x 10-4 Ω cm and 5.81 cm2 V-1 s-1, respectively
[en] The cadmium oxide (CdO) and F:CdO films have been deposited by spray pyrolysis method using cadmium acetate and ammonium fluoride as precursors for Cd and F ions, respectively. The effect of temperature and F doping on the structural, morphological, optical and Hall effect properties of sprayed CdO thin films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption and electrical measurement techniques. TGA and DTA studies, indicates the formation of CdO by decomposition of cadmium acetate after 250 deg. C. XRD patterns reveal that samples are polycrystalline with cubic structure and exhibits (2 0 0) preferential orientation. Considerable broading of (2 0 0) peak, simultaneous shifting of corresponding Bragg's angle have been observed with respect to F doping level. SEM and AFM show the heterogeneous distribution of cubical grains all over the substrate, which are randomly distributed. F doping shifts the optical gap along with the increase in the transparency of CdO films. The Hall effect measurement indicates that the resistivity and mobility decrease up to 4% F doping
[en] Highlights: • Orthorhombic structure of sprayed nanocrystalline vanadium pentoxide (V2O5) thin films. • 41% NO2 gas response with short response–recovery times of V2O5 thin film. • Rapid and good reproducible NO2 gas response of V2O5 thin film. • NO2 gas sensing mechanism based on chemisorption process is discussed. - Abstract: The nanocrystalline V2O5 thin films with different thicknesses have been grown onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD study shows that the films exhibit an orthorhombic crystal structure. The narrow scan X-ray photoelectron spectrum of V-2p core level doublet gives the binding energy difference of 7.3 eV, indicating that the V5+ oxidation state of vanadium. The FE-SEM micrographs show the formation of nanorods-like morphology. The AFM micrographs show the high surface area to volume ratio of nanocrystalline V2O5 thin films. The optical study gives the band gap energy values of 2.41 eV, 2.44 eV, 2.47 eV and 2.38 eV for V2O5 thin films deposited with the thicknesses of 423 nm, 559 nm, 694 nm and 730 nm, respectively. The V2O5 film of thickness 559 nm shows the NO2 gas response of 41% for 100 ppm concentration at operating temperature of 200 °C with response and recovery times of 20 s and 150 s, respectively. Further, it shows the rapid response and reproducibility towards 10 ppm NO2 gas concentration at 200 °C. Finally, NO2 gas sensing mechanism based on chemisorption process is discussed.
[en] Highlights: • The effect of thickness on physicochemical and NO_2 gas sensing properties of sprayed MoO_3 nanobelts has been reported. • The sprayed MoO_3 nanobelts show the NO_2 gas response of 68% for 100 ppm concentration at an operating temperature of 200 °C. • The lower detection limit of MoO_3 nanobelts based NO_2 sensor is found to be half of the IDLH value (20 ppm). - Abstract: Molybdenum trioxide (MoO_3) nanobelts have been deposited onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD patterns reveal that films are polycrystalline having an orthorhombic crystal structure. Raman spectra confirm that the films are orthorhombic in phase. The XPS study shows the presence of two well resolved spectral lines of Mo-3d core levels appearing at the binding energy values of 232.82 eV and 235.95 eV corresponding to Mo-3d_5_/_2 and Mo-3d_3_/_2, respectively. These binding energy values are assigned to Mo"6"+ oxidation state of fully oxidized MoO_3. The FE-SEM micrographs show the formation of nanobelts-like morphology. The AFM micrographs reveal that the RMS surface roughness increases from 16.5 nm to 17.5 nm with increase in film thickness from 470 nm to 612 nm and then decreases to 16 nm for 633 nm film thickness. The band gap energy is found to be decreased from 3.40 eV to 3.38 eV. To understand the electronic transport phenomenon in MoO_3 thin films, dielectric properties are studied. For 612 nm film thickness, the highest NO_2 gas response of 68% is obtained at an operating temperature of 200 °C for 100 ppm concentration with response and recovery times of 15 s and 150 s, respectively. The lower detection limit is found to be 10 ppm which is half of the immediately dangerous to life or health (IDLH) value of 20 ppm. Finally, NO_2 gas sensing mechanism in an orthorhombic MoO_3 crystal structure is discussed in detail.
[en] Highlights: • Structural, morphological and optical properties of sprayed MoO3 are studied. • The maximum NO2 gas response of 40.3% is reported. • For 20 ppm NO2, response-recovery times of 20 s and 160 s are reported. • NO2 gas sensing mechanism based on band bending model is discussed. - Abstract: In our previous report, we have reported the work on NO2 gas sensing properties of spray deposited molybdenum trioxide (MoO3) nanobelts at various substrate temperatures ranging from 300 °C to 450 °C with an interval of 50 °C. In the present work, MoO3 nanobelts have been spray deposited at optimized substrate temperature of 400 °C with different solution concentrations ranging from 10 mM to 50 mM at an interval of 10 mM solution concentration. X-ray diffraction study shows that the spray deposited MoO3 films exhibit an orthorhombic crystal structure. The formation of orthorhombic phase of MoO3 is confirmed using Raman spectroscopic study. Field emission-scanning electron microscopy images show the nanobelts-like morphology. Atomic force microscopy micrographs reveals that the root mean square (RMS) surface roughness of nanobelts increases from 12 nm to 17 nm with increase in solution concentration from 10 mM to 40 mM and then decreases to 8 nm for 50 mM solution concentration. Optical properties show that the band gap energy decreases to 3.25 eV for 50 mM solution concentration. For 40 mM solution concentration, 40.3% NO2 gas response at 200 °C is obtained for 100 ppm concentration with response and recovery times of 17 s and 153 s, respectively. Finally, energy band bending model based on chemisorption of O2 and NO2 gas on the surface of MoO3 nanobelts is discussed.
[en] Tin-doped indium oxide (ITO) thin films have been prepared by the spray pyrolysis method using indium chloride as a precursor and stannic chloride as a dopant. The effect of a precursor concentration on the structural, morphological, electrical and optical properties of films has been studied. The concentration of InCl3 in the spraying solution is varied from 6.25 to 37.5 mM keeping doping percentage of tin fixed at its optimized value of 5 wt.%. Bare glass is used as a substrate and oxygen as the carrier and reaction gas. X-ray diffraction (XRD) patterns show that films are polycrystalline and their crystallinities are dependent on the precursor concentration. A surface morphology has been observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The typical ITO film has minimum resistivity value of 2.71 x 10-3 Ω cm, whose carrier concentration and mobility were 7.45 x 1019 cm-3 and 31 cm2/(V s), respectively. In addition, the best ITO film has optical transmittance of 94.4% and figure of merit 1.20 x 10-3 Ω-1
[en] Thin films of fluorine doped tin oxide (F:SnO2) have been prepared using cost effective spray pyrolysis technique. Thin films of different thickness are obtained by varying quantity of spraying solution. Films of up to 1071 nm thickness have been deposited at a maximum growth rate of 3 nm/s. The structural, optical and electrical properties of these films have been studied. It is found that the films are tetragonal with (2 0 0) orientation. The optical study showed that the films have a bandgap of 4.15 eV. The films shows 75% transmission at 550 nm leading to a factor figure of merit of 1.25-1.7. It is found that the films show n-type conductivity with the lowest resistivity of 3.91x10-4 Ω cm, carrier density of 4.71x1020 cm-3 and mobility around 11 cm2 V-1 s-1.
[en] Cadmium selenide thin films have been deposited onto stainless steel and fluorine doped tin oxide (FTO) glass substrates by the electrodeposition process, in potentiostatic mode using cadmium acetate and selenium dioxide salts as a precursor sources with ethylenediaminetetraacetic acid (EDTA) tetra sodium salt as a complexing agent. The various preparative parameters such as deposition potential, bath composition, bath temperature, pH of the bath and deposition time have been optimized by photoelectrochemical (PEC) technique. The structural, morphological and optical properties of the deposited films have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption techniques, respectively. The X-ray diffraction analysis shows that the films are polycrystalline with hexagonal crystal structure. SEM studies reveal that the grains are uniform with uneven spherically shaped, distributed over the entire surface of the substrates. Optical absorption study shows the presence of direct transition with band gap energy 1.95 eV
[en] We report the synthesis of CuO-Poly (acrylic) acid (PAA) hybrid thin films by a cost-effective spin coating technique for supercapacitor application. Coated films were annealed at 300, 400 and 500 deg. C, to study the annealing effect on the supercapacitor behavior. Further films were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform-Raman spectroscopy (FT-Raman) and Fourier transform-Infrared spectroscopy (FT-IR) techniques. Energy dispersive spectroscopy (EDS) shows the formation of amorphous blend of CuO and Cu2O phases at 300 deg. C. Further, films annealed at 400 and 500 deg. C exhibit polycrystalline phase pure CuO with monoclinic structure. The scanning electron microscopy (SEM) micrographs show the transition of island-like structure to CuO crystals surrounded by PAA grafted composite ring with increase in annealing temperature. The possible growth mechanism of PAA and CuO bonding is discussed. Cyclic voltammetry (CV) is employed to calculate the specific capacitance (Csp) in 1 M H2SO4 electrolyte. It is observed that the Csp increases from 41 to136 F g-1 with increase in annealing temperature.