Ultrasonic Spray Pyrolysis Technique Research Articles

OBSERVATION OF NANOSPHERICAL n-SnO2/p-Si HETEROJUNCTION FABRICATED BY ULTRASONIC SPRAY PYROLYSIS TECHNIQUE

Thin film of tin oxide ( SnO 2) was prepared on p-type polished silicon wafer by ultrasonic spray pyrolysis technique using SnCl 4 precursor solution to fabricate nanospherical n - SnO 2/ p - Si heterojunction photoelectric device. Deposition of film was achieved at 400°C substrate temperature. The self-made ultrasonic spray pyrolysis system is very cheap and convenient. The microstructural, optical and electrical properties of the SnO 2 film were characterized by XRD, SEM, XPS, UV-VIS spectrophotometer, four point probe and Hall effect measurement, respectively. The SnO 2 film has the nanospherical particles. The electrical properties of heterojunction were investigated by I–V measurement, which reveals that the heterojunction shows strong rectifying behavior under a dark condition. The ideality factor and the saturation current density of this diode are 4.27 and 2.52 × 10-6 A/cm2, respectively. And the values of IF/IR (IF and IR stand for forward and reverse current, respectively) at 5 V is found to be as high as 248. The SnO 2/ p - Si heterojunction device exhibits obvious photovoltaic effect. Under an AM1.5 illumination condition, the open-circuit voltage (V oc ), short-circuit current density (J SC ), fill factor (FF) of the device are 150 mV, 3.9 × 10-3 mA/cm2 and 20.58%, respectively. High photocurrent is obtained under a reverse bias when the crystalline quality of SnO 2 film is good enough to transmit the light into p- Si . Under 6.3 mW/cm2 illumination, when the reverse bias is -5 V, the photocurrent gain is as high as 86.

Preparation and characterization of nanostructures of in-doped ZnO films deposited by chemically spray pyrolysis: Effect of substrate temperatures

We deposited undoped (ZnO) and indium-doped ZnO (IZO) films onto glass substrate via ultrasonic spray pyrolysis technique. The variation in structural, surface morphology, electrical, optical and photoluminescent properties as a function of substrate temperature is investigated. X-rays pattern confirms that as-synthesized IZO phase is grown along a (002) preferential plane. Nanosized grains (<50nm) are determined by X-ray analysis. Morphology of as-grown films shows broadened nanostructures which have grown along c-axis and nanostructures are found to be smooth (RMS∼60nm). Study by spectrophotometer reveals that the as-grown films are highly transparent in the visible and IR spectra (T∼88%), and that the bandgap is slightly narrowed (3.17eV). Electrical measurements confirm the enhancement of conductivity, ρ<1Ωcm, due to indium incorporation into the starting solution. An electron concentration of 1017cm−3 and a mobility of 3cm2/Vs are found for IZO films grown at 400°C. The photoluminescence analysis demonstrates strong yellow (2.1eV) and blue (2.8eV) light and weak green (2.3eV) emissions.

In vitro and in vivo antimicrobial properties of silver-containing hydroxyapatite prepared via ultrasonic spray pyrolysis route

Hydroxyapatite (HAp), with its high biocompatibility and osteoconductivity, readily absorbs proteins, amino acids and other substances, which in turn favor the adsorption and colonization of bacteria. To prevent bacterial growth and biofilm formation on HAp discs, silver-containing (1–20mol%) HAp (Ag-HAp) powders were synthesized using an ultrasonic spray pyrolysis (USSP) technique. The X-ray diffraction (XRD) peaks were very broad, indicating low crystallinity, and this induced the release of Ag+ ions from Ag-HAp powders. In addition, a gradual increase in Ca2+ ion release was observed. These results suggest that dissolution of Ca2+ ion in Ag-HAp triggered the release of Ag+ ions.The antimicrobial efficacy of Ag-HAp disc was tested against Staphylococcus aureus. Samples with Ag contents of more than 5mol% were found to be highly effective against bacterial colonization and biofilm formation in vitro. In vivo antibacterial tests using bioluminescent strains also showed reductions in the viability of bacteria with Ag-HAp (5mol%) discs. Biocompatibility tests using a modified Transwell® insert method showed that Ag-HAp (5mol%) discs have negative effects on osteoblast proliferation. These results indicate that Ag-HAp (5mol%) has effective antibacterial activity and good biocompatibility both in vitro and in vivo together with good biocompatibility, thus confirming its utility as a bactericidal material.

Optical Kerr phase shift in a nanostructured nickel-doped zinc oxide thin solid film

The optical Kerr effect exhibited by a nickel doped zinc oxide thin solid film was explored with femto- and pico-second pulses using the z-scan method. The samples were prepared by the ultrasonic spray pyrolysis technique. Opposite signs for the value of the nonlinear refractive index were observed in the two experiments. Self-defocusing together with a two-photon absorption process was observed with 120 ps pulses at 1064 nm, while a dominantly self-focusing effect accompanied by saturated absorption was found for 80 fs pulses at 825 nm. Regarding the nanostructured morphology of the resulting film, we attribute the difference in the two ultrafast optical responses to the different physical mechanism responsible of energy transfer generated by multiphoton processes under electronic and thermal effects.

Deposition of tin(II) sulfide thin films by ultrasonic spray pyrolysis: Evidence of sulfur exo-diffusion

Tin Sulfide (SnS) thin films were deposited by ultrasonic spray pyrolysis technique, on glass substrate heated at 280°C, with different deposition times. The used precursor SnCl2 and thiourea are dissolved in methanol. X-ray diffraction (XRD) analysis indicates that films are mainly composed with orthorhombic SnS phase at low deposition time. With increasing deposition time, the hexagonal SnS2 phases become dominant. SnO2 and metallic Sn phases have been detected with increasing deposition time. Scanning electron microscopy (SEM) observations reveal that films surfaces are rough with the presence of bubbles due to S2 gas exo-diffusion from the bulk during film growth. A model of S2 gas formation is presented.

Synthesis of conductive semi-transparent silver films deposited by a Pneumatically-Assisted Ultrasonic Spray Pyrolysis Technique

The synthesis and characterization of nanostructured silver films deposited on corning glass by a deposition technique called Pneumatically-Assisted Ultrasonic Spray Pyrolysis are reported. Silver nitrate and triethanolamine were used as silver precursor and reducer agent, respectively. The substrate temperatures during deposition were in the range of 300–450 °C and the deposition times from 30 to 240 s. The deposited films are polycrystalline with cubic face-centered structure, and crystalline grain size less than 30 nm. Deposition rates up to 600 Å min−1 were obtained at substrate temperature as low as 300 °C. The electrical, optical, and morphological properties of these films are also reported. Semi-transparent conductive silver films were obtained at 350 °C with a deposition time of 45 s.

Synthesis of novel mesoporous carbon spheres and their supported Fe-based electrocatalysts for PEM fuel cell oxygen reduction reaction

Mesoporous carbon spheres (MPCs) are synthesized using a template assisted ultrasonic spray pyrolysis technique and explored as the support materials for non-noble metal electrocatalysts intended to be used for PEM fuel cell oxygen reduction reaction (ORR). TEM images show that MPCs synthesized are the honeycomb-like carbon spheres with uniform nanosized pores. MPC's surface area, thermal stability and affinity to catalyst are improved by a second heat treatment and an acidic treatment, confirmed by BET, TGA, and electrochemical measurements, respectively. The synthesized Fe-Nx catalyst with MPC support shows an improved ORR activity when compared to the catalyst supported by commercially available Black Pearl 2000.

Enhanced photoluminescence of Y2O3:Er3+ thin films by Li+ co-doping

The enhancement of the photoluminescence from Y2O3:Er3+ thin films with Li+ co-doping is reported. The characteristic Er3+ related emission spectra showed an intensity increase by a factor of ∼4–5 times with the addition of 2% of Li+. This behavior is attributed to the distortion of the local crystalline field induced by the incorporation of Li+. The films were deposited at 500°C by ultrasonic spray pyrolysis technique on (100) silicon wafers. The films were the polycrystalline with a pure Y2O3 cubic phase. The addition of Li+ reduces the intensity of the diffraction peaks after 1%, and shifts the main diffraction peak toward large angles for Li+ doping less than 3%. FTIR spectra were used to monitor the incorporation of Li-species in the films.

Ultrasonically sprayed ZnO:Co thin films: Growth and characterization

In this work, undoped and cobalt-doped ZnO thin films were deposited at 275±5°C on glass substrates by the ultrasonic spray pyrolysis technique. The structural, electrical, optical and surface characterization of the films as a function of the cobalt concentration in the spraying solution were studied by means of x-ray diffractometer, current–voltage characteristics, UV–vis spectrophotometer and atomic force microscope, respectively. X-ray diffraction reveals that the films are polycrystalline in nature with preferred orientations of (002) for the ZnO:Co (0, 2, 4at.%) and (100) for the ZnO:Co (6at.%). The optical transmittance of all films was studied as a function of wavelength in the range of 300–1100nm. They exhibit high transparency in the visible wavelength region with some interference fringes and sharp ultraviolet absorption edges. The optical band gap and Urbach energy values of the films were found in the range of 3.250–3.301eV and 90–230meV, respectively. The electrical studies for all films were carried out by using conductivity-temperature measurements and it was seen that the electrical conductivity of ZnO films decreases slightly depending on the increasing of Co doping. Also, Co doping increases both energies of donor-like traps and activation energy for ZnO films. The surface morphology was analyzed by atomic force microscope and a strong dependence on the cobalt incorporation was found.

Phase Transition in Superconducting Thin Films of Tl System Employing a One-Zone Furnace and Deposited by Spray Pyrolysis

A study of the phase transitions in superconducting thin films of the Thallium-Barium-Calcium-Copper (TBCCO) system is carried out. In particular, it was got the Tl-1223 phase. For this purpose, and using the ultrasonic spray pyrolysis technique, Barium-Calcium-Copper precursor films were first obtained. Upon deposition of the precursor films, and as a second step, they were thallium (Tl) diffused in the one-zone furnace at 860°C. This methodology resulted in superconducting films that showed a phase transition as follows: Tl-2223 → Tl-2223 + Tl-2212 → Tl-2212 → Tl-1223, achieved between 2 and 7 hours of thallium diffusion. The evidence of the phase transitions was corroborated by the experimental results of X-ray diffraction, energy dispersive spectroscopy and resistance-temperature measurements.

Optical Characteristics of Silica Coatings Deposited by Ozone Assisted Spray Pyrolysis Technique

The synthesis of silica coatings by the Ultrasonic Spray Pyrolysis (USP) technique, using ozone and tetraethyl-orthosilicate (TEOS), is reported for different substrate temperatures in the 350 to 550°C range. Deposition rates as high as 3500 Å·min−1 at a substrate temperature of 550°C were obtained. Average roughness values of up to ∼11 Å were obtained for the different substrate temperatures and deposition times. FTIR spectroscopy measurements show characteristic SiO2 absorption bands associated with the Si-O-Si rocking, bending and stretching vibration modes at 450, 810 and 1070 cm−1, respectively. The behavior of the refractive index for these films was determined by spectral ellipsometry in the 275 to 827 nm wavelength range. It was found that for 450°C films the refractive index values lay within those reported for thermal and atomic layer deposited oxides.

Ultrasonic spray pyrolysis deposition of SnSe and SnSe2 using a single spray solution

Thin films of SnSe and SnSe2 have been deposited using the ultrasonic spray pyrolysis (USP) technique. To the best of our knowledge this is the first report of the deposition of SnSe and SnSe2 thin films using a single spray solution. The use of a single spray solution for obtaining both a p-type material, SnSe, and an n-type material, SnSe2, simplifies the deposition technique. The SnSe2 thin films have a bandgap of 1.1 eV and the SnSe thin films have a band gap of 0.9 eV. The Hall measurements were used to determine the resistivity of the thin films. The SnSe2 thin films show a resistivity of 36.73 Ω·cm and n-type conductivity while the SnSe thin films show a resistivity of 180 Ω·cm and p-type conductivity.

Fabrication of BSCCO Films on SrTiO3 Substrates Using Ultrasonic Spray Pyrolysis (USP) Technique

In this study, the BiSrCaCuO (Bi-2212) films on SrTiO3 substrates were fabricated using an ultrasonic spray pyrolysis technique (USP). Structural, electrical, magnetic, and critical current density, Jc, properties of the films fabricated were investigated under different heat treatment conditions. XRD analysis showed that the films mainly consisted of the Bi-2212 phase, but the Bi-2223 phase was also detected. Tc values of the films were found between 81 K and 88 K, depending on the heat treatment conditions. Jc values of the films were calculated using the Beans’ equation. Highest Jc value was found to be 2.93×105 A cm−2 at 5 K and 0 T for Film C. The results obviously showed that USP method is a very effective technique for fabrication of the HTc films having high Jc values as well as its simplicity, low cost, and easily coating.

Characterization of chemically sprayed CdO films on borate and phosphate glass substrates produced by melt-quenching technique

The properties of substrates used to deposit thin films are an important parameter in thin film production. Instead of using a commercial substrate, in this work, borate and phosphate glasses have been obtained by classic melt-quenching technique to be used as substrates for CdO films. Also, a microscope glass substrate has been used to compare the coating properties by other glass substrates. All films have been produced by Ultrasonic Spray Pyrolysis technique. The substrate temperature has been selected as 275 ± 5 °C. Thicknesses and some optical parameters such as refractive index and extinction coefficient have been determined by spectroscopic ellipsometry. Absorbance and transmittance spectra have been taken by UV/VIS spectrophotometer. Four-probe method has been used to determine the electrical resistivity values of the films. XRD investigations have shown that type of the substrate dramatically affects the characteristics of CdO films. CdO film deposited on phosphate glass substrate has the best structural quality. Atomic Force Microscope has been used to investigate the surface properties and roughness values of the films.

The effects of carrier gas and substrate temperature on ZnO films prepared by ultrasonic spray pyrolysis

ZnO films were deposited on glass substrates in the temperature range of 350–470°C under an atmosphere of compressed air or nitrogen (N2) by using ultrasonic spray pyrolysis technique. Structural, electrical and optical properties of the ZnO films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical two-probe and optical transmittance measurements. The ZnO films deposited in the range of 350–430°C were polycrystalline with the wurtzite hexagonal structure having preferred orientation depending on the substrate temperature. The ZnO films deposited below 400°C had a preferred (100) orientation while those deposited above 400°C mostly had a preferred (002) orientation. The resistivity values of ZnO films depended on the types of carrier gas. The ZnO thin films deposited under N2 atmosphere in the range of 370–410°C showed dense surface morphologies and resistivity values of 0.6–1.1Ω-cm, a few orders of magnitude lower than those deposited under compressed air. Hydrogen substition in ZnO possibly contributed to decreasing resistivity in ZnO thin films deposited under N2 gas. The Hall measurements showed that the behavior of ZnO films deposited at 410°C under the N2 atmosphere was n-type with a carrier density of 8.9–9.2×1016cm-3 and mobility of ∼70cm2/Vs. ZnO thin films showed transmission values at 550nm wavelength in a range of 70–80%. The values of band gaps extrapolated from the transmission results showed bandgap shrinkage in an order of milli electron volts in ZnO films deposited under N2 compared to those deposited under compressed air. The calculation showed that the bandgap reduction was possibly a result of carrier–carrier interactions.

Fabrications of Boron-Containing Apatite Ceramics via Ultrasonic Spray-Pyrolysis Route and their Surface Properties

Boron-containing hydroxyapatite (BAp) powders with Ca/(P+B) molar ratio of 1.67 (x=0.4, 0.5, and 0.6) were prepared by an ultrasonic spray-pyrolysis (USSP) technique. The resulting BAp powders were uniaxially compressed to fabricate the green compacts. The BAp ceramics were fabricated by firing the compacts at 1200 °C for 5 h. The crystalline phases of the BAp (x=0.4) ceramics were bipahses of apatite and small amounts of α-tricalcium phosphate (a-Ca3(PO4)2; α-TCP). Meanwhile, HAp and BAp (x=0.5 and 0.6) ceramics were apatite single phase. The dense BAp ceramics with relative density of 90% over were fabricated from the powder of x=0.5 and 0.6. The static contact angles of the BAp ceramics (x=0.5 and 0.6) increased with an increase of pH; meanwhile, the surface potential decreased with an increase of pH. These changes in surface properties may be due to the increase of OH group in B(OH)3 formed via dissociation of BO2 group in BAp.

Evaluation of optical parameters and characterization of ultrasonically sprayed MgO films by spectroscopic ellipsometry

MgO is a chemically stable buffer layer and a good candidate with its unique optical and structural characteristics such as low refractive index and good lattice matching for the deposition of technologically important materials. In this work, we have produced MgO films by a low cost ultrasonic spray pyrolysis technique and tried to improve their characteristics by thermal annealing. MgO films have been obtained on glass substrates at 325±5°C and annealed at two different temperatures as 500°C and 600°C for 2h. Elemental analyses have been made by energy-dispersive X-ray spectroscopy. Thicknesses, refractive indices and extinction coefficient values have been determined by spectroscopic ellipsometry technique using Cauchy–Urbach model. Band gap values of the films have been calculated using the absorbance spectra and optical method. X-ray diffraction patterns have been used to investigate the structural properties and to calculate lattice parameters. Atomic force microscope images have been taken to see the effect of thermal annealing on surface morphology. Electrical resistivity values of the films have been determined using a four-point probe set-up. As a result, annealing temperature has a strong effect on the mentioned properties and a low cost ultrasonic spray pyrolysis technique allows the production of new and alternative MgO buffer layers for technological applications.

Synthesis of Al2O3 thin films using laser assisted spray pyrolysis (LASP)

The present study reports the development of a laser assisted ultrasonic spray pyrolysis technique and synthesis of dense optical alumina films using the same. In this technique ultrasonically generated aerosols of aluminum acetylacetonate dissolved in ethanol and a laser beam (Nd:YAG, CW, 1064nm) were fed coaxially and concurrently through a quartz tube on to a hot substrate mounted on an X–Y raster stage. At the laser focused spot the precursor underwent solvent evaporation and solute sublimation followed by precursor vapor decomposition giving rise to oxide coating, the substrate is rastered to get large surface area coating. The surface morphology revealed coalescence of particles with increase in laser power. The observed particle sizes were 17nm for films synthesized without laser and 18, 21 and 25nm for films made with laser at 25, 38 and 50W, respectively. Refractive index of the films synthesized increased from 1.56 to 1.62 as the laser power increased from 0 to 50W. The stoichiometry of films was studied using XPS and the increase in interfacial layer thickness with laser power was observed from dynamic SIMS depth profiling and ellipsometry.

Synthesis and Characterization of Cu-SnO2 Nanoparticles Deposited on Glass Using Ultrasonic Spray Pyrolysis and their H2S Sensing Properties

High quality 3%Cu-SnO2 nanoparticles have been prepared onto the glass substrate by using novel and economical ultrasonic spray pyrolysis technique. The X-ray diffraction patterns showed that 3% Cu-SnO2 nanoparticles formed in tetragonal rutile structure. The intensities of peaks shown by X-ray pattern were indexed as (110), (101), (200) and (211). The microstructure, surface morphology, particle size and elemental properties of 3%Cu-SnO2 nanoparticles were characterized using, scanning electron microscope (SEM), and Transmission electron microscopy (TEM). These nanoparticles were tested for H2S sensors applications. It was observed that 3% Cu-SnO2 nanoparticles exhibited remarkable sensitivity to H2S (200 ppm) gas at 150ºC, more precisely showing good response and recovery. Keywords: Cu-SnO2, nanoparticles, ultrasonic spray pyrolysis, SEM, TEM, H2S sensors

Enhancement of the optical Kerr effect by photobleaching in nanostructured indium-doped zinc oxide thin films

A modification of the nonlinear refractive index exhibited by indium-doped zinc oxide thin solid films deposited by an ultrasonic spray pyrolysis technique, after strong femtosecond laser irradiation, is presented. We used a standard time-resolved optical Kerr gate configuration with 80 fs pulses at 830 nm in order to study the third-order optical nonlinearities of the samples. A significant enhancement of the optical Kerr response was obtained by intense femtosecond excitation, which induced a permanent bleaching in the sample. A quasi-instantaneous pure electronic nonlinearity without the contribution of nonlinear optical absorption was observed. There is a close relationship between the change in linear absorption induced in the indium-doped zinc oxide film after high-intensity irradiation and the strong third-order nonlinearity that develops in the irradiated film.