Spray Pyrolysis Deposition Technique Research Articles

Structural, optical and electrochromic properties of Nb-doped MoO 3 thin films

Niobium (Nb) doped molybdenum trioxide (MoO 3) thin films have been synthesized using spray pyrolysis deposition technique. The structural changes were observed with the help of X-ray diffraction technique. With increasing Nb concentration, the structure of MoO 3 undergoes a phase transformation from α-orthorhombic to amorphous with nano-sized grains. The thread like reticulated morphology is converted into spongy like structure at higher Nb concentration (9 at% Nb). It is seen that Nb doping can lead to significant surface morphology changes in MoO 3 films. It was found that the coloration efficiency increases with doping concentration. With increasing Nb concentration charge capacity, reversibility and electrochemical stability increases. The improvement is attributed to the amorphous structure of the doped samples that favors easy intercalation and deintercalation processes. Hence, we have successfully demonstrated formation of an adequate host for electrochromic devices with Nb (9 at%) doped MoO 3 samples.

Characterization of gas sensing HfO2 coatings synthesized by spray pyrolysis technique

Abstract Hafnium oxide (HfO2) films were deposited using the ultrasonic spray pyrolysis deposition technique. The films were prepared using hafnium oxychloride as a raw material and deposited on Corning glass substrates at temperatures ranging from 300 °C to 500 °C. Their crystalline structure was dependent on the deposition temperature. At substrate temperatures below 350 °C the deposited films were almost amorphous, while at substrate temperatures higher than 400 °C the films became the monoclinic phase of HfO2. Scanning electron microscopy and electron energy dispersion analysis showed a very rough surface with spherical particles of nearly stoichiometric HfO2. Such films were assessed as active layers for humidity and propane sensors. Furthermore, their response characteristics calculated on the basis of the real and imaginary parts of the impedance and also on the total impedance value were determined as a function of the measurement frequency. The dynamic response to different concentrations of propane was obtained. The response and recovery times were also determined. Finally, a brief discussion on the possible sensing mechanisms was also presented.

Preparation of SnO2 Transparent Conducting Films for Dye-Sensitized Solar Cells by SPD Technique

Tin oxide, SnO2, transparent conducting oxide (TCO) films for dye-sensitized solar cells (DSSCs) was investigated. We found that an electrical conductivity is not the only parameter that governs conversion efficiency of DSSC. The conversion efficiency was strongly influenced by haze ratio that is easily tuned by controlling the surface morphology of TCO layer by spray pyrolysis deposition (SPD) technique. The conversion efficiency was enhanced as high as 7.6%, attributing to an effective incident light harvest of a working electrode in the consequence of the confinement of the incident light within the cell.

Characterization of luminescent samarium doped HfO2 coatings synthesized by spray pyrolysis technique

Trivalent samarium (Sm3+) doped hafnium oxide (HfO2) films were deposited using the spray pyrolysis deposition technique. The films were deposited on Corning glass substrates at temperatures ranging from 300 to 550 °C using chlorides as raw materials. Films, mostly amorphous, were obtained when deposition temperatures were below 350 °C. However, for temperatures higher than 400 °C, the films became polycrystalline, presenting the HfO2 monoclinic phase. Scanning electron microscopy of the films revealed a rough surface morphology with spherical particles. Also, electron energy dispersive analysis was performed on these films. The photoluminescence and cathodoluminescence characteristics of the HfO2 : SmCl3 films, measured at room temperature, exhibited four main bands centred at 570, 610, 652 and 716 nm, which are due to the well-known intra-4f transitions of the Sm3+ ion. It was found that the overall emission intensity rose as the deposition temperature was increased. Furthermore, a concentration quenching of the luminescence intensity was also observed.

Fabrication of TCO Layer for Dye-Sensitized Solar Cells by Spray Pyrolysis Deposition Technique

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Study of photoactivity of tungsten trioxide (WO 3) for water splitting

The paper presents the properties of WO 3 films considering the possibility to build a photoelectrochemical cell (PECC) for hydrogen production. The photocurrent response of the PECC containing WO 3/TCO as photoanode and Pt as cathode was analysed. The morphology, crystalline structure and electrical aspects were investigated. Tungsten trioxide (WO 3) thin film with porous morphology and high crystallinity was obtained using the spray pyrolysis deposition technique.

Optochemical sensor for water monitoring based on SnO2 particle layer deposited onto optical fibers by the electrospray pyrolysis method

In this letter, experimental results on the capability of a tin dioxide (SnO2)-based silica optical fiber (SOF) sensor to detect sub-ppm ammonia concentrations in water environments, at room temperature, are presented. SnO2 sensitive layers have been deposited on the fiber end by using the simple and low cost electrostatic spray pyrolysis deposition technique. The surface morphology of the deposited SnO2 layers as well as its influence on the near field profile of the emergent electromagnetic field from the fiber coating have been investigated by means of atomic force microscopy and scanning near field optical microscopy. The room temperature adsorption measurements reveal the excellent sensor resolution of 80ppb, good recovery features, high repeatability, and fast response times (a few minutes). The results obtained demonstrate the strong potentiality of the proposed SnO2-based SOF sensor to be employed for water quality monitoring applications.

Improved electrical, optical, and structural properties of undoped ZnO thin films grown by water-mist-assisted spray pyrolysis

Undoped ZnO thin films were prepared using the ultrasonic spray pyrolysis deposition technique with zinc acetylacetonate dissolved in N,N-dimethylformamide as the source materials solution. The addition of water mist in a parallel flux to the spray solution stream was also used during deposition of the films. The addition of water mist improved the electrical characteristics of the ZnO films. Fresh ZnO samples were then thermally annealed in a H2 reducing atmosphere. X-ray diffraction patterns show mainly the wurzite crystalline ZnO phase in the films. An electrical resistivity (ρ ) of around 2.7 × 10−2 Ω cm was measured at room temperature for the best undoped ZnO film. ρ is approximately one order of magnitude lower than the resistivities found in undoped ZnO films obtained by means of similar non-vacuum deposition techniques. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and characteristics study of ZnO: (Al, Cu, I) thin films by chemical spray pyrolysis

Spray pyrolysis deposition technique has been used to grow ZnO thin films doped with different dopant species (Al, Cu, I). The optical and electrical properties of films were investigated as function of dopant type and concentration. The structural characteristics of undoped and doped ZnO films were studied using X-ray diffraction (XRD). The electrical resistivity as low as 4 × 10-2 Ωcm was obtained for ZnO:Al with 5 at.% dopant concentration. ZnO:Cu films prepared at specific conditions exhibited p-type conductivity. The optical band gap of doped ZnO films varied from 3.09 eV to 3.2 eV. XRD investigation confirmed that the doped ZnO films had preferred orientation in the direction of (101) plane. [DOI: 10.1380/ejssnt.2006.636]

In situ laser reflectometry measurements of pyrolytic ZnO film growth

In situ thin film thickness monitoring and profilometering was implemented for a spray pyrolysis deposition technique, based on measuring the reflection of a laser beam from the film–substrate system; the interference pattern obtained during film deposition was used to calculate the film thickness. Recording in situ the reflection pattern for points separated 0.5 cm along the film allowed the film profile to be obtained. The growth of pyrolitic ZnO film on glass was studied by this method. It was found that the in situ measured thickness is in good agreement with that measured by ex situ profilometering or scanning electron microscopy (SEM). SEM micrographs of the films showed that the surface is formed by elongated-shaped particles, which become rounded and larger in size as the film becomes thicker. This fact was correlated with an increment of the diffuse component of the optical spectral reflectance and transmittance and with the trend of the surface roughness factor, obtained in situ.

Porous TiO 2 thin films prepared by spray pyrolysis deposition (SPD) technique and their application to UV sensors

Porous TiO 2 thin films were prepared from titanium(IV)oxy acetylacetonate solutions by spray pyrolysis deposition (SPD) technique in air. The surface morphology and grain size of the film was easily controlled by changing species of solvent in the source solution. The TiO 2 film was employed as a light absorbing i-layer for UV sensor to deposit CuO/TiO 2/SnO 2 p– i– n junction by SPD technique. We found that the surface morphology of TiO 2 layer was very much affective on UV response, attributing to the light confinement within TiO 2 layer. Additionally, the response was further improved by reducing a carrier density in the TiO 2 layer.

Fabrication of dye-sensitized solar cells by spray pyrolysis deposition (SPD) technique

Porous TiO2 films were successfully synthesized in air from a commercial TiO2-sol by spray pyrolysis deposition (SPD) technique. The film consisted of fine TiO2 particles, approximately 30–50 nm in size, and showed the roughness factor as high as 1000. A dye-sensitized solar cell was constructed by SPD technique. In this technique, porous TiO2/dense TiO2/SnO2:F junction was prepared within 10–15 min, which drastically shortened the fabrication period of working electrodes. The photovoltaic conversion efficiency was enhanced up to 5.1% under the quasi-sunlight of AM-1.5 and 100 mW/cm2 by optimizing the porosity of TiO2 film. The result leads to an industrial production of dye-sensitized solar cells in the near future.

Fabrication of dye-sensitized solar cells by spray pyrolysis deposition (SPD) technique

Porous TiO 2 films were successfully synthesized in air from a commercial TiO 2-sol by spray pyrolysis deposition (SPD) technique. The film consisted of fine TiO 2 particles, approximately 30–50 nm in size, and showed the roughness factor as high as 1000. A dye-sensitized solar cell was constructed by SPD technique. In this technique, porous TiO 2/dense TiO 2/SnO 2:F junction was prepared within 10–15 min, which drastically shortened the fabrication period of working electrodes. The photovoltaic conversion efficiency was enhanced up to 5.1% under the quasi-sunlight of AM-1.5 and 100 mW/cm 2 by optimizing the porosity of TiO 2 film. The result leads to an industrial production of dye-sensitized solar cells in the near future.

Growth and cathodoluminescent characteristics of blue emitting cerium-doped zinc aluminate layers synthesized by spray pyrolysis technique

Cerium doped ZnAl2O4 cathodoluminescent films have been deposited by ultrasonic spray pyrolysis deposition technique. X-ray diffraction measurements on these layers have shown that their crystalline structure depends on the substrate temperature. Cerium ions have been introduced into zinc aluminate films for produce violet-blue cathodoluminescence emissions. The behavior of cathodoluminescence emission intensity has been studied, as a function of the variations on doping concentrations, in the start spraying solution, substrate temperatures and the electron accelerating voltage. Concentration quenching of the cathodoluminescence occurs at about 0.8 percent of activator (Ce) concentrations inside the synthesized films. The surface morphology characteristics of these films, as a function of the substrate temperature, and the chemical composition, as measured by energy dispersive X-ray spectroscopy, are also exhibited. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Fabrication of Dye-Sensitized Solar Cells by Spray Pyrolysis Deposition Technique

Fabrication of Dye-Sensitized Solar Cells by Spray Pyrolysis Deposition Technique

Mixed (ZnO)(x)(CdO)(1-x) policrystalline oxide films deposited by spray pyrolysis from metal nitrate solutions

Transparent conducting metal oxides are being studied and applied intensively in the optoelectronic device industry in recent years. Oxides such as SnO2, ITO, ZnO, CdO etc., are being used in thin solar cell technology, in the fabrication of gas sensor detectors, and in many other applications. ZnO and CdO exhibit complementary properties when analyzed for use as window materials in photovoltaic industry, i.e., ZnO has a wider band gap, but the undoped material is deposited with a significantly higher resistivity than CdO. Moreover, it has been demonstrated that both materials exhibit gas response. Therefore, a mixed (ZnO)X (CdO)1−X oxide might have intermediate properties making it an adequate material for both type of applications. One of the fundamental research lines directed to improve the ratio efficiency/cost in thin films solar cells technology is that related to the use of polycrystalline materials obtained by an inexpensive and suitable for mass production deposition technology. Spray pyrolysis deposition (SPD) technique satisfies to a great extent these requirements. In fact, we are engaged in a systematic study of sprayed CdO and interesting results have been obtained [1–3]. A substantial improvement of the electro-optical properties has been observed after incorporation of fluorine to the spraying solution. Mixed (ZnO)X (CdO)1−X oxide was first obtained by sol-gel technique [4] and more recently it was deposited by SPD [5]. Good crystallinity for phases corresponding to ZnO and CdO was reported to occur simultaneously after thermal treatments at temperatures higher than 400 ◦C. In the present communication we report the results of achieving depositions of mixed (ZnO)X (CdO)1−X oxides by SPD, starting from metal nitrate solutions. For intermediate X -values, peaks corresponding to both, cubic-CdO and hexagonal-ZnO phases are clearly resolved in DRX spectra for as-deposited samples, thus indicating a good crystallinity. Films were deposited on Corning 7059 glass in a SPD installation described elsewhere [1]. Two starting solutions of zinc and cadmium nitrates in distilled water, 0.1 M, were prepared and mixed in different proportions to form the spraying solutions. The studied

Black body coating by spray pyrolysis

For the first time, a rough and thick film of doped praseodymium nickel oxide [Pr 2 NiO 4+( ) has been obtained by combining spray pyrolysis deposition technique with Rapid Thermal Annealing (RTA) process. The precursors are nitrate solutions, the thermal decomposition of which has been studied. Spectral emissivity measurements in the far and mid infrared range at T=1000 K demonstrate the strong blackbody character of the film. This feature suits very well to operate a ceramic infrared radiant plate with high thermal efficiency. The applications would be apply for the heat-treatments of organic compounds such as paint, thermo-plastic, food, paper...

High emissivity of a rough Pr2NiO4 coating

A rough and thick film of doped praseodymium nickel oxide (Pr2NiO4+δ) has been obtained by combining the spray pyrolysis deposition technique with rapid thermal annealing process. The precursors are nitrate solutions. Spectral emissivity measurements from the far infrared up to the midinfrared region at T=1000 K show the strong black body character of the film. This feature is well suited to the thermal efficiency of an industrial infrared ceramic radiant plate.

Porous TiO 2 thin films synthesized by a spray pyrolysis deposition (SPD) technique and their application to dye-sensitized solar cells

Titanium dioxide (TiO 2) thin films were synthesized on glass substrates from titanium(IV)oxy acetylacetonate 2-butanol solution by a spray pyrolysis deposition (SPD) technique. The films consisted of TiO 2 leaflets and showed the oriented growth along the (2 0 0) direction. The surface area of the film was successfully increased by adding a small amount of aluminum(III) acetylacetonate (AA) in the source solution. This is because AA sublimates easily during the film formation to leave many pores within the film. A dye-sensitized solar cell was constructed with the TiO 2 film which was deposited on the fluorine-doped tin(IV) oxide layer by the SPD technique. The conversion efficiency of the cell was effectively enhanced as high as 3.2% at AA content of 0.6 at% in the source solution, attributing to the fact that the amount of a dye anchored on the surface of TiO 2 layer was the highest at this AA content. Although the conversion efficiency is relatively low, this finding leads to the possibility of an industrial production of a dye-sensitized solar cell in the near future.

Thermal decomposition of di-n-butyltin(IV) diacetate as a precursor for the spray pyrolysis deposition of oriented SnO2 thin films

[100]-Oriented SnO2 thin films were obtained on glass substrates from di-n-butyltin(IV) diacetate at 480°C by a spray pyrolysis deposition technique. The thermal decomposition processes of the starting materials were studied by vapor pressure measurement, gas chromatography, and mass spectroscopy for the elucidation of the formation mechanism of the films. Consequently, a growth model concerning the [100]-oriented SnO2 thin films was proposed on the basis of crystallographic considerations, in which the chemical species O–Sn–O appears to be the pyrolytic product of the starting material.