Pyrosol Technique Research Articles

Tunable white light emission from hafnium oxide films co‐doped with trivalent terbium and europium ions deposited by Pyrosol technique

In this paper, the photo and cathodoluminescent properties of HfO2 films optically activated with different atomic concentrations of Tb3+ and Eu3+ ions, deposited by the Pyrosol technique, are reported. These films were deposited at temperatures from 400 to 600 °C, using chlorides as raw materials. The surface morphologies of all deposited films were rough and dense. X‐ray diffraction analysis showed that the films deposited at 600 °C were polycrystalline exhibiting the HfO2 monoclinic phase. The tuning by the means of the excitation wavelength generates photoluminescence spectra, for co‐doped films, in several emissions from blue to yellow (including white light) due to the characteristic electronic transitions of Tb3+ (green), Eu3+(red) ions and the violet‐blue emission associated to the host lattice (HfO2). According to the chromaticity diagram, the best white light is reached for the sample S2 excited with 382 nm (x = 0.3343, y = 0.3406). The cathodoluminescence emission spectra for co‐doped films showed emissions from green to red (including yellow, orange and other intermediate emissions). The averaged quantum efficiency values of the sample labeled as S2 resulted between 47 and 78% depending on the excitation wavelength. In addition, XPS, TEM, SEM and decay times were performed to characterize these films.

Synthesis, characterization and luminescence studies in ZrO2:Dy3+ and ZrO2:Dy3+, Gd3+ films deposited by the Pyrosol method

ZrO2, ZrO2:Dy3+ and ZrO2:Dy3+, Gd3+ films were synthesized using the Pyrosol technique. These films have a ZrO2-metastable tetragonal crystalline structure, which is better defined as the deposition temperature increases. Photoluminescence and cathodoluminescence properties of these films were studied as a function of deposition parameters such as substrate temperature and Dy3+ and Gd3+ relative concentrations. All luminescent emission spectra showed the typical electronic transitions 4f→4f of the Dy3+ ions at 480, 574 and 655nm. The luminescent intensity is observed to increase with the Dy3+ ion concentration up to 7at.% in the spraying solution (1.8at.% inside films), higher concentration result in an inhibition of the luminescence. Incorporation of Gd3+ ions in ZrO2:Dy3+ films produced a marked increase in the luminescent emission intensity (approximately 15 times). The elemental composition and surface morphology of these films are also reported.

Preparation of Iron Oxide Nanoparticles by a Pyrosol Technique

Iron oxide nanoparticles were prepared from an iron nitrate solution by a pyrosol technique. The precursor solution was atomized by a mist generator in order to form an aerosol which was brought into a tube furnace by a controlled flowing air stream. The pyrolysis of the aerosol was occurred to form the particles inside the furnace at 350 °C. Scanning electron microscopy images have shown that a mean diameter of the particles is in good agreement with the third root of the precursor concentration. X-ray diffraction patterns have revealed that the main peaks from the samples are corresponding to the α-Fe2O3 phase.

Pyrosol deposition of anatase TiO 2 thin films starting from Ti(O iPr) 4/acetylacetone solutions

TiO 2 thin films were deposited on Si(100) and steel substrates by Pyrosol technique. The layer morphology depends on the concentration of titanium tetra-isopropoxide (TTIP) used as molecular precursor in solutions with acetylacetone (Acac). The concentration and, as a result, the viscosity of these TTIP/Acac starting solutions plays an important role on the efficiency of their nebulization and, consequently, on the microstructure and the growth kinetics of the TiO 2 thin films. The correlations between the composition of the TTIP/Acac solutions and the structure, the morphology, optical properties and the deposition rate of the films are presented and discussed. Growth rates as high as 1.8 μm/min are obtained using pure TTIP without Acac solvent. The photocatalytic activity of these Pyrosol TiO 2 thin films grown using TTIP with and without Acac solvent has been investigated and a negative effect of the solvent was found.

Temperature programmed desorption of F-doped SnO2 films deposited by inverted pyrosol technique

Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.2·10–4 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H+), 2(H2+), 12(C+), 14(N+), 15(CH3+), 16(O+), 17(OH+ or NH3+), 18(H2O+ or NH4+), 19(F+), 20(HF+), 28(CO+ or N2+), 32(O2+), 37(NH4F+), 44(CO2+), 120(Sn+), 136(SnO+) and 152(SnO2+). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400°C.

Characterization of HfO2:Mn luminescent coatings deposited by spray pyrolysis

Novel manganese doped hafnium oxide cathodoluminescent films have been synthesized by the Pyrosol technique. The material obtained is in an amorphous state up to 300 °C. For higher temperatures a polycrystalline material is obtained with a monoclinic hafnium oxide phase. The cathodoluminescence spectra show blue–green and red bands associated with the electronic transitions 4T1(4G) → 6A1(6S) of the Mn2+ ions. A dependence of the cathodoluminescence, as a function of the doping concentration, substrate temperature and electron accelerating voltage is observed. In addition, preliminary results indicate that the chlorine relative content inside the processed films has been found to have an important role on the luminescent emission intensity of the studied materials. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrical, optical and structural characterization of high-k dielectric ZrO2thin films deposited by the pyrosol technique

High-k dielectric zirconium oxide (ZrO2) thin films have been deposited on silicon substrates at temperatures from 400 to 600 °C using the spray pyrolysis technique. The films were deposited from two spraying solution concentrations (0.033 and 0.066 M) of zirconium acetylacetonate dissolved in N,N-dimethylformamide. These films were stoichiometric, transparent and with a very low surface roughness (5–40 A). The refractive index of these films was of the order of that obtained for a bulk material (2.12). Films deposited with high molar concentration presented the best electrical characteristic, have a dielectric constant in the range 12.5–17.5, depending on the deposition temperature, and can stand electric fields up to 3 MV cm−1 without observing destructive dielectric breakdown. Transmission electron microscopy measurements, indicate that the films consist of nano-crystallites of the tetragonal ZrO2 crystalline phase embedded into an amorphous matrix. Infrared spectroscopy measurements of the films show peaks associated with ZrO2 and a peak related to silicon dioxide (SiO2). The analysis of spectroscopic ellipsometry measurements on these films indicates the existence of a layer at the ZrO2/Si interface composed of SiO2 as well as ZrO2 and crystalline silicon.

On the physical properties of indium oxide thin films deposited by pyrosol in comparison with films deposited by pneumatic spray pyrolysis

This paper presents the structural, electrical and optical properties of indium oxide thin films deposited by (1) pyrosol technique in comparison with the results that were obtained by spraying the same solution using (2) a pneumatic spray system. Films were deposited at temperatures ranged between 623 and 863 K onto glass substrates and investigated by scanning electron microscopy and X-ray diffraction. The transmission and reflectance spectra were determined in the 260–2600 nm spectral range. Resistivity as low as 6×10 −3 Ω cm with high optical transmission (>90%) have been obtained in In 2O 3 thin films deposited, when the ultrasonic atomizer system was used. The figures of merit Φ TC= T 10/ R sh of films deposited using the two methods were calculated at different wavelengths. The advantages of the pyrosol method were obvious. The atomization of solution using the ultrasonic system leads to an improvement of the structural and electrical properties of films and allows the deposition of films with high transparency and electrical conductivity at lower substrate temperatures (∼673 K) compared to that needed in the case of pneumatic spray method (⩾773 K).

Characterization of ZrO2:Mn, Cl luminescent coatings synthesized by the Pyrosol technique

Abstract Manganese doped zirconia luminescent films have been deposited at temperatures ranging from 250 to 500 °C using the Pyrosol technique. The material obtained is in an amorphous state up 400 °C. For higher temperatures a polycrystalline material is obtained with a cubic and/or tetragonal crystalline zirconia phase. The photoluminescence and cathodoluminescence spectra show the bands associated with the electronic transitions 4 T 1 ( 4 G )→ 6 A 1 ( 6 S ) of the Mn2+ ions. A decrease of the luminescence, as a function of the doping concentration, substrate temperature and electron accelerating voltage is observed. The presence of chlorine seems necessary for the red luminescence. The surface morphology of the films is also presented.

Étude Raman de l'effet de taille nanométrique des cristallites sur le diagramme de phase P-T de la zircone

The phase transformations of 7, 13, 18nm nanocrystalline zirconia prepared by pyrosol technique and 10-15nm zirconia prepared by oxidation of zirconium alloys have been monitored by Raman spectrometry. It is shown that for these zirconia, the tetragonal form can be obtained either under its metastable state at ambient conditions or from the monoclinic form by application of pressure below 4 GPa and with temperature increment smaller than 300 K. The nanometric monoclinic-tetragonal equilibrium line is strongly down-shifted in temperature compared to literature data measured on usual polycrystalline zirconia. In addition, the monoclinic-orthorhombic equilibrium line is slightly shifted to higher pressure (i.e. 7 GPa). These results confirm that stresses can play a primordial role in the formation of tetragonal form in the oxidation process of zirconium alloys.

Preparation and characterization of Eu doped zirconia luminescent films synthesized by the pyrosol technique

The pyrosol method is a well-known process for de- positing films [l, 21. The main advantages of this tech- nique are its low cost, a high deposition rate, the pos- sibility to coat large areas, its ease of operation and the quality of the coatings obtained. This technique has been used to deposit successfully a variety of films such as oxides, sulfides and metals [I]. Zirconia has attracted much attention in science and technology be- cause its high melting temperature, high refractive in- dex, low thermal conductivity, hardness and corrosion barrier properties [3]. Furthermore these films are use- ful in corrosion resistance applications [4], as insulat- ing layers in very large scale integrated (VLSI) cir- cuits [5], for optical coatings [6], in buffer layers for high Tc oxide superconductors [7], etc. There are also some studies on rare earth doped luminescent zirco- nia single crystals and powders [8-101. The present contribution is devoted to the preparation and char- acterization of Zr02 : Eu photoluminescent (PL) and cathodoluminescent (CL) films synthesized by the py- rosol technique. To our best knowledge, there has been no report on luminescent coatings of Zr02

ChemInform Abstract: A Pyrosol Technique to Deposit Highly Transparent, Low‐Resistance SnO2:F Thin Films from Dimethyltin Dichloride.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Pyrosol Technique to Deposit Highly Transparent, Low‐Resistance SnO2 : F Thin Films from Dimethyltin Dichloride

Highly transparent, low‐resistance films suitable as a substrate material for thin film CdS/CdTe solar cells have been developed on 10 × 10 cm glass substrates by an ultrasonic spray pyrolysis (pyrosol) technique using dimethyltin dichloride (DMTDC) as a tin source. DMTDC, , and HF, all dissolved in water, served as the source solution. An ultrasonic vibrator operated at 1.5 MHz produced a fine spray of the source solution. It was transported, using air as a carrier gas, to moving glass plates in a belt furnace maintained at 530°C. A very high growth rate of nearly 100 Å/s was realized in this process with good homogenity, high transparency, and low resistivity. Films with a sheet resistance of less than 10 Ω/□ have been routinely prepared and their preparation technology has been well established. A proper nozzle design and exhaust system to remove the spent gases determines the technology of obtaining spot and cloud free homogeneous films in the belt furnace. A film of 5000 Å thickness exhibited the lowest electrical resistivity, of , a mobility value of , and a donor concentration of . Films of 5000–6000 Å thickness having an average transmittance of nearly 85% in the visible range and a sheet resistance of around 8 Ω/□ were used as transparent conducting oxide film substrates to fabricate thin film CdS/CdTe solar cells. A solar energy conversion efficiency of over 14% was achieved. © 1999 The Electrochemical Society. All rights reserved.

Morphological differences in ZnO films deposited by the pyrosol technique: effect of HCl

In this letter, the surface aspect of crystallized ZnO films deposited by the pyrosol technique is examined. Depending on whether the starting solution contains chlorine species or not, the crystal development is either in a pyramidal form or in a prismatic form. The influence of HCl vapor is used to explain these morphological differences.

La0.8Sr0.2Cr0.95Ru0.05 (LSCRu) as a new anode material for SOFC using natural gas

The strontium and ruthenium doped lanthanum chromite was synthesized by the Pyrosol technique. This method has allowed to insert ruthenium in the perovskite powder. The catalytic behavior for the methane reforming was determined using a catalytic bench. In the presence of a few percent of water vapor, this material transforms the methane into hydrogen without generating carbon deposition. The electrochemical behavior of this material as anode has been studied by impedance spectroscopy under Ar/H2O, H2/H2O and CH4/H2O mixtures. The overpotential resistance values are of the same order of magnitude under hydrogen and under methane. An additional contribution at low frequencies is observed under argon, resulting probably of the electrode polarization.

Experimental survey of different precursor/solvent pairs for the deposition of tin dioxide by pyrosol

In order to prepare tin dioxide (SnO 2) based films by the pyrosol technique, different mixtures of tin precursors (chlorinated and nonchlorinated salts) and solvents (methanol, butanol and acetylacetone) have been tested. Depending on the surface aspect, the obtained deposits have been classified into three categories; there are smooth, slightly faceted and faceted surfaces. Smooth surfaces are obtained when the solvent has a high nebulization rate or when the salt has a high molecular weight. The development of facets occurs when the salt is light or when gaseous HCl is present in the pyrolysis region. The optical and electrical characteristics of the corresponding films are also discussed.

Oxygen Reduction at La0.5Sr0.5MnO3 Thin Film/Yttria‐Stabilized Zirconia Interface Studied by Impedance Spectroscopy

thin films were prepared by a pyrosol technique. Films were characterized by x‐ray diffraction and scanning electron microscopy analysis. Their electrical resistance was measured, and they showed a semiconductive behavior. The η(i) curves were drawn at 800 and 900°C and impedance spectroscopy was performed during polarization. At low polarization, the oxygen reduction takes place at the triple contact points and is progressively delocalized over the whole surface of the electrode. At high polarizations, two components of the impedance have been identified. The first, at high frequency, is correlated with an atomic rearrangement of the electrode (either in the bulk or at the surface), which favors the electrode reaction. At low frequencies, the impedance has been attributed to a concentration impedance due to at least two adsorbed species.

Oxygen Reduction at La0.5Sr0.5Mno3 Thin Film/Yttria Stabilized Zirconia Interface Studied by Impedance Spectroscopy

La0.5Sr0.5MnO3 thin films were prepared by a pyrosol technique. Films were characterized by Xray diffraction and SEM analysis. Their electrical resistance was measured and they showed a semiconductive behaviour. The η(i) curves were drawn at 800°C and 900°C and impedance spectroscopy was performed during polarization. At low polarization, the oxygen reduction takes place at the triple contact points and is progressively delocalized to the whole surface of the electrode. At high polarizations, two components of the impedance have been identified. The first one, at high frequency, is correlated with an atomic rearrangement of the electrode (either in the bulk or at the surface), which favours the electrode reaction. At low frequencies, the impedance has been attributed to a concentration impedance due to at least two adsorbed species.

Inter-relationship between deposition temperature and morphology of SnO2 films deposited by a pyrosol process

Abstract SnO 2 films have been deposited on hot alumina substrates using a pyrosol technique. Depending on the deposition temperature (from 450 up to 600 °C), the textures range from dense to porous deposits. The morphologies obtained are discussed according to models developed for conventional CVD techniques where the deposition temperatures are much greater than for the pyrosol method.