Synthesis of ZrO{sub 2} and Y{sub 2}O{sub 3}-doped ZrO{sub 2} thin films using self-assembled monolayers
0
Citation
0
Reference
20
Related Paper
Abstract:
Undoped or Y{sub 2}O{sub 3}-doped ZrO{sub 2} thin films were deposited on self-assembled monolayers (SAMs) with either sulfonate or methyl terminal functionalities on single-crystal silicon substrates. The undoped films were formed by enhanced hydrolysis of zirconium sulfate (Zr(SO{sub 4}) {center_dot} 4H{sub 4}O) solutions in the presence of HCl at 70 C. Typically, these films were a mixture of two phases: nanocrystalline tetragonal- (t-) ZrO{sub 2} and an amorphous basic zirconium sulfate. However, films with little or no amorphous material could be produced. The mechanism of film formation and the growth kinetics have been explained through a coagulation model involving homogeneous nucleation, particle adhesion, and aggregation onto the substrate. Annealing of these films at 500 C led to complete crystallization to t-ZrO{sub 2}. Amorphous Y{sub 2}O{sub 3}-containing ZrO{sub 2} films were prepared from a precursor solution containing zirconium sulfate, yttrium sulfate (Y{sub 2}(SO{sub 4}){sub 3} {center_dot} 8H{sub 2}O), and urea (NH{sub 2}CONH{sub 2}) at pH 2.2--3.0 at 80 C. These films also were fully crystalline after annealing at 500 C.Keywords:
Nanocrystalline material
Tetragonal crystal system
Cite
Barium titanate (BaTiO 3 ) powders were prepared by a polymerized complex method based on the Pechini‐type reaction route, wherein a mixed solution of citric acid (CA), ethylene glycol (EG), and barium and titanium ions, with a molar ratio of CA:EG:Ba:Ti = 10:40:1:1, was polymerized to form a transparent resin, which was used as a precursor for BaTiO 3 . Characterization of the initial precursor solution of EG, CA, and barium and titanium ions by Raman scattering and 13 C‐NMR spectroscopy indicated that barium and titanium ions were simultaneously stabilized with CA to form a barium‐titanium mixed‐metal CA complex with a stoichiometry similar to Ba:Ti:CA = 1:1:3. Raman and 13 C‐NMR spectra of the liquid mixture at various reaction stages indicated that the fundamental coordination structure of the mixed‐metal complex remained almost unchanged throughout the polymerization process. X‐ray diffractometry (XRD) measurements indicated formation of pseudo‐cubic BaTiO 3 free from BaCO 3 and TiO 2 when the barium‐titanium polymeric precursor was heat‐treated in air at 500°C for 8 h or at 600°C for 2 h. However, the Raman spectra of the same powders indicated the formation of tetragonal (rather than cubic) BaTiO 3 , with traces of high‐temperature hexagonal BaTiO 3 stabilized at room temperature. XRD of a pyrolyzed product at 500°C for 2 h revealed a simple mixture of BaTiO 3 and an intermediate phase, Ba 2 Ti 2 O 5 . CO 3 . A solid‐state reaction between BaCO 3 and TiO 2 was concluded as not being responsible for the BaTiO 3 formation; rather, BaTiO 3 formed directly by thermal decomposition of the intermediate Ba 2 Ti 2 O 5 . CO 3 phase at temperatures >500°C. In addition, by Raman scattering measurements, the intermediate Ba 2 Ti 2 O 5 . CO 3 phase was found to be unstable in ambient air, yielding BaCO 3 as one of the decomposed products.
Barium
Barium titanate
Cite
Citations (121)
Abstract ChemInform 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.
Carbon fibers
Cite
Citations (0)
Thin films of crystalline TiO 2 were deposited on self‐assembled organic monolayers from aqueous TiCl 4 solutions at 80°C; partially crystalline ZrO 2 films were deposited on top of the TiO 2 layers from Zr(SO 4 ) 2 solutions at 70°C. In the absence of a ZrO 2 film, the TiO 2 films had the anatase structure and underwent grain coarsening on annealing at temperatures up to 800°C; in the absence of a TiO 2 film, the ZrO 2 films crystallized to the tetragonal polymorph at 500°C. However, the TiO 2 and ZrO 2 bilayers underwent solid‐state diffusive amorphization at 500°C, and ZrTiO 4 crystallization could be observed only at temperatures of 550°C or higher. This result implies that metastable amorphous ZrTiO 4 is energetically favorable compared to two‐phase mixtures of crystalline TiO 2 and ZrO 2 , but that crystallization of ZrTiO 4 involves a high activation barrier.
Tetragonal crystal system
Metastability
Cite
Citations (23)
Zeolite ZSM-5 films of 5-10 {mu}m thickness were grown on macroporous {alpha}-Al{sub 2}O{sub 3} disks placed horizontally in a clear synthesis solution (SiO{sub 2}, Al{sub 2}O{sub 3}, Na{sub 2}O, TPA{sub 2}O, H{sub 2}O) and subjected to 12-24 hours hydrothermal reaction at 150-180{degrees}C. After extensive experimentation, synthesis compositions were identified that gave films of well intergrown ZSM-5 crystals. The films appeared free of cracks or pinholes in SEM and had pure gas n-C{sub 4}H{sub 10}:i-C{sub 4}H{sub 10} permeance ratio of 18 and 31 at 30{degrees}C and 185{degrees}C, respectively. The H{sub 2}:i-C{sub 4}H{sub 10} permeance ratio was 151 and 54 at 30{degrees}C and 185{degrees}C, respectively. The role of substrate pore size and composition of the synthesis solution on membrane structure and properties will be discussed.
Permeance
Hydrothermal Synthesis
ZSM-5
Stoichiometry
Cite
Citations (0)
The use of M[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} [M = Ti, Zr, Hf] and related compounds to form thin films of Group IV metalcarbides has been investigated. Zirconium carbide can be deposited on Si substrates from Zr[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} at temperatures in the range of 300 to750{degrees}C and pressures from 10{sup {minus}2} to 10{sup {minus}4} torr. The effects of deposition conditions on the resulting material has been examined by SEM, XPS, and AES. In situ mass spectrometry and analysis of the hydrocarbon fragments generated in the reactor have also been studied. The mechanism of decomposition of Zr[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} under conditions approximating the CVD experiment is related to solution phase decomposition studies and to properties of the resulting thin films. Variation of the coordination sphere of the group IV metal has allowed for a preliminary determination of desirable ligands for this system. Studies with Zr[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} showed that crystalline films can be deposited at high temperature (>550{degrees}C) regardless of pressure. Auger electron spectroscopy depth profiling trends indicated all films to be uniform in composition (with a constant metal to carbon ratio) and to contain some residual oxygen in the bulk. X-ray photoelectron spectroscopymore » shows carbon to be present in carbidic and graphitic forms, while zirconium is single phase with a small amount of zirconium dioxide present in the bulk.« less
Auger electron spectroscopy
Homoleptic
Cite
Citations (0)
artificial passivation films were formed on Pt substrates by low pressure metallorganic chemical vapor deposition technique using iron(III) acetylacetonate and chromium(III) acetylacetonate as precursors at substrate temperatures of 150-350°C. Relationships between the crystal structure, and also the chemical state of constituent elements, and the corrosion resistance were examined on the films in acid solutions. The films deposited above 300°C had crystalline structures, and those deposited below 250°C had amorphous structures. The films deposited above 250°C had a high amount of M‒O‐type chemical bonds, and those deposited below 200°C had a high amount of M‒OH‐type chemical bonds. The films deposited above 300°C hardly dissolved in 1.0 M HCl and those deposited below 250°C, however, easily dissolved in the solution. The dissolution rate of the films in the solution increased with decreasing substrate temperature. Passive and transpassive current densities of the films in were dependent on the substrate temperature and increased with decreasing the temperature. When polarized cathodically in and 0.5 M HCl, the films deposited below 250°C dissolved due to the reduction of the component in the films. The reduction of component was, however, suppressed on the films deposited above 300°C. Therefore, with increasing crystallinity and amount of M‒O‐type chemical bonds, the corrosion resistance of the films increases in HCl and solutions. © 1999 The Electrochemical Society. All rights reserved.
Passivation
Chemical state
Cite
Citations (13)
An overlayer of Fe{sub 2}O{sub 3} on nanoscale MgO crystallites was prepared by adsorption of Fe(acac){sub 3} followed by heat treatment. This [Fe{sub 2}O{sub 3}]MgO composite served as a high-capacity reagent for reaction/decomposition of CCl{sub 4} to form [Fe{sub 2}O{sub 3}]MgCl{sub 2} plus CO{sub 2}. The Fe{sub 2}O{sub 3} overlayer served as a catalyst for efficient Cl{minus}/O{sub 2{minus}} ion exchange with the inner layers of MgO. The [Fe{sub 2}O{sub 3}]MgO high surface area composite is a promising reagent for the one-step decomposition/mineralization of chlorocarbon and chlorofluorocarbons at temperature near 400 C.
Overlayer
Cite
Citations (8)
Conventional solid state reactions are diffusion limited processes that require high temperatures and long reaction times to reach completion. In this work, several solution based methods were utilized to circumvent this diffusion limited reaction and achieve product formation at lower temperatures. The solution methods studied all have the common goal of trapping the homogeneity inherent in a solution and transferring this homogeneity to the solid state, thereby creating a solid atomic mixture of reactants. These atomic mixtures can yield solid state products through diffusionless mechanisms. The effectiveness of atomic mixtures in solid state synthesis was tested on three classes of materials, varying in complexity. A procedure was invented for obtaining the highly water soluble salt, titanyl nitrate, TiO(NO3)2, in crystalline form, which allowed the production of titanate materials by freeze drying. The freeze drying procedures yielded phase pure, nanocrystalline BaTiO3 and the complete SYNROC-B phase assemblage after ten minute heat treatments at 600 C and 1,100 C, respectively. Two novel methods were developed for the solution based synthesis of Ba2YCu3O7-x and Bi2Sr2Ca2Cu3O10. Thin and thick films of Ba2YCu3O7-x and Bi2Sr2Ca2Cu3O10 were synthesized by an atmospheric pressure, chemical vapor deposition technique. Liquid ammonia solutions of metal nitrates were atomized with a stream of N2O and ignited with a hydrogen/oxygen torch. The resulting flame was used to coat a substrate with superconducting material. Bulk powders of Ba2YCu3O7-x and Bi2Sr2Ca2Cu3O10 were synthesized through a novel acetate glass method. The materials prepared were characterized by XRD, TEM, SEM, TGA, DTA, magnetic susceptibility and electrical resistivity measurements.
Nanocrystalline material
Atomic diffusion
Cite
Citations (0)
Conventional solid state reactions are diffusion limited processes that require high temperatures and long reaction times to reach completion. In this work, several solution based methods were utilized to circumvent this diffusion limited reaction and achieve product formation at lower temperatures. The solution methods studied all have the common goal of trapping the homogeneity inherent in a solution and transferring this homogeneity to the solid state, thereby creating a solid atomic mixture of reactants. These atomic mixtures can yield solid state products through {open_quotes}diffusionless{close_quotes} mechanisms. The effectiveness of atomic mixtures in solid state synthesis was tested on three classes of materials, varying in complexity. A procedure was invented for obtaining the highly water soluble salt, titanyl nitrate, TiO(NO{sub 3}){sub 2}, in crystalline form, which allowed the production of titanate materials by freeze drying. The freeze drying procedures yielded phase pure, nanocrystalline BaTiO{sub 3} and the complete SYNROC-B phase assemblage after ten minute heat treatments at 600{degrees}C and 1100{degrees}C, respectively. Two novel methods were developed for the solution based synthesis of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}. Thin and thick films of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} were synthesized by an atmospheric pressure, chemical vapor deposition technique. Liquid ammonia solutions of metal nitrates were atomized with a stream of N{sub 2}O and ignited with a hydrogen/oxygen torch. The resulting flame was used to coat a substrate with superconducting material. Bulk powders of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} were synthesized through a novel acetate glass method. The materials prepared were characterized by XRD, TEM, SEM, TGA, DTA, magnetic susceptibility and electrical resistivity measurements.
Nanocrystalline material
Atomic diffusion
Cite
Citations (0)
Ultra-thin films of Mg and MgO were grown on {alpha}-Al{sub 2}O{sub 3} (10{bar 1}2) surfaces (r-cut sapphire) and studied using reflection high energy electron diffraction (RHEED) and x-ray photoelectron spectroscopy (XPS). When Mg is deposited at 30 C in ultra-high vacuum (UHV), the first monolayer of Mg atoms chemically bonds to the oxygen anions of the sapphire surface. At Mg coverages above a monolayer, a polycrystalline metallic Mg overlayer is formed. Annealing above 250 C in UHV causes the metallic Mg to desorb from the surface. However, annealing above 250 C in 10{sup {minus}6}torr O{sub 2}produces a polycrystalline MgO film. This MgO film recrystallizes after annealing in O{sub 2} at 900 C for 60 minutes and exhibits a crystallographic orientation of MgO (100) {vert_bar}{vert_bar} {alpha}-Al{sub 2}O{sub 3} (10{bar 1}2). RHEED indicates that the recrystallized MgO layer dewets the sapphire surface and forms islands. When Mg is deposited at 30 C in 10{sup {minus}6} torr O{sub 2}, a polycrystalline MgO layer is created. This layer also becomes recrystallized and dewet the sapphire surface after extended annealing in O{sub 2} at 900 C. No evidence for a MgAl{sub 2}O{sub 4} spinel phase was observed.
Overlayer
Nanocrystalline material
Cite
Citations (0)