Thin Films (thin + film)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Thin Films

  • alloy thin film
  • aln thin film
  • batio3 thin film
  • block copolymer thin film
  • carbon thin film
  • copolymer thin film
  • cugase2 thin film
  • dioxide thin film
  • epitaxial thin film
  • ferroelectric thin film
  • gan thin film
  • hybrid thin film
  • mesoporou thin film
  • metal oxide thin film
  • multilayer thin film
  • nanocomposite thin film
  • nanocrystalline thin film
  • nitride thin film
  • organic semiconductor thin film
  • organic thin film
  • oxide thin film
  • pentacene thin film
  • polycrystalline thin film
  • polymer thin film
  • pzt thin film
  • semiconductor thin film
  • silicon thin film
  • sno2 thin film
  • tio2 thin film
  • titanate thin film
  • titania thin film
  • very thin film
  • zinc oxide thin film
  • zno thin film

  • Terms modified by Thin Films

  • thin film deposition
  • thin film formation
  • thin film sensor
  • thin film solar cell
  • thin film structure
  • thin film transistor

  • Selected Abstracts


    Comparison of Electrochemical and Surface Plasmon Resonance Immunosensor Responses on Single Thin Film

    ELECTROANALYSIS, Issue 20 2008
    Ryoji Kurita
    Abstract This paper reports results obtained when comparing an electrochemical enzyme immunosensor and a surface plasmon resonance (SPR) based immunosensor on the same gold surface installed in an electrochemical SPR flow cell. Simultaneous electrochemical and SPR measurements were performed on a gold surface modified with multilayers of poly- L -lysine and poly-styrenesulfonate assembled with the layer-by-layer method. First, we obtained the SPR response induced by the formation of an immunocomplex from the shift in the SPR angle by injecting an anti tumor necrosis factor-, antibody solution labeled with alkaline phosphatase into the flow cell containing the multilayer modified with tumor necrosis factor-,. Then we compared this SPR result with that obtained for the electrochemical oxidation current of p -aminophenol catalyzed by alkaline phosphatase from p -aminophenolphosphate on the same gold film. We compared the two immunosensor responses obtained using the different measurement principles and found that there was a high correlation efficient of 0.973 between them. This was because we were able to immobilize the immunoreagents with good stability and without losing the transport of the enzyme product in the multilayer whose thickness we easily controlled with nanometer scale accuracy. We also report that the detection limit of our electrochemical immunosensor after optimization was around 100,pg/mL (0.4,pM), which is one of the lowest values yet reported for an electrochemical immunosensor. [source]


    Growth of Metal Nanoparticles in a Sol-Gel Silica Thin Film

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007
    Miroslava Malenovska
    Abstract Silica films on glass substrates with homogeneously dispersed platinum, gold or silver nanoparticles were prepared by sol-gel processing mixtures of tetraethoxysilane and {3-[(2-aminoethyl)amino]propyl}triethoxysilane complexes of the corresponding metal ions, followed by dip-coating and hydrogen treatment of the films at elevated temperatures. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


    Dewetting of an Organic Semiconductor Thin Film Observed in Real-time,

    ADVANCED ENGINEERING MATERIALS, Issue 4 2009
    Stefan Kowarik
    We study the growth and the post-growth dewetting process of the organic semiconductor diindenoperylene (DIP) using real-time X-ray reflectivity measurements. We show that a DIP monolayer deposited in UHV onto silicon oxide dewets via the formation of bilayer islands. From the time resolved structural data we estimate the rate constant for interlayer diffusion of DIP molecules. Post-growth AFM measurements confirm the conclusions from the X-ray data and show the morphology of the dewetted film. [source]


    Lateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3-hexylthiophene) Thin Film

    ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
    Kaname Kanai
    Abstract How annealing influences the morphology of a highly regioregular poly(3-hexylthiophene) (RR-P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high-molecular-weight (MW) RR-P3HT films tend to show low crystallinity even after annealing, it is found that high-MW RR-P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR-P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high-MW RR-P3HT film. [source]


    Grayscale Photopatterning of an Amorphous Polymer Thin Film Prepared by Photopolymerization of a Bisanthracene-Functionalized Liquid-Crystalline Monomer

    ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
    Hideyuki Kihara
    Abstract A method for grayscale photopatterning of an amorphous polymer film derived from a bisanthracene-functionalized liquid-crystalline monomer is developed. Solution photopolymerization of a monomer with two anthracene moieties, one at each end, affords an amorphous polymer. A combination of irradiation with patterned UV light and heating results in photopatterning on thin films prepared from the polymer. On non-irradiated areas of the film, the polymer reverts to the monomer owing to the thermal back-reaction of the anthracene photodimer, forming an ordered phase. On irradiated areas remaining in the amorphous phase, the thermal back-reaction is suppressed. This phenomenon results in a clear contrast and visual images on the film under polarized light. Grayscale photopatterning is also made possible for the solution-polymerized polymer by controlling the intensity of exposure. In addition, rewritable photopatterning can be achieved by melt photopolymerization of the monomer. The new photopatterning is essentially nondestructive because it needs neither image development nor anthracene-excitation light for reading. [source]


    Molecular Auxetic Behavior of Epitaxial Co-Ferrite Spinel Thin Film

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
    Matjaz Valant
    Abstract In functional oxide materials so-called molecular auxetic behavior is extremely rare. Here, it is reported in the CoFe2O4 spinel structure. A CoFe2O4 epitaxial thin film under compressive axial strain also reduces its cell dimensions in the transverse direction with a Poisson's ratio of ,0.85. A hinge-like honeycomb network in the spinel structure is identified as being responsible for the negative Poisson's ratio. This phenomenon has a substantial effect on the functional properties of CoFe2O4 and enables the construction of a new class of nano-devices. [source]


    Self-Assembled Nanoscale Ring Arrays from a Polystyrene- b -polyferrocenylsilane- b -poly(2-vinylpyridine)Triblock Terpolymer Thin Film

    ADVANCED MATERIALS, Issue 37 2009
    Vivian P. Chuang
    Hollow ring arrays with an outer and inner diameter of 33 and 11,nm, respectively, are formed from a thin film of poly-(styrene- b -ferrocenylethylmethylsilane- b -2-vinyl pyridine) (PS- b -PFS- b -P2VP) triblock terpolymer with a core/shell cylindrical morphology. The PS minority block forms a core surrounded by a PFS shell in a P2VP matrix; the core/shell structure is oriented perpendicularly to the film surface. The PS core and P2VP matrix blocks are partly removed using oxygen reactive ion etching, leaving ring patterns made from oxidized PFS. [source]


    Nanowire-Induced Wurtzite InAs Thin Film on Zinc-Blende InAs Substrate

    ADVANCED MATERIALS, Issue 36 2009
    Jiming Bao
    InAs pyramids and platelets on a zinc-blende InAs substrate are found to exhibit a wurtzite crystal structure. Induced by wurtzite InAs nanowires, wurtzite InAs thin film and its associated zinc-blende/wurtzite heterocrystalline heterostructures may open up new opportunities in band-gap engineering and related device applications. [source]


    Fabrication of a High-Brightness Blue-Light-Emitting Diode Using a ZnO-Nanowire Array Grown on p-GaN Thin Film

    ADVANCED MATERIALS, Issue 27 2009
    Xiao-Mei Zhang
    Bright n-ZnO nanowire/p-GaN film hybrid heterojunction light-emitting-diode (LED) devices are fabricated by directly growing n-type ZnO-nanowire arrays on p-GaN wafers. UV,blue electroluminescence emission was observed from the heterojunction diodes, and the heterojunction LED device exhibited a high sensitivity in responding to UV irradiation. [source]


    Patterning a Poly(3,4-ethylenedioxythiophene) Thin Film Using a Liquid Crystalline Network,

    ADVANCED MATERIALS, Issue 3 2005
    O. Catanescu
    Polymerization and patterning of a conductive polymer thin film via a new approach involving a well-ordered polymer matrix previously obtained using a liquid-crystalline template is reported here. The resulting conductive polymer (PEDOT, poly(3,4-ethylenedioxythiophene)) was shown by scanning electron microscopy (SEM) to be very well aligned at a submicrometer level (see Figure). [source]


    Synthesis and High Metallic Conductivity of Layer-Structured Sr2N Thin Film Deposited onto MgO(001) Substrate.

    CHEMINFORM, Issue 31 2004
    Kei Inumura
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Sensitized Emission from Lanthanide-Doped Nanoparticles Embedded in a Semiconductor Sol,Gel Thin Film,

    CHEMPHYSCHEM, Issue 11 2007
    Sri Sivakumar Dr.
    Abstract In2O3 sol,gel thin films made with LaF3:Ln3+ (Ln=Er, Nd, and Eu) nanoparticles were prepared and showed sensitized emission of the lanthanide ions after In2O3 matrix excitation. The excitation spectra showed an In2O3 absorption band in addition to the excitation peaks of the lanthanide ions, clearly demonstrating that there is energy transfer from the In2O3 matrix to Ln3+ (Er3+, Nd3+, and Eu3+). Similarly, HfO2 and ZrO2 sol,gel thin films made with LaF3:Ln3+ nanoparticles also showed energy transfer from the semiconductor matrix to the lanthanide ions. [source]


    Effect of Platinum and Ruthenium Incorporation on Voltammetric Behavior of Nitrogen Doped Diamond-Like Carbon Thin Films

    ELECTROANALYSIS, Issue 23 2009
    W. Khun
    Abstract Nitrogen doped diamond-like carbon thin films with or without platinum and ruthenium incorporation (N-DLC or PtRuN-DLC) were deposited on highly conductive p-Si substrates by DC magnetron sputtering to study the effect of Pt and Ru doping on the voltammetric performance of the N-DLC films. The potential windows of these film electrodes were measured in different electrolytic solutions, such as H2SO4, HCl and KCl. The cyclic voltammograms obtained from the N-DLC film electrodes in these solutions showed wide potential windows while the introduction of Pt and Ru into the film electrodes apparently narrowed down the potential windows due to their catalytic activities. [source]


    Insertion Reactions of an Aminogermylene and Formation of a Single-Source Precursor for GeTe Thin Films

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2009
    Tianniu Chen
    Abstract Insertion reactions between a liquid germylene 1, and either a carbodiimide or dialkyl telluride lead to the formation of the group-14-metal(II) guanidinate complex 2 or the stable group-14-metal terminal alkyl tellurolate compound 3, respectively. The complexes 2 and 3 were structurally elucidated by multinuclear NMR and single-crystal X-ray crystallography. The use of 3 as a single-source precursor (SSP) for the MOCVD of GeTe films was demonstrated. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Nb-Doped VO2 Thin Films Prepared by Aerosol-Assisted Chemical Vapour Deposition

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2007
    Clara Piccirillo
    Abstract Niobium-doped vanadium dioxide (VxNb1,xO2, x = 0,0.037) thin films were prepared by aerosol-assisted chemical vapour deposition (AACVD) of vanadyl(IV) acetonate and niobium(V) ethoxide in ethanol. Samples were analysed by EDX, XRD, Raman, XPS and SEM. The analyses confirmed the deposition of niobium, even if no separated phase was formed; the morphological structure of the films was affected by the dopant presence. The thin films showed thermochromic behaviour, with a marked change in optical properties above and below the switching temperature. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


    Tungsten Oxide and Tungsten Oxide-Titania Thin Films Prepared by Aerosol-Assisted Deposition , Use of Preformed Solid Nanoparticles

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2007
    Uzma Qureshi
    Abstract Aerosol-assisted deposition (AAD) was used to deposit films of WO3 from a suspension of solid nanoparticulate WO3 in toluene. Titania films were deposited by the aerosol-assisted chemical vapour deposition of [Ti(OiPr)4] in the presence of WO3 nanoparticles. The WO3 and TiO2 films exhibited photoactivity and photoinduced superhydrophilicity, further the titania films showed very unusual highly crenulated microstructures. These microstructures could not be obtained by sol-gel, atmospheric pressure chemical vapour deposition or evaporation routes. Furthermore, the microstructures could not be obtained from [Ti(OiPr)4] in the absence of nanoparticulate WO3. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


    Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties,

    ADVANCED ENGINEERING MATERIALS, Issue 12 2009
    Christian Klever
    Abstract Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read-out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non-contact read-out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000,nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6,nm while the individual layer thickness ratio tTiN/tFeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as-deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency-dependent permeability) are described. Finally, the suitability of the coatings for the use in remote-interrogable wear sensor applications is briefly discussed. [source]


    Thermal Investigation of Al2O3 Thin Films for Application in Cutting Operations,

    ADVANCED ENGINEERING MATERIALS, Issue 7 2009
    Kirsten Bobzin
    Crystalline PVD ,-Al2O3 coatings offer great potential for use in high-speed cutting operations. They offer specific high temperature features, like high hot hardness and high oxidation resistance. However, the reasons for the high thermal stability of this system are not clearly understood. In this paper, the phase and oxidation stability of thin ,-Al2O3 films (as illustrated in the micrograph) are investigated. [source]


    In situ Grazing Incidence Scattering Investigations During Magnetron Sputtering Deposition of FePt/Ag Thin Films (Adv. Eng.

    ADVANCED ENGINEERING MATERIALS, Issue 6 2009
    Mater.
    The cover picture shows an grazing incidence small angle X-ray scattering pattern of a granular Ag(6nm)-FePt(7.5nm)-Ag-FePt thin film using an in-situ magnetron sputtering chamber measured directly after growth at the Beamline BM20 (ROBL) at the ESRF. The sequential deposition provides separated, faceted FePt nanoislands without any magnetic property degradation and with magnetic moments preferentially oriented parallel to layer surface. The central part of the picture was blocked by a beam stop to avoid an over-saturation of the CCD detector. More details can be found in the article by Jrg Grenzer et al. on page 478. [source]


    In situ Grazing Incidence Scattering Investigations During Magnetron Sputtering Deposition of FePt/Ag Thin Films,

    ADVANCED ENGINEERING MATERIALS, Issue 6 2009
    Valentina Cantelli
    Using in situ synchrotron X-ray grazing incidence scattering experiments we investigated FePt islands mediated by Ag. FePt has been deposited by DC-magnetron sputtering on amorphous Si/SiO2 substrate at 400,C, to support the formation of the hard ferromagnetic L10 -FePt phase during growth. The sequential Ag/FePt deposition provides separated FePt nanoislands without magnetic property degradation. We obtained magnetic moments preferentially oriented parallel to layer surface. [source]


    Relationship between Condition of Deposition and Properties of W-Ti-N Thin Films Prepared by Reactive Magnetron Sputtering,

    ADVANCED ENGINEERING MATERIALS, Issue 3 2006
    V. Kuchuk
    A correlation between the film properties of nitrides, oxides etc., and their structure, is of fundamental importance , not only for thin solid films physics but also for practical applications. The structure of the films depends on deposition methods and their parameters. The relationship between properties (chemical and phase compositions, surface morphology, and electrical resistivity) and nitrogen partial pressure of reactive magnetron sputtered W-Ti-N thin films has been discussed here in detail. [source]


    Time,Temperature,Transformation (TTT) Diagrams for Crystallization of Metal Oxide Thin Films

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
    Jennifer L. M. Rupp
    Abstract Time,temperature,transformation (TTT) diagrams are proposed for the crystallization of amorphous metal oxide thin films and their specific characteristics are discussed in comparison to glass-based materials, such as glass-ceramics and metallic glasses. The films crystallize from amorphous to full crystallinity in the solid state. As an example the crystallization kinetics for a single-phase metal oxide, ceria, and its gadolinia solid solutions are reported made by the precipitation thin-film method spray pyrolysis. The crystallization of an amorphous metal oxide thin film generally follows the Lijschitz,Sletow,Wagner (LSW) Ostwald ripening theory: Below the percolation threshold of 20 vol% single grains crystallize in the amorphous phase and low crystallization rates are measured. In this state no impact of solute on crystallization is measurable. Once the grains form primary clusters above the threshold the solute slows down crystallization (and grain growth) thus shifting the TTT curves of the doped ceria films to longer times and higher temperatures in comparison to undoped ceria. Current views on crystallization of metal oxide thin films, the impact of solute dragging, and primary TTT diagrams are discussed. Finally, examples on how to use these TTT diagrams for better thermokinetic engineering of metal oxide thin films for MEMS are given, for example, for micro-Solid Oxide Fuel Cells and resistive sensors. In these examples the electrical properties depend on the degree of crystallinity and, thereby, on the TTT conditions. [source]


    Thin Films: Self-Assembled Heteroepitaxial Oxide Nanocomposite Thin Film Structures: Designing Interface-Induced Functionality in Electronic Materials (Adv. Funct.

    ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
    Mater.
    Achieving self-assembling/self-organizing systems is the holy grail of nanotechnology, as presented in the Feature Article by J. L. MacManus-Driscoll on page 2035. Multifunctionality or enhanced functionality can emerge as a result of self-assembly of two oxides in nano-composite films. Checkerboards, ordered nanochains, nanorods, or random nanoparticle structures are all possible structures and they influence the resulting properties in different ways. It is now possible to predict the nanocomposite structure that will form from a given starting composition. [source]


    Synthesis of Poly(4-vinylpyridine) Thin Films by Initiated Chemical Vapor Deposition (iCVD) for Selective Nanotrench-Based Sensing of Nitroaromatics

    ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
    Wyatt E. Tenhaeff
    Abstract A new nanoscale sensing concept for the detection of nitroaromatic explosives is described. The design consists of nitroaromatic-selective polymeric layers deposited inside microfabricated trenches. As the layers are exposed to nitroaromatic vapors, they swell and contact each other to close an electrical circuit. The nitroaromatic selective polymer, poly(4-vinylpyridine) (P4VP), is deposited in the trenches using initiated chemical vapor deposition (iCVD). P4VP is characterized for the first time as a selective layer for the absorption of nitroaromatic vapors. The Flory,Huggins equation is used to model the swelling response to nitroaromatic vapors. The Flory,Huggins interaction parameter for the P4VP,nitrobenzene system at 40,C is 0.71 and 0.25 for P4VP,4-nitrotoluene at 60,C. Sensing of nitrobenzene vapors is demonstrated in a prototype device, while techniques to improve the performance of the design in terms of response time and sensitivities are described. Modeling shows that concentration and mass limits of detection of 0.95,ppb and 3 fg, respectively, can be achieved. [source]


    Nanocrystalline Electroplated Cu,Ni: Metallic Thin Films with Enhanced Mechanical Properties and Tunable Magnetic Behavior

    ADVANCED FUNCTIONAL MATERIALS, Issue 6 2010
    Eva Pellicer
    Abstract Nanocrystalline 3,m thick Cu1,xNix (0.45,,,x,,,0.87) films are electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates, from a citrate- and sulphate-based bath containing sodium lauryl sulphate and saccharine as additives. The films exhibit large values of reduced Young's modulus (173,<,Er,<,192,GPa) and hardness (6.4,<,H,<,8.2,GPa), both of which can be tailored by varying the alloy composition. The outstanding mechanical properties of these metallic films can be ascribed to their nanocrystalline nature,as evidenced by X-ray diffraction, transmission electron microscopy, and atomic force microscopy,along with the occurrence of stacking faults and the concomitant formation of intragranular nanotwins during film growth. Due to their nanocrystalline character, these films also show very low surface roughness (root mean square deviation of around 2,nm). Furthermore, tunable magnetic properties, including a transition from paramagnetic to ferromagnetic behavior, are observed when the Ni percentage is increased. This combination of properties, together with the simplicity of the fabrication method, makes this system attractive for widespread technological applications, including hard metallic coatings or magnetic micro/nano-electromechanical devices. [source]


    Vertically Aligned Nanocomposite Thin Films as a Cathode/Electrolyte Interface Layer for Thin-Film Solid Oxide Fuel Cells

    ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009
    Jongsik Yoon
    Abstract A thin layer of a vertically aligned nanocomposite (VAN) structure is deposited between the electrolyte, Ce0.9Gd0.1O1.95 (CGO), and the thin-film cathode layer, La0.5Sr0.5CoO3 (LSCO), of a thin-film solid-oxide fuel cell (TFSOFC). The self-assembled VAN nanostructure contains highly ordered alternating vertical columns of CGO and LSCO formed through a one-step thin-film deposition process that uses pulsed laser deposition. The VAN structure significantly improves the overall performance of the TFSOFC by increasing the interfacial area between the electrolyte and cathode. Low cathode polarization resistances of 9,,10,4 and 2.39,, were measured for the cells with the VAN interlayer at 600 and 400,C, respectively. Furthermore, anode-supported single cells with LSCO/CGO VAN interlayer demonstrate maximum power densities of 329, 546, 718, and 812,mW cm,2 at 550, 600, 650, and 700,C, respectively, with an open-circuit voltage (OCV) of 1.13,V at 550,C. The cells with the interlayer triple the overall power output at 650,C compared to that achieved with the cells without an interlayer. The binary VAN interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte. [source]


    Crystallization and Grain Growth Kinetics for Precipitation-Based Ceramics: A Case Study on Amorphous Ceria Thin Films from Spray Pyrolysis

    ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009
    Jennifer L. M. Rupp
    No abstract is available for this article. [source]


    Electric Field-Directed Convective Assembly of Ellipsoidal Colloidal Particles to Create Optically and Mechanically Anisotropic Thin Films

    ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
    Manish Mittal
    Abstract A method of simultaneous field- and flow-directed assembly of anisotropic titania (TiO2) nanoparticle films from a colloidal suspension is presented. Titania particles are oriented by an alternating (ac) electric field as they simultaneously advect towards a drying front due to evaporation of the solvent. At high field frequencies (,,>,,25,kHz) and field strengths (E,>,300,V cm,1), the particles orient with their major axis along the field direction. As the front recedes, a uniform film with thicknesses of 1,10,m is deposited on the substrate. The films exhibit a large birefringence (,n,,,0.15) and high packing fraction (,,=,0.75,,0.08), due to the orientation of the particles. When the frequency is lowered, the particle orientation undergoes a parallel,random,perpendicular transition with respect to the field direction. The orientation dependence on field frequency and strength is explained by the polarizability of ellipsoidal particles using an interfacial polarization model. Particle orientation in the films also leads to anisotropic mechanical properties, which are manifested in their cracking patterns. In all, it is demonstrated that the field-directed assembly of anisotropic particles provides a powerful means for tailoring nanoparticle film properties in situ during the deposition process. [source]


    Layer-By-Layer Dendritic Growth of Hyperbranched Thin Films for Surface Sol,Gel Syntheses of Conformal, Functional, Nanocrystalline Oxide Coatings on Complex 3D (Bio)silica Templates

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Guojie Wang
    Abstract Here, a straightforward and general method for the rapid dendritic amplification of accessible surface functional groups on hydroxylated surfaces is described, with focus on its application to 3D biomineral surfaces. Reaction of hydroxyl-bearing silica surfaces with an aminosilane, followed by alternating exposure to a dipentaerythritol-derived polyacrylate solution and a polyamine solution, allows the rapid, layer-by-layer (LBL) build-up of hyperbranched polyamine/polyacrylate thin films. Characterization of such LBL-grown thin films by AFM, ellipsometry, XPS, and contact angle analyses reveals a stepwise and spatially homogeneous increase in film thickness with the number of applied layers. UV,Vis absorption analyses after fluorescein isothiocyanate labeling indicate that significant amine amplification is achieved after the deposition of only 2 layers with saturation achieved after 3,5 layers. Use of this thin-film surface amplification technique for hydroxyl-enrichment of biosilica templates facilitates the conformal surface sol,gel deposition of iron oxide that, upon controlled thermal treatment, is converted into a nanocrystalline (,9.5,nm) magnetite (Fe3O4) coating. The specific adsorption of arsenic onto such magnetite-coated frustules from flowing, arsenic-bearing aqueous solutions is significantly higher than for commercial magnetite nanoparticles (,50,nm in diameter). [source]


    Crystallization and Grain Growth Kinetics for Precipitation-Based Ceramics: A Case Study on Amorphous Ceria Thin Films from Spray Pyrolysis

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Jennifer L. M. Rupp
    Abstract The introductory part reviews the impact of thin film fabrication, precipitation versus vacuum-based methods, on the initial defect state of the material and microstructure evolution to amorphous, biphasic amorphous-nanocrystalline, and fully nanocrystalline metal oxides. In this study, general rules for the kinetics of nucleation, crystallization, and grain growth of a pure single-phase metal oxide thin film made by a precipitation-based technique from a precursor with one single organic solvent are discussed. For this a complete case study on the isothermal and non-isothermal microstructure evolution of dense amorphous ceria thin films fabricated by spray pyrolysis is conducted. A general model is established and comparison of these thin film microstructure evolution to kinetics of classical glass-ceramics or metallic glasses is presented. Knowledge on thermal microstructure evolution of originally amorphous precipitation-based metal oxide thin films allows for their introduction and distinctive microstructure engineering in devices-based on microelectromechanical (MEMS) technology such as solar cells, capacitors, sensors, micro-solid oxide fuel cells, or oxygen separation membranes on Si-chips. [source]