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Substrate Surface (substrate + surface)
Selected AbstractsModeling of Coating Process, Phase Changes, and Damage of Plasma Sprayed Thermal Barrier Coatings on Ni-Base Superalloys,ADVANCED ENGINEERING MATERIALS, Issue 3 2010Tilmann Beck The paper gives an overview on the modeling activities on plasma sprayed thermal barrier coating in the frame of TFB 63. In the first part, through-process modeling of the APS deposition of a ZrO2 based TBC is described. Starting from simulation of the plasma jet, heat transfer into the powder particles, particle melting, particle impact on the substrate surface, and solidification is simulated. A homogenization method is introduced to describe the mechanical properties of the resulting TBC. The second part shows simulation of interdiffusion and phase transformations of MCrAlY and intermetallic oxidation protection coatings on several cast Ni-base alloy substrates. Finally, FEM-based damage simulation of oxidation protection coatings by transversal fatigue cracks during thermomechanical fatigue loading as well as by delamination of the TBC during thermocyclic loading is discussed. [source] Capillary Force Lithography: A Versatile Tool for Structured Biomaterials Interface Towards Cell and Tissue Engineering,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Kahp-Yang Suh Abstract This Feature Article aims to provide an in-depth overview of the recently developed molding technologies termed capillary force lithography (CFL) that can be used to control the cellular microenvironment towards cell and tissue engineering. Patterned polymer films provide a fertile ground for controlling various aspects of the cellular microenvironment such as cell,substrate and cell,cell interactions at the micro- and nanoscale. Patterning thin polymer films by molding typically involves several physical forces such as capillary, hydrostatic, and dispersion forces. If these forces are precisely controlled, the polymer films can be molded into the features of a polymeric mold with high pattern fidelity and physical integrity. The patterns can be made either with the substrate surface clearly exposed or unexposed depending on the pattern size and material properties used in the patterning. The former (exposed substrate) can be used to adhere proteins or cells on pre-defined locations of a substrate or within a microfluidic channel using an adhesion-repelling polymer such as poly(ethylene glycol) (PEG)-based polymer and hyaluronic acid (HA). Also, the patterns can be used to co-culture different cells types with molding-assisted layer-by-layer deposition. In comparison, the latter (unexposed substrate) can be used to control the biophysical surrounding of a cell with tailored mechanical properties of the material. The surface micropatterns can be used to engineer cellular and multi-cellular architecture, resulting in changes of the cell shape and the cytoskeletal structures. Also, the nanoscale patterns can be used to affect various aspects of the cellular behavior, such as adhesion, proliferation, migration, and differentiation. [source] Microstructured Arrays of TiO2 Nanotubes for Improved Photo-Electrocatalysis and Mechanical StabilityADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Daoai Wang Abstract The preparation of micropatterned TiO2 nanotubes (NTs) with tunable morphologies by combining laser micromachining technology and an anodization method is reported. The micropatterned structure can be easily designed and fabricated by laser micromachining a titanium substrate, further anodization of which gives nanotube arrays perpendicularly oriented to the titanium surface. The patterned TiO2 NTs show dramatically improved photocurrent and photocatalytic performances because of their enhanced surface area and light-harvesting capability. The photocurrent density and incident-photon-to-current efficiency at the peak absorption increases by 48 and 39%, respectively, compared to a TiO2 NT array without a patterned structure. It was also found that micropatterning dramatically improves the mechanical stability of the TiO2 NTs on the substrate, which otherwise were liable to peel off from the substrate surface. The strategy will reasonably expand the application of TiO2 NTs in a variety of fields that require enhanced photo-electrocatalysis and mechanical stability. [source] The effect of habitat complexity on the functional response of a seed-eating passerineIBIS, Issue 3 2009DAVID J. BAKER Recent population declines of seed-eating farmland birds have been associated with reduced overwinter survival due to reductions in food supply. An important component of predicting how food shortages will affect animal populations is to measure the functional response, i.e. the relationship between food density and feeding rate, over the range of environmental conditions experienced by foraging animals. Crop stubble fields are an important foraging habitat for many species of seed-eating farmland bird. However, some important questions remain regarding farmland bird foraging behaviour in this habitat, and in particular the effect of stubble on farmland bird functional responses is unknown. We measured the functional responses of a seed-eating passerine, the Chaffinch Fringilla coelebs, consuming seeds placed on the substrate surface in three different treatments: bare soil, low density stubble and high density stubble. Stubble presence significantly reduced feeding rates, but there was no significant difference between the two stubble treatments. Stubble reduced feeding rates by reducing the maximum attack distance, i.e. the distance over which an individual food item is targeted and consumed. The searching speed, handling time per seed, proportion of time spent vigilant, duration of vigilance bouts and duration of head-down search periods were unaffected by the presence of stubble. The frequency of vigilance bouts was higher in the bare soil treatment, but this is likely to be a consequence of the increased feeding rate. We show the influence of a key habitat type on the functional response of a seed-eating passerine, and discuss the consequences of this for farmland bird conservation. [source] A Simple Method for the Attachment of Polymer Films on Solid Substrates,ADVANCED MATERIALS, Issue 3 2003M. Yan The immobilization of polymer thin films on solid substrates has been achieved using a very simple method, involving spin coating the polymer, followed by UV irradiation. A robust film remains on the substrate surface after solvent extraction. The procedure could be employed to fabricate patterned polymer thin films via photolithography (see Figure). [source] Periodic models in quantum chemical simulations of F centers in crystalline metal oxidesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2007Yuri F. Zhukovskii Abstract We present a survey of recent first principles simulations of the neutral oxygen vacancies (F centers) existing as native or radiation-induced point defects in various crystalline metal oxides in different forms (bulk, bare substrate surface, and on the interface with metal adsorbates). We mainly consider periodic models in calculations of point defects using the metal oxide supercell or cyclic clusters. We compare different formalisms of first principles calculations, mostly the Density Functional Theory (DFT) as implemented in the framework of either localized basis set of atomic orbitals or delocalized basis sets of plane waves. We analyze in detail the structural and electronic properties of F centers in binary oxides of light metals (MgO and Al2O3), and ternary metal oxides (SrTiO3, BaTiO3, PbTiO3, KNbO3, and PbZrO3 perovskites). When available, we compare results of ab initio periodic defect calculations with experimental data, results of the first principles cluster calculations (both embedded and molecular) as well as with semi-empirical calculations. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Mechanism studies on CVD of boron carbide from a gas mixture of BCL3, CH4, and H2 in a dual impinging-jet reactorAICHE JOURNAL, Issue 3 2009Mustafa Karaman Abstract Nearly pure boron carbide free from impurities was produced on a tungsten substrate in a dual impinging-jet chemical vapor deposition reactor from a BCl3, CH4, and H2 mixture. The Fourier Transform Infrared (FTIR) analysis proved the formation of reaction intermediate BHCl2, which is proposed to occur mainly in the gaseous boundary layer next to the substrate surface. Among a large number of reaction mechanisms proposed only the ones considering the molecular adsorption of boron carbide on the substrate surface gave reasonable fits. In the proposed mechanism dichloroborane is formed in the gas phase only as a by-product. Boron carbide, on the other hand, is formed through a series of surface reactions involving adsorbed boron trichloride, adsorbed methane and gas phase hydrogen. The simultaneous fit of the experimental rate data to the model expressions gave correlation coefficient values of 0.977 and 0.948, in predicting the B4C and BHCl2 formation rates, respectively. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Optimal operation of GaN thin film epitaxy employing control vector parametrizationAICHE JOURNAL, Issue 4 2006Amit Varshney Abstract An approach that links nonlinear model reduction techniques with control vector parametrization-based schemes is presented, to efficiently solve dynamic constraint optimization problems arising in the context of spatially-distributed processes governed by highly-dissipative nonlinear partial-differential equations (PDEs), utilizing standard nonlinear programming techniques. The method of weighted residuals with empirical eigenfunctions (obtained via Karhunen-Loève expansion) as basis functions is employed for spatial discretization together with control vector parametrization formulation for temporal discretization. The stimulus for the earlier approach is provided by the presence of low order dominant dynamics in the case of highly dissipative parabolic PDEs. Spatial discretization based on these few dominant modes (which are elegantly captured by empirical eigenfunctions) takes into account the actual spatiotemporal behavior of the PDE which cannot be captured using finite difference or finite element techniques with a small number of discretization points/elements. The proposed approach is used to compute the optimal operating profile of a metallorganic vapor-phase epitaxy process for the production of GaN thin films, with the objective to minimize the spatial nonuniformity of the deposited film across the substrate surface by adequately manipulating the spatiotemporal concentration profiles of Ga and N precursors at the reactor inlet. It is demonstrated that the reduced order optimization problem thus formulated using the proposed approach for nonlinear order reduction results in considerable savings of computational resources and is simultaneously accurate. It is demonstrated that by optimally changing the precursor concentration across the reactor inlet it is possible to reduce the thickness nonuniformity of the deposited film from a nominal 33% to 3.1%. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Exploring spatiotemporal patterns in early stages of primary succession on former lignite mining sitesJOURNAL OF VEGETATION SCIENCE, Issue 2 2008Birgit Felinks Abstract Questions: 1. Does random colonization predominate in early stages of primary succession? 2. Do pioneer species facilitate the establishment of later arriving species? 3. Does an initially random distribution change to an aggregated pattern with ongoing succession? Location: Lignite mining region of Lower Lusatia, eastern Germany. Methods: Individual plants were mapped along a 2 m × 28 m transect during three successive years and classified into two groups (1) the pioneer Corynephorus canescens and (2),all other species'. Using the pair-correlation function, univariate point pattern analysis was carried out by applying a heterogeneous Poisson process as null model. Bivariate analysis and a toroidal shift null model were applied to test for independence between the spatial patterns of the two groups separately for each year, as well by exploring spatiotemporal patterns from different years. Results: In the first year Corynephorus and ,all other species' showed an aggregated pattern on a spatial scale > 40 cm and in the second and third years a significant attraction for distances between 4 and 12 cm, with an increasing radius in the third year. The analyses of interspecific spatiotemporal dynamics revealed a change from independence to attraction between distances of 4 cm and 16 cm when using Corynephorus as focal species. However, applying ,all other species' as focal points results in a significant attraction at distances up to 60 cm in the first year and a diminishing attraction in the second and third years with distances , 6 cm. Conclusions: Facilitative species-species interactions are present in early stages of primary succession, resulting mainly from pioneer species acting as physical barriers and their ability to capture diaspores being drifted by secondary dispersal along the substrate surface. However, due to gradual establishment of perennial species and their ability of lateral extension by vegetative dispersal, facilitation may influence spatial pattern formation predominantly on short temporal and fine spatial scales. [source] Highly (001)-textured WS2,x films prepared by reactive radio frequency magnetron sputteringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004K. Ellmer Abstract Highly (001)-oriented WS2,x films were grown onto oxidized silicon substrates by reactive magnetron sputtering from a metallic tungsten target in argon-hydrogen sulfide mixtures. The best films with respect to the van-der-Waals orientation, i.e. with the (001) planes parallel to the substrate surface, were grown by excitation of the plasma with radio frequency of 27.12 MHz. These films exhibit the largest grains and the lowest film strain. It is shown that this effect is not due to the lower deposition rate at this high excitation frequency. Instead it was found that the lower DC voltage at the sputtering target is advantageous for the film growth since the bombardment of the growing film by highly energetic particles is avoided by this type of plasma excitation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impact of nitridation on structural and optical properties of MOVPE-grown m-plane GaN layers on LiAlO2PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009C. Mauder Abstract In this paper, we investigate the influence of the nitridation of LiAlO2 substrates on the growth of m-plane (1-100) GaN layers by metal-organic vapour phase epitaxy (MOVPE). Before thin film deposition, we performed an in-situ substrate pretreatment by exposing the wafer to NH3 for different times between no pretreatment and 300 s. The properties of subsequently grown layers show a significant dependency on this nitridation step. We find that this procedure is essential for obtaining pure m-plane GaN films and has a beneficial effect on the X-ray rocking curve (XRC) full width at half maximum (FWHM) value, which decreases by almost two orders of magnitude. Deposited layers with NH3 pretreatment also exhibit much smoother surfaces with a reduction of the root mean square (RMS) roughness value from ,20 to ,6 nm. Additionally, the nitridation greatly increases the GaN band edge emission intensity in room temperature (RT) photoluminescence (PL) spectroscopy. Furthermore, we compare the sensitivity of the substrate against water for uncoated LiAlO2 wafers with and without nitridation process. While the untreated surface shows a clear roughening when dipped into de-ionized (DI) water for 5 min, we can see no significant impact on the nitridated substrate surface. This indicates a change in surface composition which protects the sensitive substrate surface and provides good conditions for the nucleation of high-quality m-plane GaN films. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Formation of "air-gap" structure at a GaN epilayer/substrate interface by using an InN interlayerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003A. Yamamoto Abstract We propose a new technique for "air-gap" formation at a GaN/sapphire interface by using an InN interlayer. This is aimed to grow epitaxial GaN films with reduced stress and cracks. First, an InN interlayer of about 0.2 ,m thick is grown at 600 °C in atmospheric pressure. Then a 30 nm-thick GaN buffer layer is grown on the InN layer at 550 °C. The substrate temperature is ramped up to 1000 °C in the NH3 flow, and finally a 1.5 ,m-thick GaN epilayer is grown on the annealed GaN buffer layer using nitrogen carrier gas. Consequently, an "air-gap" structure is naturally formed close to the substrate surface. During the ramping period of substrate temperature, the InN layer decomposes due to its thermal instability and metallic In is formed. It is found that metallic In drops as a result of InN decomposition contribute to the air-gap formation. No cracks are found on the GaN surface and a reduced stress in the layer is confirmed by PL and Raman shift measurements. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Plasma-Assisted Atomic Layer Deposition of Al2O3 at Room TemperaturePLASMA PROCESSES AND POLYMERS, Issue S1 2009Tommi O. Kääriäinen Abstract A new design of plasma source has been used for the plasma-assisted atomic layer deposition (PA-ALD) of Al2O3 films at room temperature. In this PA-ALD reactor the plasma is generated by capacitive coupling directly in the deposition chamber adjacent to the substrate but can be separated from it by a grid to reduce the ion bombardment while maintaining the flow of radicals directly to the substrate surface. During the ALD cycle a mixture of nitrogen and argon was introduced into the reactor to act as a purge gas between precursor pulses and to facilitate the generation of a plasma during the plasma cycle. Sequential exposures of TMA and excited O2 precursors were used to deposit Al2O3 films on Si(100) substrates. A plasma discharge was activated during the oxygen gas pulse to form radicals in the reactor space. The experiments showed that the growth rate of the film increased with increasing plasma power and with increasing O2 pulse length before saturating at higher power and longer O2 pulse length. The growth rate saturated at the level of 1.78 Å·cycle,1. EDS analysis showed that the films were oxygen rich and had carbon as an impurity. This can be explained by the presence of bonds between hydrocarbons from the unreacted TMA precursor and excess oxygen in the film. ATR-FTIR spectroscopy measurements indicated a change in growth mechanism when the distance between the location of the radical generation and the substrate was varied. A similar effect was observed with the use of different plasma power levels. [source] Structure and Corrosion of Magnetron Sputtered Pure Mg Films on Silicon SubstratesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Michael Störmer Abstract Physical vapor deposition (PVD) was used to prepare pure magnesium coatings on silicon substrates at various argon pressures and deposition angles. The film morphology was observed to depend on the deposition conditions. The approximately 3 µm thick Mg films exhibited columnar growth with voided boundaries and a fiber texture of the basal planes parallel to the substrate surface, which is typical of low temperature deposition. At low pressure and angle, the films were more compact, the surface roughness was lower, the texture was stronger, and the corrosion performance was improved. A free corrosion potential of ,1,735 mV and a corrosion rate of 335 µm per year were determined. [source] 8% Efficient thin-film polycrystalline-silicon solar cells based on aluminum- induced crystallization and thermal CVDPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2007I. Gordon Abstract A considerable cost reduction could be achieved in photovoltaics if efficient solar cells could be made from polycrystalline-silicon (pc-Si) thin films on inexpensive substrates. We recently showed promising solar cell results using pc-Si layers obtained by aluminum-induced crystallization (AIC) of amorphous silicon in combination with thermal chemical vapor deposition (CVD). To obtain highly efficient pc-Si solar cells, however, the material quality has to be optimized and cell processes different from those applied for standard bulk-Si solar cells have to be developed. In this work, we present the different process steps that we recently developed to enhance the efficiency of pc-Si solar cells on alumina substrates made by AIC in combination with thermal CVD. Our present pc-Si solar cell process yields cells in substrate configuration with efficiencies so far of up to 8·0%. Spin-on oxides are used to smoothen the alumina substrate surface to enhance the electronic quality of the absorber layers. The cells have heterojunction emitters consisting of thin a-Si layers that yield much higher Voc values than classical diffused emitters. Base and emitter contacts are on top of the cell in interdigitated finger patterns, leading to fill factors above 70%. The front surface of the cells is plasma textured to increase the current density. Our present pc-Si solar cell efficiency of 8% together with the fast progression that we have made over the last few years indicate the large potential of pc-Si solar cells based on the AIC seed layer approach. Copyright © 2007 John Wiley & Sons, Ltd. [source] Plasma-Enhanced Atomic Layer Deposition of Palladium on a Polymer Substrate,CHEMICAL VAPOR DEPOSITION, Issue 6-7 2007A. Ten, Eyck Abstract In this paper, a method for the plasma-enhanced (PE) atomic layer deposition (ALD) of palladium on air-exposed, annealed poly(p -xylylene) (Parylene-N, or PPX) is presented. Palladium is successfully deposited on PPX at 80,°C using a remote, inductively coupled, hydrogen/nitrogen plasma with palladium (II) hexafluoroacetylacetonate (PdII(hfac)2) as the precursor. By optimizing the mixture of hydrogen and nitrogen, the polymer surface is modified to introduce active sites allowing the chemisorption of the PdII(hfac)2. In addition, enough free hydrogen atoms are available at the surface for ligand removal and Pd reduction, while at the same time, enough hydrogen atoms are consumed in the plasma to ensure there is no visible degradation of the PPX. X-ray photoelectron spectroscopy (XPS) measurements of the substrate after hydrogen/nitrogen plasma treatment at 50,W clearly show the presence of nitrogen bound to the substrate surface. XPS measurements of the deposited Pd films indicate good quality for both substrates, suggesting that the substrate temperature was low enough to prevent dissociation of the hfac ligand and adequate scavenging of the hfac ligand by the available atomic hydrogen. The remote hydrogen/nitrogen plasma enables Pd film deposition on polymer surfaces, which do not typically react with the Pd precursor, and are not catalysts for the dissociation of molecular hydrogen. [source] Preparation of Pt,Ru Alloyed Thin Films Using a Single-Source CVD Precursor,CHEMICAL VAPOR DEPOSITION, Issue 3 2003S.-F. Huang Abstract Treatment of (dimethylaminomethyl)ruthenocene with cis -Pt(DMSO)2Cl2 led to the formation of a ruthenocenyl platinum complex [CpRu(,5 -C5H3CH2NMe2)Pt(DMSO)Cl] (1); subsequent treatment of 1 with [Na(hfac)] afforded an air-stable Pt,Ru complex [CpRu(,5 -C5H3CH2NMe2)Pt(hfac)] (2). Its volatility and other physical data relevant to CVD experiments were assessed by thermogravimetric analysis (TGA). The Pt,Ru thin films were then deposited at two deposition temperatures, 300,°C and 400,°C, using O2 as the reactive carrier gas. The as-deposited thin films were characterized using energy dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Results indicated the formation of a homogeneous Pt,Ru solid solution at the lower deposition temperature. However, upon raising the temperature to 400,°C, phase separation between Pt and Ru occurred, which then induced the growth of RuO2 grains at the substrate surface and caused depletion of the alloy in ruthenium. The electrocatalytic activities of the films, in respect of methanol oxidation, were investigated, in half-cell experiments, by cyclic voltammetry. [source] Motif Reconstruction in Clusters and Layers: Benchmarks for the Kawska,Zahn Approach to Model Crystal FormationCHEMPHYSCHEM, Issue 4 2010Theodor Milek Abstract A recently developed atomistic simulation scheme for investigating ion aggregation from solution is transferred to the morphogenesis of metal clusters grown from the vapor and layers deposited on a substrate surface. Both systems are chosen as benchmark models for intense motif reorganization during aggregate/layer growth. The applied simulation method does not necessarily involve global energy minimization after each growth event, but instead describes crystal growth as a series of structurally related configurations which may also include local energy minima. Apart from the particularly favorable high-symmetry configurations known from experiments and global energy minimization, we also demonstrate the investigation of transient structures. In the spirit of Ostwald's step rule, a continuous evolution of the aggregate/layer structure during crystal growth is observed. [source] Intrinsic adhesion force of lubricants to steel surfaceJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2004Jonghwi Lee Abstract The intrinsic adhesion forces of lubricants and other pharmaceutical materials to a steel surface were quantitatively compared using Atomic Force Microscopy (AFM). A steel sphere was attached to the tip of an AFM cantilever, and its adhesion forces to the substrate surfaces of magnesium stearate, sodium stearyl fumarate, lactose, 4-acetamidophenol, and naproxen were measured. Surface roughness varied by an order of magnitude among the materials. However, the results clearly showed that the two lubricants had about half the intrinsic adhesion force as lactose, 4-acetamidophenol, and naproxen. Differences in the intrinsic adhesion forces of the two lubricants were insignificant. The lubricant molecules were unable to cover the steel surface during AFM measurements. Intrinsic adhesion force can slightly be modified by surface treatment and compaction, and its tip-to-tip variation was not greater than its difference between lubricants and other pharmaceutical particles. This study provides a quantitative fundamental basis for understanding adhesion related issues. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:2310,2318, 2004 [source] Integrated surface modification of fully polymeric microfluidic devices using living radical photopolymerization chemistryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Robert P. Sebra Abstract Surface modification using living radical polymerization (LRP) chemistry is a powerful technique for surface modification of polymeric substrates. This research demonstrates the ability to use LRP as a polymer substrate surface-modification platform for covalently grafting polymer chains in a spatially and temporally controlled fashion. Specifically, dithiocarbamate functionalities are introduced onto polymer surfaces using tetraethylthiuram disulfide. This technique enables integration of LRP-based grafting for the development of an integrated, covalent surface-modification method for microfluidic device construction. The unique photolithographic method enables construction of devices that are not substrate-limited. To demonstrate the utility of this approach, both controlled fluid flow and cell patterning applications were demonstrated upon modification with various chemical functionalities. Specifically, poly(ethylene glycol) (375) monoacrylate and trifluoroethyl acrylate were grafted to control fluidic flow on a microfluidic device. Before patterning, surface-functionalized samples were characterized with both goniometric and infrared spectroscopy to ensure that photografting was occurring through pendant dithiocarbamate functionalities. Near-infrared results demonstrated conversion of grafted monomers when dithiocarbamate-functionalized surfaces were used, as compared to dormant control surfaces. Furthermore, attenuated total reflectance/infrared spectroscopy results verified the presence of dithiocarbamate functionalities on the substrate surfaces, which were useful in grafting chains of various functionalities whose contact angles ranged from 7 to 86°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1404,1413, 2006 [source] Formation of CdO dots on atomically flat ZnO surfacesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006M. Ebihara Abstract Atomically flat terraced ZnO surfaces were prepared with thermal annealing in air. CdO dots were successfully formed on the ZnO substrate surfaces with in-situ post-growth thermal annealing of CdO layers grown by metalorganic molecular-beam epitaxy. Well-organized alignment of the CdO dots along surface atomic-step edges on the terraced surfaces is demonstrated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparison of ECR plasma pretreatment techniques for ZnO atomic layer epitaxy on the sapphire substratePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2004Kyoungchul Shin Abstract ZnO films were grown on sapphire substrates treated with ECR plasma by the atomic layer epitaxy (ALE) technique. ZnO nucleation enhancing effects of oxygen, hydrogen, and argon plasma treatments were compared. The incubation period for ZnO nucleation was measured by using scanning electron microscopy (SEM) and Auger electron emission spectrometric (AES) analysis. The incubation period for ZnO nucleation on the Al2O3 substrate not treated with plasma was more than 40 ALE cycles. The incubation period was shortened down to less than 35 cycles by argon or hydrogen ECR plasma pretreatment and to less than 30 cycles by oxygen ECR plasma pretreatment. It was found that a microwave power of 300W and a plasma exposure times of 10 min were appropriate for oxygen ECR plasma treatment of sapphire substrate surfaces to enhance ZnO nucleation. Higher power and longer exposure time would not be effective or would rather aggravate than enhance ZnO nucleation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thin films of Co3O4, MnCo2O4 and their solid solution as electrocatalyst: study of their magnetic propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2004E. Ríos Abstract We present magnetic measurements performed on the MnxCo3,xO4 (0 , x , 1) solid solution, prepared by spray pyrolysis. Thin films of about 20 ,m thickness were obtained after depositing aqueous metal nitrates precursors on Ti or conducting glass substrates. Powder material scratched from the substrate's surface was used for physico-chemical characterization. Presence of two oxidation states for each metal ion (Mn3+,Mn4+; Co2+,Co3+) triggers specific conduction mechanisms and double-exchange magnetic interactions. The ferromagnetic components are enhanced when x(Mn) increases, in detriment of the antiferromagnetic interactions. The ordering temperature Tc changes with x (from 22 K up to room temperature, for x = 0 up to x = 1). Based in the paramagnetic moment ,eff obtained at T > Tc, we propose a cationic distribution which can be nicely compared to the one obtained from crystallographic analyses. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||