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Nanostructured copper thin film used for catalysis

CARVALHO, Alexsander Tressino de; LIMA, Roberto da Rocha; SILVA, Lilian Marques; FACHINI, Estevao; SILVA, Maria Lucia Pereira da
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.07%
Catalytic properties of copper thin films deposited in small channels and cavities were tested using Raman microscopy and mass spectroscopy (MS) techniques, mainly. The catalytic surface conditions were addressed visually and chemically by optical microscopy and X-ray photoelectron spectroscopy (XPS), respectively. The experimental conditions of present work induced copper oxidation; eventually a number of carbon species and graphite remained on the catalytic surface. Quartz crystal microbalance and mass spectroscopy data support both adsorption and catalysis phenomena. MS showed CO2 formation during n-hexane heating process but not to 2-propanol, probably due to redox reactions. XPS of copper surface present in the cavity after catalysis tests detected Cu2O and a range of possible carbon species. The adsorption and catalytic performance of copper films deposited in cavities and microchannels were quite similar. A simple miniaturized device for microanalysis was proposed. (C) 2007 Elsevier B.V. All rights reserved.

Construção de equipamento de plasma para obtenção de filmes finos e compósitos úteis na fabricação de sensores.; Design and manufacturing of a plasma reactor useful for thin film and composite production on sensor development.

Lima, Roberto da Rocha
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/03/2009 Português
Relevância na Pesquisa
56.19%
Equipamentos de plasma são muito utilizados para polimerização de filmes finos, orgânicos e inorgânicos. Filmes finos têm uma vasta gama de aplicações no desenvolvimento de dispositivos MEMS (MicroElectroMechanical Systems), tais como sensores, detectores, pré-concentradores, etc. Portanto, neste trabalho é apresentado um equipamento de polimerização por plasma com características distintas, o que permite seu uso para obtenção de novos filmes finos e/ou compósitos em uma única etapa de fabricação. Os filmes obtidos são formados por partes orgânicas distintas, ou mesmo por regiões adsorventes ou repelentes. Alguns filmes possuem partículas orgânicas em mistura com o filme fino, o que facilita o controle da rugosidade e da área superficial, permitindo seu uso em sistemas de retenção. O projeto do reator permite deposições por plasma introduzindo, simultaneamente e sem interrupção do processo, reagentes incompatíveis em plasma ou mesmo a formação seqüencial de camadas, sem a necessidade de abertura do reator entre as etapas do processo (etapa única). O projeto da câmara de plasma foi simulado usando FEMLAB 3.2® e caracterizado utilizando traçadores. Simularam-se fluxo de gás e partículas além de campo elétrico e magnético. As simulações e resultados experimentais mostraram boa coerência. O fluxo permaneceu sem grande vorticidade em toda a faixa de trabalho e o campo magnético foi adequado para o confinamento do plasma. Foram depositados filmes úteis para desenvolvimento de sensores e adsorventes...

Fabricação e caracterização de guias de onda baseadas em filmes finos e vidros de óxido de metal pesado dopados com Er3+ e Yb3+ e contendo nanopartículas metálicas para aplicações em dispositivos fotônicos; Fabrication and characterization of waveguides based in thin films and heavy metal oxide glasses doped with Er³+ and Yb³+ and containing metallic nanoparticles for applications in photonic devices.

Silva, Davinson Mariano da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/11/2012 Português
Relevância na Pesquisa
46.38%
O presente trabalho tem como objetivo estudar a produção e caracterização de filmes finos do tipo GeO2-PbO (GP) produzidos por sputtering-RF com e sem nanopartículas (INPS) metálicas e codopados com íons de Er³+/Yb³+ para a produção de amplificadores ópticos. A incorporação dos íons de terras-raras (TR) foi verificada a partir dos espectros de emissão. Estudos relacionados ao tempo de decaimento radiativo do Er³+ também foram conduzidos. A susceptibilidade óptica não-linear de terceira ordem é reportada em 532 e 800nm. Os valores de índice de refração e absorção não-linear na presença de NPs metálicas é mais do que uma ordem de grandeza superior aos mesmos filmes sem as NPs metálicas. A produção de guias de onda do tipo rib e do tipo pedestal baseados nos filmes GP foi realizada a partir de litografia óptica seguida por processo de corrosão por plasma. A influência dos parâmetros dos processos usados em função das características dos guias também é reportada. Os guias ópticos foram caracterizados por Microscopia Eletrônica de Varredura (MEV), Microscopia de Força Atômica (AFM) e por medidas de perdas de propagação e ganho óptico. As perdas por propagação mínimas observadas foram de ~1...

Propriedades estruturais, eletrônicas e magnéticas de filmes finos de materiais magnéticos; Structural, electronic and magnetic thin film properties of magnetic materials

Alexandre Abdalla Araujo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/02/2008 Português
Relevância na Pesquisa
46.5%
A Física de superfícies, interfaces e filmes finos vem se desenvolvendo muito rapidamente nas últimas décadas com o aparecimento de inúmeras técnicas experimentais para estudo das propriedades de superfície. Por outro lado, tem ocorrido um grande avanço dos equipamentos de informática e dos métodos computacionais, com o desenvolvimento de novos algoritmos, os quais já permitem o estudo de sistemas mais complexos como interfaces, defeitos, filmes-finos e nanofios, contendo um número cada vez maior de átomos. Um considerável interesse em superfícies e na deposição de filmes finos sobre superfícies, envolvendo metais, tem sido motivado pela possibilidade de se conseguir novas propriedades magnéticas e eletrônicas, incluindo temperaturas acima da temperatura ambiente, visando avanços tecnológicos em dispositivos eletrônicos. Nosso trabalho representa uma estratégia bastante promissora nessa área, pois nele identificamos claramente a possibilidade de produção de filmes finos com caráter ferromagnético half-metallic (isto é, com um canal de condução eletrônico semicondutor e outro metálico). Conforme pudemos mostrar, este caráter foi atingido a partir de pequenas variações de parâmetro de rede...

Piezoresistive silicon thin film sensor array for biomedical applications

Alpuim, P.; Correia, Vítor; Marins, Emílio Sérgio; Rocha, J. G.; Trindade, Isabel; Lanceros-Méndez, S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 09/03/2011 Português
Relevância na Pesquisa
56.07%
N-type hydrogenated nanocrystalline silicon thin film piezoresistors, with gauge factor −28, were deposited on rugged and flexible polyimide foils by Hot-wire chemical vapor deposition using a tantalum filament heated to 1750 °C. The piezoresistive response under cyclic quasi-static and dynamical (up to 100 Hz) load conditions is reported. Test structures, consisting of microresistors having lateral dimensions in the range from 50 to 100 μm and thickness of 120 nm were defined in an array by reactive ion etching. Metallic pads, forming ohmic contacts to the sensing elements, were defined by a lift-off process. A readout circuit for the array consisting in a mutiplexer on each row and column of the matrix is proposed. The digital data will be processed, interpreted and stored internally by an ultra low-power micro controller, also responsible for the communication of two-way wireless data, e.g. from inside to outside the human body.© 2011 Elsevier B.V. All rights reserved; Fundação para a Ciência e a Tecnologia (FCT)

Ultra-thin solid oxide fuel cells: materials and devices

Kerman, Kian
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
Português
Relevância na Pesquisa
56.19%
Solid oxide fuel cells are electrochemical energy conversion devices utilizing solid electrolytes transporting O2- that typically operate in the 800 - 1000 °C temperature range due to the large activation barrier for ionic transport. Reducing electrolyte thickness or increasing ionic conductivity can enable lower temperature operation for both stationary and portable applications. This thesis is focused on the fabrication of free standing ultrathin (<100 nm) oxide membranes of prototypical O2- conducting electrolytes, namely Y2O3-doped ZrO2 and Gd2O3-doped CeO2. Fabrication of such membranes requires an understanding of thin plate mechanics coupled with controllable thin film deposition processes. Integration of free standing membranes into proof-of-concept fuel cell devices necessitates ideal electrode assemblies as well as creative processing schemes to experimentally test devices in a high temperature dual environment chamber. We present a simple elastic model to determine stable buckling configurations for free standing oxide membranes. This guides the experimental methodology for Y2O3-doped ZrO2 film processing, which enables tunable internal stress in the films. Using these criteria, we fabricate robust Y2O3-doped ZrO2 membranes on Si and composite polymeric substrates by semiconductor and micro-machining processes...

Sample fabrication and experimental design for studying interfacial creep at thin film/silicon interfaces

Thornell, Mark E.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
56.19%
Approved for Public Release; Distribution is Unlimited; This thesis developed the sample fabrication and experimental design for studying interfacial creep at thin film / Silicon interfaces. The specific interface of study was the crystalline interface created by Positive Vapor deposition of a metallic thin film on a very smooth Silicon substrate. Emphasis was placed on development and refinement of the fabrication techniques necessary to produce test samples that provide valid reproduction of the interfacial stress state in isolation from other stresses inherent in the complete device. Test sample fabrication utilized traditional laboratory methods combined with leading edge methodology in two fabrication steps; namely diffusion bonding of an Silicon substrate / PVD Aluminum thin film / Silicon substrate composite structure and micro-machining Silicon through the use of a TMAH based etchant. In conjunction with the sample development a test platform was designed, fabricated, assembled, and aligned to provide for isolated parametric characterization of the proposed interfacial creep model. The results of this characterization are anticipated to be of significant utility in improving the design for fabrication and reliability of current and next generation microelectronic and microelectro-mechanical devices.

Sample fabrication and experimental approach for studying interfacial sliding in thin film-substrate systems

Burkhard, Michael A.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
56.11%
The purpose of this thesis was to develop an experimental methodology to determine the mechanisms and kinetics of sliding at the interface between a metallic thin film and substrate. A methodology was developed and used to study interfacial sliding of aluminum films on silicon substrates and copper films on fused quartz substrates. The methodology employed a lap shear type of geometry to load the interface between the film and substrate in shear. The results of the studies were inconclusive with regard to interfacial sliding. In the case of Al-Si, the sample fabrication process increased the interfacial amplitude to an extent that the sliding rate was essentially zero. In the case of Cu-Fused Quartz, chromium film was added to the sample to aid the adhesion of Cu to fused quartz and as a result reduced the sliding rate below detectable levels.

Biocompatibility evaluation of sputtered zirconium-based thin film metallic glass-coated steels

Subramanian, Balasubramanian; Maruthamuthu, Sundaram; Rajan, Senthilperumal Thanka
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
Publicado em 01/10/2015 Português
Relevância na Pesquisa
46.48%
Thin film metallic glasses comprised of Zr48Cu36Al8Ag8 (at.%) of approximately 1.5 μm and 3 μm in thickness were prepared using magnetron sputtering onto medical grade 316L stainless steel. Their structural and mechanical properties, in vitro corrosion, and antimicrobial activity were analyzed. The amorphous thin film metallic glasses consisted of a single glassy phase, with an absence of any detectable peaks corresponding to crystalline phases. Elemental composition close to the target alloy was noted from EDAX analysis of the thin film. The surface morphology of the film showed a smooth surface on scanning electron microscopy and atomic force microscopy. In vitro electrochemical corrosion studies indicated that the zirconium-based metallic glass could withstand body fluid, showing superior resistance to corrosion and electrochemical stability. Interactions between the coated surface and bacteria were investigated by agar diffusion, solution suspension, and wet interfacial contact methods. The results indicated a clear zone of inhibition against the growth of microorganisms such as Escherichia coli and Staphylococcus aureus, confirming the antimicrobial activity of the thin film metallic glasses. Cytotoxicity studies using L929 fibroblast cells showed these coatings to be noncytotoxic in nature.

Characteristics of plasmonic at a metal /chiral sculptured thin film interface

Babaei, F.; Omidi, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/01/2013 Português
Relevância na Pesquisa
56.12%
The propagation of surface plasmon polariton at an interface of metallic thin film and chiral sculptured thin film theoretically has been investigated using the transfer matrix method in the Kretschman configuration. The optical absorption of structure as a function of polar incident angle for linear polarization P and S has been calculated at different structural parameters. The results show that exist multiple plasmon peaks for P-polarization, while there are the weak plasmon peaks when incident of light is S- polarized plane wave.

Thin-film based phase plates for transmission electron microscopy fabricated from metallic glasses

Dries, M.; Hettler, S.; Schulze, T.; Send, W.; Müller, E.; Schneider, R.; Gerthsen, D.; Luo, Y.; Samwer, K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/10/2015 Português
Relevância na Pesquisa
46.37%
Thin-film based phase plates are meanwhile a widespread tool to enhance the contrast of weak-phase objects in transmission electron microscopy (TEM). The thin film usually consists of amorphous carbon, which suffers from quick degeneration under the intense electron-beam illumination. Recent investigations have focused on the search for alternative materials with an improved material stability. This work presents thin-film based phase plates fabricated from metallic glass alloys, which are characterized by a high electrical conductivity and an amorphous structure. Thin films of the zirconium-based alloy Zr65.0Al7.5Cu27.5 (ZAC) are prepared and their phase-shifting properties are tested. The ZAC-alloy film is investigated by different TEM techniques, which reveal a range of beneficial characteristics. Particularly favorable is the small probability for inelastic plasmon scattering, which is promising to improve the performance of thin-film based phase plates in phase-contrast TEM.

Dissipationless Spin Transport in Thin Film Ferromagnets

König, Jürgen; Bønsager, Martin Chr.; MacDonald, Allan H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
56.02%
Metallic thin film ferromagnets generically possess spiral states that carry dissipationless spin currents. We relate the critical values of these supercurrents to micromagnetic material parameters, identify the circumstances under which the supercurrents will be most robust, and propose experiments which could reveal this new collective transport behavior.; Comment: 4 pages, 3 figures

Selective reflection technique as a probe to monitor the growth of a metallic thin film on dielectric surfaces

Martins, Weliton Soares; Oriá, Marcos; Chevrollier, Martine; de Silans, Thierry Passerat
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/10/2013 Português
Relevância na Pesquisa
56.2%
Controlling thin film formation is technologically challenging. The knowledge of physical properties of the film and of the atoms in the surface vicinity can help improve control over the film growth. We investigate the use of the well-established selective reflection technique to probe the thin film during its growth, simultaneously monitoring the film thickness, the atom-surface van der Waals interaction and the vapor properties in the surface vicinity.; Comment: 7 pages, 5 figures

Microwave induced elastic deformation of a metallic thin film

Wang, S. B.; Chan, C. T.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/04/2013 Português
Relevância na Pesquisa
66.13%
The microwave induced elastic deformation of a metallic thin film is computed numerically and we found that the deformation can be significantly enhanced at resonance. We show that an analytical transmission line model can reproduce the numerical results almost quantitatively and at the same time reveal the underlying physics.; Comment: 8 pages,3 figures

Electric-field Controlled Magnetization Switching in Co/Pt thin-Film Ferromagnets

Siddique, A.; Gu, S.; Witte, R.; Ghahremani, M.; Nwokoye, C. A.; Aslani, A.; Kruk, R.; Provenzano, V.; Bennett, L. H.; Della Torre, E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/11/2015 Português
Relevância na Pesquisa
56.16%
A study of dynamic and reversible voltage controlled magnetization switching in ferromagnetic Co/Pt thin film with perpendicular magnetic anisotropy at room temperature is presented. The change in the magnetic properties of the system is observed in a relatively thick film of 15 nm. A surface charge is induced by the formation of electrochemical double layer between the metallic thin film and non-aqueous lithium LiClO4 electrolyte to manipulate the magnetism. The change in the magnetic properties occurred by the application of an external electric field. As the negative voltage was increased, the coercivity and the switching magnetic field decreased thus activating magnetization switching. The results are envisaged to lead to faster and ultra-low power magnetization switching as compared to spin-transfer torque (STT) switching in spintronic devices.; Comment: 5 pages, 8 figures

Spin-Hall Conductivity and Electric Polarization in Metallic Thin Films

Wang, Xuhui; Xiao, Jiang; Manchon, Aurelien; Maekawa, Sadamichi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
56.03%
We predict theoretically that, when a normal metallic thin film (without bulk spin-orbit coupling, such as Cu or Al) is sandwiched by two insulators, two prominent effects arise due to the interfacial spin-orbit coupling: a giant spin-Hall conductivity due to the surface scattering and a transverse electric polarization due to the spin-dependent phase shift in the spinor wave functions.; Comment: Accepted for publication as a Rapid Communication in Physical Review B

Magnetoresistance in Thin Permalloy Film (10nm-thick and 30-200nm-wide) Nanocontacts Fabricated by e-Beam Lithography

García García, Nicolás; Cheng, Hao; Lu, Yonhua; Muñoz, Manuel; Yifang, Chen; Zhengqi, Lu; Yun, Zhou; Genhua, Pan; Zheng, Cui; Pasa, A. A.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Pre-print Formato: 408853 bytes; application/pdf
Português
Relevância na Pesquisa
56.07%
15 pages, 4 figures. Accepted by APL.-- Final full-text version published 24 Aug 2006, available at: http://dx.doi.org/10.1063/1.2337538; In this paper we show spin dependent transport experiments in nanoconstrictions ranging from 30 to 200nm. These nanoconstrictions were fabricated combining electron beam lithography and thin film deposition techniques. Two types of geometries have been fabricated and investigated. We compare the experimental results with the theoretical estimation of the electrical resistance. Finally we show that the magnetoresistance for the different geometries does not scale with the resistance of the structure and obtain drops in voltage of 20mV at 20 Oe.; This work has been supported by the BMR-NMP-EU project.; Peer reviewed

Quasifree Mg–H thin films

Baldi, A.; Palmisano, V.; González Silveira, Marta; Pivak, Y.; Slaman, M.; Schreuders, H.; Dam, B.; Griessen, R.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2009 Português
Relevância na Pesquisa
56.02%
The thermodynamics of hydrogen absorption in Pd-capped Mgfilms are strongly dependent on the magnesium thickness. In the present work, we suppress such dependency by inserting a thin Ti layer between Mg and Pd. By means of optical measurements, we show that the surface energy contribution to the destabilization of MgH2 is negligible. The inserted Ti layer prevents Mg–Pd alloy formation at the Mg/Pd interface, leading to quasifree Mgfilms and enhancing the kinetics of hydrogen desorption. Our observations are important for the development of thin film devices.

Thin film adhesion measurement using excimer laser ablation test

Lee, Wen-Chieh
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
66.47%
An excimer laser incident on a metallic thin film is used to measure the adhesion between the film and the substrate. The initial optical absorption leads to electron excitation. After collisions and degradation of the excited electrons, the absorbed energy is transferred into various kinds of energy among which the major one is thermal. The superheated surface undergoes vapor explosion which serves as one source of shock wave to break the thin film. The evaporated particles may recoil back to the surface constructing another shock wave to break the film. In addition, a tensile stress may be formed by the large difference of thermal expansion between metallic thin film and polymeric substrate. All these effects cooperate to cause the cracking of the metallic thin film. This thesis provides the theoretical models to explain how the various mechanisms work on adhesion evaluation. Based on these understandings, the experimental data of laser ablation test is more suggestive and meaningful than the tape test which is sometimes ambiguous due to undiscerned effects. The experimental results show that laser ablation is sensitive to small differences in adhesion. In addition, the laser ablation test has a broader range of measurement as compared to that of tape test. One thing to be noticed is that laser ablation test is strongly affected by the thickness of the film.

Analysis and control of self-assembled heteroepitaxial thin-film surface patterns

McGill, Jacob
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
56.26%
Vlachos, Dionisios G.; Ogunnaike, Babatunde; Thin-films are a broad and important class of materials. Numerous examples of thin-films exist across a wide range of problem domains including bi-metallic catalysts [40, 38], polymer films for catalysis [22], ferroelectric films for piezoelectric sensors and actuators [3], and magnetic films for medical imaging devices [49] and high-density data storage [20, 80]. Thin-films often exhibit some degree of self-assembly, a process that involves a transition from a low-ordered state to a high-ordered state without external stimuli. In thin-films, self-assembly is driven by the interactions between the adsorbate molecules that compose the film. In particular, short-range attractive forces and long-range repulsive forces (e.g., strain induced through a lattice mismatch with the substrate) are necessary to give rise to self-assembly. By manipulating the balance between the intermolecular forces, using process conditions or other external factors, it will be shown that one can drive arbitrary initial patterns toward a target pattern. A number of challenges must be overcome before one can control thin-film surface morphologies using self-assembly. Specifically, self-assembly of thin-films is an inherently multiscale problem. This means that the actual process of self-assembly occurs at microscopic length and time scales (i.e....