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Estudo das propriedades estruturais e ópticas em materiais nanoestruturados a base de silício.; Study of structural and optical properties in nanostructured silicon based films.

Ribeiro, Márcia
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 11/05/2009 PT
Relevância na Pesquisa
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Esta tese de doutorado tem por objetivo aprofundar as pesquisas realizadas no mestrado, a saber, da caracterização e estudo das propriedades estruturais e ópticas de filmes de oxinitreto de silício (SiOxNy:H) ricos em silício depositados pela técnica de deposição química a vapor assistida por plasma a baixa temperatura (PECVD). Os resultados obtidos no mestrado indicaram que os filmes de SiOxNy:H ricos em silício apresentam emissão luminescente na faixa do visível cuja intensidade e freqüência de emissão estão em correlação com o excesso de silício. Os resultados sugeriram que o excesso de silício na matriz do SiOxNy:H estava disposto na forma de aglomerados de silício de dimensões nanométricas responsáveis por efeitos de tamanho quântico bem como a estados radiativos na interface dos aglomerados com a matriz isolante. Neste trabalho a fim de avaliar o efeito da separação de fases, do tamanho quântico, e da interface, foram produzidos sistemas nanoestruturados a base de silício com total e parcial separação de fases para caracterizar e analisar suas propriedades ópticas e estruturais e compará-las com as dos filmes ricos em silício. Assim foram produzidas multicamadas de a-Si:H de poucos nanômetros de espessura com materiais dielétricos. Em algumas destas multicamadas foi promovida a mistura parcial das camadas por meio de bombardeamento iônico. O estudo nas estruturas de multicamadas permitiu caracterizar e analisar as propriedades estruturais e ópticas de materiais nanoestruturados com total e parcial separação de fases para posteriormente contrastá-los com as características dos filmes de oxinitreto de silício ricos em silício. A fim de analisar a influência da interface nas propriedades ópticas destes sistemas as multicamadas foram fabricadas com dois dielétricos diferentes: o óxido de silício e o ni treto de silício. A espessura das camadas dielétricas foi mantida fixa entanto que a das camadas de silício foi variada para avaliar efeitos de confinamento no silício. A caracterização foi feita utilizando técnicas de absorção óptica no UV-Vis...

Influência da deposição de filmes finos de TiN e ZrN multicamadas na resistência ao desgaste microabrasivo da liga Ti-40Zr obtida por metalurgia do pó

Dias, Felipe da Cruz
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Tese
POR
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Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2014.; Titânio e suas ligas são conhecidos por apresentarem excelentes propriedades mecânicas e inúmeras possibilidades de utilização de acordo com sua composição. Entretanto a baixa resistência ao desgaste restringe o uso de ligas de titânio em atividades que envolvam abrasão. O objetivo deste trabalho foi avaliar a influência da deposição de filmes finos de TiN e ZrN multicamadas na resistência ao desgaste microabrasivo da liga Ti-40Zr obtida por metalurgia do pó. Os filmes foram obtidos por deposição física de vapores por feixe de elétrons, com três diferentes configurações: Ti/TiN, Ti/TiN/ZrN e Ti/TiN/ZrN/TiN. Ensaios de desgaste microabrasivo por esfera livre foram realizados com duas diferentes suspensões abrasivas: uma à base de carbeto de silício, com concentração volumétrica de 0,20 e outra à base de sílica, com concentração volumétrica de 0,23. Foram estudados também 5 diferentes modelos de equações de desgaste com intuito de verificar o que melhor se ajusta com os resultados obtidos experimentalmente, a partir dos coeficientes de determinação e correlação. Foram realizadas caracterizações por meio de ensaio de riscamento...

Influence of low energy argon plasma treatment on the moisture barrier performance of hot wire-CVD grown SiNx multilayers

Majee, Subimal; Cerqueira, M. F.; Tondelier, Denis; Geffroy, Bernard; Bonnassieux, Yvan; Alpuim, P.; Bourée, Jean Eric
Fonte: IOP Science Publicador: IOP Science
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
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The reliability and stability are key issues for the commercial utilization of organic photovoltaic devices based on flexible polymer substrates. To increase the shelf-lifetime of these devices, transparent moisture barriers of silicon nitride (SiNx) films are deposited at low temperature by hot wire CVD (HW-CVD) process. Instead of the conventional route based on organic/inorganic hybrid structures, this work defines a new route consisting in depositing multilayer stacks of SiNx thin films, each single layer being treated by argon plasma. The plasma treatment allows creating smoother surface and surface atom rearrangement. We define a critical thickness of the single layer film and focus our attention on the effect of increasing the number of SiNx single-layers on the barrier properties. A water vapor transmission rate (WVTR) of 2 x 10-4 g/(m2 day) is reported for SiNx multilayer stack and a physical interpretation of the plasma treatment effect is given.; PICS (French–Portuguese No. 5336) project; Direction des Relations Extérieures, Ecole Polytechnique

Multilayered micro/nanocrystalline CVD diamond coatings for biotribology; Revestimentos multicamada de diamante CVD micro/nanocristalino para biotribologia

Salgueiredo, Ermelinda da Conceição Portela
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
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In the present work multilayered micro/nanocrystalline (MCD/NCD) diamond coatings were developed by Hot Filament Chemical Vapour Deposition (HFCVD). The aim was to minimize the surface roughness with a top NCD layer, to maximize adhesion onto the Si3N4 ceramic substrates with a starting MCD coating and to improve the mechanical resistance by the presence of MCD/NCD interfaces in these composite coatings. This set of features assures high wear resistance and low friction coefficients which, combined to diamond biocompatibility, set this material as ideal for biotribological applications. The deposition parameters of MCD were optimized using the Taguchi method, and two varieties of NCD were used: NCD-1, grown in a methane rich gas phase, and NCD-2 where a third gas, Argon, was added to the gas mixture. The best combination of surface pre-treatments in the Si3N4 substrates is obtained by polishing the substrates with a 15 μm diamond slurry, further dry etching with CF4 plasma for 10 minutes and final ultrasonic seeding in a diamond powder suspension in ethanol for 1 hour. The interfaces of the multilayered CVD diamond films were characterized with high detail using HRTEM, STEM-EDX and EELS. The results show that at the transition from MCD to NCD a thin precursor graphitic film is formed. On the contrary...

Freestanding and Reactive Thin Films Fabricated by Covalent Layer-by-Layer Assembly and Subsequent Lift-Off of Azlactone-Containing Polymer Multilayers

Buck, Maren E.; Lynn, David M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 19/10/2010 EN
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We report an approach to the fabrication of freestanding and amine-reactive thin films that is based on the reactive layer-by-layer assembly and subsequent lift-off of azlactone-containing polymer multilayers. We demonstrate that covalently crosslinked multilayers fabricated using the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and a primary amine-containing polymer [poly(ethyleneimine) (PEI)] can be delaminated from planar glass and silicon surfaces by immersion in mildly acidic aqueous environments to yield flexible freestanding membranes. These freestanding membranes are robust and can withstand exposure to strong acid, strong base, or incubation in high ionic strength solutions that typically lead to the disruption and erosion of polymer multilayers assembled by reversible weak interactions (e.g., ‘polyelectrolyte multilayers’ assembled by electrostatic interactions or hydrogen bonding). We demonstrate further that these PEI/PVDMA assemblies contain residual reactive azlactone functionality that can be exploited to chemically modify the films (either directly after fabrication or after they have been lifted off of the substrates on which they were fabricated) using a variety of amine-functionalized small molecules. These freestanding membranes can also be transferred readily onto other objects (for example...

Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide

de Heer, Walt A.; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
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After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultrahigh vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The Georgia Tech team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high-quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the “furnace grown” graphene. Graphene multilayers grown on the carbon-terminated face of SiC...

Si solid-state quantum dot-based materials for tandem solar cells

Conibeer, Gavin; Perez-Wurfl, Ivan; Hao, Xiaojing; Di, Dawei; Lin, Dong
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 21/03/2012 EN
Relevância na Pesquisa
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The concept of third-generation photovoltaics is to significantly increase device efficiencies whilst still using thin-film processes and abundant non-toxic materials. A strong potential approach is to fabricate tandem cells using thin-film deposition that can optimise collection of energy in a series of cells with decreasing band gap stacked on top of each other. Quantum dot materials, in which Si quantum dots (QDs) are embedded in a dielectric matrix, offer the potential to tune the effective band gap, through quantum confinement, and allow fabrication of optimised tandem solar cell devices in one growth run in a thin-film process. Such cells can be fabricated by sputtering of thin layers of silicon rich oxide sandwiched between a stoichiometric oxide that on annealing crystallise to form Si QDs of uniform and controllable size. For approximately 2-nm diameter QDs, these result in an effective band gap of 1.8 eV. Introduction of phosphorous or boron during the growth of the multilayers results in doping and a rectifying junction, which demonstrates photovoltaic behaviour with an open circuit voltage (VOC) of almost 500 mV. However, the doping behaviour of P and B in these QD materials is not well understood. A modified modulation doping model for the doping mechanisms in these materials is discussed which relies on doping of a sub-oxide region around the Si QDs.

Reactive Polymer Multilayers Fabricated by Covalent Layer-by-Layer Assembly: 1,4-Conjugate Addition-Based Approaches to the Design of Functional Biointerfaces

Bechler, Shane L.; Lynn, David M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
28.238506%
We report on conjugate addition-based approaches to the covalent layer-by-layer assembly of thin films and the post-fabrication functionalization of biointerfaces. Our approach is based on a recently reported approach to the ‘reactive’ assembly of covalently-crosslinked polymer multilayers driven by the 1,4-conjugate addition of amine functionality in poly(ethyleneimine) (PEI) to the acrylate groups in a small-molecule pentacrylate species (5-Ac). This process results in films containing degradable β-amino ester crosslinks and residual acrylate and amine functionality that can be used as reactive handles for the subsequent immobilization of new functionality. Layer-by-layer growth of films fabricated on silicon substrates occurred in a supra-linear manner to yield films ~750 nm thick after the deposition of 80 PEI/5-Ac layers. Characterization by AFM suggested a mechanism of growth that involves the reactive deposition of nanometer-scale aggregates of PEI and 5-Ac during assembly. IR spectroscopy studies revealed covalent assembly to occur by 1,4-conjugate addition without formation of amide functionality. Additional experiments demonstrated that acrylate-containing films could be post-functionalized via conjugate addition reactions with small-molecule amines that influence important bio-interfacial properties...

The coupling between localized surface plasmons and excitons via Purcell effect

Wang, Feng; Li, Dongsheng; Yang, Deren; Que, Duanlin
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 07/12/2012 EN
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The coupling between localized surface plasmons (LSPs) within silver nanostructures and excitons in a silicon-rich silicon nitride (SiNx) matrix has been demonstrated via the Purcell effect. A simple model is employed for the estimation of the Purcell factor as well as the average position of excitons within a luminescence matrix. The estimated average position of the excitons is located at approximately 40 nm beneath the top surface of the SiNx films. The approaches for further improving the optoelectrical properties of the luminescence matrix are anticipated based on the model we adopted. The optimization of the thickness of the luminescence matrix as well as the size and shape of metal nanostructures may be the alternative approaches. Besides, the application of multilayers with the luminescence matrix inserted between barrier layers (we defined it as confined structures here) may be also an available choice. Our work may provide a deep comprehension on the coupling between LSPs and excitons, which is not limited to a certain luminescence material but with unconfined structures.

pH-responsive drug delivery system based on hollow silicon dioxide micropillars coated with polyelectrolyte multilayers

Alba, María; Formentín, Pilar; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluís F
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 21/08/2014 EN
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We report on the fabrication of polyelectrolyte multilayer-coated hollow silicon dioxide micropillars as pH-responsive drug delivery systems. Silicon dioxide micropillars are based on macroporous silicon formed by electrochemical etching. Due to their hollow core capable of being loaded with chemically active agents, silicon dioxide micropillars provide additional function such as drug delivery system. The polyelectrolyte multilayer was assembled by the layer-by-layer technique based on the alternative deposition of cationic and anionic polyelectrolytes. The polyelectrolyte pair poly(allylamine hydrochloride) and sodium poly(styrene sulfonate) exhibited pH-responsive properties for the loading and release of a positively charged drug doxorubicin. The drug release rate was observed to be higher at pH 5.2 compared to that at pH 7.4. Furthermore, we assessed the effect of the number of polyelectrolyte bilayers on the drug release loading and release rate. Thus, this hybrid composite could be potentially applicable as a pH-controlled system for localized drug release.

Tunable optical filters with wide wavelength range based on porous multilayers

Mescheder, Ulrich; Khazi, Isman; Kovacs, Andras; Ivanov, Alexey
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 22/08/2014 EN
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A novel concept for micromechanical tunable optical filter (TOF) with porous-silicon-based photonic crystals which provide wavelength tuning of ca. ±20% around a working wavelength at frequencies up to kilohertz is presented. The combination of fast mechanical tilting and pore-filling of the porous silicon multilayer structure increases the tunable range to more than 200 nm or provides fine adjustment of working wavelength of the TOF. Experimental and optical simulation data for the visible and near-infrared wavelength range supporting the approach are shown. TOF are used in spectroscopic applications, e.g., for process analysis.

Enhancement of electroluminescence from embedded Si quantum dots/SiO2multilayers film by localized-surface-plasmon and surface roughening

Li, Wei; Wang, Shaolei; Hu, Mingyue; He, Sufeng; Ge, Pengpeng; Wang, Jing; Guo, Yan Yan; Zhaowei, Liu
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 03/07/2015 EN
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In this paper, we prepared a novel structure to enhance the electroluminescence intensity from Si quantum dots/SiO2multilayers. An amorphous Si/SiO2 multilayer film was fabricated by plasma-enhanced chemical vapor deposition on a Pt nanoparticle (NP)-coated Si nanopillar array substrate. By thermal annealing, an embedded Si quantum dot (QDs)/SiO2 multilayer film was obtained. The result shows that electroluminescence intensity was significantly enhanced. And, the turn-on voltage of the luminescent device was reduced to 3 V. The enhancement of the light emission is due to the resonance coupling between the localized-surface-plasmon (LSP) of Pt NPs and the band-gap emission of Si QDs/SiO2 multilayers. The other factors were the improved absorption of excitation light and the increase of light extraction ratio by surface roughening structures. These excellent characteristics are promising for silicon-based light-emitting applications.

SiC-Based Multilayer for Applications in Extreme Environment - H2 Generation Plants

VEGA BOLIVAR Claudia
Fonte: Centro Comum de Pesquisa da Comissão Européia Publicador: Centro Comum de Pesquisa da Comissão Européia
Tipo: PhD Theses Formato: CD-ROM
ENG
Relevância na Pesquisa
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The purpose of this research is to develop SiC-based multilayers, for applications in extreme environment such as H2 generation plants. Tape casting technology, followed by debinding and sintering at very high temperature (~2200 °C) has been used. In Europe H2 generation processes are being studied under the project HycycleS1, that focuses at the qualification and enhancement of materials and components, in particular ceramics of the SiC family, for key steps of thermochemical cycles for solar or nuclear hydrogen generation. SiC-based materials for applications in extreme environments are developed within the European project ExtreMat. This project has identified the generation of hydrogen as a possible spin off of research activities. HycycleS (Materials and components for Hydrogen production by sulphur based thermochemical cycles) is a project funded under 7th Framework Programme. ExtreMat is funded within the 6th Framework Programme and it targets on the creation of new multifunctional materials. The aim of this research is to develop multilayer SiC for applications in hydrogen generation plants based on thermochemical cycle "S-I" or cycle hybrid thermochemical-electrolytic. The structured components of such facilities (tanks, tubular heat exchangers...

Nanostructured porous silicon photonic crystal for applications in the infrared

Recio-Sánchez, Gonzalo; Torres-Costa, Vicente; Manso-Silván, Miguel; Martín-Palma, Raúl José
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
ENG
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In the last decades great interest has been devoted to photonic crystals aiming at the creation of novel devices which can control light propagation. In the present work, two-dimensional (2D) and three-dimensional (3D) devices based on nanostructured porous silicon have been fabricated. 2D devices consist of a square mesh of 2 μm wide porous silicon veins, leaving 5x5 μm square air holes. 3D structures share the same design although multilayer porous silicon veins are used instead, providing an additional degree of modulation. These devices are fabricated from porous silicon single layers (for 2D structures) or multilayers (for 3D structures), opening air holes in them by means of 1KeV argon ion bombardment through the appropriate copper grids. For 2D structures, a complete photonic band gap for TE polarization is found in the thermal infrared range. For 3D structures, there are no complete band gaps, although several new partial gaps do exist in different high-symmetry directions. The simulation results suggest that these structures are very promising candidates for the development of low-cost photonic devices for their use in the thermal infrared range

Strong vertical light output from thin silicon rich oxide/SiO₂ multilayers via in-plane modulation of photonic crystal patterns

Ren, Fang-Fang; Yu, M. B.; Ye, J. D.; Chen, Q.; Tan, S. T.; Lo, G. Q.; Kwong, D. L.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica Formato: 4 pages
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Three-dimensional-confined structures with triangular-lattice air-hole photonic crystal patterns were fabricated to enhance the light output from silicon rich oxide/SiO₂multilayer stack. The intensity and profile of spontaneous emission were found to be efficiently modulated by controlling the optical modes of the periodic arrays via varying their structural parameters. With lattice constant/radius of 700nm∕280nm, the photoluminescence intensity was found to be enhanced by nearly nine times in the vertical direction. The mechanisms for different enhancement features have been theoretically analyzed based on coherent scattering and quantum electrodynamic effects, well supporting the experimental observation.

Elaboration, characterization of Cr-N based coatings

TLILI, Brahim; NOUVEAU, Corinne; GUILLEMOT, Gildas
Fonte: American Institute of Physics Publicador: American Institute of Physics
EN
Relevância na Pesquisa
38.34141%
Cr, CrN and CrAlN monolayers were synthesized by RF dual magnetron sputtering on AISI4140 steel and silicon substrates at 200°C. Multilayers coatings based on the three mono-layers such as CrN/CrAlN and Cr/CrN/CrAlN were also synthesized only on Si. The physico-chemical and mechanical properties of the layers were determined by AFM, SEM+WDS, stress, roughness and nanoindentation measurements. The influence of the thickness on the mechanical properties of the monolayers stresses has been studied and as a consequence we compared the mono and multilayers stress state.

Probing individual layers in functional oxide multilayers by wavelength-dependent Raman scattering

Kreisel, J.; Weber, M. C.; Dix, N.; Sánchez, F.; Thomas, P. A.; Fontcuberta, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Integration of functional oxides on silicon requires the use of complex heterostructures involving oxides of which the structure and properties strongly depend on the strain state and strain-mediated interface coupling. The experimental observation of strain-related effects of the individual components remains challenging. Here we report a Raman scattering investigation of complex multilayer BaTiO3/LaNiO3/CeO2/YSZ thin film structures on silicon. It is shown that the Raman signature of the multilayers differs significantly for three different laser wavelengths (633, 442 and 325 nm). Our results demonstrate that Raman scattering at various wavelengths allows both the identification of the individual layers of a functional oxide multilayers and monitoring their strain state. It is shown that all layers of the investigated multilayer are strained with respect to the bulk reference samples, and that strain induces a new crystal structure in the embedded LaNiO3. Based on this, we demonstrate that Raman scattering at various wavelengths offers a well-adapted, non-destructive probe for the investigation of strain and structure changes, even in complex thin film heterostructures.; Comment: Revised version, accepted for publication in Adv. Funct. Mater

Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide

de Heer, Walt. A.; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/03/2011
Relevância na Pesquisa
28.667686%
After the pioneering investigations into graphene-based electronics at Georgia Tech (GT), great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an invaluable material for fundamental two-dimensional electron gas physics showing that only EG is on route to define future graphene science. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultra-high vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The GT team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the "furnace grown" graphene. Graphene multilayers grown on the carbon-terminated face of SiC...

Electrical Detection of Self-Assembled Polyelectrolyte Multilayers by a Thin Film Resistor

Neff, Petra A.; Naji, Ali; Ecker, Christof; Nickel, Bert; von Klitzing, Regine; Bausch, Andreas R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/01/2006
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The build up of polyelectrolyte multilayers (PEMs) was observed by a silicon-on-insulator (SOI) based thin film resistor. Differently charged polyelectrolytes adsorbing to the sensor surface result in defined potential shifts, which decrease with the number of layers deposited. We model the response of the device assuming electrostatic screening of polyelectrolyte charges by mobile ions within the PEMs. The Debye screening length inside the PEMs was found to be increased compared to the value corresponding to the bulk solution. Furthermore the partitioning of mobile ions between the bulk phase and the polyelectrolyte film was employed to calculate the dielectric constant of the PEMs and the concentration of mobile charges.; Comment: 18 pages, 5 figures

Caracterización estructural mediante elipsometría espectral de multicapas basadas en SiO2; Structural characterisation of SiO2 based multilayers using spectroscopic ellipsometry

Alonso, M. I.; Garriga, M.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 431278 bytes; application/pdf
SPA
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[ES] Se han caracterizado capas de óxidos subestequiométricos de silicio (SiOx) y estructuras gruesas de guías de onda mediante elipsometría espectral. Para ello ha sido necesario desarrollar un método de ajuste que permita analizar en detalle espectros complicados de elipsometría, como los obtenidos en estructuras multicapa gruesas (~10 μm) típicas de dispositivos modernos de óptica integrada. La elipsometría es la técnica más adecuada para la caracterización detallada de esas estructuras, pero la extracción mediante ajuste de los parámetros deseados es a menudo impracticable con los métodos usuales. Nuestro método se basa en parametrizar las constantes ópticas desconocidas con funciones spline. El método es aplicable tanto a materiales con una variación suave de las constantes ópticas como a materiales que presenten estructuras agudas debidas a transiciones electrónicas en el rango de energía analizado.; [EN] We have characterised PECVD-grown non-stoichiometric silicon oxides (SiOx) and thick waveguide structures based on these materials with spectroscopic ellipsometry. We have developed a fit method that allows detailed analysis of complicated ellipsometric spectra, such as those of thick (~10 μm) multilayer structures found in modern integrated optics devices. Ellipsometry should be the natural choice for thorough nondestructive characterisation of those heterostructures...