This dissertation presents an experimental investigation of heat transport through solid- solid and solid-liquid interfaces. Heat transport is a process initiated by the presence of a thermal gradient. All interfaces offer resistance to heat flow in the form of temperature drop at the interface. In micro and nano scale devices, the contribution of this resistance often becomes comparable to, or greater than, the intrinsic thermal resistance offered by the device or structure itself. In this dissertation, I report the resistance offered by the interfaces in terms of interface thermal conductance, G, which is the inverse of Kapitza resistance and is quantified by the ratio of heat flux to the temperature drop. For studying thermal transport across interfaces, I adapted a non-contact optical measurement technique called Time-Domain Thermoreflectance (TDTR) that relies on the fact that the reflectivity of a metal has a small, but measurable, dependence on temperature. The first half of this dissertation is focused on investigating heat transport through thin films and solid-solid interfaces. The samples in this study are thin lead zirconate- titanate (PZT) piezoelectric films used in sensing applications and dielectric films such as SiOC:H used in semiconductor industry. My results on the PZT films indicate that the thermal conductivity of these films was proportional to the packing density of the elements within the films. I have also measured thermal conductivity of dielectric films in different elemental compositions. I also examined thermal conductivity of dielectric films for a variety of different elemental compositions of Si, O, C, and H, and varying degrees of porosity. My measurements showed that the composition and porosity of the films played an important role in determining the thermal conductivity. The second half of this dissertation is focused on investigating heat transport through solid-liquid interfaces. In this regard, I functionalize uniformly coated gold surfaces with a variety of self-assembled monolayers (SAMs). Heat flows from the gold surface to the sulfur molecule, then through the hydrocarbon chain in the SAM, into the terminal group of the SAM and finally into the liquid. My results showed that by changing the terminal group in a SAM from hydrophobic to hydrophilic, G increased by a factor of three in water. By changing the number of carbon atoms in the SAM, I also report that the chain length does not present a significant thermal resistance. My results also revealed evidence of linear relationship between work of adhesion and interface thermal conductance from experiments with several SAMs on water. By examining a variety of SAM-liquid combination, I find that this linear dependency does not hold as a unified hypothesis. From these experiments, I speculate that heat transport in solid-liquid systems is controlled by a combination of work of adhesion and vibrational coupling between the omega-group in the SAM and the liquid. / Ph. D.

The classical theory of colloids and surface science has universally been applied in modeling and calculations involving solid-liquid interfaces encountered in natural and engineered environments. However, several discrepancies between the observed behavior of charged solid-liquid interfaces and predictions by classical theory have been reported in the past decades. The hypothesis that the mean-field, pseudo-one-component approximation adopted within the framework of the classical theory is responsible for the differences observed is tested in this work via the application of modeling and experimental techniques at a molecular level. Silica and silicon nitride are selected as model charged solid surfaces, and mixtures of symmetric and asymmetric indifferent and non-indifferent electrolytes are used as liquid phases. Canonical Monte Carlo simulations (CMC) of the electrical double layer (EDL) structure of a discretely charged planar silica surface, embedded in solutions of indifferent electrolytes, reveal the presence of a size exclusion effect that is enhanced at larger values of surface charge densities. That effect translates into an unexpected behavior of the interaction forces between a charged planar surface and a spherical particle. CMC simulations of the electrostatic interactions and calculations of the EDL force between a spherical particle and a planar surface, similarly charged, reveal the presence of two attractive force components: a depletion effect almost at contact and a long-range attractive force of electrostatic origin due to ion-ion correlation effects. Those two-force components result from the consideration of discreteness of charge in the interaction of solid-liquid interfaces, and they contradict the classical theory predictions of electrostatic repulsive interaction between similarly charged surfaces. Direct interaction force measurements between a charged planar surface and a colloidal particle, performed by atomic force microscopy (AFM), reveal that, when indifferent and non-indifferent electrolytes are present in solution, surface charge modification occurs in addition to the effects on the EDL behavior reported for indifferent electrolytes. Non-uniformity and even heterogeneity of surface charge are detected due to the action of non-indifferent, asymmetric electrolytes. The phenomena observed explain the differences between the classical theory predictions and the experimental observations reported in the open literature, validating the hypothesis of this work.

Multi-chip integration with emerging technologies such as a 3D IC stack or 2.5D interposer is primarily enabled by the off-chip interconnections. The I/O density, speed and bandwidth requirements for emerging mobile and high-performance systems are projected to drive the interconnection pitch to less than 20 microns by 2015. A new class of low-temperature, low-pressure, high-throughput, cost-effective and maufacturable technologies are needed to enable such fine-pitch interconnections. A range of interconnection technologies are being pursued to achieve these fine-pitch interconnections, most notably direct Cu-Cu interconnections and copper pillars with solder caps. Direct Cu-Cu bonding has been a target in the semiconductor industry due to the high electrical and thermal conductivity of copper, its high current-carrying capability and compatibility with CMOS BEOL processes. However, stringent coplanarity requirements and high temperature and high pressure bonding needed for assembly have been the major barriers for this technology. Copper-solder interconnection technology has therefore become the main workhouse for off-chip interconnections, and has recently been demonstrated at pitches as low as 40 microns. However, the current interconnection approaches using copper-solder structures are not scalable to finer feature sizes due to electromigration, and reliability issues arising with decreased solder content. Solid Liquid Inter-Diffusion (SLID) bonding is a promising solution to achieve ultra-fine-pitch and ultra-short interconnections with a copper-solder system, as it relies on the conversion of the entire solder volume into thermally-stable and highly electromigration-resistant intermetallics with no residual solder. Such a complete conversion of solders to stable intermetallics, however, relies on a long assembly time or a subsequent post-annealing process. To achieve pitches lower than 30 micron pitch, this research aims to study two ultra-short copper-solder interconnection approaches: (i) copper pillar and solder cap technology, and (ii) a novel technology which will enable interconnections with improved electrical performance by fast and complete conversion of solders to stable intermetallics (IMCs) using Solid Liquid Diffusion (SLID) bonding approach. SLID bonding, being a liquid state diffusion process, combined with a novel, alternate layered copper-solder bump structure, leads to higher diffusion rates and a much faster conversion of solder to IMCs. Moreover this assembly bonding is done at a much lower temperature and pressure as compared to that used for Cu-Cu interconnections. FEM was used to study the effect of various assembly and bump-design characteristics on the post-assembly stress distribution in the ultra-short copper-solder joints, and design guidelines were evolved based on these results. Test vehicles, based on these guidelines, were designed and fabricated at 50 and 100 micron pitch for experimental analysis. The bumping process was optimized, and the effect of current density on the solder composition, bump-height non-uniformity and surface morphology of the deposited solder were studied. Ultra-short interconnections formed using the copper pillar and solder cap technology were characterized. A novel multi-layered copper-solder stack was designed based on diffusion modeling to optimize the bump stack configuration for high-throughput conversion to stable Cu3Sn intermetallic. Following this modeling, a novel bumping process with alternating copper and tin plating layers to predesigned thicknesses was then developed to fabricate the interconnection structure. Alternate layers of copper and tin were electroplated on a blanket wafer, as a first demonstration of this stack-technology. Dies with copper-solder test structures were bonded using SLID bonding to validate the formation of stable intermetallics.

Orientador: David Mendez Soares / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T00:49:55Z (GMT). No. of bitstreams: 1 Gomes_WyllersonEvaristo1983-_D.pdf: 5303870 bytes, checksum: ba3a86db4d3713f9b80b91fba5545795 (MD5) Previous issue date: 2015 / Resumo: Neste trabalho, pesquisamos o uso de filmes autoorganizados sobre o eletrodo de ouro da microbalança de cristal de quartzo eletroquímica, EQCM. Focamos a pesquisa na interação física da superfície sólida funcionalizada com o meio líquido. Desenvolvemos uma metodologia para compreender a dinâmica de variação dos parâmetros medidos, pela EQCM durante um experimento (perturbação) em meio líquido. Introduzimos a representação bidimensional da variação da freqüência de ressonância e da resistência de ressonância do cristal de quartzo da EQCM, ?f e ?R respectivamente, durante uma perturbação, usando o tempo como parâmetro. A metodologia foi utilizada para soluções aquosas de sais, álcool, líquidos apolares como ciclohexano, n-hexano, soluções de sacarose. Mostramos que líquidos reais apresentam viscoelasticidade. Também testamos a perturbação causada pela aplicação de campo elétrico nas interfaces sólido/soluções iônicas em condições em que o eletrodo é polarizável. Mostramos a possibilidade de formação de nanoestruturas gasosas, nanobolhas. Estendemos a pesquisa para a superfície do ouro funcionalizado com filmes de tiol, S-layers (proteínas de membrana de bactéria), e adsorção de lipossomos zwiteriônicos. A interface sólido/líquido também foi estudada relativamente às características hidrofóbicas da funcionalidade devido à sua microestrutura superficial (superfície superhidrofóbica). Usamos as técnicas de microscopia de força atômica, AFM, e de Raman confocal, paralelamente às nossas pesquisas com a EQCM. Para complementar o estudo de campos elétricos aplicados a interfaces, estudamos também os efeitos macroscópicos da aplicação desses campos a líquidos dielétricos como a água. Pesquisamos o fenômeno da ponte líquida usando líquidos dielétricos isolantes apróticos / Abstract: In this work, we have studied the use of self-assembling films onto gold electrode of the electrochemical quartz crystal microbalance, EQCM. The main objective is to understand the physical interaction of the functionalized solid surface with the liquid medium. We have developed a methodology to understand the dynamics of variation of the parameters measured by the EQCM in liquid medium. We also have introduced the two-dimensional representation of the variation of resonance frequency and resonance resistance of the quartz crystal of the EQCM, ?f and ?R respectively. The measurements were taken during a perturbation, using time as parameter. The methodology was used for aqueous salt solutions, alcohol, nonpolar liquids such as cyclohexane, n-hexane and sucrose solutions. We showed that real liquids exhibit viscoelasticity. We also tested the perturbation caused by the application of electric field at solid interfaces/ionic solutions, under conditions in which the electrode is polarizable. We showed the possibility of formation of gaseous nanostructures, nanobubbles. We extended the study to gold electrode thiol-functionalized surfaces, gold surfaces covered by S-layers films (membrane proteins of bacteria), and then adsorption of zwitterionic liposomes. The solid/liquid interface was also studied in relation to hydrophobic functionality due to its surface microstructure (superhydrophobic surface). We use the atomic force microscopy, AFM, and confocal Raman techniques, parallel to our research with EQCM. In addition to the study of electric fields applied to interfaces, we also studied the macroscopic effects of the application of these fields to the dielectric liquids like water. We researched the phenomenon of liquid bridge using insulating dielectric aprotic liquids / Doutorado / Física / Doutor em Ciências / 2010/140031-3 / CNPQ

Depuis son invention en 1986, les microscopes à force atomique (AFM) ont été des puissants outils pour la caractérisation des matériaux et des propriétés des matériaux à l'échelle nanométrique. Cette thèse est entièrement dédiée à la mesure de l'interaction entre une sonde AFM et une surface avec une nouvelle technique AFM appelée Force Feedback Microscopy (FFM). La technique a été développée et utilisée pour l'étude d'échantillons biologiques. Le principe central de la technologie FFM est que la force totale moyenne appliquée à la pointe est égal à zéro. En conséquence, en présence d'une interaction pointe-échantillon, une force égale et contraire doit être appliquée à la pointe par une boucle de rétroaction. La force de réaction est ici appliquée à la pointe à travers le déplacement d'un petit élément piézoélectrique positionné à la base du levier AFM. La boucle de rétroaction permet d'éviter instabilités mécaniques tels que le saut au contact, permettant la mesure complète de la courbe d'interaction. En plus, il donne la possibilité de mesurer simultanément les parties élastique et inélastique de l'interaction. La technique a été appliquée à l'étude des interactions à l'interface solide/gaz, avec un intérêt particulier pour l'observation de la formation et de la rupture des ponts capillaires entre pointe et échantillon. Ensuite, on a focalisé notre attention aux interfaces solide/liquide. Dans ce contexte, courbes complètes de type DLVO sont caractérisées d'un point de vue élastique et dissipatif. Nous avons développé des nouveaux modes d'imagerie AFM pour l'étude des biomolécules. Images de phospholipides et de l'ADN à force constante ont été réalisées et certaines propriétés mécaniques comme le module de Young des échantillons ont été évaluées. En plus, nous avons réalisé une étude spectroscopique de l'élasticité et du coeffcient d'amortissement de l'interaction entre des cellules vivantes de type PC12 et une pointe AFM en nitrure de silicium. L'étude montre que le FFM est un instrument capable de mesurer l'interaction à des fréquences qui ne sont pas nécessairement liées aux résonances caractéristiques du levier. L'étude spectroscopique pourrait avoir dans le futur des applications importantes pour l'étude des biomolécules et des polymères.

Dans ce travail, l'adsorption de protéines globulaires sur des surfaces modifiées a été investiguée par ellipsométrie et par réflectivité de neutrons.<p><p>L'adsorption de myoglobine deutérée sur des monocouches hydrophobes d'OTS et de PS a été étudiée par réflectivité de neutrons pour des solutions de protéines de différentes concentrations (de 1 mg/ml à 0.01 mg/ml). A basse concentration, les protéines adsorbées se dénaturent et s'étalent sur le substrat hydrophobe et l'adsorption résulte en une fine couche dense en protéines. Sur le PS, les protéines s'étalent moins, ce qui est en accord avec la moindre hydrophobicité du PS. A haute concentration, une couche supplémentaire peu dénaturée est observée au-dessus de la première couche.<p><p>La cinétique d'adsorption primaire de HSA a été étudiée par ellipsométrie sur des brosses de PEG (Mw = 35700 Da) de différentes densités de greffage. Les résultats confirment que les brosses de PEG répriment l'adsorption de protéines. En outre, l'adsorption est très rapide sur le PS, tandis que sur les brosses, l'adsorption est plus lente. Le comportement à temps long de la quantité adsorbée Γ en fonction de la densité de greffage σ est en accord semi-quantitatif avec une théorie développée par Halperin et basée sur les différentes contributions à l'énergie libre d'une protéine adsorbée. Il a également été mis en évidence un régime pour lequel le taux d'adsorption dΓ/dt décroît exponentiellement avec la quantité de protéines adsorbées Γ.<p><p>L'adsorption de protéines (lysozyme, HSA et myoglobine) a ensuite été étudiée sur des brosses de PNIPAM en fonction des paramètres de la brosse et de la température. Les brosses ont été greffées par ATRP à partir d'une monocouche d'OEG (oligo éthylène glycol) silanisé contenant du brome comme initiateur. Il a été montré que l'adsorption primaire sur la surface de greffage est inférieure à 0.1 mg/m^2 et que l'adsorption ternaire dans la brosse, en dessous et au-dessus de la LCST, ne dépasse pas 1 mg/m^2 (~ 2% de fraction volumique en protéines). La résistance à l'adsorption a été associée à la présence d'une région hydrophile superficielle qui pourrait présenter une barrière cinétique à l'adsorption des protéines dans le cœur moins polaire de la brosse.<p><p>L'ensemble de ces résultats montre que les propriétés interfaciales du substrat jouent un rôle crucial dans les processus d'adsorption des protéines. <p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished