Rozprawy doktorskie na temat „Thin Film Solver”

Formation of zinc oxide nanostructured thin films at different temperatures on Al-coated silicon and lithium niobate substrates by hydrothermal method was presented. The comparison of morphology of nanostructured thin films formed by hydrothermal and electrodeposition method was carried out. The opportunity to use the hydrothermal method instead electrodeposition to obtain nanostructured films on a conductive layer was shown. The dependence of morphology and crystallinity from growth temperature was established using scanning electron microscopy and X-ray diffractometry. The application of synthesized films as sensing layer of acoustic wave based and electrochemical sensors could enhance its sensitivity to pollutants in gas or liquid phases by an active area increasing. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35191

Thesis (M.S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Tummala Rao; Committee Member: Pulugurtha Raj; Committee Member: Wong C P. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Mesoporous TiO2 thin film has been considered as a benchmark material in the applications of dye sensitised solar cells (DSSCs) due to a combination of the physical properties that are inherent to the metal oxide and its particular structuring, in addition to its chemical stability and commercial availability. For DSSCs, a more important functionality of mesoporous TiO2 thin films is their extremely high surface and internal surface areas, resulting in high adsorption of dye molecules. However, a major drawback of fabrication of mesoporous TiO2 thin films is its high-temperature furnace sintering at 450à ̄‚°C-500à ̄‚°C for 30 min. The high-temperature process prevents the possibility of integrating different electro-optical devices on the same substrate, and the sintering time required would be a hurdle for potentially rapid manufacturing of mesoporous metal oxide thin films for DSSCs. This thesis demonstrates for the first time the use of a fibre laser with a wavelength of 1070 nm and a pulse width of milliseconds for generation of 1) mesoporous nanocrystalline (nc) TiO2 thin films on ITO coated glass, and 2) compact TiO2 layer and mesoporous TiO2 film on ITO coated glass. The first one was achieved by complete vaporisation of organic binder and inter-connection of TiO2 nanoparticles; and the second one was achieved by full crystallisation of TiO2 precursor to form the compact TiO2 layer and the same sintering process described above. Both processes were one-step, and achieved by stationary laser beam irradiation of 1 minute, compared with 30 min for furnace-sintering to form a mesoporous TiO2 film, and 2 h for two-step furnace treatment to form compact layer and mesoporous film on ITO glass. No thermally damaging of the ITO layers and the glass substrates was observed. The DSSC with the laser-sintered TiO2 photoanode at the optimised laser processing condition of 85 W/cm2 and 100 ms/50 ms pulse mode reached higher power conversion efficiency (PCE) of 3.20% for the TiO2 film thickness of 6 à ̄­m compared with 2.99% for the furnace-sintered; the DSSC with the laser-treated compact TiO2 layer and mesoporous TiO2 film on ITO glass at the optimised laser treatment condition of 85 W/cm2 and 125 ms/25 ms, reached 5.76% compared to 4.83% with the furnace-treated. Electrochemical impedance spectroscopy (EIS) studies revealed that the laser sintering effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films. It is believed that the use of the fibre laser with over 40% wall-plug efficiency offers an economically-feasible, industrial viable solution to the major challenge of rapid fabrication of large scale, mass production of mesoporous metal oxide thin film based solar energy systems, potentially for perovskite and monolithic tandem solar cells, in the future. Another part of the thesis presents a detailed investigation on the improvement of photovoltaic performance of furnace-sintered TiO2 films on ITO-coated glass using an excimer laser with a wavelength of 248 nm and possesses a rectangular beam profile and has a full width at half maximum (FWHM) pulse duration of 13-20 ns. This was achieved by modifying the surface of the furnace-sintered TiO2 films to increase the roughness, which led to increased optical absorbance via light-trapping. The laser process was carried out with variation of laser fluence and number of pulses per unit area. Under the optimised laser fluence of 34 mJ/cm2 and number of pulses of 50, the DSSC with the laser-modified TiO2 photoanode showed a high power conversion efficiency of 2.99% than 2.10% without the laser treatment. EIS studies showed that the films modified under the optimised laser parameter effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films.

Second generation solar cells based on thin film semiconductors emerged as a result of the past ten years of intense research in the thin film preparation technology. Thin film solar cell technology can be cost effective as it uses comparatively cheap materials suitable for solar building integration. Chemical Vapour Deposition (CVD) is a well-known method for the deposition of high quality thin films. This thesis describes the synthesis of novel tin(II)dithiocarbamate [Sn(S2CNEt2)2] and bis(diphenylphosphinediselenoato) tin(II) [Sn(Ph2PSe2)2] and these complexes as single source precursor for the deposition of SnS and SnSe and by using the combination of [Sn(Ph2PSe2)2] with [Cu(acac)2], Cu2SnSe3 thin films were deposited by AACVD. By using suitable combinations of metal complexes ([nBu2Sn(S2CNEt2)2], [Cu(S2CNEt2)2] [Zn(S2CNEt2)2] [Zn(Se2CNEt2)2] [Zn(acac)2], [Sn(OAc)4], [Cu(PPh3){Ph2P(Se)NP(Se)Ph2}] thin films and nanocomposites of CZTS, CFTS, CZTSe, CFTSe, CZFTS, , CZFTSe, CZTSSE, CFTSSe and CZFTSSe were prepared. The effect of precursor concentration and deposition temperature on the structure, morphology and composition of the thin films were studied in detail using by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and elemental mapping. This thesis addressing the structural inhomogeneity, control of growth and material characterization is expected to yield closer performance parity between CZTS-Se and CIGS solar cells. A series of systematic experiments were carried out. Through AACVD and simple solvothermal methods CZFTS nanoparticles and thin films were prepared. The simple, potentially, low-cost nature of the CZTS nanoparticles and the enhancement of charge carrier mobility achieved suggest that these nanoparticles have potential in the improvement of OFETs and perhaps other organic electronic devices.

The orientation changes of perpendicular cylindrical microdomains in polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) thin films upon annealing in different solvent vapors were investigated by in situ grazing incidence small-angle X-ray scattering (GISAXS) and ex situ scanning force microscopy (SFM). The swelling of P4VP perpendicular cylinders (C⊥) in chloroform, a non-selective solvent vapor, leads to the reorientation to in-plane cylinders through a disordered state in a particular kinetic pathway in the phase diagram upon drying. On the other hand, the swelling of the P4VP perpendicular cylinders in a selective solvent vapor (i.e., 1,4-dioxane) induces a morphological transition from cylindrical to ellipsoidal as a transient structure to spherical microdomains; subsequent solvent evaporation resulted in shrinkage of the matrix in the vertical direction, merging the ellipsoidal domains into the perpendicularly aligned cylinders. In this paper, we have discussed the mechanism based on the selectivity of the solvent to the constituting blocks that is mainly responsible for the orientation changes.

Organic electronics based on π-conjugated semi-conductor raises new technology, such as organic film transistors, e-paper, and organic photovoltaic cells that can be implemented cost-effectively on large-area applications. Currently, the device performance is limited by low charge carrier mobility. Poly(3-hexylthiophene) (P3HT) and organic field effect transistors (OFET) is used as a model to investigate morphology of the organic film and corresponding electronic properties. In this thesis, processing parameters such as boiling points and solubility are controlled to impact the micro- and macro-morphology of the film to enhance the charge transport of the device. Alternative approach to improve ordering of polymer chains and increase in charge transport without post-treatment of P3HT solution is studied. The addition of high boiling good solvent to the relatively low boiling main solvent forms ordered packing of π-conjugated polymers during the deposition process. We show that addition of 1% of dichlorobenzene (DCB) to the chloroform based P3HT solution was sufficient to improve wetting and molecular structures of the film to increase carrier mobility. Systematic study of solvent-assisted re-annealing technique, which has potential application in OFET encapsulation and fabrication of top-contact OFET, is conducted to improve mobility of OFET, and, to suggest a cost-effective processing condition suitable for industrial application. Three process parameters: boiling point, polarity, and solubility are investigated to further understand the trend of film response to the solvent-assisted technique. We report the high boiling non-polar solvents with relatively high RED values promote highest improvement in molecular packing and formulate crystalline structure of the thin film, which increases the device performance.

Tethered polymer layers at solid-fluid interfaces are used widely in a variety of surface science applications. Although many of these applications require exposure to dynamic flow conditions, flow field penetration into densely grafted polymer brushes, is still a question open to debate despite the fact that it is a fundamental process crucial to mass transport through these polymer films. Although most theoretical work has indicated flow field penetration into polymer films, with varying predicted penetration depths predicted, the limited experimental attempts to investigate this phenomenon have resulted in inconsistent conclusions due to lack of a proper analytical method. To help resolve this controversy, in this Dissertation, a new spectroscopic method, FRET-TIRFM, based on a combination of Förster resonance energy transfer (FRET) and total internal reflectance fluorescence microscopy (TIRFM), is developed to provide the first direct, quantitative measurements on flow field penetration by measuring linear diffusion coefficients of small molecules through densely grafted, thin poly(N-isopropylacryl-amide) (pNIPAM) films. Decay curves from FRET of the acceptor with a donor covalently attached at the substrate surface were fit to a combined Taylor-Aris-Fickian diffusion model to obtain apparent linear diffusion coefficients of the acceptor molecules for different flow rates. These values can then be used to obtain quantitative estimates of flow field penetration depths. For a pNIPAM surface of 110 nm dry thickness, with a 0.6 chain/nm² grafting density, apparent diffusion coefficients ranging from 1.9-9.1 × 10-12 cm²/s were observed for flow rates ranging from 100 to 3000 μL/min. This increase in apparent diffusion coefficient with applied fluid flow rate is indicative of flow field penetration of the polymer film. The depth of penetration of the flow field is estimated to range from ~6% of the polymer film thickness to ~57% of the film thickness in going from 100 to 3000 μL/min flow rate of a good solvent. Factors other than flow rate that may impact flow field penetration were also investigated using this new FRET-TIRFM method. Solvent quality and polymer brush grafting density are the two most important parameters due to the fact that they influence changes in tethered polymer chain conformation. This work demonstrates that polymer films are most penetrable in a good solvent and least penetrable in a poor solvent under identical flow conditions. These findings are consistent with polymer chain conformational changes going from extended brushes to compact globules. For flow rates ranging from 100 to 3000 μL/min, flow field penetration depth ranges from ~6% of the film thickness to ~57% of film thickness for a good solvent compared to ~4% to ~19% for a poor solvent. Thus, by simply changing solvent quality from good to poor, flow field penetration decreases by about 38%. Grafting density has a less pronounced effect than solvent quality on penetration depth, probably due to the small range of grafting densities chosen for study. However, a roughly 10-20% difference in penetration depth was observed between high density (0.60 chain/nm²) and low density (0.27 chain/nm²) pNIPAM surfaces in the same solvent. Changes in grafting density have a less significant impact in a good solvent compared to a poor solvent. This is most likely caused by the fact that grafting density impacts polymer chain conformation mainly through polymer-polymer repulsion, which becomes less significant in a solvent that better solvates the polymer. For the two extreme cases studied here at flow rates ranging from 100 to 3000 μL/min, the penetration depth is estimated to range from ~4-19% of the original solvent-swollen film thickness for high density pNIPAM films in a poor solvent and from ~7-67% for low density films in a good solvent. One important assumption that underlies all of this work is that the dominant mass transport mechanism for small molecules in dense polymer brushes is diffusion. This assumption was further validated through the use of two different small molecule quenchers, RhB and 2-nitrobenzylalcohol. These molecules are significantly different in size, charge, and structure, and operate by different quenching mechanisms. Despite these differences, the results for flow field penetration are statistically the same for both. These observations validate the assumption of diffusive mass transport in these films.

Dans un premier temps, ce travail a concerné la réalisation de microparticules chargées en agent antimicrobien suivant la technique de microencapsulation par évaporation de solvant en émulsion simple. Différentes morphologies ont été obtenues avec des microparticules éloignées du standard lisse, démontrant des cicatrices et des défauts, de la rugosité ou encore des trous. Les paramètres ainsi que les mécanismes physico-chimiques responsables des dégradations morphologiques ont été identifiés et discutés. Il a été démontré que les paramètres de formulation tels que la masse et masse molaire du polymère ou encore la présence de tensioactifs ainsi que les paramètres du procédé tels que la force et la vitesse de cisaillement modifient l'état de surface finale des microparticules. Ce travail a notamment prouvé qu'il existe une compétition entre la cinétique d'évaporation du solvant et la vitesse de coalescence des gouttelettes d'émulsion qui est à l'origine des dégradations morphologiques. Suite à cette étude, les microsphères résultantes contenant de l'alcool phényléthylique ont été enduites à la surface du conditionnement primaire polyoléfine sous forme de films minces de différentes épaisseurs grâce à la technique de revêtement par immersion. L'introduction de microparticules au sein du liant ralentit la diffusion de l'agent antimicrobien en augmentant le nombre de matrices polymériques à traverser pour atteindre le milieu extérieur. La réalisation de telles couches a permis d'obtenir des libérations sur des périodes supérieures à au moins trois mois ce qui est 15 fois plus important que celles obtenues pour l'agent antimicrobien non encapsulé. Ce travail de thèse a également étudié l'activité antimicrobienne de l'alcool phényléthylique au sein d'une émulsion. Il a été mesuré le partage de l'alcool phényléthylique entre les phases aqueuse, huileuse et micellaire de l'émulsion. Les résultats obtenus ont permis de développer un modèle mathématique calculant la fraction en agent antimicrobien libre présent en solution aqueuse. Ce dernier a été corrélé à des dosages de l'émulsion et des mesures microbiologiques utilisant les cinq souches microbiennes du challenge test sur 14 jours. Ainsi, il a été démontré que les calculs permettent de prédire la concentration en conservateur nécessaire afin d'assurer la protection antimicrobienne des formulations. Cette étude a notamment prouvé que la quantité d'alcool phényléthylique nécessaire à la conservation des formulations est respectivement 1,6 et 4,3 fois plus importante dans une solution micellaire et une émulsion par rapport à une solution aqueuse
First, this work focused on the formulation of microparticles loaded with antimicrobial agent using the emulsion/solvent evaporation method. Several morphologies have been obtained with nonsmooth microparticles characterized by scars and defects, roughness and holes. The parameters and the physico-chemical mechanisms involved in these morphological deteriorations have been identified and discussed. It has been shown that the formulation and processing parameters as the polymer mass and molar mass, the surfactant as well as the speed and shear rate of the propeller play a key role in the final microparticles surface states. This study proved that there is a competition between solvent evaporation and the coalescence of emulsion droplets which is responsible for the morphological degradations. Following this study, the resulting microspheres loaded with phenylethyl alcohol were dispersed in a binder and coated as thin films of various thicknesses by the dip-coating method at the polyolefin surface. It has been measured that the use of microparticles slows the antimicrobial agent diffusion by increasing the number of polymeric matrices that have to be crossed in order to reach the external medium. Such thin films resulted in an antimicrobial agent delivery up to 3 months which is 15 times higher than the delivery obtained for the non-encapsulated antimicrobial agent. The antimicrobial activity of the phenylethyl alcohol in an emulsion has also been investigated. The phenylethyl alcohol partition between the water phase, the oil phase and the micellar phase of an emulsion has been measured. These results led to the development of a mathematical model calculating the fraction of free antimicrobial agent present in the aqueous phase. It has been correlated with emulsion dosages and microbiological measurements using the five microorganisms of the challenge test during 14 days. It has been demonstrated that calculations enable the prediction of the antimicrobial agent concentration needed to ensure the antimicrobial protection. In particular, this work proved that the phenylethyl alcohol quantity necessary for antimicrobial protection is respectively 1.6 and 4.3 times higher for a micellar solution and an emulsion compared to an aqueous solution

Le développement à grande échelle des microbatteries pour des applications diverses comme l’alimentation de secours de certains composants électroniques dans les téléphones portables nécessite une compatibilité avec le procédé de solder-reflow employé dans le domaine de la microélectronique. Dans ce contexte, cette étude porte sur la mise au point d’un nouveau procédé de réalisation de couches minces d’oxysulfures de titane lithiés (LixTiOySz) pour une utilisation en tant qu’électrode positive dans une microbatterie Li-ion. Tout d’abord ce travail a débuté par la synthèse et la caractérisation de plusieurs compositions de sulfures de titane lithiés à l’état massif par réaction en solution de TiS2 ou TiS3 avec le n-butyllithium mais aussi par réaction à l’état solide à haute température entre les précurseurs TiS2, Li2S et Ti. Par la suite, des couches minces de LixTiOySz ont été déposées par pulvérisation cathodique radiofréquence à effet magnétron de cibles réalisées à partir des matériaux lithiés à l’état massif. La composition chimique de ces dépôts dépend de celle de la cible utilisée ce qui permet d’obtenir des couches plus ou moins riches en lithium et en soufre. En revanche, elles sont toutes très mal cristallisées, denses et elles ne présentent pas de structuration particulière. Enfin, les caractérisations électrochimiques des dépôts de LixTiOySz, à la fois en électrolyte liquide et solide, ont permis de mettre en évidence une corrélation entre leur composition chimique et leur comportement électrochimique. Globalement, ces dernières sont performantes, compatibles avec le solder-reflow et donc tout à fait intéressante pour l’application
Large-scale development of microbatteries for various applications such as back-up power sources for cell phone electronic components needs suitability with reflowing process that is often used in microelectronic. Here we report on the development of a new realization process to produce lithiated titanium oxysulfides (LixTiOySz) thin films for use as positive electrode in Li-ion microbatteries. First of all, this work began with synthesis and characterization of several lithiated titanium sulfides compounds prepared by reaction between TiS2 or TiS3 with n-butyllithium but also by solid state reaction at high temperature between TiS2, Li2S and Ti. Then, LixTiOySz thin films were sputtered by magnetron effect radio-frequency sputtering from targets made of lithiated materials previously synthesized. The chemical composition of those films depends on the target one and allows obtaining thin films with different lithium and sulfur contents. In contrast, they are all amorphous, dense and they don’t have a morphological structuration. Finally, electrochemical characterizations of thin films, both in liquid and solid electrolyte, have highlighted a correlation between their chemical composition and their electrochemical behavior. Taken as a whole, LixTiOySz thin films are powerful, suitable with reflowing process and thus very interesting for the application

Surface chemical gradients are materials that exhibit continuous, gradually varying chemical or physical properties along and across the length of a substrate. As a result, each point on the gradient surface can represent an individual sample. They are broadly classified as chemical and physical gradients depending upon the properties that the gradient exhibits. A physical gradient involves a continuous variation of physical properties such as surface roughness and film porosity on the micrometer scale. Chemical gradients involve a gradual variation of chemical properties such as polarity, acidity and basicity, etc. Such gradients have found various applications in cell adhesion, nanoparticle absorption, etc. Because of the multitude of potential applications of acid-base gradient materials in separation science and biological applications, the main work of this dissertation work is focused on the preparation and fundamental, molecular level investigation of acid-base gradients on siloxane surfaces. In this work, we focused on the preparation and characterization of surface charge gradients. Charged gradients are gradients that contain charged functional groups that are spatially distributed along the length of the substrate. They can interact with each other or with other species in solution by electrostatic interactions. They can also play a key role in governing the interaction of macromolecules and bacteria on surfaces, the wetting of surfaces, the layer-by-layer (LBL) assembly of thin films, reactions in catalysis, and the separation of charged species in chromatography. Therefore, understanding localized interactions between surface functional groups and charged species in solution are particularly relevant to the development of surfaces resistant to biofouling, antimicrobial surfaces, catalytic surfaces, multi-layered composite thin films, and imprinted surfaces for chemical sensing and separations. Thus, it is of great of interest to develop methodologies to create and study heterogeneous and homogeneous charged surfaces with well-defined properties. There have been several different methods developed for the preparation of charged gradients. First a chemical gradient is prepared and then the chemical gradient is converted to charged gradient by a chemical approach. Silane-based methods for the preparation of chemical gradients are among those that are widely used because of the straightforwardness of the chemistry involved and also the availability of silanes with various chemical functionalities. A few of these silane based approaches such as the vapor-diffusion method and liquid diffusion method have been used for various applications so far. Most of these methods are only able to prepare surface chemical gradients for a specific application mainly because of their limitations in terms of gradient-length scale and chemistry involved. In this work, we used a procedure already developed in our lab to prepare chemical gradients from different functionalized alkoxysilanes; we call this procedure the ‘controlled-rate infusion method (CRI)’. This method can be adapted to different substrates and can form gradients at various length-scales, such as few hundred microns to tens of centimeters. The CRI method involves the infusion of an organoalkoxysilane solution into a container with a substrate mounted vertically so that time-dependent exposure along the substrate forms a gradient in chemical functionality from bottom to the top. The most important attribute of this method is that the local steepness of the gradient can be systematically controlled by simply changing the rate of infusion. The steepness of the gradient can also be changed at predefined positions along its length by programming the rate of infusion. CRI can also be used to prepare gradients containing multiple functionalities, termed multicomponent chemical gradients. The different chemical functionalities can be oriented in different directions to produce gradients where functionalities can be oriented along the same or opposed directions producing aligned and opposed multicomponent chemical gradients, respectively. In this work, the multicomponent gradients were converted to charge gradients via chemical reaction with 30% H2O2. Using controlled rate infusion and this technique, aligned or opposed multicomponent charge gradients containing NH3+, SO3- and SiO- groups were prepared. By infusing 3-aminopropyltriethoxysilane (APTEOS) and 3-mercaptopropyltriethoxysilane (MPTMOS) in the same or opposed direction, gradients containing charged species in different locations relative to each other along the length of the substrate were made. The gradient properties in each case were different and correlated to the way they were prepared i.e., where the gradients were oriented in an aligned or opposed fashion. Surface wettability and local surface charge, etc were found to be entirely different depending on the type of charge gradients (aligned and opposed). In another example, SiO- and NH3+ opposed gradients were prepared by infusing APTEOS on different base layers prepared from tetramethoxysilane (TMOS), phenyltrimethoxysilane (PTMOS), dimethyldimethoxysilane (DMDMOS) or octyltrimethoxysilane (OTMOS) followed by protonation of the surface amines. The gradient profiles and surface wettability were found to be independent of each other and dependent of the type of the base layer. In summary, this dissertation work focuses mainly on the preparation of multicomponent charge gradients and their molecular level characterization by a multitude of different analytical methods including XPS spectroscopy, tapping mode atomic force microscopy (TM-AFM), zeta potential measurement, and SCA and DCA measurements. CRI has incredible flexibility and adaptability, which was confirmed by extending it to different siloxane base films and creating gradients with different functionalities. Multicomponent charge gradients containing acid and base functionalities can be prepared and optimized for and acid base catalysis reactions such Michael addition as well as aldol, Henry, and Knoevenagel condensations.

L’étude s’inscrit dans le cadre d’un projet Européen 3Dice, dont l’objectif est d’améliorer la fiabilité mécanique d’un composant microélectronique innovant. La miniaturisation du composant induit des difficultés lors de la caractérisation mécanique. Le développement de méthodes de caractérisation est nécessaire. La flexibilité du composant microélectronique est de plus en plus demandée. Les joints de connexion subissent souvent un pré-chargement. La tolérance du joint aux pré-chargements est intéressante à étudier. Cette thèse s’est déroulée autour de ces deux problématiques. Les méthodes de caractérisation de la couche mince métallique, la résine chargée en silice et le joint de connexion sont développées. L’étude de la fatigue du joint de connexion est effectuée
This work is a part of an European fund project ‘3Dice’ which aims to improve the mechanical reliability of an innovated microelectronic product. The miniaturization of microelectronic component causes the difficulties to determine mechanical properties of materials involved. The development of experimental methods for microelectronic materials’ characterization is necessary. The flexibility of the products is an additional requirement recently in microelectronic field. The solder joint’s tolerance to the pre-load is interesting to investigate. The thesis is carried out based on these two topics. The characterization methods of thin film, resin with fillers and solder joint are developed. The fatigue behavior of solder joint is investigated under different displacement ratios

Dans cette étude, nous nous intéressons particulièrement au séchage d'une enduction (colle à eau) soumise à des contraintes radiatives et convectives. L'apport d'énergie nécessaire à la vaporisation du solvant provient essentiellement d'un émetteur de rayonnement infrarouge. Dans un premier temps, nous avons procédé à la caractérisation physico-chimique du produit, en l'occurrence une colle à papier. Quelques propriétés intrinsèques ont été déterminées au laboratoire pour être utilisées dans une modélisation des transferts de matière et de chaleur et enfin le choix de l'émetteur infrarouge utilisé dans toutes nos opérations de séchage. Dans une deuxième partie, l'émetteur infrarouge a fait l'objet d'une caractérisation thermique. La technique utilisée est la thermographie infrarouge pour déterminer le champ de température de la plaque. A partir du champ de température, nous avons résolu numériquement l'équation inverse du bilan énergétique pour déterminer les densités de flux. L'analyse des résultats expérimentaux de séchage nous a permis de vérifier la validité du modèle, purement diffusif, décrivant d'une manière satisfaisante le comportement de la colle. Les résultats de caractérisation de l'émetteur nous ont permis de déterminer la disposition géométrique de plusieurs émetteurs afin d'avoir un séchage relativement homogène sur tout le produit. L'ensemble des résultats est utilisé pour concevoir une installation de séchage par rayonnement infrarouge qui sera expérimentée sur site industriel.

Des masques polymères à porosité contrôlée sont fabriqués à partir de films minces de copolymères à blocs auto-organisés polystyène-b-polylactide (PS-PLA) et polystyrène-b-poly(méthacrylate de méthyle) (PS-PMMA). Les films doivent être réorganisés grâce à une exposition aux vapeurs de solvant (THF ou DCE) pour obtenir des cylindres perpendiculaires à la surface, dans le volume et arrangés de façon hexagonale à longue distance. L'extraction sélective des domaines minoritaires conduit alors à des films minces poreux de PS. La mise en place de nouvelles techniques de caractérisation (analyse des images AFM, analyse MEB de répliques de système poreux, ellipso-porosimétrie) a permis d'évaluer l'influence de nombreux paramètres (nature du substrat, épaisseur du film, mode de dépôt, nature du solvant, temps et mode d'exposition aux vapeurs du solvant, ...) sur la morphologie des films (surface, interface substrat/film, volume) et sur la cinétique de réorganisation. Des mélanges de copolymères à blocs A-B et d'homopolymères C (PS-PMMA/PLA, PS-PLA/PMMA, PS-PLA/PEO, PS-PEO/PLA, PS-PEO/PMMA, PS-PMMA/PEO) sont également étudiés. L'ajout d'homopolymères permet dans certains cas, d'améliorer la réorganisation des films de copolymères à blocs. Il permet également une augmentation des tailles caractéristiques du système. L'homopolymère C se localise au centre des domaines du bloc minoritaire B si χA-C> χB-C et χA-C > χA-B. Par exemple, dans le cas du mélange PS-PMMA/PLA, des cylindres perpendiculaires à la surface et organisés de façon hexagonale sont observés après exposition aux vapeurs de THF avec incorporation des domaines d'homopolymères PLA au centre des domaines de PMMA.

Etude des processus de relaxation dephasante (t2) de molecules de colorant (cresyl violet) dissoutes dans 1 film mince de colle cellulosique en fonction de la temperature. Utilisation d'une technique d'optique non lineaire, de type melange a 4 ondes: la spectroscopie coherente en lumiere incoherente. Afin d'interpreter les resultats, mise au point d'un 1er modele assimilant le niveau excite a un continuum d'etats vibrationnels, calcul considere comme etape preliminaire d'un calcul plus sophistique. Elaboration d'un 2eme modele decrivant l'action d'une excitation non lineaire sur un systeme a 2 niveaux en prenant en consideration les effets de bord des bande et d'ecart a la resonance. 2 valeurs du parametre t2 en fonction de la temperature sont deduites

Matter at small scales is not a continuum. Whenever we are dealing with phenomena which have disparate time and length scales, we have to rely on multiscale modelling approach in order to capture the complete physics. A common scenario in multiphase flow simulations is the formation of thin fluid films in between colliding fluid masses or between a fluid mass and a surface. These films are very thin (O(100nm)) and during the Direct Numerical Simulations (DNS) of multiphase flows it is impractical to resolve their thickness fully due to highly disparate time and length scales. Our approach here is to couple a complex thin film model derived analytically to a finite volume solver (and can also be used for standard interface capturing technique like Volume of Fluid method) so that we can capture the formation and evolution of thin films which come into existence in the sub-grid thickness. In the present work, we have formulated a thin film model where viscous forces, surface tension forces and long-range intermolecular forces play the dominant role. Since the modelled equation is highly stiff in nature and these films in realistic scenarios are spread over a large area, we have developed a parallel solver for solving the resulting set of equations. We propose an algorithm to couple the thin film model to a finite volume solver. First, we study a simple square domain containing a single phase, undergoing a shear flow with periodic flow in the horizontal direction, that is simulated using finite volume method coupled to a complex thin film model. Next, we develop a robust multiphase flow solver using Coupled Level-set Volume of Fluid method as the interface capturing technique and propose an algorithm to couple the rigorously validated multiphase solver to the thin film model.

abstract: Moore's law has been the most important driving force for the tremendous progress of semiconductor industry. With time the transistors which form the fundamental building block of any integrated circuit have been shrinking in size leading to smaller and faster electronic devices.As the devices scale down thermal effects and the short channel effects become the important deciding factors in determining transistor architecture.SOI (Silicon on Insulator) devices have been excellent alternative to planar MOSFET for ultimate CMOS scaling since they mitigate short channel effects. Hence as a part of thesis we tried to study the benefits of the SOI technology especially for lower technology nodes when the channel thickness reduces down to sub 10nm regime. This work tries to explore the effects of structural confinement due to reduced channel thickness on the electrostatic behavior of DG SOI MOSFET. DG SOI MOSFET form the Qfinfet which is an alternative to existing Finfet structure. Qfinfet was proposed and patented by the Finscale Inc for sub 10nm technology nodes. As part of MS Thesis we developed electrostatic simulator for DG SOI devices by implementing the self consistent full band Schrodinger Poisson solver. We used the Empirical Pseudopotential method in conjunction with supercell approach to solve the Schrodinger Equation. EPM was chosen because it has few empirical parameters which give us good accuracy for experimental results. Also EPM is computationally less expensive as compared to the atomistic methods like DFT(Density functional theory) and NEGF (Non-equilibrium Green's function). In our workwe considered two crystallographic orientations of Si,namely [100] and [110].
Dissertation/Thesis
Masters Thesis Electrical Engineering 2016

碩士
國立中興大學
化學工程學系所
95
SnPb olders have been used as the principal joining materials in electronic packaging due to many well-known advantages, like low cost, good wettability, and proper melting point. However, the usage of Pb in electronic products has a serious concern because the toxicity of Pb may cause detrimental effects on environment and human health. Therefore, searching for a proper candidate to replace SnPb solders is currently an urgent issue in electronic industry. Various Pb-free solders have been proposed, where eutectic SnZn alloy (Sn-9 wt% Zn) is one of the most potential candidates because of its lower cost and a melting point (198.5 ℃) that is closer to that of the conventional eutectic SnPb alloy (183 ℃). Interfacial reactions between solders and metallic substrates have been an important subject in electronic packaging, However, the Cu substrate is usually in the form of thin film in advanced electronic packaging, such as in the under-bump-metallization(UBM) of a flip-chip joint . The major difference between bulk and thin-film substrates is that the availability of the component that is involved in the interfacial reaction is limited for the thin-film substrate but is almost infinite for the bulk one. In this present study, two types of Cu substrates were used. Interfacial reactions between eutectic SnZn solder and bulk or thin-film Cu substrates are investigated and compared. The thicknesses of bulk and thin-film Cu substrates are 0.5 mm and 4000 Å、3 μm、6 μm、10 μm, respectively. Different dominant reaction products and interfacial microstructures are observed in these two types of interfacial reactions. In the bulk Cu、3 μm and 6 μm type, the Cu5Zn8 phase is the dominant reaction product under reflow and solid-state annealing. However, the CuZn5 phase becomes the dominant reaction product in the 4000 Å and 3 μm thin-film Cu type. The Cu5Zn8 phase in the bulk Cu type remains uniform microstructure after reflow. But after solid-state annealing, the Cu5Zn8 phase in the bulk Cu type fractures and the Cu6Sn5 and Cu3Sn phases are formed at the Cu5Zn8/Cu interface. The CuZn5 phase in the thin-film Cu type ripens after reflow and the phase morphology is transformed from uniform layer into separated scallops. In-situ observation of the interfacial microstructure after solid-state annealing reveals that prominent deformation occurs in the solder region close to the interface in the bulk Cu type.While in the 4000 Å thin-film Cu type, the CuZn5 grain is extruded out of the interface.

碩士
國立交通大學
材料科學與工程系所
93
Electroless plating technique was utilized to prepare the cobalt-phosphorous (Co-P) thin film to serve as the diffusion barrier layer of lead-tin (Pb-Sn) solder. Co-P/solder interfacial reactions were characterized in order to evaluate the feasibility of electroless Co-P layer as the under bump metallurgy (UBM) for flip-chip bonding. After depositing Ti/Cu layer on Si wafer, we immersed the samples in the electroless plating bath for 5 min to obtain the Co-P layer with thickness about 600 nm. The analyses using Auger electron spectroscopy (AES) and energy dispersive spectrometer (EDX) indicated that the phosphorous contents in Co-P films decreases with the increase of film thickness and the average contents are higher than 10 at.% for the specimens prepared in this work. X-ray diffraction (XRD) analysis revealed that the electroless Co-P layers are nanocrystalline granular structure. Cross-sectional scanning electron microscopy (SEM) was adopted to examine the interfacial reactions of electroless Co-P layer and Pb-Sn solder. For the samples annealed at 250�aC in N2 ambient, the thickness of intermetallic compounds (IMCs) at Co-P/solder interface increased with the time of thermal treatment. However, there was no distinct raise of thickness of IMCs after 6-hr annealing. The EDX line scan analysis revealed that during the interdiffusion of Sn, Cu, and Co, the Sn remains at the interface of Co-P layer after the Cu wetting layer was totally consumed. The fact that Sn and Cu underlayer could not penetrate Co-P layer after 250�aC, 24-hr annealing evidenced that the Co-P layer may serve as a good diffusion barrier of UBM structure for both Cu interconnect and solder bumping for Cu-ICs. The excellent diffusion retardation ability of Co-P should result from the amorphous nature provided by the high-phosphorous content in Co layer.

碩士
國立中興大學
材料科學與工程學系所
104
The intermetallic compounds SnTe formed at interfaces between thermoelectric materials (n-type Bi2Te2.55Se0.45 and p-type Bi0.4Sb1.6Te3) and lead-free solders (Sn-Cu) after annealing at 200 oC. The SnTe formed influences the mechanical properties of the joint and the reliability of the thermoelectric materials. Although nickel is commonly used as a diffusion barrier in commercial thermoelectric modules, several studies have verified the Ni migrates to thermoelectric materials during cycles and causes a loss in efficacy during high temperature. In this research, the influence of cobalt thin film plating to p-type and n-type thermoelectric materials on the interface characterization and thermoelectric properties is studied using a electroplating. Solder was connected with cobalt by reflow at 250 oC after cobalt film plating to substrates to serve as the diffusion barrier, and interfacial reaction in the solder joints aged at 200 oC for varies times was systematically investigated. The CoSn3 compound formed at the interface of Sn-Cu/Co/Bi2Te2.55Se0.45 and Sn-Cu/Co/Bi0.4Sb1.6Te3. The results indicate that cobalt thin film could be a suitable diffusion barrier for Bi2Te2.55Se0.45, but not used for Bi0.4Sb1.6Te3. According to some literature and results that try plating Co-Se thin film to strengthen the barrier effect for applying to Bi0.4Sb1.6Te3.

Thin film nanostructures may be defined as assemblies, arrays, or randomly distributed nanoparticles, nanowires, or nanotubes, which together form a layer of materials supported on a substrate surface. Because such nanostructures are supported on a substrate surface, their potential applications cover a wide area in optical, magnetic, electrochemical, electromagnetic, and optoelectronic devices. The focus of the present thesis is the development of methodologies to grow certain thin film nanostructures of some transition metal oxides (TMOs), including copper oxides and LixCoO2, through CVD, sol-gel, and electromagnetic radiation-mediated approaches. The work towards this objective can be divided into three parts: first, the design, synthesis, and systematic identification of novel metalorganic precursors of copper (monometallic) and Li and Co (bimetallic); second, the growth of nanostructured oxides thin films using these precursors; and third, the application of electromagnetic radiation to control or tailor the growth of as grown nanostructures. The underlying growth mechanisms substantiated by appropriate evidence have been put forward, wherever found relevant and intriguing. It may be added that the principal objective of the work reported here has been to explore the several ideas noted above and examine possibilities, rather than to study any specific one of them in significant detail. It is hoped earnestly that this has been accomplished to a reasonable extent. Chapter 1 reviews briefly the reports available in the literature on three specific methods of growing thin films nanostructures, namely chemical vapour deposition, sol-gel processing and light-induced approach. The objective of this chapter has been to provide the background of the work done in the thesis, and is substantiated with a number of illustrative examples. Some of the fundamental concepts involved, viz., plasmons and excitons, have been defined with illustration wherever found relevant in the context of the work. Chapter 2 describes the various techniques used for synthesis and characterisation of the metalorganic complexes as well as of the thin films. This chapters covers mostly experimental details, with brief descriptions of the working principles of the analytical procedures adopted, namely, infrared spectroscopy, mass spectroscopy, elemental analysis, and thermal analysis for characterisation of the metalorganic complexes. This is followed by a similarly brief account of techniques employed to characterize the thin films prepared in this work, viz., glancing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), electrostatic force microscopy (EFM), transmission electron microscopy (TEM), glancing incidence infra-red spectroscopy (GIIR) and, UV-visible spectroscopy. The metalorganic chemical vapour deposition (MOCVD) systems built in house and used for growth of films are described in detail. The topics in the different sections of the chapter are accompanied by pertinent diagrams. Chapter 3 deals with the design, synthesis and characterisation of novel polynuclear complexes of copper and cobalt. Keeping in mind the various advantages such as low toxicity, ease of synthesis, non-pyrophoricity, and low temperature volatility, of environmentally benign complexes based on biologically compatible such as triethanolamine, diethanolamine, the objective has been to synthesize complexes containing triethanolamine and diethanolamine of transition metals such as cobalt and copper, and to investigate their applicability in MOCVD processes as a novel class of precursors. With the notion of ‘better’ and efficient design of precursors, an attempt has been made, through a semi-empirical modeling, to understand the correlation between volatility and various intrinsic molecular parameters such as lattice energy, vibrational-rotational energy, and internal symmetry. Chapter 4 discusses the growth of nanoporous Cu4O3-C composite films through the MOCVD process employing Cu4(deaH)(dea)(oAc)5.(CH3)2CO as the precursor. The various characteristic aspects of as-grown films, such as their crystallinity, morphology, and composition have been covered elaborately in various sections of this chapter. The chapter describes the efficient guiding and confining of light exploiting the photonic band gap of these nanoporous films, which indicates the potential usefulness of these and similar films as optical waveguides. A model described in the literature on absorbing photonic crystals, wherein a periodically modulated absorption entails an inevitable spatial modulation of dispersion, i.e., of the index contrast to open a photonic band gap, has been used to calculate the indices of refraction of one of these nanoporous films. The chapter also reports briefly the preliminary electrochemical investigations carried out on a typical film, examining the notion of its application as the anode in a Li-ion rechargeable battery. Chapter 5 describes the synthesis of nanocrystalline LixCoO2 films by the sol-gel method. Reports available in literature indicate that the various phases of LixCoO2 are extremely sensitive to processing temperature, making it difficult to control dimensionality of a given phase using temperature as one of process parameters. We have investigated the possibility of using incoherent light to tailor the particle size/shape of this material. The as-grown and irradiated films were characterised by X-ray diffraction, and by microscopic and spectroscopic techniques.Optical spectroscopy was carried out in order to gain insight into the physico-chemical mechanism involved in such structural and morphological transformation. Chapter 6 deals with the synthesis of self-assembled nanostructures from the pre-synthesized nanocrystals building blocks, through optical means of exciton formation and dissociation. It has been demonstrated that, upon prolonged exposure to (incoherent) ultraviolet-visible radiation, LixCoO2 nanocrystals self-assemble into acicular architectures, through intermediate excitation of excitons. Furthermore, it has been shown that such self-assembly occurs in nanocrystals, which are initially anchored to the substrate surface such as that of fused quartz. This new type of process for the self-assembly of nanocrystals, which is driven by light has been investigated by available microscopic and spectroscopic techniques. Chapter 7 describes the stabilisation of chemically reactive metallic lithium in a carbonaceous nanostructure, viz., a carbon nanotube, achieved through the MOCVD process involving a lithium-alkyl moiety. This moiety is formed in situ during deposition through partial decomposition of a metalorganic precursor synthesized in house, which contains both lithium and cobalt. It is surmised that the stabilization of metallic Li in the nanostructure in situ occurs through the partial decomposition of the metalorganic precursor. Quantitative X-ray photoelectron spectroscopy carried out on such a film reveals that as much as 33.4% metallic lithium is trapped in carbon. Lastly, Chapter 8 briefly highlights the outlook for further investigations suggested by the work undertaken for this thesis. Novel precursors derived from biologically compatible ligands can open up possibility of growing new type of micro/nano-structures, and of unusual phases in the CVD grown films. Furthermore, it is proposed that the novel method of growth and alignment of nanocrystals through irradiation with incoherent light, employed for the specific material LixCoO2, may be employed for various other metallic and semiconducting materials.

Thin film nanostructures may be defined as assemblies, arrays, or randomly distributed nanoparticles, nanowires, or nanotubes, which together form a layer of materials supported on a substrate surface. Because such nanostructures are supported on a substrate surface, their potential applications cover a wide area in optical, magnetic, electrochemical, electromagnetic, and optoelectronic devices. The focus of the present thesis is the development of methodologies to grow certain thin film nanostructures of some transition metal oxides (TMOs), including copper oxides and LixCoO2, through CVD, sol-gel, and electromagnetic radiation-mediated approaches. The work towards this objective can be divided into three parts: first, the design, synthesis, and systematic identification of novel metalorganic precursors of copper (monometallic) and Li and Co (bimetallic); second, the growth of nanostructured oxides thin films using these precursors; and third, the application of electromagnetic radiation to control or tailor the growth of as grown nanostructures. The underlying growth mechanisms substantiated by appropriate evidence have been put forward, wherever found relevant and intriguing. It may be added that the principal objective of the work reported here has been to explore the several ideas noted above and examine possibilities, rather than to study any specific one of them in significant detail. It is hoped earnestly that this has been accomplished to a reasonable extent. Chapter 1 reviews briefly the reports available in the literature on three specific methods of growing thin films nanostructures, namely chemical vapour deposition, sol-gel processing and light-induced approach. The objective of this chapter has been to provide the background of the work done in the thesis, and is substantiated with a number of illustrative examples. Some of the fundamental concepts involved, viz., plasmons and excitons, have been defined with illustration wherever found relevant in the context of the work. Chapter 2 describes the various techniques used for synthesis and characterisation of the metalorganic complexes as well as of the thin films. This chapters covers mostly experimental details, with brief descriptions of the working principles of the analytical procedures adopted, namely, infrared spectroscopy, mass spectroscopy, elemental analysis, and thermal analysis for characterisation of the metalorganic complexes. This is followed by a similarly brief account of techniques employed to characterize the thin films prepared in this work, viz., glancing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), electrostatic force microscopy (EFM), transmission electron microscopy (TEM), glancing incidence infra-red spectroscopy (GIIR) and, UV-visible spectroscopy. The metalorganic chemical vapour deposition (MOCVD) systems built in house and used for growth of films are described in detail. The topics in the different sections of the chapter are accompanied by pertinent diagrams. Chapter 3 deals with the design, synthesis and characterisation of novel polynuclear complexes of copper and cobalt. Keeping in mind the various advantages such as low toxicity, ease of synthesis, non-pyrophoricity, and low temperature volatility, of environmentally benign complexes based on biologically compatible such as triethanolamine, diethanolamine, the objective has been to synthesize complexes containing triethanolamine and diethanolamine of transition metals such as cobalt and copper, and to investigate their applicability in MOCVD processes as a novel class of precursors. With the notion of ‘better’ and efficient design of precursors, an attempt has been made, through a semi-empirical modeling, to understand the correlation between volatility and various intrinsic molecular parameters such as lattice energy, vibrational-rotational energy, and internal symmetry. Chapter 4 discusses the growth of nanoporous Cu4O3-C composite films through the MOCVD process employing Cu4(deaH)(dea)(oAc)5.(CH3)2CO as the precursor. The various characteristic aspects of as-grown films, such as their crystallinity, morphology, and composition have been covered elaborately in various sections of this chapter. The chapter describes the efficient guiding and confining of light exploiting the photonic band gap of these nanoporous films, which indicates the potential usefulness of these and similar films as optical waveguides. A model described in the literature on absorbing photonic crystals, wherein a periodically modulated absorption entails an inevitable spatial modulation of dispersion, i.e., of the index contrast to open a photonic band gap, has been used to calculate the indices of refraction of one of these nanoporous films. The chapter also reports briefly the preliminary electrochemical investigations carried out on a typical film, examining the notion of its application as the anode in a Li-ion rechargeable battery. Chapter 5 describes the synthesis of nanocrystalline LixCoO2 films by the sol-gel method. Reports available in literature indicate that the various phases of LixCoO2 are extremely sensitive to processing temperature, making it difficult to control dimensionality of a given phase using temperature as one of process parameters. We have investigated the possibility of using incoherent light to tailor the particle size/shape of this material. The as-grown and irradiated films were characterised by X-ray diffraction, and by microscopic and spectroscopic techniques.Optical spectroscopy was carried out in order to gain insight into the physico-chemical mechanism involved in such structural and morphological transformation. Chapter 6 deals with the synthesis of self-assembled nanostructures from the pre-synthesized nanocrystals building blocks, through optical means of exciton formation and dissociation. It has been demonstrated that, upon prolonged exposure to (incoherent) ultraviolet-visible radiation, LixCoO2 nanocrystals self-assemble into acicular architectures, through intermediate excitation of excitons. Furthermore, it has been shown that such self-assembly occurs in nanocrystals, which are initially anchored to the substrate surface such as that of fused quartz. This new type of process for the self-assembly of nanocrystals, which is driven by light has been investigated by available microscopic and spectroscopic techniques. Chapter 7 describes the stabilisation of chemically reactive metallic lithium in a carbonaceous nanostructure, viz., a carbon nanotube, achieved through the MOCVD process involving a lithium-alkyl moiety. This moiety is formed in situ during deposition through partial decomposition of a metalorganic precursor synthesized in house, which contains both lithium and cobalt. It is surmised that the stabilization of metallic Li in the nanostructure in situ occurs through the partial decomposition of the metalorganic precursor. Quantitative X-ray photoelectron spectroscopy carried out on such a film reveals that as much as 33.4% metallic lithium is trapped in carbon. Lastly, Chapter 8 briefly highlights the outlook for further investigations suggested by the work undertaken for this thesis. Novel precursors derived from biologically compatible ligands can open up possibility of growing new type of micro/nano-structures, and of unusual phases in the CVD grown films. Furthermore, it is proposed that the novel method of growth and alignment of nanocrystals through irradiation with incoherent light, employed for the specific material LixCoO2, may be employed for various other metallic and semiconducting materials.

碩士
國立成功大學
材料科學及工程學系碩博士班
101
The photovoltaic industry is fast growing and the fabrication of solar cells has been kept improving. Nowadays, the main type of solar cell development is thin-film solar cells. However, most of studies focus on the solar cell structure to enhance the photovoltaic conversion efficiency rather than improving the solar module packaging process. For module packaging process, the bus wire bonding and the encapsulation of solar cells are needed in the fabrication of thin-film solar cell. In order to keep stable photovoltaic conversion efficiency after module packaging, good bonding strength is required between copper ribbon and aluminum back electrode of thin-film solar cell. Inkjet printing technology is a non-contact direct fabrication process, which can control precise droplet size and position and reduce material consumption. This study used lead-free solder as bonding material by inkjet printing process and module packaging technology for getting better quality of solar cell modules. In this study, Sn3.0Ag0.5Cu solders were successfully printed by using inkjet printing technology for bonding of thin-film solar cell modules. The results show that the peel strength of lead-free solder is better than that of silver paste when the dot spacing of lead-free droplets is lower than 200 μm. In other words, the amount of lead-free solder is over than 50 μg/mm2. As the bonding strength increases, the efficiency loss decreases. The optimum results of low efficiency loss degrade 1.5 % and good photovoltaic conversion efficiency is over 8.3 %.

碩士
國立中央大學
化學工程與材料工程研究所
90
Due to the concern of human health and the environment issue, Japan and European Union has set a schedule to ban the usage of lead-bear- -ed solders. According to the Ministry of Trade and Industry(MITI) regulations, all electronic productions containing lead-beared solders can not sale in Japan after year of 2002. It has been the trend to use lead-free solders in microelectronics and semiconductor industries. Unfortunately, no lead-free solder that can be fully replace lead-beared solders. So, it is an urgent issue to study suitable lead-free solders in current electronic Industries. Some board level’s package, BGA and SMT, have been successfully on the lead-free solder. But some important and key package technologies , such as C4(Controlled Collapse Chip Connection) and metal heat spreader interconnected with the solder, can not be solved at the moment. CTE(Coefficient Thermal Expansion) mismatch between Si chip and metal generates the huge thermal stress. So, solder gluing heat spreader and Si wafer is easily to crack after temperature cycling. Present lead-free solders can not endure the huge thermal stress. So it is important to find a lead-free solder that is compliant and can endure the huge thermal stress. Having high ductility and well mechanicial property, In-Sn alloys have potential to be used to joint Si chip and metal heat spreader. To cause the fatigue fracture in solder joint, intermetallic compound plays very important role. If intermetallic compound is too thickness, int- -erface between the solder and the under bump metallization(UBM) is volunable. Cu is traditional UBM. However, lead-free solders are often Sn--rich alloys, those Sn-rich alloys react easily and rapidly to form Sn-Cu intermetallic compound. After Cu UBM is consumed by soldering reaction, spalling will occur at the interface between the solder and the UBM.Comparing to Cu, Ni reacts slower with Sn-rich alloys. So, here, we select Ni as UBM substrate. To understand reaction mechanism between In-Sn alloy and bulk-Ni,we designed a experiment to study In-Sn alloy on bulk-Ni, such as wetting angle and intermetallic compound formation. The experimental conditions are: 1.the reflowing time are 10 min＆1 min、2.the reflowing temperature are isothermal 250℃ and 20℃ above melting point of alloys. There are four differential experiment. We can study the wetting reaction between SnIn/Ni 、SnAgCu/Ni systems. Experimental result will have big contribution on lead-free solder or reactive wetting studies.

碩士
國立交通大學
材料科學與工程系所
96
In this study, electromigration study in SnCu lead-free solder joints with thin-film under-bump-metallization and Cu substrate pad was conducted. We found that there was sever damage on the substrate side (anode side), and the damage on chip side (cathode side) was little. The damage on substrate side included void formation, dissolution of copper, and intermetallic compound formation. The voids almost separated Cu pad from the solder. We used microstructure analysis and 3-dimension simulation to investigate the electromigration mechanism in the area between Cu pad and solder. The higher diffusion rate of Cu in the SnCu solder was responsible for the serious void formation in the interface between Cu pad and the solder layers. Therefore, the surface becomes the weakest region during electromigration.

博士
國立交通大學
材料科學與工程學系
100
Diffusion barrier characteristics of electroless amorphous and polycrystalline Co(W,P) (termed a-Co(W,P) and poly-Co(W,P) hereafter) to eutectic PbSn, SnBi and SnAgCu (SAC) solders are investigated in this study. The samples were treated by liquid- and solid-state aging tests and the alloy reactions and diffusion barrier capabilities were evaluated. For PbSn and SAC systems, the activation energy of intermetallic compound (IMC) growth (Ea), interfacial bonding strength and failure modes were also analyzed. In all solder/a-Co(W,P) samples subjected to liquid-state aging, spallation of IMC into solder, formation of a nano-crystalline P-rich layer at reacting interface, and the recrystallization of Co(W,P) containing Co2P precipitates were observed. The IMCs observed in PbSn and SnBi samples were mainly CoSn2 and CoSn3, whereas that in SAC sample were mixture of CoSn3 and (Co,Cu)Sn3. As to solders/a-Co(W,P) samples subjected to solid-state aging, IMCs resided on the P-rich layer without spallation. In the samples containing poly-Co(W,P), thick IMC neighboring to an amorphous W-rich layer was seen regardless of the solder and aging types. It was found that the amorphous W-rich layers could not inhibit subsequent alloy reactions. Hence, diffusion barrier capability should be correlated to the nature of chemical bonds, rather than the amorphism of microstructure. Moreover, a-Co(W,P) was a composite-type barrier, i.e., sacrificial- plus stuffed-type barrier, while poly-Co(W,P) is mainly a sacrificial-type barrier. Analytical results indicated that the P content in Co(W,P) is a crucial factor affecting the structural evolution at the solder/electroless Co(W,P) interface. The values of Ea’s for IMC growth in PbSn/a-Co(W,P) and PbSn/poly-Co(W,P) samples were separately equal to 338.6 and 167.5 kJ/mol, whereas the Ea’s of IMC growth were 110.7 and 81.8 kJ/mol for SAC/a-Co(W,P) and SAC/poly-Co(W,P) samples, respectively. Ball shear test revealed the ductile mode dominates the failure in PbSn/a-Co(W,P), PbSn/poly-Co(W,P) and SAC/poly-Co(W,P) samples in most aging conditions, whereas interfacial break dominates at short-time aged samples and pad lift dominates when aging time was long in SAC/a-Co(W,P) case. Analytical results indicated that the decrement of bonding strength due to pad lift failure was ascribed to the deterioration of adhesion due to high P content, loss of toughness due to the formation of Co2P precipitates and the thermal stress induced by the change of CTE due to the recrystallization in aged Co(W,P) layer although high P content might enhance barrier capability. The P content of electroless plating layer affects not only the alloy reactions at solder/Co(W,P) interface, but also the diffusion barrier characteristics and reliability of solder joints.

碩士
國立清華大學
材料科學工程學系
93
Lead-tin solder has played an important role in microelectronic packaging for the past few decades. The current density and the operation temperature in the packaged devices rise substantially with the increase in device density and functionality for integrated circuits, which may result in severe reliability problems of solder joints. In this study, the soldering reaction between eutectic lead-tin solders and copper thin films and the evolution of solder microstructure and wetting precursors under electric current stressing were investigated. The patterned copper thin film samples were prepared by conventional photolithography techniques. The sample was placed on a preheated hotplate with a solder ball sitting on the center of the Cu strip. The solder melted and reacted with the Cu metallization after applying an electric current through the Cu strip. The results showed that there was an asymmetric distribution of Pb precipitates in the anode side and the cathode side of the solder. It was found that Pb precipitates aggregated and formed in columnar shape at the anode side, and the length of the Pb columnar precipitates increased proportionally with both the current density applied and the reaction time. The direction of the Pb columnar precipitates appeared to depend on the direction of the current applied. Besides, the activation energy for the growth of Pb columnar precipitates was measured to be 165.1 KJ/mole. The effect of electric current on solder wetting behavior and solder precursor was also investigated. An asymmetric distribution of Pb precipitate and intermetallic compounds was observed in the precursor bands of both sides of the solder. It was also found that the width of the solder precursor band was mainly affected by the temperature and the flux applied on the samples during soldering reaction instead of the stressing electric current.

碩士
國立成功大學
材料科學(工程)學系
84
In this research, the Al/Mo/Pd and Al/r-Mo2N/Pd films were investigated thin for the potential applications as the under bump metallurgy between silicon and solder.The Al/Mo/Pd and Al/r-Mo2N/Pd thin films were prepared on silicon by sputtering. The solder was coated onto the thin films using wave soldering . Various wave soldering parameters including solder temperature , conveyor speed , and preheat temperature were investigated for their effects on solder bump morphology. This work applied reflow to raise the height of solder bump .Furthermore, the effects of reflow with /without flux on bump height were also discussed. The experimental results revealed that the optimum conditions for wave soldering are at a solder temperature of 275℃ , conveyor speeds between 0.5 and 1 m/min,and preheat temperatures of above 70℃. The bump heights achieved prior to reflow is similar to those achieved with reflow in the presence of flux . The reflow of solder bumps with flux at higher concen -trations was able to raise bump height, but resulted in dewetting of the solder bump edge. During wave soldering, the intermetallic compounds PdSn4, PdSn3, PdSn2, Pb3Pd5,Pb9Pd13,and PbPd2 were formed between Pd deposit and molten solder. Heat treatment did not give rise to any compound other than those previou -sly described.Pd provides a good wetting layer as it tends to react with solder to intermetallic compound. Mo and r-Mo2N remained after the Si/Al/Mo/Pd and Si/Al/r-Mo2N/Pd films were heat treated at 150 ℃ for 1000 hours.A small amount of Al and Pd at -oms diffused into Mo and r-Mo2N deposits . Similar results exist for Si/ Al/Mo/Pd/Pb-Sn and Si/Al/-Mo2N/Pd/Pb-Sn combinations . Accordingly,Mo and r-Mo2N are capable of preventing the interdiffusion between Al and solder.

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Controlling polymer thin-film morphology and crystallinity is crucial for a wide range of applications, particularly in thin-film organic electronic devices. In this work, the crystallization behavior of a model polymer, poly(ethylene oxide) (PEO), during spincoating is studied. PEO films were spun-cast from solvents possessing different polarities (chloroform, THF and methanol) and probed via in situ grazing incidence wide angle x-ray scattering. The crystallization behavior was found to follow the solvent polarity order (where chloroform < THF < methanol) rather than the solubility order (where THF > chloroform > methanol). When spun-cast from non-polar chloroform, crystallization largely followed Avrami kinetics, resulting in the formation of morphologies comprising large spherulites. PEO solutions cast from more polar solvents (THF and methanol) do not form well-defined highly crystalline morphologies and are largely amorphous with the presence of small crystalline regions. The difference in morphological development of PEO spun-cast from polar solvents is attributed to clustering phenomena that inhibit polymer crystallization. This work highlights the importance of considering individual components of polymer solubility, rather than simple total solubility, when designing processing routes for the generation of morphologies with optimum crystallinities or morphologies.

The exploitation of solar energy has become a necessity for sustainable development. One of the approaches has been the use of photovoltaic materials to convert this never-ending energy source in electrical energy. For this approach to be reliable, it ought to combine high efficiency with low production costs, while also promising flexible devices. Perovskite structured compounds act as the light harvesting material in solar cells and can be produced using simple methods such as solvent-engineering and spin coating. This work focuses on the study of perovskite compounds ABX3, where A is methylammonium or caesium cations, B is a lead cation and X is a halide ion such as bromine, chlorine and iodine. These films were produced via spin coating and the solvent-mix used was DMF:DMSO in different ratios (2:3, 3:2 and 4:1). The influence of toluene dropping during the spinning process was also studied. The careful tuning of these processes allowed the formation of poly-crystalline perovskite films, deposited on top of Glass/FTO/ZTO-NPs, that presented optical absorbance values between 80-90% and optical bandgaps of 1.5 eV for MAPbI3 and 1.7 eV for MAPbI2Br0.85Cl0.15, as expected from the state-of-art materials.

Bien que ce soit un procédé industriel répandu, les films de copolymères à blocs préparés par trempage (« dip-coating ») sont moins étudiés que ceux obtenus par tournette (« spin-coating »). Pourtant, il est possible grâce à cette technique de contrôler précisément les caractéristiques de ces films. Au-delà de la méthode de fabrication, la capacité de modifier la morphologie des films trempés à l’aide d’autres facteurs externes est un enjeu primordial pour leur utilisation dans les nanotechnologies. Nous avons choisi, ici, d’étudier l’influence d’une petite molécule sur la morphologie de films supramoléculaires réalisés par « dip-coating » à partir de solutions de poly(styrène-b-4-vinyl pyridine) (PS-P4VP) dans le tétrahydrofurane (THF). En présence de 1-naphtol (NOH) et d’1-acide napthoïque (NCOOH), qui se complexent par pont hydrogène au bloc P4VP, ces films donnent, respectivement, une morphologie en nodules (sphères) et en stries (cylindres horizontaux). Des études par spectroscopie infrarouge ont permis de mesurer la quantité de petite molécule dans ces films minces, qui varie avec la vitesse de retrait mais qui s’avère être identique pour les deux petites molécules, à une vitesse de retrait donnée. Cependant, des études thermiques ont montré qu’une faible fraction de petite molécule est dispersée dans le PS (davantage de NOH que de NCOOH à cause de la plus faible liaison hydrogène du premier). La vitesse de retrait est un paramètre clé permettant de contrôler à la fois l’épaisseur et la composition du film supramoléculaire. L’évolution de l’épaisseur peut être modélisée par deux régimes récemment découverts. Aux faibles vitesses, l’épaisseur décroît (régime de capillarité), atteint un minimum, puis augmente aux vitesses plus élevées (régime de drainage). La quantité de petite molécule augmente aux faibles vitesses pour atteindre un plateau correspondant à la composition de la solution aux vitesses les plus élevées. Des changements de morphologie, à la fois liés à l’épaisseur et à la quantité de petite molécule, sont alors observés lorsque la vitesse de retrait est modifiée. Le choix du solvant est aussi primordial dans le procédé de « dip-coating » et a été étudié en utilisant le chloroforme, qui est un bon solvant pour les deux blocs. Il s’avère qu’à la fois la composition ainsi que la morphologie des films de PS-P4VP complexés sont différentes par rapport aux expériences réalisées dans le THF. Premièrement, la quantité de petite molécule reste constante avec la vitesse de retrait mais les films sont plus riches en NCOOH qu’en NOH. Deuxièmement, la morphologie des films contenant du NOH présente des stries ainsi que des lamelles à plat, tandis que seules ces dernières sont observables pour le NCOOH. Ce comportement est essentiellement dû à la quantité différente de petite molécule modulée par leur force de complexation différente avec le P4VP dans le chloroforme. Enfin, ces films ont été utilisés pour l’adsorption contrôlée de nanoparticules d’or afin de guider leur organisation sur des surfaces recouvertes de PS-P4VP. Avant de servir comme gabarits, un recuit en vapeurs de solvant permet soit d’améliorer l’ordre à longue distance des nodules de P4VP, soit de modifier la morphologie des films selon le solvant utilisé (THF ou chloroforme). Ils peuvent être ensuite exposés à une solution de nanoparticules d’or de 15 nm de diamètre qui permet leur adsorption sélective sur les nodules (ou stries) de P4VP.
Although it is an important industrial process, block copolymer thin films obtained by dip-coating have been far less studied than those obtained by spin-coating. However, this technique allows precise control of film properties and morphologies without the need for subsequent annealing. Besides the process itself, the ability to modify the morphology of block copolymer thin films is of interest for their use in nanotechnology applications. Here, we investigated supramolecular thin films of poly(styrene-b-4-vinyl pyridine) (PS-P4VP) dip-coated from tetrahydrofuran (THF) solutions containing small molecules that hydrogen bond to P4VP. In the initial dip-coating conditions, films complexed with 1-naphthol (NOH) show a dot morphology (spheres), whereas those containing 1-naphthoic acid (NCOOH) show a stripe morphology (horizontal cylinders). It was discovered that the amount of small molecule in the film, measured by infrared spectroscopy, varies with dip-coating rate, but is the same for both small molecules at any given rate. A thermal study showed that a small fraction of the small molecule, more NOH than NCOOH due to the weaker H-bond of the former, is dispersed in the PS phase, thus rationalizing the difference in their morphology evolution with rate. Thus, the dip-coating rate is a key parameter for controlling both the average film thickness and, for supramolecular polymers, the film composition. We observed that the evolution of the thickness with rate can be modeled by two regimes, in accordance with a recent literature study on dip-coated sol-gel films. At low rates, the thickness first decreases (capillarity regime), reaches a minimum and, at higher rates, increases (draining regime), resulting in a V-shaped film thickness/dip-coating rate curve. In parallel, the amount of small molecule in the film increases with rate in the capillarity regime before reaching a plateau corresponding to the solution composition in the draining regime. Morphology changes, related to the film thickness and the small molecule content, are therefore observed by modifying the dip-coating rate. We further show that the dip-coating solvent also influences the composition and morphology of the film, by comparing the use of chloroform (CHCl3), which is a good solvent for both blocks, with THF, which is a non-solvent for P4VP. With CHCl3, the small molecule content remains constant with the dip-coating rate, although it is higher for NCOOH than for NOH. Furthermore, the morphology of NOH-containing PS-P4VP thin films shows stripes and flat-on lamellae, whereas those containing NCOOH show only flat-on lamellae. This is attributed to the difference in their small molecule content, possibly modulated by the reduction in solubility of the P4VP block in CHCl3 when complexed with the small molecule. Finally, dip-coated films were used as templates for the controlled adsorption of gold nanoparticles. Prior to adsorption, solvent annealing was applied to the films either to improve the long-range order of the P4VP dots or to change the film morphology, which is dependent on the solvent used (THF or chloroform). They were then exposed to a 15-nm gold nanoparticles solution, which allows the selective adsorption on the P4VP dots (or stripes). It was possible to adsorb one nanoparticle per P4VP dot by matching their diameters.