There are numerous reports of attempts to deposit thick coatings of chromium-nickel and chromium-nickel-iron and although high quality deposits have been obtained these have been limited to very thin coatings only. The purpose of the present work was to identify and understand the controlling factors preventing continuous deposition and the build-up of thick coatings, and to develop a suitable process for such thick coatings. An amide electrolyte system was chosen asworking model for its relative simplicity and the high quality chromium-nickel deposits obtained from this system. This bath was investigated initially using conventional operating techniques (Constant Current) to establish its general characteristics. High quality deposits were obtained for thin coatings only. The need for a major change of operating philosophy was identified as essential. A number of published hypotheses explaining the failure of continuous deposition were experimentally tested and shown not to apply. Electrolytically generated chromium (II) has been identified to be an important controlling factor on the quality and composition of chromium-nickel alloys codeposited from amide electrolytes. The control of the low transient chromium (II) level, necessary for the maintenance of high quality codeposition with constant composition, can be achieved as follows. A controlled potential is required, in combination with circulation and agitation of the electrolyte and the generation of the chlorine gas as the preferred anodic product. The combination of the three techniques is necessary for the control of chromium (II) and if any of the three techniques are not employed sustained deposition fails. Chromium (II) has further been identified to catalyse an electrochemical ageing of the bath. Reproducible high quality true metallic deposits of constant composition of chromium-nickel and chromium-nickel-iron can be obtained to a thickness of several hundred microns. These have shown to display a laminar structure on etching and possible causes have been considered. Mossbauer spectroscopy and x-ray diffraction have shown that chromium-nickel-iron deposits contain a significant quantity of micro-crystalline austenite phase ~, fcc) with a dominant ferrite (e<, bcc) phase.

A eletrodeposição de ligas magnéticas de ferro, níquel e cobalto, além de permitir um maior controle sobre a composição e geometria dos filmes obtidas apresenta um fenômeno curioso: o filme apresenta uma maior quantidade do metal menos nobre do que a concentração do íon metálico no banho, o que contradiz o esperado termodinamicamente. A esse fenômeno deu-se o nome de codeposição anômala. A codeposição anômala já foi bastante estudada e muitos mecanismos foram propostos, mas não há um consenso na comunidade científica sobre eles. Os aditivos são usados nesses banhos para diversos fins, mas fora o seu efeito na composição dos filmes pouco é conhecido sobre seu papel no processo. Essa tese apresenta estudos realizados na tentativa de compreender o mecanismo da codeposição anômala da liga CoNi e a influência de glicina, o aditivo escolhido, no fenômeno. Várias técnicas de análise acopladas às técnicas eletroquímicas são empregadas, como a microbalança eletroquímica de cristal de quartzo, a espectroscopia no infravermelho por reflexão externa e medidas de stress no crescimento do filme. A presença do aditivo no banho da liga altera a composição da mesma, aumentando a quantidade do metal menos nobre, cobalto. A análise gravimétrica sugere que o aditivo mantém o pH superficial por meio do efeito tamponante ao mesmo tempo em que complexa com os íons metálicos, o que ocorre mesmo em meio ácido onde a concentração do agente complexante, glicinato, é baixa. A diferença entre suas constantes de complexação com os íons metálicos explica seu papel na composição do filme. A glicina torna o mecanismo de redução do níquel semelhante ao do cobalto além de indicar a ocorrência de fenômenos de oxidação na superfície do mesmo. A glicina pouco se adsorve sobre o eletrodo, mas há indícios através do stress de haver uma adsorção inicial sobre o Au. Há evidências da ocorrência de adsorção de hidrogênio na superfície do eletrodo, o que, acoplado com os altos valores de calor de adsorção, sugerem que o fenômeno da codeposição anômala pode estar atrelado à adsorção de H sobre os diferentes metais / Magnetic alloys, mainly the ones made of Fe, Ni or Co, have great technological importance, being used in many parts of our daily life, such as in magnetic recording devices. The electrodeposition of those alloys, which enables a greater control over the process, presents a curious phenomenon: the film has a greater amount of the less noble metal than the bath, something not expected thermodynamically. This phenomenon is called anomalous codeposition and it has been widely studied and although many mechanisms are available none is unanimous amongst the scientific community. Additives have been used to various extents in this baths but outside of controlling the composition of the film little is known. This thesis presents studies attempting to comprehend the anomalous codeposition mechanism of CoNi alloy and to understand the influence of glycine, the additive chosen, on the phenomenon. Many analytical techniques, coupled with electrochemical ones, have been used, such as quartz crystal electrochemical microbalance, external reflection FTIR spectroscopy and stress measurements during the film growth. The presence of glycine in the bath alters the film composition by increasing the quantity of the least noble metal, cobalt. The analysis through gravimetry suggests that glycine keeps the pH values at the surface by acting as a buffer and at the same time it forms complexes with the metallic ions. The different values of complexation constants with different metals explains its role in the film composition. Glycine changes the nickel reduction mechanism to one similar to that of cobalt. Besides that, its presence indicates that oxidation phenomena are happening at the surface of nickel films. The additive shows no signs of adsorption on the electrode, but stress measurements indicates that perhaps an initial adsorption on gold may happen. There are evidences that hydrogen adsorption may be happening in the electrodes surface which, coupled with the high values of heat of adsorption, suggests that the anomalous codeposition phenomenon may be linked to the effect of this species on different metals.

A eletrodeposição de ligas magnéticas de ferro, níquel e cobalto, além de permitir um maior controle sobre a composição e geometria dos filmes obtidas apresenta um fenômeno curioso: o filme apresenta uma maior quantidade do metal menos nobre do que a concentração do íon metálico no banho, o que contradiz o esperado termodinamicamente. A esse fenômeno deu-se o nome de codeposição anômala. A codeposição anômala já foi bastante estudada e muitos mecanismos foram propostos, mas não há um consenso na comunidade científica sobre eles. Os aditivos são usados nesses banhos para diversos fins, mas fora o seu efeito na composição dos filmes pouco é conhecido sobre seu papel no processo. Essa tese apresenta estudos realizados na tentativa de compreender o mecanismo da codeposição anômala da liga CoNi e a influência de glicina, o aditivo escolhido, no fenômeno. Várias técnicas de análise acopladas às técnicas eletroquímicas são empregadas, como a microbalança eletroquímica de cristal de quartzo, a espectroscopia no infravermelho por reflexão externa e medidas de stress no crescimento do filme. A presença do aditivo no banho da liga altera a composição da mesma, aumentando a quantidade do metal menos nobre, cobalto. A análise gravimétrica sugere que o aditivo mantém o pH superficial por meio do efeito tamponante ao mesmo tempo em que complexa com os íons metálicos, o que ocorre mesmo em meio ácido onde a concentração do agente complexante, glicinato, é baixa. A diferença entre suas constantes de complexação com os íons metálicos explica seu papel na composição do filme. A glicina torna o mecanismo de redução do níquel semelhante ao do cobalto além de indicar a ocorrência de fenômenos de oxidação na superfície do mesmo. A glicina pouco se adsorve sobre o eletrodo, mas há indícios através do stress de haver uma adsorção inicial sobre o Au. Há evidências da ocorrência de adsorção de hidrogênio na superfície do eletrodo, o que, acoplado com os altos valores de calor de adsorção, sugerem que o fenômeno da codeposição anômala pode estar atrelado à adsorção de H sobre os diferentes metais / Magnetic alloys, mainly the ones made of Fe, Ni or Co, have great technological importance, being used in many parts of our daily life, such as in magnetic recording devices. The electrodeposition of those alloys, which enables a greater control over the process, presents a curious phenomenon: the film has a greater amount of the less noble metal than the bath, something not expected thermodynamically. This phenomenon is called anomalous codeposition and it has been widely studied and although many mechanisms are available none is unanimous amongst the scientific community. Additives have been used to various extents in this baths but outside of controlling the composition of the film little is known. This thesis presents studies attempting to comprehend the anomalous codeposition mechanism of CoNi alloy and to understand the influence of glycine, the additive chosen, on the phenomenon. Many analytical techniques, coupled with electrochemical ones, have been used, such as quartz crystal electrochemical microbalance, external reflection FTIR spectroscopy and stress measurements during the film growth. The presence of glycine in the bath alters the film composition by increasing the quantity of the least noble metal, cobalt. The analysis through gravimetry suggests that glycine keeps the pH values at the surface by acting as a buffer and at the same time it forms complexes with the metallic ions. The different values of complexation constants with different metals explains its role in the film composition. Glycine changes the nickel reduction mechanism to one similar to that of cobalt. Besides that, its presence indicates that oxidation phenomena are happening at the surface of nickel films. The additive shows no signs of adsorption on the electrode, but stress measurements indicates that perhaps an initial adsorption on gold may happen. There are evidences that hydrogen adsorption may be happening in the electrodes surface which, coupled with the high values of heat of adsorption, suggests that the anomalous codeposition phenomenon may be linked to the effect of this species on different metals.

No description available.

Des couches minces contenant des phases intermétalliques présent et des propriétés et de combinaisons de propriétés qui ne sont que partiellement explorées. Elles portent des solutions potentielles pour conférer des multifonctionnalités à des matériaux avancés requis par les secteurs industriels et sont source derupture et de l'innovation. Leur élaboration par dépôt chimique en phase vapeur à partir de précurseurs métallo-organiques (MOCVD) permet un dépôt conforme sur, et la fonctionnalisation de surfaces complexes, avec un temps de traitement court et à un coût modéré.Pour ceci, il est nécessaire de contrôler les réactions chimiques complexes et des mécanismes de transport impliqués. La modélisation informatique du procédé, alimentée avec des données obtenues par des expériences de dépôt ciblées, est un outil intégré pour l'étude et la compréhension des phénomènes qui se produisent à différentes échelles,de l’échelle macroscopique à celle nanométrique. La MOCVD de composés intermétalliques Al-Fe est étudiée en tant que paradigme de la mise en oeuvre d'une telle approche combinée, expérimentale et théorique. La phase approximanteAl13Fe4 est particulièrement ciblée,en raison de son intérêt comme alternative peu onéreuse aux catalyseurs à base de métaux noble dans l'industrie chimique. La mise au point du dépôt de la phase Al13Fe4est subordonnée à l'étude des proc /min à 185oC. La simulation du procédé prédit des vitesses de croissance en bon accord avec ces résultats, en particulier dans la gamme 139oC-227oC. La modélisation multi-échelle prédit la rugosité RMS avec précision, permettant ainsi le contrôle des propriétés telles que la résistivité électrique. La possibilité d'obtenir des films MOCVD de Fe à faible contamination en O et C est explorée dans la gamme 130oC-250oC à partir de fer pentacarbonyle, Fe(CO)5. La morphologie de la surface des films dépend fortement de la température de dépôt; elle devient plus lisse au-dessus de200oC, qui correspond aussi à la vitesse de croissance maximale, 60nm/min. La vitesse de dépôt diminue fortement lorsque la pression augmente. Les prédictions de la modélisation macroscopique reproduisent précisément ce comportement. Elles indiquent que la diminution de la vitesse de croissance à des températures et des pressions élevées est due à l’augmentation de la décomposition du précurseur en phase gazeuse et à l'inhibition de la réactivité de surface par le ligand CO. Le modèle multi échelle conduit à des valeurs RMS en bon accord avec les mesures expérimentales, en particulier à des températures plus élevées. Suite à l’étude des deux procédés, des co-dépôts d'Al-Fe effectués à 200oCrésultent en des films riches en Alavec une microstructure poreuse et rugueuse. Ceux-ci ne contiennent pas de phases intermétalliques et sont riches en oxygène dû à la réaction d'Al avec les ligandscarbonyles. Afin d’éliminer la contamination, des dépôts séquentiels d'Al et de Fe sont réalisés, ce dernier dans des conditions modifiées à 140oC, 40Torr et 10 min. Ces films sont exemptes d’hétéroélements et présentent un rapport atomique Al:Fe13:4. Diffraction des rayons X et microscopies électroniques révèlent qu’un recuit in situ à 575oC pendant 1 h conduit à des films à gradient de la composition sur l'épaisseur,composés de la phase approximantem-Al13Fe4 conjointement avec des phases intermétalliques Al-Fesecondaires. Il est ainsi démontré que des procédés MOCVD sont appropriés pour obtenir des films constitués d'alliages intermétalliques.Ces films multifonctionnels,appliqués de façon conforme sur des surfaces complexes sont utiles pour un grand nombre d'applications. / Films containing intermetallic compounds exhibit properties and combination of properties which are only partially explored. They carry potential solutions to confer multifunctionality to advanced materials required by industrial sectors and to become a source of breakthrough and innovation.Metalorganic chemical vapor deposition (MOCVD) potentially allows conformal deposition on, and functionalization of complex surfaces, with high throughput and moderate cost. For this reason, it is necessary to control the complex chemical reactions and the transport mechanisms involved in a MOCVD process. In this perspective, computational modeling of the process, fed with experimental information from targeted deposition experiments, provides an integrated tool for the investigation and the understanding of the phenomena occurring at different length scales, from the macro- to the nanoscale. The MOCVD of Al-Fe intermetallic compounds is investigated in the present thesis as a paradigm of implementation of such a combined, experimental and theoretical approach. Processing of the approximant phase Al13Fe4 is particularly targeted, due to its potential interest as low-cost and environmentally benign alternative to noble metal catalysts in the chemical industry. The attainment of the targeted Al13Fe4 intermetallic phase passes through the investigation of the MOCVD of unary Al and Fe films. The MOCVD of Al from dimethylethylamine alane (DMEAA) in the range 139oC-241oC results in pure films. Increase of the deposition temperature yields higher film density and decreased roughness. The Aldeposition rate increases to a maximum of 15.5 nm/min at 185oC and then decreases. Macroscopic simulations of the process predictdeposition rates in sufficient agreement with experimental measurements, especially in the range 139oC-227oC. At higher temperatures, competitive gas phase and surface phenomena cannot be captured by the applied model. Multiscale modeling of the process predicts the RMS roughness of the films accurately, thus allowing the control of properties such as electrical resistivity which depend on the microstructure. The MOCVD of Fe from iron pentacarbonyl, Fe(CO)5, is investigated in the range 130oC-250oC for the possibility toobtain fairly pure Fe films with low Oand C contamination. The surface morphology depends strongly on the temperature and changes are observed above 200oC. The Fe deposition rate increases up to 200oC, to a maximum of 60 nm/min, and then decreases. Moreover, the deposition rate decreases sharply with increasing pressure. Computational predictions capture accurately the experimental behavior and they reveal that the decrease athigher temperatures and pressures is attributed to the high gas phase decomposition rate of the precursor and to inhibition of the surface fromCO. The multiscale model calculates RMS roughness in good agreement with experimental data, especially at higher temperatures. Upon investigation of the two processes, aseries of Al-Fe co-depositions performed at 200oC results in Al-rich films with a loose microstructure. They contain no intermetallic phases and they are O-contaminated due to the reaction of the Al with the carbonyl ligands. Sequential deposition of Al and Fe followed by in situ annealing at 575oC for 1 h is applied to bypass the Ocontamination. The process conditions of Fe are modified to 140oC, 40 Torr and 10 min resulting in O-free films with Al:Fe atomic ratio close to the targeted 13:4 one. Characterization techniques including X-ray diffraction, TEM and

[pt] Nesta dissertação foram estudadas as propriedades ópticas, eletroquímicas, elétricas e morfológicas de novos compostos fluorescentes para o desenvolvimento de OLEDs. Para isto, foram estudadas algumas sondas moleculares fluorescentes utilizadas na área biomédica como agentes antitumorais e marcadores ópticos fluorescentes: a) N,N - diisonicotinoil-2-hidroxi-5 metilisoftaldeído diidrazona (DMD); b) 2-(5 -isotiocianato-2 -hidroxifenil)benzoxazol, (5ONCS); c) 1,1 -dipireno (DIPI) e d) 7,7 -terc-butil-1,1- dipireno (TDIPI). Todos estes compostos foram sintetizados por Grupos de pesquisa brasileiros e depositados termicamente em forma de filmes finos no nosso Laboratório. No decorrer do estudo de fabricação dos OLEDs, os dispositivos bicamada baseados no DMD e no 5ONCS se mostraram pouco eficientes devido principalmente à baixa condutividade do DMD e à elevada rugosidade da camada de 5ONCS. A solução destes problemas foi encontrada na técnica de codeposição, que consiste na evaporação simultânea de uma matriz orgânica e de um dopante (DMD ou 5ONCS) numa única camada. Desta forma, foi possível alcançar um aumento da mobilidade das cargas nas camadas co-depositadas alem de favorecer a transferência de energia da matriz para o dopante. Os OLEDs fabricados nestas condições permitiram observar, pela primeira vez, a eletroluminescência dos compostos DMD e 5ONCS. Já os OLEDs baseados nas moléculas DIPI e TDIPI apresentaram eletroluminescência sem a necessidade da co-deposição. Em particular, no caso do OLED baseado no TDIPI foi possível alcançar uma luminância de 1430 cd/m2 com uma eficiência de 2,65 porcento a 1mA. Os resultados deste trabalho evidenciam a potencialidade do uso destes materiais para a fabricação de OLEDs para aplicações na área de iluminação. / [en] In this study the optical, electrochemical, electrical and morphological properties of new fluorescent compounds were studied in order to develop OLEDs based upon these materials. For this purpose some fluorescent molecular probes used in the biomedical field as antitumor agents and fluorescent optical probes were studied: a) N,N diisonicotinoyl-2-hydroxy-5-methylisophthalaldehyde dihydrazone (DMD ), b) 2 - (5 -isothiocyanato -2-hydroxyphenyl) benzoxazole ( 5ONCS ), c) 1,1 - dipyrene (DIPI) and d) 7,7 -tertbutyl- 1,1-dipyrene (TDIPI ). All these compounds were synthesized by Brazilian research groups and then thermally deposited as thin films in our Laboratory. During the study for the fabrication of OLEDs, bilayer devices based on DMD and 5ONCS proved to have low efficiency mainly due to the low conductivity of the DMD and the high roughness of the 5ONCS layer. The solution of these problems was found in the codeposition technique, which consists in the simultaneous evaporation of an organic matrix (host) and a dopant (guest) (5ONCS or DMD) in a single layer. Thus, it was possible to achieve an increase in the charge mobility in the co-deposited layers as well as energy transfer from the guest to the host. The OLEDs fabricated in these conditions allowed the observation, for the first time, of the electroluminescence of DMD and 5ONCS. On the other hand, the DIPI and TDIPI based OLEDs presented good electroluminescence without the need for co-deposition. In particular, in the case of the TDIPI it was possible to achieve a luminance of 1430 cd/m2 with an efficiency of 2.65 percent at 1 mA. The results of this work showed the potential of these materials for the fabrication of OLEDs for lighting applications.

[pt] Esta dissertação de mestrado apresenta como proposta a investigação, a síntese e a caracterização de novos complexos baseados em terras-raras para aplicação em diodos orgânicos emissores de luz (OLEDs). Para isto, três complexos beta-dicetonatos de Európio foram estudados. O foco da investigação consistiu nos dois novos complexos [Eu(hfac)3dpso] e [Eu(hfac)3dbso], sintetizado pelo nosso grupo, cuja principal diferença consistiu em avaliar o comportamento do complexo [Eu(hfac)3X], em função de dois ligante ancilares: dpso e dbso. O que poderá implicar na variação da absorção do complexo e também no processo de transferência de energia dos ligantes para o íon de Európio. Além disso, um terceiro complexo comercial [Eu(dbm)3phen] foi empregado com o objetivo de ser utilizado como referência para a fabricação e a otimização da arquitetura dos OLEDs. Estes complexos beta-dicetonatos com ligantes ancilantes coordenados por N ou O foram caracterizados através de diferentes técnicas (ótica, eletroquímica e morfológica), sob a forma de filmes finos e em pó. A partir do estudo e da otimização do OLED baseado no complexo [Eu(dbm)3phen] se chegou a arquitetura que apresentou um compromisso entre a performance do OLED e o grau de complexidade associado a fabricação. A camada emissora se baseou na técnica de codeposição, onde uma matriz Spiro-2CBP foi escolhida de tal forma que: 1) a energia possa ser transferida para o dopante, no caso, [Eu(dbm)3phen] e 2) que a mobilidade efetiva no transporte de portadores de carga aumente em relação a baixa mobilidade comum em complexos de beta-dicetonas. A arquitetura otimizada foi ITO/ MoO3(10nm)/TAPC(30nm)/ Spiro-2CBP:[Eu(dbm)3phen] (30nm, 10 porcento)/ TPBi(40nm)/LiF(0.1nm)/ Al(100nm). A partir desta arquitetura, foram fabricados os outros dispositivos OLEDs com os complexos [Eu(hfac)3dpso] e [Eu(hfac)3dbso]. Em estudo comparativo, de acordo com as medidas de eficiência fotométrica de corrente (EFC), verificou-se que o OLED baseado no complexo de [Eu(hfac)3dpso] apresentou uma eficiência superior ao OLED com [Eu(hfac)3dbso] apresentando um ganho de 7.5 porcento, para uma densidade de corrente em torno de 75mA/cm2. Em resumo, considerando os resultados dos OLEDs e também da disposição dos níveis de energia tripleto dos ligantes hfac, dbso e dpso, verifica-se que ambas indicam que o complexo [Eu(hfac)3dpso] apresente um melhor desempenho que o complexo [Eu(hfac)3dbso]. / [en] This master thesis presents as research, manufacture and characterization of new rare-earth-based complexes for application in light-emitting organic diodes (OLEDs). For this, three europium beta-dicetonated complexes were studied. The focus of the investigation was the two new complexes, [Eu(hfac)3dpso] and [Eu(hfac)3dbso], synthesized in our group, whose main difference was to evaluate the behavior of the complex [Eu(hfac)3X], as a function of two ancillary ligands: dpso and dbso. This may imply variations in the absorption of the complex and also in the process of energy transfer from ligands to the Europium ion. Also, a third commercial complex [Eu(dbm)3phen] was employed as a reference for the manufacture and optimization of OLED architecture. These beta-diketonated complexes with N or O coordinated binding ligands were characterized by different techniques (optical, electrochemical and morphological) in both thin film and powder form. From the study of OLED optimization based on the complex [Eu(dbm)3phen], the architecture that presented a compromise between the OLED s performance and the degree of complexity associated with its fabrication. The emitter layer was based on the co-deposition technique, where a Spiro-2CBP matrix was chosen because: 1) good energy transfer to the dopant, in this case [Eu(dbm)3phen] and 2) the effective charge mobility in the co-deposited layer is higher than the common mobility in beta-diketone complexes. The optimized architecture was ITO / MoO3 (10nm) / TAPC (30nm) / Spiro-2CBP: [Eu(dbm)3phen] (30nm, 10 percent) / TPBi (40nm) / LiF (0.1nm) / Al (100nm). From this architecture other OLEDs devices were fabricated with the complex [Eu(hfac)3dpso] and [Eu(hfac)3dbso]. The comparative study, according to the current efficiency measurements, found that the [Eu(hfac)3dpso] complex-based OLED had higher efficiency than the [Eu(hfac)3dbso] OLED with a gain of 7.5 percent for a current density of around 75mA /cm2. In summary, considering the OLED results and also the arrangement of the triplet energy levels of the hfac, dbso and dpso ligands, both imply that the [Eu(hfac)3dpso] complex has a better performance than the complex [Eu(hfac)3dbso].