This thesis presents a study of the electrical properties and gas sensitivity of thin films of four different organic materials. These are: (i) Langmuir-Blodgett (LB) films of tetrabutylammonium Ni(dmit)(_2) complex (Bu(_4)-Ni(dmit)(_2) complex) mixed with tricosanoic acid (TA); (ii) thin films of polypyrrole (PPy) mixed with palmitic acid (PA) obtained using the LB technique followed by two solid state reactions; (iii) cast films of polycyanopropylmethylsiloxane (PCMS); and (iv) LB films of a co-ordination polymer?5,5' methylenebis (N-hexadecylsalicydeneamine) (MBSH) (poly(CuMBSH)). LB films of (Bu(_4)-Ni(dmit)(_2) complex)/TA were characterised by electrical measurements?(AC in the frequency range 10(^2)-10(^6) Hz) at room temperature. For the other three types of films, characterisation of the structure and electrical behaviour (DC and AC in the frequency range 10(^2)-10(^6) Hz) on varying the temperature (in the range 90 - 298 K) and during the exposure to benzene, ethanol, acetonitrile and water (concentrations in the range 10(^2) -10(^5) ppm) was undertaken. During exposure to vapours, reversible changes in the electrical properties of the films were observed. The electrical behaviour and the changes during exposure to vapours were interpreted in terms of models in the literature, assuming a bulk dissolution of the vapours in the organic films. In all cases an 'anomalous' response to water was observed. For poly(CuMBSH), this effect was interpreted in terras of a Low Frequency Dispersion. The device characteristics for gas sensing applications are also discussed. Estimated minimum detectable concentrations were between 1-100 ppm for the three organic solvent vapours. Moreover, it is shown that the fi-equency behaviour for the admittance changes of the PCMS and poly(CuMBSH) devices could be exploited for the improvement of the sensitivity of a single device. The unique response of all the films to water vapour could be useful for its discrimination.

<p>Vertically aligned nanocomposite (VAN) configuration has been recognized as the state-of-the-art architecture in the complex oxide epitaxial thin films, which are constructed by two immiscible phases simultaneously and vertically growing on a given substrate and forming various columnar microstructures, such as nanopillars embedded in matrix, nanomaze, and nanocheckboard. Due to its architectural features, VAN structure enables a powerful control on the multifunctionalities via vertical strain engineering, microstructural variations, and interfacial coupling. It provides flexibility in complex oxide designs with various functionalities (e.g., electrical, magnetic, optical, etc.), as well as a platform to explore the correlations between strain, microstructure, and multifunctionalities of the nanocomposite thin films.</p> <p>In this dissertation, integrated VAN systems with multilayer configuration have been constructed as a new three-dimensional (3D) framework, e.g., inserting 1-3 layers of CeO₂ (or LSMO) interlayers into the La_0.7Sr_0.3MnO₃ (LSMO)-CeO₂ VAN system and forming 3D interconnected CeO₂ (or LSMO) skeleton embedded in LSMO matrix. This new VAN 3D framework enables both lateral and vertical strain engineering simultaneously within the films and obtains highly enhanced magnetotransport properties, such as the record high magnetoresistance (MR) value of ~51-66%, compared with its VAN single layer counterpart. In order to demonstrate the flexibility of this design, other systems such as 3D ZnO framework embedded in LSMO matrix have been constructed to explore the thickness effects of the ZnO interlayers on the magnetotransport properties of the LSMO-ZnO system. The maximum MR value is obtained at the ZnO interlayer thickness of ~2 nm, which enables the optimal magnetoresistance tunneling effect. Meanwhile, the significance of the interlayer selection in the microstructure and magnetoresistance properties of the LSMO-ZnO system has been investigated by varying the interlayer materials yttria-stabilized zirconia (YSZ), CeO₂, SrTiO₃, BaTiO₃, and MgO. The formed 3D heterogeneous framework provides a new dimension to tailor the microstructure, strain and functionalities within the films.</p> <p>Moreover, a new strain engineering approach with engineered tilted interfaces has been demonstrated by multilayering different VAN layers with various two phase ratio and creating a hybrid nanodumbbell structure within the LSMO-CeO₂ VAN thin films. The nanodumbbell structure accomplishes a more efficient strain engineering and exhibits highly enhanced magnetic and magnetoresistance properties, compared with its VAN single layer and interlayer counterparts. </p> <p>These examples presented in the thesis demonstrate the flexibility and potential of 3D strain engineering in complex VAN systems and a higher level of property control, coupled with unique microstructures and interfaces. Beyond perovskites, these 3D designs can be extended to other material systems for a broader range of applications, such as energy conversion and storage related applications.</p>

<p>Electromigration in thin films is a well known failure mode for scaled microelectronics. While our understanding of electromigration physics has improved immensely in the last few decades, there are still some gaps in literature. In particular, the influence of interfaces on the mass transport rate is not well understood. Through reliability studies conducted on passivated metals films, marked improvement in electromigration lifetimes was observed. Specifically, some choices of materials for passivation appear to perform better than others. Qualitatively this improvement in electromigration performance is attributed to surface adhesion. However, a theoretical connection is largely missing in the literature. Lane et al. through in-situ electromigration experiments and separate interfacial debond experiments on sandwich specimens showed that a correlation exists between the void growth rate and the debond energy. However, a fundamental understanding of the relation between the two is missing. In this study we explore the connection between interfacial adhesion and void growth in a current driven system. Several experiments with varying test conditions are carried out on Blech-like test structures with different capping layers. The influence of these capping layers is captured through direct void growth measurements. Comparison of activation energy associated with electromigration was made against existing literature. It was found to be consistent with values reported for surface/interface dominated diffusion mechanisms. Further, an extension is proposed to the phase growth relations derived in existing literature to include the effect of surface adhesion. Interfacial adhesion energy ratios are extracted from the electromigration experiments for two of the test structures (Cu-Ta and Cu-SiNx) tested in this study. This ratio is compared to values reported in literature for the two interfaces and they show good agreement with experimental data.<br></p>

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2017 / This research has considered an idealistic non-interleaved planar transformer wherein only the electromagnetic parasitic capacitive and inductive elements arising out of the transformer geometry are taken into account, without considering material limitations. A suitable model for the planar transformer is used to analyse its frequency and power transfer characteristics; this model was validated by three dimensional electromagnetic simulations of various planar transformer structures in FEKO simulation software. The capacitive and inductive parasitics in this model have been found to be functions of the dielectric thickness. The theoretical bandwidth for the planar transformer is defined in this research as a function of dielectric thickness. The effect of dielectric thickness of the transformer windings on the bandwidth of the transformer is analysed, based on the premise that the inherent parasitic capacitive and inductive elements would affect the transfer characteristics of the transformer. Upon conclusion of this analysis, it is found that the dielectric thickness of a planar transformer can be optimised such as to present an optimised bandwidth. A closed form analytic expression for the optimum dielectric thickness value is derived and presented in this research. In a design example of a 4:1 50W transformer presented in this research, it has been shown that the bandwidth can be improved by 384%, along with a power density improvement of 45%, upon choosing of an optimum dielectric thickness of 0.156mm to replace a standard 0.4mm thick dielectric. It should be noted that the results derived in this research are purely theoretical, justified by many idealisations and assumptions that are argued throughout the research. It is thus expected that practical results should at best approach the theoretical results, due to the known non-ideal nature of reality. / CK2018

Orientador: Marystela Ferreira / Banca: Thiago Regis Longo Cesar da Paixão / Banca: Laura Oliveira Peres Philadelphi / Banca: Nilson Cristino da Cruz / Banca: Margarida Juri Saeki / Resumo: Neste trabalho, foram desenvolvidos biossensores eletroquímicos enzimáticos fabricados com óxido de grafeno reduzido (rGO) e funcionalizado depositados pelas técnicas LbL (Layer-by-Layer) e Langmuir-Blodgett (LB) para a detecção de glicose. Para isso, primeiramente foi sintetizado quimicamente o óxido de grafeno (GO) pela oxidação do grafite, em seguida, o GO foi reduzido para aumentar a sua condutividade elétrica e foi funcionalizado em meio estabilizante contendo cloridrato de poli(dialildimetilamônio), formando o GPDDA, ou poli(4-estireno sulfônico) PSS, formando GPSS. Com isso, foi possível formar dispersões aquosas estáveis das nanofolhas de grafeno, essencial para a fabricação de filmes LbL. Em um primeiro momento, foram fabricados biossensores com filmes LbL contendo GPDDA, GPSS e a enzima glucose oxidase (Gox). O desempenho desses biossensores na detecção de glicose foi avaliado em função do número de bicamadas contendo Gox. O melhor desempenho na detecção de glicose foi apresentado pelo biossensor com o filme LbL com a arquitetura (GPDDA/GPSS)/(GPDDA/GPSS)2. Este biossensor apresentou limite de detecção de 13,4 µmol.L-1, sensibilidade 2,47 μA.cm-2.mmol-1.L e faixa analítica entre 0,04 e 0,95 mmol.L-1. Este biossensor foi eficiente na detecção de glicose na presença de interferentes comumente encontrados em fluidos corporais, alimentos e fármacos. Quando avaliado na detecção de glicose em amostras reais, recuperou 100,8% para uma solução eletrolítica comercial e 88,8%... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, enzymatic electrochemical biosensors fabricated with reduced graphene oxide (rGO) and functionalized deposited by the LbL (Layer-by-Layer) and LangmuirBlodgett (LB) techniques were developed for the detection of glucose. Firstly, to get this, graphene oxide (GO) was chemically synthesized by the oxidation of graphite and after GO was reduced to increase its electrical conductivity and it was functionalized in stabilizing medium containing the poly (diallyl dimethyl ammonium chloride) PDDA, forming the GPDDA, or poly (4-styrene sulphonic) PSS, forming GPSS. Hence, stable aqueous dispersions of graphene nanosheets were formed, essential for the fabrication of LbL films. In a first moment, biosensors with LbL films containing GPDDA, GPSS and the enzyme glucose oxidase (Gox) were fabricated. The performance of these biosensors in the detection of glucose was evaluated as a function of the number of bilayers containing Gox. The best performance in the detection of glucose was presented by the biosensor with the LbL film with the architecture (GPDDA/GPSS)/(GPDDA/GPSS)2. It presented a detection limit of 13.4 μmol.L-1, sensitivity 2.47 μA.cm-2 .mmol-1 .L and analytical range between 0.04 and 0.95 mmol.L-1 . This biosensor was efficient in detecting glucose in the presence of interferents commonly found in body fluids, foods and drugs. When evaluated in the detection of glucose in real samples, it recovered 100.8% for a commercial electrolytic solution and 88.8% for lactose-free milk. In a second moment, biosensors were fabricated from LB films containing the same materials used to fabricate the biosensors with LbL films (GPDDA, GPSS and Gox), in order to compare the two methods of films deposition in the performance of the biosensors. The performance of biosensors fabricated with LB films was evaluated in relation to the amount of deposited... (Complete abstract electronic access below) / Doutor

Neste trabalho foram produzidos filmes finos de nitreto de carbono pelo método de deposição de íons e vapor (IVD) que consiste em evaporar um material (carbono) sobre um substrato e, simultaneamente, realizar sobre ele um bombardeamento por íons (N POT.+). Foram produzidas amostras com energia dos íons de 0,5, 0,8, 2,0, 5,0 e 10,0 keV e razão de transporte TR(C/N) = 04, 1,0, 1,5, 2,0 e 3,0, onde TR(C/N) é o quociente do número de átomos de carbono evaporados pelo canhão eletrônico e o número de íons acelerados que chegam simultaneamente ao mesmo substrato. Os filmes foram produzidos com espessuras de 200, 500 e 1000 nm sobre substratos de Si(100), sílica fundida e carbeto de tungstênio. As propriedades dos filmes analisadas por meio de espectroscopia de fotoeléctrons induzidos por Raios X (XPS), espectrofotometria do infravermelho por transformadas de Fourier (FT-IR), espectrofotometria do visível e ultravioleta, difração de Raios X (XRD) e ensaios de dureza Knoop. Os espectros de XPS foram utilizados para a análise do estado das ligações entre carbono e nitrogênio e também para se estimar a razão de composição CR(C/N) entre átomos de carbono e nitrogênio presentes nos filmes. Foram analisados os picos de C-1s POT. ½ e N-1s POT. ½ e a relação entre suas áreas forneceu a CR(C/N). Para amostras ricas em nitrogênio, o espectro XPS apresentou um pico de C-1s POT. ½ bem proeminente a 286.3 eV. De acordo com nossos resultados este pico pode ser atribuído à presença de ligação tripla CN. Os espectros de FT-IR apresentaram uma banda bem larga de 800 a 1700 CM POT.-1 e um pico proeminente centrado em 2190 CM POT.-1. Este último é atribuído à presença de ligação tripla CN e confirmou a formação de nitreto de carbono. Os estudos de difração de raios-X indicaram que os filmes formados apresentam uma estrutura amorfa ou que contenha pequenos cristalitos não detectáveis por XRD. A dureza e o band gap ótico das amostras mostraram uma forte dependência em relação à energia do feixe de íons e a CR(C/N). Filmes formados a baixa energia de implante (0,5 e 0,8 keV) e alta incorporação de nitrogênio (CR(C/N)=0,6~0,7) apresentaram alta dureza Knoop de até 63 GPa e band gap ótico de até 2,7 eV. Simulações computadorizadas foram utilizadas para ajudar no entendimento dos processos envolvidos na formação de filmes. / In this work thin carbon nitride films were produced by the ion and vapor deposition method (IVD). This method consists of the evaporation of a material (carbon) over a substrate and simultaneously to bombard this same substrate with an ion beam (N POT.+). Samples were produced with ion implantation energies of 0.5, 0.8, 2.0, 5.0 and 10.0 keV and transport ratio TR(C/N) = 0.4, 1.0, 1.5, 2.0 and 3.0, TR(C/N) is the ratio between the number of evaporated carbon atoms by the electron gun and the number of accelerated ions that simultaneously arrive at the substrate. The thicknesses of the produced films were 200, 500 and 1000 nm on Si(100) wafers, fused silica and tungsten carbide substrates. The properties of the films were analyzed by X-ray induced photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectrophotometry, UV-VIS spectrophotometry, X-ray diffraction (XRD) and Knoop hardness test. The XPS spectra were used for the analyzes of the carbon and nitrogen bonding states and also for the estimation of the composition ratio CR(C/N) between carbon and nitrogen atoms in the films. The analyzes were carried specifically for C-1s POT. ½ and N-1s POT. ½ peaks and the CR(C/N) was estimated from the area ratio of the respective peaks. For nitrogen rich samples, the XPS spectra showed a prominent C-1s POT. ½ peak at 286.3 eV. This peak can be attributed to the presence of the triple bonding CN from our experimental results. The FT-IR spectra showed a wide band between 800 and 1700 CM POT.-1 and a prominent peak centered at 2190 CM POT.-1. This last peak is attributed to the CN triple bonding and confirmed the carbon nitride formation. X-ray diffraction patterns showed that all the films, that were formed has an amorphous structure or contained small crystallites not detectable by XRD. Hardness and optical band gap showed a strong dependence on the ion beam energy and the CR(C/N). Films deposited at low ion energy (0.5 and 0.8 keV) and high nitrogen incorporation (CR(C/N)=0.6~0.7) showed high Knoop hardness of up to 63 GPa and optical band gap of up to 2.7 eV. Computer simulations were used to understand the processes involved in the formation of the films.

Neste trabalho foram estudadas as propriedades magnéticas e características estruturais de filmes finos bicamadas e multicamadas formados com Ni{x}Cu{1-x} (ferromagneto, 50 x 90 e níquel puro), NiO, FeMn e IrMn (antiferromagnetos). Ligas de níquel-cobre podem ser classificadas como fracamente ferromagnéticas. Ferromagnetismo fraco gera efeitos únicos em propriedades de transporte eletrônico, junções com supercondutores e sistemas de exchange bias. Sendo uma solução sólida extremamente simples, diversas propriedades do NiCu dependem linearmente da estequiometria da liga. Os filmes finos foram depositados via magnetron sputtering em substratos monocristalinos de Si (100) a temperatura ambiente. A estrutura cristalina foi caracterizada por difração de raios-X e a morfologia foi analisada por retroespalhamento Rutherford. Propriedades magnéticas foram medidas com um SQUID a temperaturas entre 5K e 300K (curvas ZFC/FC e de magnetização a diferentes temperaturas) e com um VSM a temperatura ambiente (curvas de magnetização em diferentes ângulos no plano do filme). As amostras com Ni{x}Cu{1-x} mais ricas em cobre apresentam os maiores campos coercivo e de exchange bias a baixas temperaturas, mas os menores em altas temperaturas, geralmente respeitando as temperaturas de bloqueio indicadas nas curvas ZFC/FC. O acoplamento na interface das bicamadas NiO/Ni{x}Cu{1-x} foi muito reduzido em temperaturas mais altas, não sendo observada anisotropia unidirecional nas medidas a temperatura ambiente. As constantes de interação J{int} foram calculadas para as bicamadas Ni{x}Cu{1-x}/FeMn e Ni{x}Cu{1-x}/IrMn a 5K e temperatura ambiente. O sistema Ni/IrMn apresentou o maior valor dessa constante em ambas as temperaturas, diminuindo muito com o acréscimo de cobre na camada Ni{x}Cu{1-x}. O sistema Ni{90}Cu{10}/FeMn apresentou os maiores valores em ambas as temperaturas (excluindo o de níquel puro), comparável até com Ni/IrMn no caso de 5K. Esse comportamento pode ser explicado por uma maior afinidade entre as estruturas do FeMn e Ni{x}Cu{1-x} na direção [111], o que favorece a formação da face (111) no FeMn, mais consistentemente do que no IrMn. Nenhuma das multicamadas estudadas se comportou como uma válvula de spin, mas foi observado um aumento na coercividade e supressão do exchange bias, provavelmente por causa de acoplamento entre as camadas ferromagnéticas. / In this work, a study of magnetic properties and structural characteristics of bilayered and multilayered thin films was carried out. These films were made with Ni{x}Cu{1-x} (ferromagnet, 50 x 90 and pure nickel) and NiO, FeMn or IrMn as antiferromagnets. Nickel-copper alloys may be classified as weakly ferromagnetic. Weak ferromagnetism generates unique effects in electron transport, junctions with superconductors and exchange bias systems. Being an extremely simple solid solution, many properties of the NiCu alloy have a linear dependence with its stoichiometry. The thin films were deposited via magnetron sputtering on Si (100) monocrystalline substracts at room temperature. The crystalline structure was characterized by X-ray diffraction, while the morphology was analyzed by Rutherford back-scattering. Magnetic properties were measured by SQUID at temperatures between 5K and 300K (ZFC/FC curves and magnetization curves at different temperatures) and by VSM at room temperature (magnetization curves at varying angles at the film plan). The samples with copper-richer Ni{x}Cu{1-x} showed the largest coercive and exchange bias fields in lower temperatures, but the lowest ones in higher temperatures, usually following the blocking temperatures denoted by the ZFC/FC curves. The interfacial coupling in NiO/Ni{x}Cu{1-x} was very weak in higher temperatures, not showing unidirectional anisotropy at room temperature. The J{int} exchange interaction constants were calculated for the Ni{x}Cu{1-x}/FeMn and Ni{x}Cu{1-x}/IrMn bilayers at 5K and room temperature. Ni/IrMn had the largest values at both temperatures, heavily decreasing with the copper content in the Ni{x}Cu{1-x} layer. Ni{90}Cu{10}/FeMn showed the largest values at both temperatures (except for the pure Ni sample), even reaching the values of Ni/IrMn at 5K. This behavior may be explaned by a greater matching between the FeMn and Ni{x}Cu{1-x} crystalline structures on the [111] direction, which favors the formation of the (111) FeMn face more consistently than the corresponding IrMn face. All the studied multilayers showed no spin valve behavior, but an increased coercivity and supressed exchange bias were observed, probably because of coupling between the ferromagnetic layers.

Os filmes moleculares constituídos por complexos polipiridínicos de rutênio, clusters trigonais de acetato de rutênio e porfirinas polimetaladas, tem sido investigados de forma sistemática, proporcionando uma ampla variedade de interfaces funcionais, para uso em dispositivos eletrônicos, sensores, células electrocatalíticas e de fotoconversão de energia. Tais filmes tem sido gerados por meio de métodos conhecidos como dip coating, drop casting, e deposição química/eletroquímica, apresentando aspectos morfológicos extremamente ricos, os quais foram investigados nesta tese, por meio de microscopia de varredura de sonda. Estudos de microscopia de força atômica foram dirigidos para os filmes moleculares gerados por dip coating. As imagens foram analisadas com bons resultados através do Programa da Gwyddion, permitindo a avaliação dos parâmetros de rugosidade envolvidos nas formas e distribuição dos grãos superficiais. Os filmes obtidos por drop casting foram investigados por meio da microscopia de força atômica, MACMode, apresentando uma grande variedade morfológica, associada principalmente com o processo de dewetting, sob a influência de interações moleculares específicas. A eletropolimerização dos complexos foi monitorada por meio de AFM condutivo, permitindo sondar as características condutoras dos filmes poliméricos. Filmes de DNA e nanopartículas magnéticas ancoradas sobre superfície de ouro foram investigados através de AFM MACMode, e AFM magnético, respectivamente. Finalmente, uma nova abordagem de sondas ultrassensitivas, foi explorada através da imobilização de nanopartículas magnéticas sobre MACLevers, ampliando os limites de detecção gravimétrica até sub-picograma. / Molecular films constituted by ruthenium polypyridine complexes, triangular ruthenium acetate clusters, and polymetallated porphyrins have been systematically investigated, providing a wide range of functional interfaces for electronic devices, sensors, photoconversion and electrocatalytical cells. Such films have been generated by dip coating, drop casting and electrochemical deposition, displaying very rich morphological aspects, which have been investigated by means of scanning probe microscopy. AFM studies have been carried out for the molecular films generated by dip coating. The images were successfully analysed using the Gwyddion software, allowing the evaluation of the rugosity parameters determining the grain shapes and distribution over the films. The films obtained by drop casting have been investigated by means of MACMode SFM, exhiting a wide variety of morphologies, mainly associated with the dewetting of the samples, under the influence of specific molecular interactions. Electropolymerization of molecular complexes have been monitored by SFM techniques, including the electroconducting mode to probe the conductivity of the polymeric films. Gold anchored films of DNA and magnetic nanoparticles have also been successfully investigated by MACMode SFM and magnetic SFM techniques, respectively. Finally, a new approach for ultra-sensitive probes, based on the immobilization of magnetic nanoparticles onto the MACLevers has been devised, allowing the detection of sub-picogram amounts of analytes

Motivados por trabalhos anteriores que analisaram diferentes comportamentos entre cristais e filmes policristalinos, relacionados com a cristalinidade e a concentração de impurezas, neste trabalho investigamos métodos de obtenção e processamento de filmes de haletos alcalinos dopados. Durante este trabalho foi montado um sistema de evaporação que disponibilizou a utilização de duas fontes de evaporação para a produção de amostras: resistiva e via feixe de elétrons. Apresentamos uma comparação entre resultados de caracterizações dos filmes produzidos e de monocristais existentes na literatura. A fim de se obter filmes dopados com impurezas mono e divalente e, também, duplamente dopados, alguns métodos alternativos de processamento foram investigados. A partir da comparação entre os sistemas KCl:(In +, Tl+ e Cu+) determinamos a dependência da cristalinidade em função do tamanho do íon dopante. O efeito da temperatura do substrato durante a evaporação foi investigado para o sistema KCl:Tl+, e comparado com resultados obtidos em filmes submetidos a tratamentos térmicos. Para a obtenção de filmes do sistema KCl:Yb2+:CN-, a preparação dos materiais precursores é um aspecto muito importante a ser considerado, a fim de se reproduzir nos filmes propriedades similares às dos monocristais. Nesse sentido, para evaporação foram utilizados o próprio cristal e pastilhas dos sais precursores obtidas a partir de técnicas de processamento cerâmico. A caracterização óptica dos filmes foi feita através de espectroscopia de absorção óptica e luminescência. A morfologia foi observada através de microscopia eletrônica de varredura e de força atômica, e a estrutura determinada por técnica de difração de raios X / The present work has been motivated by previous research on doped alkali halides films, that had been compared with single crystals, yielding different features, wich were related to crystallinity and impurity concentration. Preparation and processing techniques of doped alkali halides polycrystalline films have been investigated in this work. Two different evaporation sources have been used for samples production: resistive and via electron beam gun. Main results presented here are used to compare single crystals and films. In order to prepare single and double doped films, we have also tried several processing methods. From investigation of KCl:Tl+ system we have determined crystallinity dependency with impurity ion size. The KCl:Tl+ system has been used to verify the effect of substract temperature during evaporation. Results have been compared with films submited to thermal annealing. To obtain double doped KCI:Yb2+ :CN- films, we were very careful with preparation of precursor materials, since we intended to reproduce single crystals physical properties. Then, we have used single crystal itself for evaporation, besides pressed power pieces from precursor salts, obtained from ceramics processing technique. Optical absorption and photoluminescence have been carried out to perform optical characterization of evaporated films. Morphology has been observed by atomic force microscopy and scanning electron microscopy, and film structure has been observed by X-ray diffraction technique

Muitos organismos vivos, tal como seus constituintes, são formados por sistemas químicos complexos que envolvem a interação entre compostos orgânicos e inorgânicos ligados química e/ou fisicamente. Nestes sistemas as matrizes orgânicas são geralmente compostas por macromoléculas como polissacarídeos e proteínas. Essas moléculas têm o papel de direcionar a nucleação e o crescimento da porção inorgânica. O uso de superfícies metálicas adequadas recobertas por este tipo de filme híbrido tem potencial aplicação em implantes de substituição óssea, no qual são requeridas superfícies quimicamente inertes, mas que ao mesmo tempo estimulem processos de calcificação. Nesta tese estudou-se o crescimento de CaCO3 sobre superfícies metálicas de alumínio e aço inox recobertas por matrizes orgânicas compostas por diferentes poliânions e pelo policátion quitosana, na forma de filmes montados camada-a-camada (do inglês LbL), na presença ou não de fosfolipídeos (filmes Langmuir-Blodgett), formando um meio confinado para o crescimento do mineral. Diferentes técnicas foram utilizadas: microscopia eletrônica, microscopia de força atômica, espectroscopias de reflexão nas regiões do Uv-vis, e do infravermelho, Raman, espalhamento e difração de raios-X. Estudou-se a influência de diferentes grupos carregados dos fosfolipídeos e dos poliânions, tal como sua conformação, no crescimento de CaCO3. O tipo de interação entre o poliânion e a quitosana leva ao crescimento de matrizes poliméricas com diferenças em suas espessuras e capacidade de retenção de líquido, modificando as condições de supersaturação local e influenciando no tipo de estrutura de CaCO3. Puderam ser identificados dois polimorfos formados sobre os filmes orgânicos de poli(ácido acrílico) e quitosana, sugerindo que existem dois diferentes sítios onde a nucleação pode ser iniciada: a partir da solução de CaCl2 aprisionada na matriz polimérica e o outro a partir dos íons cálcio ligados como contra-íons aos grupos negativamente carregados do poliânion. Na presença do pré-recobrimento LB, a natureza da cabeça polar do fosfolipídeo direciona o tipo de ligação e crescimento da matriz polimérica, que levam ao crescimento de partículas de CaCO3 com morfologia e tamanho variados, explicados em termos da presença de ambientes com diferenças de concentrações locais de Ca2+. Além disso, verificou-se que a rugosidade superficial dos suportes metálicos pode favorecer a formação do polimorfo de CaCO3 cineticamente mais estável, mostrando que o processo de cristalização sobre estes suportes é um processo governado por difusão. A hidrofilicidade dos suportes é aumentada pela presença da matriz orgânica e pela presença de CaCO3 sobre as matrizes. O crescimento de CaCO3 em meios confinados tridimensionais, formados por membranas de policarbonato modificadas com filme finos de polieletrólitos, também foi estudado. Este tipo de molde leva à formação de estruturas cilíndricas que seguem a morfologia dos poros da membrana. A presença de poli(ácido acrílico) leva a formação de estruturas cilíndricas ocas, enquanto que cilindros completamente preenchidos foram formados nos poros contendo quitosana na última camada. Estes resultados foram explicados com base em diferenças na etapa de nucleação: na presença de PAA a nucleação de CaCO3 deve iniciar-se a partir dos íons Ca2+ ligados ao poliânion que, por sua vez, está ligado diretamente às paredes do molde; já na presença que quitosana, com maior capacidade de retenção de liquido e sem interação específica com Ca2+ a nucleação e seqüente cristalização devem ocorrer por todo o poro da membrana. As estruturas formadas são em sua maioria monocristais de calcita hexagonal orientadas na direção cristalográfica <2 -2 1>. / Some living organisms as well as their constituents are formed by complex chemical systems which involves the interaction among organic and inorganic compounds bounded physically or chemically. In these systems the organic matrices are usually composed by macromolecules like polysaccharides and proteins. These molecules have an important hole in tailoring the nucleation and the sequent growth of the inorganic portion. Metallic surfaces coated with these hybrid films have potential application as implants for bone substitution for which the surfaces must be chemically inert but at the same time they should stimulate calcification processes. In this present thesis we studied the growth of CaCO3 over aluminium and stainless steal surfaces coated with layer-by-layer films composed by different polyanions and chitosan as polycation, in the presence or not of phospholipids (Langmuir-Blodgett films). These organic matrices formed a confined medium within which CaCO3 particles were growth. Different techniques were applied in order to understand these systems: electronic microscopy, atomic force microscopy, UV-Vis and infrared reflection spectroscopy, Raman, and X-ray scattering and diffraction. We studied the influence of the different charged groups of the phospholipids and the polyanion as well as their conformation on CaCO3 growth. The type of interaction between the polycation and the polyanions tailors the growth of the organic matrices, forming films with different thickness and different water retention abilities which change the local supersaturation conditions changing the structure of the CaCO3 formed. Two types of CaCO3 polymorphs were growth over poly(acrylic acid) (PAA) and chitosan films suggesting that there are two sites where the nucleation can be started: the CaCl2 solution retained in the gel-like organic films and the Ca2+ ions bounded to the negative groups of the polyanion. In the presence of the LB pre-coating, the nature of the phospholipid polar head tailors the binding and the growth of the polymeric matrices leading to the formation of CaCO3 particles with difference in their sizes and morphologies. This result was explained in basis of the differences in the Ca2+ local concentrations in each situation. Moreover, it was observed that the surface roughness of the supports can favour the formation of vaterite, the kinetically most stable CaCO3 polymorph, showing that the crystallization may be guided by diffusion processes. The hidrophilicity of the supports was improved by the presence of both organic and hybrid films. The growth of CaCO3 in tridimentional confined mediums was done using LbL modified polycarbonate membranes as template. This template leads to the formation of cylindrical CaCO3 particles following the morphology of the membrane pores. CaCO3 tube-like structures were formed in presence of PAA, while rod-like structures were formed in presence of chitosan in the top LbL layer. These results were explained on basis of the difference in the nucleation stages: in the presence of PAA the nucleation starts on the Ca2+ ions bounded to the polyanion that is linked to the walls of the template; in the presence of chitosan that presents higher water retention ability and has no specific interaction with Ca2+ ions, the nucleation and sequent crystallization should occur through the entire pore of the membrane. The electron diffraction patterns showed that the CaCO3 structures are single crystals of the calcite polymorph oriented in < 2 -2 1> crystallographic direction.