Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-02-20T13:22:28Z No. of bitstreams: 0 / Made available in DSpace on 2015-02-20T13:22:28Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2015-03-26T13:35:19Z (GMT). No. of bitstreams: 1 texto completo.pdf: 7178569 bytes, checksum: b7f915a255beb77386b9a40b7b8113cd (MD5) Previous issue date: 2012-07-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work consists of the optical characterization of CdMnTe films grown on glass substrate. The films were deposited by the technique of molecular beam epitaxy (MBE) and characterized by optical spectroscopy and ellipsometry. The energy gap for films with different manganese concentration was determined. We demonstrate the increase in gap energy as concentration of manganese increases. The pronounced interference fringes observed show the good optical quality of the films grown. By ellipsometry technique we can observe the behavior of the refractive index and extinction coefficients a function of manganese concentration. We have also obtained values of sample thickness and growth rate. / Este trabalho consiste na caracterização ótica de filmes de CdMnTe crescidos sobre substratos de vidro. Os filmes foram depositados pela técnica de epitaxia por feixe molecular (MBE) e caracterizados através de espectroscopia ótica e elipsometria. Foram determinados parâmetros como gap dos filmes em função da concentração de manganês. Podemos comprovar o aumento do gap com o aumento da concentração de manganês. As franjas de interferência nos mostram a boa qualidade dos filmes crescidos. Através da técnica de elipsometria podemos observar o comportamento do índice de refração e do coeficiente de extinção em função da concentração de manganês. Foram obtidos também os valores da espessura e taxa de crescimento dos filmes.

Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-02-20T13:22:28Z No. of bitstreams: 0 / Made available in DSpace on 2015-02-20T13:22:28Z (GMT). No. of bitstreams: 0 / Filmes finos de óxido de nióbio têm sido usados em muitas aplicações tecnológicas. Existem pelo menos três óxidos estáveis de nióbio: NbO, NbO2 e Nb2O5 e cada um deles tem propriedades específicas. O Nb2O5 é a forma termodinamicamente mais estável e apresenta propriedades físicas e químicas únicas, como alto índice de refração, band gap largo, excelente estabilidade química e resistência à corrosão, baixa absorção óptica no campo da luz visível até regiões próximas ao infra-vermelho, sendo amplamente utilizados como filtros de interferência óptica de alta qualidade. Neste trabalho foram depositados filmes de óxido de nióbio por meio da técnica de sputtering reativo sobre substratos de silício e borossilicato. Os filmes finos foram obtidos com vazão de oxigênio variando entre 15 e zero sccm. O objetivo deste trabalho foi a caracterização das propriedades ópticas dos filmes. Foram avaliados o índice de refração e a espessura pela técnica de elipsometria, o band gap pelo método de Tauc e a razão atômica e a densidade superficial por meio de Espectrometria de Retroespalhamento Rutherford (RBS). Foram obtidos espectros de transmitância e refletância por Espectrofotometria UV/Vis/NIR e o coeficiente de extinção foi calculado pelo método de Hong. Todos estes parâmetros são importantes para aplicação em dispositivos ópticos. Nos filmes depositados com vazão de oxigênio de 15 sccm foi observado que o índice de refração aumenta com o aumento da espessura dos filmes e que o composto formado foi Nb2O5. Para uma vazão de 2,0 sccm foi encontrado o composto NbO2 e o filme apresentou alta absorção ótica. Os resultados sugerem que outros óxidos de nióbio ou nióbio metálico foram incorporados nos filmes conforme o fluxo de oxigênio foi diminuído. Foi observada uma relação direta entre a diminuição da vazão de oxigênio durante a deposição e um aumento da quantidade de nióbio nos filmes, acompanhados de um aumento do índice de refração e da densidade superficial. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Ce travail est une contribution à l'étude de l'interaction entre des couches minces de silicium amorphe hydrogéné (a-Si:H) et un plasma d'hydrogène, dans un réacteur de dépôt par PECVD (Plasma Enhanced Chemical Vapor Deposition). Le suivi in situ de la cinétique de gravure par l'hydrogène atomique est réalisé par ellipsométrie UV-visble. Les différents paramètres de plasma (température, puissance radiofréquence, pression du gaz H2, type de dopage du matériau) pouvant impacter cette cinétique ont été sondés. L'analyse des spectres d'ellipsométrie spectroscopique, à l'aide d'un modèle optique approprié, a permis de mettre en évidence leurs effets sur le temps de formation de la couche modifiée par l'hydrogène, son épaisseur et son excès d'hydrogène, ont été analysés. Le même traitement au plasma d'hydrogène appliqué à des jonctions i/p et i/n, révèle un comportement particulier de la cinétique de gravure dans la zone de jonction. Ce comportement a été interprété dans le cadre d'un modèle simple de diffusion de l'hydrogène sous champ électrique. / This work is a contribution to the study of the interaction between hydrogenated amorphous silicon (a-Si:H) thin films and hydrogen plasma in a PECVD (Plasma Enhanced Chemical Vapor Deposition) reactor. The kinetics of silicon etching by atomic hydrogen is monitored in situ by UV - visble ellipsometry .Several plasma parameters (temperature, RF power, H2 gas pressure, the doping of the material) that may impact the kinetics were probed. An analysis of the spectroscopic ellipsometry spectra, thanks to an appropriate optical model, allowed evidencing their effects on the time constant, the thickness and the hydrogen excess of the H-modified layer.The same hydrogen plasma treatment repeated on i/p and i/n H base junctions revealed a particular behavior of the etching kinetics in the junction zone. This effect is interpreted in the frame of a simple of hydrogen diffusion model under an electric field.

This diploma thesis is focused on preparation of perovskite methylammonium lead bromide thin film layers and also thin film layers of its precursors, namely methylammonium bromide and lead(II) bromide, by spin-coating from the solution; and optical characterisation of the prepared thin film layers by UV-VIS spectroscopy and spectroscopical ellipsometry. Methylammonium bromide does not absorb in visible nor ultraviolet region, the maximum absorption of lead(II) bromide occurred in ultraviolet region, methylammonium lead bromide absorbs in visible region. Optical band gaps were determined by Tauc method to (3,5 ± 0,1) eV for lead(II) bromide and 2,15 eV, respectively 2,25 eV for perovskite. Refractive indices and extinction coefficients were determined by ellipsometry in range of wavelengths from 290 nm to 830 nm and their dependence with layer thickness was discussed. Ellipsometry model used in this thesis consist on Tauc-Lorentz oscillators for methylammonium bromide, methylammonium lead bromide and partially for lead(II) bromide, which another part is formed by New Amorphous oscillator.

Thesis in theoretical part is focused on the principle of spectroscopic ellipsometry and formation of thin films by plasma-enhanced chemical vapor deposition (PECVD). In the experimental part we describe the deposition system, ellipsometer and mathematical evaluation of ellipsometric data, materials used for film formation and processing of the samples. Single-layer and multilayer structures of polymeric materials were prepared. We revealed that the optical properties of thin films are independent of film thickness. We also described the effect of the effective power and deposition gas mixture on optical properties of thin films.

In this investigation, the cation distribution in ferrites of spinel-type structure is spectroscopically investigated with respect to the observed magnetic behavior. The ferrite thin films were fabricated by pulsed laser deposition and consequently annealed at different temperatures as well as atmospheres. Structural properties were determined with various methods and the crystalline quality was examined. The dielectric function line-shape was parametrized based on empirical evidence and was found to be dominated by electronic transitions between d orbitals of Fe2+ cations as well as transitions from O 2p to 3d and 4s orbitals of iron and zinc cations. The strongest magneto-optical response was observed for transitions involving cations, which correspond to lattice disorder and inversion within the normal spinel structure. With the decrease in the substrate temperature during fabrication, a decrease in the magnetic response was observed. The diminishing ferrimagnetic order was directly correlated to the decrease in strength of the transitions, involving Fe3+ on tetrahedral lattice sites. After thermal treatment in argon atmosphere and at a temperature below the deposition temperature, the increase in the magnetic response was explained through the facilitation of oxygen vacancies. With the increase in treatment temperature, a decrease in ferrimagnetic order was related to the recrystallization of the disordered spinel structure toward a more stable normal configuration, evident in the dielectric function spectra. The cationic configuration distribution in the surface as well as the bulk region, as a function of Zn concentration, was determined from approximation of the XPS and the dielectric function spectra, respectively. The difference in the cation configuration distribution, in films of predominantly inverse configuration, was related to the weak magnetic response, as opposed to films of predominantly normal spinel configuration. Our results demonstrate that a defect-rich surface region could serve as a possible explanation for the ferrimagnetic order in a nominally non-magnetic normal spinel ZnFe2O4. In combination with structural property determination, the net magnetic behavior is explained through the local cationic disorder, determined from the parametrization of the dielectric function spectra in a wide spectral range.:1 Introduction 2 Theoretical background and fundamental considerations 2.1 Spinel ferrite crystal structure 2.2 Crystal field stabilization energy 2.3 Band structure description 2.4 Verwey transition 2.5 Magnetic exchange interactions 3 Sample preparation and modification 3.1 Macroscopic spinel film formation 3.2 Pulsed laser deposition 3.3 Thermal treatment 3.4 Sample overview 4 Methods and general properties 4.1 Structure characterization techniques 4.1.1 X-ray diffraction 4.1.2 X-ray reflectivity 4.1.3 Energy dispersive X-ray spectroscopy 4.1.4 Focused ion beam and scanning electron microscopy 4.1.5 Raman spectroscopy 4.2 Surface properties 4.2.1 Atomic force microscopy 4.2.2 X-ray photoelectron spectroscopy 4.3 Dielectric tensor properties 4.4 Spectroscopic ellipsometry 4.5 Magneto-optical Kerr effect 4.6 Magneto-static properties 5 Results and discussion 5.1 Magnetic and optical properties of Fe3O4 thin film and single crystal 5.2 Magneto-optical properties of ZnxFe3−xO4 thin films 5.3 Fabrication temperature dependent ferrimagnetic order 5.4 Thermally induced structural stabilization 5.5 Cation configuration in dependence on the Zn concentration 5.5.1 Structural property determination 5.5.2 Composition characterization 5.5.3 Magneto-static behavior 5.5.4 Section summary and discussion 6 Summary and outlook Bibliography List of article contributions Selbstständigkeitserklärung Acknowledgments

For the development of smart surfaces high attention is focused on stimuli-responsive polymers. Since type and rate of response to environmental stimuli can be regulated by chain length, composition, architecture and topology, polymer films offer a variety of opportunities to develop such stimuli-responsive surfaces. Here polymer brush surfaces designed for a controlled adsorption of proteins and a switchable activity of immobilized enzymes are presented. The work is focused on temperature as well as pH-sensitive binary brushes, consisting of poly(N-isopropylacrylamide) (PNIPAAm) and poly(acrylic acid) (PAA), and their swelling behavior as well as their protein adsorption affinity is compared to the corresponding homopolymer brushes. All polymer brushes are covalently grafted by ester bonds to an anchoring layer of poly(glycidyl methacrylate), that itself is grafted via ether bonds to a silicon surface. Methodical investigations of layer thickness and refractive index of the brushes in the swollen state and after protein adsorption are carried out with in-situ spectroscopic ellipsometry, varying the brush composition and the solution parameters pH, salt concentration and temperature. The ellipsometric findings are correlated to results of contact angle, atomic force microscopy and zeta-potential measurements as well as colorimetric assays of enzyme activities at the brush surface. Furthermore the swelling of PNIPAAm brushes and protein adsorption at PAA Guiselin brushes are investigated in more detail with attenuated total reflexion Fourier-transform infrared spectroscopy and quartz crystal microbalance with dissipation, respectively.

The major part of my dissertation consists of thin films deposited using atomic layer deposition on flat and powder substrates. It details the various optimization experiments for process parameters like dose time, purge time, temperature, and pressure on silicon shards and powder substrates. Spectroscopic ellipsometry (SE) was used to characterize these films over a wide wavelength range (191-1688 nm). An optical model with a BEMA (Bruggeman effective medium approximation) layer was used to fit the ellipsometric data to investigate the optical properties of the alumina surface. The optimized process parameters on the flat surfaces were used for coating powder substrates. I propose a set of experiments to optimize the conditions for coating of powders and high aspect ratio structures by atomic layer deposition (ALD). The coated powders were analyzed by surface analytical techniques like X-ray photoelectron spectroscopy, spectroscopic ellipsometry, transmission electron microscopy, energy X-ray dispersive spectroscopy (EDAX), and BET. The first chapter introduces the technique of atomic layer deposition, and details its advantages and limitations over conventional thin film deposition techniques like chemical vapor deposition and physical vapor deposition. The second chapter details the initial deposition experiments performed on flat surfaces and characterization of thin films using surface analytical tools. I conducted multi-sample analysis on eleven different thin films for calculation of optical constants of alumina. The third chapter introduces thin film deposition experiments performed on powder substrates, several challenges associated with achieving conformal thin films and characterization. The fourth chapter details the experiments to achieve unilateral ALD achieved on one side of the substrates. The fifth chapter details various unconventional materials including liquid water, Coca-Cola, a coffee bean, nitrogen gas, human tooth, and printed office paper, which were analyzed by near ambient pressure XPS (NAP-XPS). This dissertation contains appendices of other tutorial articles I wrote on obtaining optical constants liquid samples using spectroscopic ellipsometry, and good experimental techniques for maintenance of vacuum equipment.

The major part of my dissertation consists of thin films deposited using atomic layer deposition on flat and powder substrates. It details the various optimization experiments for process parameters like dose time, purge time, temperature, and pressure on silicon shards and powder substrates. Spectroscopic ellipsometry (SE) was used to characterize these films over a wide wavelength range (191-1688 nm). An optical model with a BEMA (Bruggeman effective medium approximation) layer was used to fit the ellipsometric data to investigate the optical properties of the alumina surface. The optimized process parameters on the flat surfaces were used for coating powder substrates. I propose a set of experiments to optimize the conditions for coating of powders and high aspect ratio structures by atomic layer deposition (ALD). The coated powders were analyzed by surface analytical techniques like X-ray photoelectron spectroscopy, spectroscopic ellipsometry, transmission electron microscopy, energy X-ray dispersive spectroscopy (EDAX), and BET. The first chapter introduces the technique of atomic layer deposition, and details its advantages and limitations over conventional thin film deposition techniques like chemical vapor deposition and physical vapor deposition. The second chapter details the initial deposition experiments performed on flat surfaces and characterization of thin films using surface analytical tools. I conducted multi-sample analysis on eleven different thin films for calculation of optical constants of alumina. The third chapter introduces thin film deposition experiments performed on powder substrates, several challenges associated with achieving conformal thin films and characterization. The fourth chapter details the experiments to achieve unilateral ALD achieved on one side of the substrates. The fifth chapter details various unconventional materials including liquid water, Coca-Cola, a coffee bean, nitrogen gas, human tooth, and printed office paper, which were analyzed by near ambient pressure XPS (NAP-XPS). This dissertation contains appendices of other tutorial articles I wrote on obtaining optical constants liquid samples using spectroscopic ellipsometry, and good experimental techniques for maintenance of vacuum equipment.