Motivated by the need for a Ge surface passivation layer, chemical vapor deposition of thin (< 10 nm) films of amorphous boron carbo-nitride (BCxNy) on Ge(100) surfaces were studied to assess film continuity, interface bonding, Ge oxidation prevention, and electrical passivation. BCxNy nominally 2.5-5 nm thick continuously covers Ge(100), as determined by ion scattering spectroscopy and two angle resolved x-ray photoelectron spectroscopy (ARXPS) techniques. ARXPS analysis reveals no evidence of an interfacial layer due to elemental intermixing at the BCxNy-Ge(100) interface. High resolution transmission electron microscopy images of HfO₂ / BCxNy / Ge(100) cross-sections reveal abrupt BCxNy-Ge(100) interfaces. XPS was used to track Ge oxidation of BCxNy-covered Ge(100) upon exposure to ambient, 50 °C deionized water, and a 250 °C atomic layer deposition HfO₂ process. If the BCxNy layer is continuous ([greater-than or equal to] ~ 4 nm), the underlying Ge(100) surface is not oxidized despite incorporation of O into BCxNy. Thinner films ([less than or equal to] 3.2 nm) permitted Ge(100) oxidation in each oxidizing environment studied. Ge nanowires with a 5.7 nm BCxNy coating were resistant to oxidation for at least 5 months of ambient exposure. C-V and I-V measurements were made for metal-insulator-semiconductor (MIS) structures fabricated from n-Si(100) and n-Ge(100) wafers passivated with 4.5-5 nm BCxNy. C-rich BC0.61N0.08 films studied up to this point exhibited large amounts of hysteresis and fixed negative charge, so they were abandoned in favor of N-rich BCxNy (0.09 [less than or equal to] x [less than or equal to] 0.15, 0.38 [less than or equal to] y [less than or equal to] 0.52). N-rich BCxNy grown at 275-400 °C showed that lower deposition temperatures resulted in improved electrical characteristics, including decreased hysteresis, lower VFB shift, lower leakage current, and less C-V stretch-out. The electrical improvement is attributed to decreased bulk and interfacial defects in BCxNy deposited at lower temperatures. Even for the lowest growth temperature studied (275 °C), BCxNy-passivated Ge(100) devices had considerable hysteresis and electrical characteristics worsened after a post-metallization anneal. BCxNy-passivated Si(100) devices outperformed similar Ge(100) devices, likely due to the higher interface state densities at the BCxNy-Ge(100) interface associated with the higher relative inertness of Ge(100) to thermal nitridation. / text

Made available in DSpace on 2015-05-14T12:14:15Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 9771925 bytes, checksum: 18e09223967768516f9115888a6485b4 (MD5) Previous issue date: 2013-02-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The ability to manipulate the adsorption process is very desirable. The possibility of understanding and eventually modifying the underlying mechanism is an intriguing task in fundamental physics as well as useful for applications. Indeed, the ability to control the adsorption processes is motivated by the control of thin film growth, by exploring ways to transfer patterns to a surfaces in development of microelectronics, as well as by constructing nanometer-scaled structures which are very important in the development of quantum devices. A first theoretical proposal (De Silans et al. 2006) has been done on controlling the adsorption of cold alkali atoms in dielectric surfaces using laser light. In 2007, Balykin and co-workers (Afanasiev et al. 2007) demonstrated laser-induced adsorption of hot atoms on a surface. They reported that sending a powerful near resonant laser to the interface between a dielectric surface and an alkali vapour leads to the formation of a metallic thin film, and demonstrated the possibility of using such a technique for sub-micrometer lithography. The aim of this work is to systematically study the process of laser induced hot atomic cesium vapor adsorption so as to understand the underlying mechanism as well as to control the process. We monitor the rate of a thin film growth during an induced adsorption process onto a characterized crystalline surface (sapphire) for a prescribed set of experimental conditions in order to be able to decipher, at the atomic level, the rules governing the evolution of the growth (physisorption or chemisorption), and to explore ways to tailor the film shape (lithography). To probe the film growth, we detect the transmission of a He:Ne laser, thus monitoring the time evolutionof the film's thickness. In this way we obtain the growth rate as a function of experimental parameters (vapour density, laser frequency and power and surface temperature). The data obtained we used to model the physical processes involved in the light-induced adsorption. / A compreensão do mecanismo de adsorção tem sua importância tanto do ponto de vista fundamental, no que concerne a identificação das interações átomo e superfície, como também tem um forte apelo tecnológico. Controlar o processo de adsorção é motivado, por exemplo, pelo controle do crescimento de filmes finos, explorando maneiras de transferir padrões espaciais para uma superfície particularmente visando á litografia, com aplicações evidentes em microeletrônica. Com essa motivação geral estudamos nessa tese processos de interação de átomos com superfícies dielétricas na presença de lasers ressonantes. Uma primeira proposta de um mecanismo para controlar, via laser, o processo de adsorção de átomos alcalinos frios em uma superfície dielétrica foi apresentado em (De Silans et al. 2006). Em 2007, Balykin e colaboradores (Afanasiev et al. 2007) observaram o processo de adsorção de átomos alcalinos de um vapor térmico sobre uma superfície dielétrica. Eles relataram que incidindo um laser quase ressonante na interface dielétrico vapor alcalino formava-se um filme fino metálico e demonstram também a possibilidade de usar tal técnica para litografia sub-micrométrica. O objetivo desse trabalho é estudar sistematicamente o processo de adsorção induzida por laser de vapor atômico de césio térmico em uma superfície dielétrica, para compreender o mecanismo do processo que abre a possibilidade do controle desse processo de litografia. Desta forma, nós monitoramos a taxa de crescimento do filme em uma superfície de safira para um conjunto de condições experimentais com a finalidade de ser capaz de decifrar, no nível atômico, as regras que governam o crescimento do filme, e explorar maneiras de manipular o perfil do filme. Para sondar o crescimento do filme, nós monitoramos a transmissão de um laser não ressonante. Desta maneira, obtemos a taxa de crescimento do filme em função dos parâmetros experimentais (densidade do vapor, frequência e potência do laser e a temperatura da superfície). Os dados obtidos foram usados para modelar o processo físico envolvido, que nos permite descrever de forma bastante completa, as etapas desse processo de adsorção induzida por laser. Além desse estudo sistemático da adsorção induzida por laser, fizemos durante o desenvolvimento desse trabalho uma série de estudos de técnicas para a estabilização de laser semicondutores em uma transição atômica.

O caráter aleatório e não homogêneo do crescimento de filmes finos, por processo de deposição, leva à formação de uma superfície rugosa que obedece, em geral, a uma geometria fractal. A dinâmica de crescimento da superfície do filme pode ser descrita por meio de modelos de crescimento discretos, simulações numéricas e equações diferenciais estocásticas. Os modelos e as equações nos fornecem os expoentes críticos, que descrevem o comportamento da rugosidade com a escala de observação e tempo de deposição. Crescemos filmes de platina e ouro através da técnica de implantação e deposição de íons por imersão em plasma metálico. Determinamos experimentalmente os expoentes críticos por meio de microscopia de tunelamento. Comparamos os nossos resultados experimentais com previsões dadas por alguns modelos teóricos. Verificamos que há um bom acordo entre eles e as previsões dadas pela equação estocástica de Kardar, Parisi e Zhang. A estrutura cristalina dos materiais também foi analisada por meio de difração de raios x. / The randomness and inhomogeneities in the growth of thin films generate a rough surface obeying, in general, fractal geometry. The growth dynamics of film surface can be described by theoretical discrete models, numerical simulations and stochastic differential equations. Models and equations give the critical exponents that describe the behavior of roughness with the observation scale and deposition time. We have synthesized platinum and gold films by metal plasma immersion ion implantation and deposition. We have measured the critical exponents by Scanning Tunneling Microscopy. Our experimental results were compared with some theoretical models predictions. We verified that there is a good agreement between them and the theoretical predictions given by the Kardar, Parisi and Zhang stochastic equation. The crystallographic structure was also analyzed by X-ray diffraction.

There has been growing interest in designing and development of suitable micro or nano drug delivery system with the ability to target site specifically and release the payload in a predetermined fashion. Recently a new type of system called polyelectrolyte microcapsules and thin films have been proposed and developed for applications such as, biomedical devices to micro sensing and drug delivery. Owing to its advantages of mild preparation conditions, multifunctionality, with programmable characteristics and to encapsulate large amount of materials, it has shown immense potential. In the present research, multilayer polyelectrolyte thin films composed of Poly(methacrylic acid) (PMA) and Poly (vinyl pyrrolidone) (PVP) were deposited on the flat substrates using layer by layer (LBL) technique. The film growth and its deconstruction under physiological conditions were characterized using UV Visible spectrophotometer and Scanning Electron Microscopy (SEM). Hollow microcapsules composed of PMA and PVP were also produced with the help of sacrificial silica template using the same LBL adsorption technique. After coating the desired number of PVP and PMA layers, the colloidal template was removed with a buffer system composed of Hydrofluoric acid (HF) and Ammonium fluoride (NH4F). The obtained capsules were characterized for its surface morphology using SEM and Atomic Force Microscopy (AFM). The hydrogen bonding in capsule formation was confirmed by Fourier Transform Infrared Spectroscopy (FTIR). Encapsulation and release with the microcapsules was carried out using Rifampicin (Antitubercular drug) as a model drug. The interaction of empty and drug loaded capsules with Mycobacterium Smegmatis cell line was investigated. It was found that the empty capsules did not affect the cell growth indicating their biocompatibility. Confocal microscopy studies with Doxorubicin (anticancer drug), which is a naturally fluorescent molecule, showed the drug is indeed encapsulated inside the hollow capsule. From the above studies, it was concluded that polyelectrolyte capsules have the potential to be used for delivering drugs.

O caráter aleatório e não homogêneo do crescimento de filmes finos, por processo de deposição, leva à formação de uma superfície rugosa que obedece, em geral, a uma geometria fractal. A dinâmica de crescimento da superfície do filme pode ser descrita por meio de modelos de crescimento discretos, simulações numéricas e equações diferenciais estocásticas. Os modelos e as equações nos fornecem os expoentes críticos, que descrevem o comportamento da rugosidade com a escala de observação e tempo de deposição. Crescemos filmes de platina e ouro através da técnica de implantação e deposição de íons por imersão em plasma metálico. Determinamos experimentalmente os expoentes críticos por meio de microscopia de tunelamento. Comparamos os nossos resultados experimentais com previsões dadas por alguns modelos teóricos. Verificamos que há um bom acordo entre eles e as previsões dadas pela equação estocástica de Kardar, Parisi e Zhang. A estrutura cristalina dos materiais também foi analisada por meio de difração de raios x. / The randomness and inhomogeneities in the growth of thin films generate a rough surface obeying, in general, fractal geometry. The growth dynamics of film surface can be described by theoretical discrete models, numerical simulations and stochastic differential equations. Models and equations give the critical exponents that describe the behavior of roughness with the observation scale and deposition time. We have synthesized platinum and gold films by metal plasma immersion ion implantation and deposition. We have measured the critical exponents by Scanning Tunneling Microscopy. Our experimental results were compared with some theoretical models predictions. We verified that there is a good agreement between them and the theoretical predictions given by the Kardar, Parisi and Zhang stochastic equation. The crystallographic structure was also analyzed by X-ray diffraction.

Ce mémoire de thèse présente le développement d'un dispositif expérimental spécialement conçu pour l'étude de la diffraction d'atomes rapides et son utilisation pour suivre la croissance de couches minces sur un bâti d'épitaxie. Des études de surfaces de KBr(100) et de NaCl(100) avec ce nouveau dispositif sont présentées. Nous nous sommes intéressés notamment à la forme du potentiel que les atomes perçoivent lorsqu'ils diffusent sur une surface de KBr(100). Nous avons également mis en évidence lors de ces études un nouveau régime de diffraction qui semble correspondre à des mouvements longitudinaux et normaux cohérents. Grâce à des images mieux résolues, nous avons montré comment la diffraction d'atomes rapides permet d'observer et quantifier des défauts topologiques comme la mosaïcité. Une étude d'une surface d'Argent (110) est aussi présentée. Elle a permis d'observer la diffraction d'atomes rapides sur les métaux, montrant ainsi que GIFAD est applicable aux trois types de matériaux (isolants, semi-conducteurs et métaux) et que les processus d’excitations électroniques sur ces surfaces ne détruisent pas complètement la cohérence. Enfin des premiers résultats de GIFAD en tant que technique de suivi de croissance par épitaxie sont présentés dans ce travail. / This Ph.D memoir presents the development work of an experimental setup especially designed for the study of the fast atom diffraction and its use as a method to control the thin films growth in an epitaxy chamber. Studies of the surfaces of KBr(100) and NaCl(001) with this new setup are presented. A new diffraction regime which may correspond to coherent longitudinal and normal motions is identified. The enhanced resolution allows observation of topological defects such as the surface mosaicity. A study of the Ag(100) surface is also presented showing that fast atom diffraction can be observed on metal surface as that the inelastic excitations processes do not completely destroy the coherence. Finally, we present the first results obtained with GIFAD as a method to control thin film growth.