Propriedades estruturais e ópticas de filmes finos de óxido de titânio depositados por PECVD

Orientador: Mário Antônio Bica de MoraesTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb WataghinResumo: Neste trabalho foram investigados os processos de deposição a plasma de filmes finos de óxido de titânio e da formação de partículas nas descargas empregadas nas deposições. Os filmes foram produzidos por uma técnica inédita de deposição derivada a partir do PECVD (Plasma Enhanced Chemical Vapor Deposition) convencional. Nesta técnica, inteiramente desenvolvida neste trabalho e que denominamos PECVD modificado, os filmes são depositados sobre um terceiro eletrodo posicionado fora da região intensa do plasma. As amostras produzidas a partir de plasmas de misturas de tetraisopropoxititânio (TiPT)-He-Ar e TiPT -He-O2, em diferentes condições de pressão no reator, temperatura e polarização do substrato foram analisadas pelas espectroscopias de reflexão-absorção no infravermelho (IRRAS), fotoelétrons de raios-X (XPS), retroespalhamento Rutherford (RBS) e de transmissão no ultravioleta-visível (UV-VIS). Além disto foram também empregadas difração de raios-X (XRD), microindentação e o método das duas pontas de medida de resistividade elétrica. A formação de partículas nos plasmas foi investigada por imageamento CCD, espalhamento de laser (LLS), espectroscopia de emissão óptica actinométrica (EEOA), sonda de Langmuir, microscopia eletrônica de varredura (SEM) e microanálise eletrônica (EPMA)Abstract: In this work, the plasma deposition of thin titanium oxide films and plasma particle formation processes have been investigated. The films were produced in a newly developed deposition technique derived from the conventional PECVD (Plasma Enhanced Chemical Vapor Deposition) proceedure. In this technique, which has been named modified PECVD, the films are deposited onto an additional electrode placed out of the intense plasma region. The samples produced in plasmas of titaniumtetraisopropoxide (TiPT)-He-Ar and TiPT-He-O2 mixtures in several condictions of reactor pressure and substrate temperature and bias were characterized by infrared reflectance-absorption (IRRAS), X-ray photoelectron (XPS), Rutherford Backscattering (RBS) and transmittion ultraviolet-visible (UV-VIS) spectroscopies. Furthermore, X-ray diffaction (XRD), microindentation and the two probe method have also been applied. The plasma particle formation has been investigated by CCD imaging, laser light scattering (LLS), actinometric optical emission spectroscopy (AOES), Langmuir probe, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA)DoutoradoFísicaDoutor em Ciência

Innovative low temperature plasma approach for deposition of alumina films

Alumina films were deposited from a new plasma method using aluminum acetylacetonate (AAA) powder as precursor. The AAA was sputtered in argon and oxygen plasma mixtures. It was investigated the effect of the oxygen proportion (O2%) on the properties of the coatings. Deposition rate was derived from the layer height measured by profilometry. The elemental composition and molecular structure of the films were determined by Rutherford backscattering and infrared spectroscopies, respectively. Grazing incidence X-ray diffraction was used to investigate the microstructure of the films while hardness was determined by nanoindentation technique. Inspections on the surface morphology and on the film composition were conducted associating scanning electron microscopy and energy dispersive spectroscopy. Incorporation of oxygen affects the plasma kinetics and consequently the properties of the coatings. As moderated concentrations of oxygen ( 25%) are incorporated, the structure become rich in metallic aluminum with carbon rising at low proportions. The deposited layer is not homogeneous in thickness once the chemical composition of the precursor is changed by the action of the reactive oxygen plasma. Oxygen ablation on the film surface also contributes to the lack of homogeneity of the structure, especially as high oxygen proportions are imposed. Hardness data (0.5-2.0 GPa) corroborated the idea of an amorphous structure. Based on the results presented here it was possible to identify the oxygen concentration in the plasma atmosphere which mostly removed organics while preserving the stoichiometric alumina precipitation, subject of great relevance as one considers the reduction in the energy necessary for the creation of fully oxide coatings.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Estadual Paulista Laboratório de Plasmas TecnológicosUniversidade Federal de São Paulo (UNIFESP) Departamento de Ciências Exatas e da TerraUniversidade de São Paulo Departamento de Física NuclearUniversidade de São Paulo Departamento de Física AplicadaUNIFESP, Depto. de Ciências Exatas e da TerraSciEL

Electrochemical characterization of samples of commercial steel treated with acetylene plasma

104-111Cutting tools have been employed in wood processing must be corrosion and wear resistant due to the acidic composition of wood and the wear generated during cutting, which lead to the deterioration of steel saws. Hydrogenated amorphous carbon films possess mechanical, tribological and barrier properties that can increase the hardness, wear and corrosion resistance of this type of tool. This work has involved an investigation of the effectiveness of plasma-deposited amorphous carbon thin films in protecting commercial carbon steel saws. Before deposition, the substrates were sputter-cleaned in argon plasma (19.27 Pa; 50 W) for 180 s. The films have been deposited using acetylene and argon mixtures excited by a radio frequency power supply (13.56 MHz, 70 W). The concentration of acetylene in the mixture has been varied in the inverse proportion to that of argon so as to maintain a constant total gas pressure of 1.8 Pa. The deposition time was 3600 s. The chemical behavior of the coated saws have been evaluated by electrochemical impedance spectroscopy (EIS) and polarization curves.Surface images of the plasma-coated samples have been recorded by scanning electron microscopy (SEM). The results have indicated that the plasma treatment has increased the corrosion resistance of carbon steel samples in acidic solutions

Electrochemical characterization of samples of commercial steel treated with acetylene plasma

Cutting tools have been employed in wood processing must be corrosion and wear resistant due to the acidic compositionof wood and the wear generated during cutting, which lead to the deterioration of steel saws. Hydrogenated amorphouscarbon films possess mechanical, tribological and barrier properties that can increase the hardness, wear and corrosionresistance of this type of tool. This work has involved an investigation of the effectiveness of plasma-deposited amorphouscarbon thin films in protecting commercial carbon steel saws. Before deposition, the substrates were sputter-cleaned inargon plasma (19.27 Pa; 50 W) for 180 s. The films have been deposited using acetylene and argon mixtures excited by aradio frequency power supply (13.56 MHz, 70 W). The concentration of acetylene in the mixture has been varied in theinverse proportion to that of argon so as to maintain a constant total gas pressure of 1.8 Pa. The deposition time was 3600 s.The chemical behavior of the coated saws have been evaluated by electrochemical impedance spectroscopy (EIS) andpolarization curves.Surface images of the plasma-coated samples have been recorded by scanning electron microscopy(SEM). The results have indicated that the plasma treatment has increased the corrosion resistance of carbon steel samples inacidic solutions

DNA for nano-bio scale computation of chemical formalisms using Higher Order Logic (HOL) and analysis using an interdisciplinary approach

Bio-molecular computing, 'computations performed by bio-molecules', is already challenging traditional approaches to computation both theoretically and technologically. Often placed within the wider context of ´bio-inspired' or 'natural' or even 'unconventional' computing, the study of natural and artificial molecular computations is adding to our understanding of biology, physical sciences and computer science well beyond the framework of existing design and implementation paradigms. In this introduction, We wish to outline the current scope of the field and assemble some basic arguments that, bio-molecular computation is of central importance to computer science, physical sciences and biology using HOL - Higher Order Logic. HOL is used as the computational tool in our R&D work. DNA was analyzed as a chemical computing engine, in our effort to develop novel formalisms to understand the molecular scale bio-chemical computing behavior using HOL. In our view, our focus is one of the pioneering efforts in this promising domain of nano-bio scale chemical information processing dynamics