A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120°C and 1 kgf/cm 2 for 2 min, followed by a 10 min post-baking at 100°C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-j titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon ($0.01 cm 2 /V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.

The orientational order of liquid crystals (LCs) induced by periodic patterned substrates has been investigated with cells coated by azopolymer films that could be photoaligned in a controlled way. Two regimes were observed depending on the period of the patterns: (i) above 3.0 microm the LC follows the direction imposed by the patterned substrate since the energy stored in the surface potential minimizes the elastic energy of the LC medium. (ii) For periods smaller than 1.0 microm a homogeneous in-plane state was induced and the LC did not follow the orientation imposed by the surface. This in-plane transition could be explained qualitatively by a theoretical model based on the competition between the Frank-Oseen elastic energy and the phenomenological surface potential. The results also suggest an out-of-plane transition for the LC director as the period was reduced. These results agree with data in the literature for patterned substrates with completely distinct architectures. This indicates that for a particular LC sample the overall behavior depends basically on the texture period instead of the texture architecture. The textures were characterized with a scanning near-field optical microscope (SNOM), which allowed simultaneous morphological and optical images in the submicrometer range.

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Dedico este trabalho aos meus pais e à minha família.iii AgradecimentosGostaria de agradecer as várias pessoas que contribuíram de forma direta ou indireta para a realização deste trabalho.Em especial, ao Toninho, pela oportunidade e voto de confiança para a realização deste trabalho, pela orientação e dedicação, sugestões e conselhos sempre dados de modo preciso e sempre pacientes, e principalmente pela sua amizade; Ao Seabra, pelos ensinamentos em sua área de pesquisa e principalmente pela paciência e insistência nas horas de dificuldade; Ao Jeroen, eterno amigo, que ensinou todos os detalhes e procedimentos no manuseio do SNOM de forma precisa e carinhosa; À Alessandro, Angela, Regina, Luiz, Narcizo, companheiros de trabalho que desde o início acompanharam os meus primeiros passos; À Gabriel, Simone, Gilderlon e Erick, valeu pela companhia, amizade e brincadeiras que tornaram o convívio no Laboratório mais carinhoso e agradável; Ao Sergio, Marcelo, Iran, Paulo e Marcos, obrigada pela predisposição e paciência por me ajudarem sempre; Aos meus Pais, minha avó, e meus irmãos (Renata, Camila e Divino), pelo apoio incondicional durante todos esses anos, desde os meus primeiros passos e em todos os momentos bons e ruins; pela infinita paciência e compreensão nas várias vezes que estive ausente, por ser o que vocês são... Sem vocês seria impossível essa minha caminhada. Optical Microscope (SNOM-MO) falls in this context due to be a technique of microscopy with high spatial resolution and magnetic sensitivity, estimated to be ∆M = 2 x 10 -12 emu. In contrast to traditional optical microscopes, SNOM deals with evanescent electromagnetic radiation and, consequently, the resolution is no longer limited by the Rayleigh criterion.The SNOM-MO is a powerful tool to obtain local magnetic information through differential susceptibility and local hysteresis loops. Using this last technique, an experimental micromagnetic mapping was made for the magnetization vector on a square amorphous CoFeSiBNb object. The experimental results obtained provided information about the two chiralities existing in its closure magnetic domain structure, whose behavior is determined mainly by the shape anisotropy. The study also showed that pinnings generated by defects on surface´s object exerted great influence on the dynamic of the magnetization vectors. Due to the large amount of local magnetic information, this kind of study becomes a potential background for the development of more accurate and complete theoretical models.The experimental results demonstrate resolution better than 125 nm. This study has allowed us to access intrinsic magnetic behaviors that motivated an interesting discussion about magnetic pinnings, rotation of magnetization, reversal magnetic fields and local anisotropy.In addition, also special attention was given to the optimization of instrumental technique in order to make the SNOM-MO a measurement instrument with nanometer resolution. Among these efforts we emphasize the production of tips by FIB technique and the int...

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