Estudo e aplicação das propriedades elétricas, térmicas e mecânicas de materiais amorfos piezoresistivos em transdutores de pressão. / Study and application of eletrical properties, thermal and mechanical of amorphus matherials in piezoresistive.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This tesis presents the piezoresistivity theoretical and experimental study for two materials with amorphous structure. The first material is the Diamond Like Carbon and the other is the Indium Tin Oxide. The work includes the bibliographic study, theoretical and practical design of structures for testing individual and piezoresistors configured in bridge, in addition to the completion of the characterizations electrical, mechanical and thermal according to a proposed experimental arrangement. The experimental characterizations have been implemented using the technique of cantilever and the theory of small deflections. The different materials analyzed showed the piezoresistive effect with some order of magnitude and a sign of sensitivity to mechanical stress of tension consistent with the characteristics expected for these types of films. Both films respond to changes in temperature in a very linear and have a direction of dependency with the temperature according to the literature. The films of free doping have curves of current and voltage characteristics for this type of material indicating a mechanism of electric conduction very complex because of its diversity of microstructures and processes related to the parameters of the deposition and films with nitrogen are more thermally stable with coefficients of order of - 4900 ppm/ºC. The results indicate the existence of two types of charge carriers responsible for the average mobility and hence the resistivity and the piezoresistive effect. The films of indium tin oxide free and with some oxygen content in plasma presents characteristics of decreased electrical resistance to mechanical stress and exhibit effects of piezoresistive in the range of - 12 to - 23. Samples of these films with oxygen showed a factor of very low mechanical sensitivity and are less stables to thermal effect the samples free of oxygen. The films studied can be used in certain applications such strain gauges or even in piezoresistive pressure sensors, after adequate process of deposition and thermal annealing.

ASSUNTO(S)

filmes finos circuitos integrados sensores eletromecânicos dlc amorphous films piezoresistors sensors ito filmes amorfos

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