Optical and electrical characterization of photoconductive and photorefractive materials / Caracterização optica e eletrica de materiais fotocondutores e fotorrefrativos

AUTOR(ES)

Renata Montenegro Pereira

DATA DE PUBLICAÇÃO

2007

RESUMO

The objective of this work was the characterization of photoconductive and photo-refractive materials using optical and electrical techniques. The most important property of these materials is photoconductivity so that we concentrated in the measurement of this quantity. One of the most studied materials in our laboratory, Bi12TiO20, is poorly photoconductive and, because of that, the standard technique using a white lamp followed by a monochromator, to select the illumination wavelength on the sample, has shown a very poor sensistivity. In order to improve the measurement we have therefore developed a system based on an array of almost monochromatic LEDs (Light-Emitting Diodes) with different wavelengths, which are able to provide with greater light intensity than with the classical system. We also propose a different system for the data collection and processing, which considers the exponential distribution of light along the sample?s thickness, due to the characteristic bulk absorption of these materials. Our results have shown that the new instrument and the new data processing method allow us to obtain much more information about the materials under analysis than would be possible with the classical method. The new technique was applied to the study of pure and doped B i12TiO20, as well as Bi12Ga O20 and CdTe. The results, together with further information obtained from other techniques (holography and modulated photocurrent), have allowed us to detect some localized states inside the bandgap of the materials and therefore get a better insight of their structure that is very important for the understanding of their photoconductivity properties

ASSUNTO(S)

photoconductivity photorefractive materials fotocondutividade sillenites crystals cristais selenitas telureto de cadmio materiais fotorrefrativos cadmium tellurides

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