Nanocomposites and nanostructures of II-VI and IV-VI semiconductors / Nanocompositos e nanoestruturas de semicondutores das familias II-VI e IV-VI

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The development of nanostructures and their applications constitute one of the most exciting scientific areas. A great number of studies in this area concern the preparation methods. Generally, they are classified in physical and chemical methods. The former class is based on molecular beam and lithography techniques, while the latter involves chemical reactions where crystal growth can be controlled and stabilized. In this Thesis, II-VI and IV-VI semiconductor nano(micro)structures were prepared according to three different approaches. In the first one, nanocomposites were obtained through the encapsulation of CdS and PbS nanocrystals into a porous and transparent commercial glass, named Vycor®. Glass pieces were impregnated with single-source precursors and, then, thermally treated in order to achieve in situ pyrolysis, making use of the porous environment as the stabilizer for the crystal growth. Quantum confinement effects in the optical spectrum and transmission electron micrographs characterized the nanometric dimensions of the occluded phase. In the second approach, a technique known as molecular templating by coordenant solvents was employed in order to obtaining CdS, PbS and ZnS nano(micro)crystals showing unusual morphologies. Single-source precursors were solvothermically treated in such solvents leading to CdS nanowires, PbS microstars and ZnS-ethylenediamine intercalates. In the last approach, colloidal CdSe nanocrystals with different size ranges (2 up to 7 nm) were prepared and employed in the study of the local structure and vibrational dynamics of CdSe as a function of crystal size reduction and substitution of the covering agent used in the synthetic procedure.

ASSUNTO(S)

nanofios nanocristais nanocomposite nanocrystals semiconductors semicondutores nanowires nanocompositos

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