Etude des proprietés physiques des couches minces et des poudres du SiO2 dopées au Cobalt

Abstract

This study is to develop and characterize and thin silicon oxide layers powders SiO 2 doped with different content of cobalt ( 1 , 3 and 5% by volume ) and treated in a temperature area 400-500 ° C for thin films , and 800-1000 ° C for the powders , which are obtained by the sol- gel . These thin films are deposited on glass substrates and porous silicon. We have shown the influence of the thickness, the rate of dopant and the annealing temperature on optical, structural and thermal properties of thin films and xerogels. For this, various investigative techniques were used: DSC, XRD, FTIR, Raman spectroscopy, atomic force microscopy (AFM) and UV-visible spectroscopy. The results obtained by DSC showed that doping with 5 % Co relative to the other which is doped to 1 % Co , causes a shift of phase transformations : Co , Co 3O 4 , to the low temperatures. So doped with 5% Cobalt leads to a beginning of the acceleration of the crystallization phase Co , Co 3O4 relative to the doped with 1% Cobalt state . The results of the diffractions spectra of X xerogels SiO 2 doped two cobalt concentrations show that the formation of phases : Co 3O 4 , silicat Cobalt ( Co 2SiO 4 ) Depond depending on the annealing temperature , and the content of cobalt . And on the other hand, the Raman spectrum confirmed these results. The transmission spectra of thin silicon oxide layers doped indicate that they are transparent in the visible and UV opaque. The calculation of the refractive index and the porosity of the thin film of SiO2 doped with Cobalt, from the transmittance spectra, show a variation of the latter depending on the annealing temperature, the thickness and the content of Cobalt. While, the optical gap increases.