Elaboration et caractérisation par RX d’oxydes sous forme de couches minces

Abstract

The subject of this thesis deals with the development and characterization of thin films of iron oxide. The objective is to optimize the parameters for development of thin films crystallized well. The preparation of thin films studied was carried out by the sol-gel developed in the laboratory method. Two kinds of aqueous solutions were used to make these thin layers. The first type of solution is formed of a mixture of 1 ml of FeCl3 and 3 ml of HCl and the second type of solution consists of a mixture of 3 ml of FeCl3 and 1 ml of HCl. Each of the two types is used to prepare several series of thin layers. Each set corresponds to a given concentration of [Fe3+] and it consists of several thin films prepared at various annealing temperatures. The series from the first type of solution have not led to a diffraction. The thin films prepared from the second type of solution have also, showed an insufficient crystallization except in the case of the series that resulted from the concentration of 0.05 [Fe3+]. It is this series of layers that allowed, therefore, to continue the work of memory analysis. Another series of layers obtained based on the concentration of 0.06 has proved well crystallized. Thin films of good crystallinity were subjected to X-ray analysis, SEM, in the IR and UV Visible. The X-ray analysis was used to evaluate the average size of the crystallites constituting the layers. Thus, the average sizes found for the crystallites grow with annealing temperature: the size from 20 nm to 130 nm. The microstrain serving on well-crystallized thin films were estimated by analyzing the diffraction patterns. The values of deformations of lattice planes vary between 1/1000 and 7/1000. The SEM images show that the morphology of the layers varies depending on the temperature. Average morphology is first needles, low temperature and gets thick when the temperature increases, with a curved shape of grains at 550 ° C. The spectra obtained by UV spectroscopy show that the transmittance of the thin film of Fe2O3 increases substantially as a function of the annealing temperature. There is a ""gap"" significantly larger between the layer which have not undergone annealing and other layers obtained with annealing. Furthermore, IR spectroscopy spectra show intense absorption peaks at wave numbers of around .2400 cm-1, 3350 cm-1 corresponding to the layer to 350 °C and around 2800 cm-1 and 3400 cm-1 for the layer without annealing.