Résumé:
In this dissertation, we used chemical spray pyrolysis method for the growth of pristine, annealed, and magnesium (Mg) doped tin dioxide (SnO2) thin films, for their application in the detection of toxic gases. The synthesis of tin dioxide thin films, their characterizations as well as their gas sensing performances have been investigated. The spray pyrolysis method has proved its compatibility and its suitability for growing pristine and doped thin films within a single step deposition process at moderate temperatures (≤ 400°C). Furthermore, various analyzing techniques have been used to examine the structure, morphology, and composition
of the synthesized films. The results showed that thermal annealing at 450°C improved the crystallinity and homogeneity of the Mg-doped SnO2 films. The gas sensing characteristics in the presence of toxic gases, showed that the increase of the Mg doping level up to 1.6 at.% within the SnO2 films has improved their responses, their sensitivities, as well as their partial selectivities mainly towards ethanol (the response is almost fourteen times higher). Thus, we were able to propose an explanatory model for the interaction of the sensitive layers surface with gas molecules. The latter is based on the defects introduced in the films, the subsequent decrease in the crystallites’ size and the formation of different phase that led to the improvement of the interaction between the adsorbed oxygen species and the target gas molecules.
