Caracterização de camadas de TiO2:Al2O3 por refletividade de raios-x

• Autor(a) principal: Bazoni, Raniella Falchetto
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4261
• topic: ALD; Refletividade; Ajustes; Softwares; ALD; Reflectivity; Fits; Softwares; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

In this work, ultra-thin layers of oxides grown using the technique of atomic layer deposition were characterized by measurements of x-ray reflectivity. TiO2:Al2O3 samples were grown using titanium isopropoxide (Ti(Hi-Pr)4), trimethylaluminum (Al(CH3)3) and water. The proportion of alumina was changed from 8 to 44% by varying the number of cycles of each precursor. TiO2:NiO samples were also grown using nickelocene (NiCp2) and water as precursors for NiO. The x-ray reflectivity measurements were performed at the Brazilian Synchrotron Light Laboratory and showed a reduction in deposition rate during growth of the TiO2:NiO series of samples, which prevented its use in the remainder of the study. The experimental data of TiO2:Al2O3 samples were analyzed using 03 simulation software: MOTOFIT, a free package designed to run on the IGOR Pro platform, and two MATHEMATICA codes; a first one based on kinematic approximation and another based in the Parrat recursion s method. The fitting procedure was based on two models: single layer, considering alumina as dopant, and multilayer, with sample composed of alternate layers of TiO2 and Al2O3. We conducted a detailed comparison of the results obtained from the softwares and models used and analyzed the influence of various parameters on the fits obtained. The fittings allowed the determination of various sample parameters, such as electron density and thickness of each layer and the roughness of the various interfaces. Comparing the software, we found that the best fits to the experimental data were obtained using the Parrat recursion s method. The multilayer model resulted in a better fit, reflecting the repetitive nature of the growth process, although the interface roughness values obtained were too large compared to layer thickness. Irrespective of software and the model used, the results show that atomic layer deposition can be used to obtain layers with controlled thickness and roughness less than 1 nm, independent of the number of cycles used in the deposition process.