| Summary: | 碩士 === 國立交通大學 === 照明與能源光電研究所 === 105 === In this study, titanium oxide（TiO2）films were grown on FZ p-type Si substrates by an atomic layer deposition（ALD）system with TiCl4 and H2O precursors at different temperatures（80°C, 100°C, 150°C and 200°C）. The crystal structure, surface roughness, composition, and effective minority carrier lifetime of TiO2 thin films were characterized by X-ray diffraction（XRD）, Automatic ellipsometer, Secondary ion mass spectrometer（SIMS）and Photo-conductance decay meter（PCD）respectively. The results show that a TiO2 film grown at 80°C by ALD is capable of providing stable and excellent c-Si surface passivation on undiffused p-type surfaces. The surface passivation properties of ALD TiO2 thin films depend on deposition temperature. The surface passivation ability decreases with the increase of deposition temperature. The formation of anatase phase in TiO2 thin films was found to be the reason for the deterioration of passivation ability of as-deposited TiO2 films.
In addition, the passivation properties are attributed to a good chemical passivation combined with an increased field effect passivation by negative charges. The chemical passivation is associated with a decrease of recombination active defects through H atoms which diffuse to these defects during deposition. The Cl was the reason for the amount of negative charges within the TiO2 film. The SIMS measurement indicate that annealing can not increase O, H and Cl within the TiO2 films.
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