N-DOPED TiO2 THIN FILMS GROWN BY MOCVD FOR HETEROGENEOUS PHOTOCATALYSIS

Reference	Presenter	Authors (Institution)	Abstract
06-106	EDUARDO CESAR OLIVEIRA	OLIVEIRA, E.C.(INSTITUTO DE PESQUISAS ENERGETICAS E NUCLEARES); Bento, R.T.(Instituto de Pesquisas Energéticas e Nucleares); Szurkalo, M.(Instituto de Pesquisas Energéticas e Nucleares); Correa, O.V.(IPEN); Pillis, M.F.(IPEN/CNEN);	Titanium dioxide is the most studied material among the several semiconductors employed in advanced oxidative processes for water decontamination. TiO2 thin films are recognized for its good performance under UV light. In this process, the TiO2 catalyst photo-activated generates hydroxyl radicals as a result of the absorption of radiation (UV-vis light). However, the band gap energy for anatase TiO2 phase is 3.2 eV, limiting its use only under ultraviolet (UV) irradiation (? < 380 nm), that corresponds to about 5% of the sun light spectrum. Doping TiO2 films with nitrogen can reduce the band gap, and the semiconductor can be activated under visible light. In this work, TiO2 and nitrogen-doped TiO2 (N-doped TiO2) thin films were grown on borosilicate substrates at 400ºC by using metalorganic chemical vapor deposition (MOCVD). Titanium IV isopropoxide was used as titanium and oxygen precursors. The nitrogen-doping was carried out during the TiO2 deposition and ammonia was used as nitrogen precursor with flow rates of 0.2 and 0.5 L min-1. The films were characterized by atomic force microscopy, field emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy techniques. The photocatalytic studies were done by measuring the degradation of methyl orange dye for 5h under UV and visible light. The results showed that both the doped and the undoped films presented rounded well-defined grains and columnar structures. X-ray diffraction analyses show the formation of nitrogen-content phases besides anatase. Under UV-light the undoped film showed the best behavior whereas the N-doped TiO2 films exhibited a promising photocatalytic behavior under visible light.
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