Structure and photoluminescence of the TiO2 films grown by atomic layer deposition using tetrakis-dimethylamino titanium and ozone

TiO2 films were grown on silicon substrates by atomic layer deposition (ALD) using tetrakis-dimethylamino titanium and ozone. Amorphous TiO2 film was deposited at a low substrate temperature of 165 degrees C, and anatase TiO2 film was grown at 250 degrees C. The amorphous TiO2 film crystallizes to anatase TiO2 phase with annealing temperature ranged from 300 degrees C to 1,100 degrees C in N-2 atmosphere, while the anatase TiO2 film transforms into rutile phase at a temperature of 1,000 degrees C. Photoluminescence from anatase TiO2 films contains a red band at 600 nm and a green band at around 515 nm. The red band exhibits a strong correlation with defects of the under-coordinated Ti3+ ions, and the green band shows a close relationship with the oxygen vacancies on (101) oriented anatase crystal surface. A blue shift of the photoluminescence spectra reveals that the defects of under-coordinated Ti3+ ions transform to surface oxygen vacancies in the anatase TiO2 film annealing at temperature from 800 degrees C to 900 degrees C in N-2 atmosphere.