Abstract
<b> </b><b> </b>Undoped and nitrogen-doped titanium dioxide (TiO2) thin films of 400 nm thick deposited by spray pyrolysis were structurally and optically characterized. The effect of substrate temperature on the optical properties of the films was also investigated. Structural studies of the films were undertaken by X-ray diffraction (XRD). Energy dispersive X-ray (EDX) spectrum analysis was used to confirm the presence of nitrogen atoms in the film after doping. The optical properties such as refractive index (n), energy band gap (Eg) and Urbach energy (Eu) were determined from spectrophotometric measurements of reflectance and transmittance for both undoped and doped films. The Undoped films had an energy band gap of 3.25 eV while the doped films had band gap of 2.90 eV. The Urbach energy increased from 1.00 eV for undoped films to 1.04 eV for the nitrogen-doped films. The reduction in energy band gap and increase in Urbach energy was attributed to the introduction of nitrogen impurity tail states on either the conduction band or the valence band of the titanium dioxide.
Highlights
Titanium dioxide, TiO2, has gained considerable attention because of its applications as a photocatalyst[1], solar cell electrodes[2] and gas sensors[3].The structure and optical properties of TiO2 depend to a large extend on the deposition technique
This paper reports on the structural and optical properties of N2-doped TiO2 films deposited by the spray pyrolysis technique and investigates the widening the spectral limit of solar radiation through increased absorption
The band gaps of TiO2 thin film coated on Microscope glass slides (MGS) was observed to be higher than the band gaps recorded for TiO2 thin film coated on Fluorine Doped Tin Oxide (FTO) for all cases of substrate temperatures, which can be accounted for from the fact that the coating on FTO substrates is a combination of TiO2 thin film and fluorine doped tin oxide resulting in effectively a much thicker film(s) compared to the one(s) coated on MGS
Summary
TiO2, has gained considerable attention because of its applications as a photocatalyst[1], solar cell electrodes[2] and gas sensors[3]. A number of techniques have been used to deposit TiO2 films: direct current reactive magnetron sputtering and thermal annealing method[4], pressing method[5] and dip coating[6]. Another method of influencing the properties of TiO2 films is by doping with elements like indium (In) and chromium (Cr)[7] cadmium (Cd), cesium (Ce) and iron (Fe)[8] on TiO2 films obtained by r.f sputtering. This paper reports on the structural and optical properties of N2-doped TiO2 films deposited by the spray pyrolysis technique and investigates the widening the spectral limit of solar radiation through increased absorption
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